q:
I upgraded to a dual Mk9 extruder, and quickly discovered how critical it is to get the ends of both nozzles exactly level with each other -- that is, equally distant from the build plate at all times. Otherwise the lower one will crash against the plastic just extruded by the higher one.

So, what's a good procedure for getting the nozzles accurately level? About all I've figure out is to move the heads down close to Z=0, and then run X and Y back and forth and eyeball and adjust; then move even closer to Z=0 and repeat. Is there a better / more efficient way?

[A]
Make sure that the
bed is level
. As the saying goes, a level bed is next to godliness or something like that. Pay extra attention to the direction the nozzles are offset by (if one nozzle is offset on the X-axis, pay extra attention to the bed leveling along the X-axis).
This can be done with just one nozzle and a business card or piece of paper
.
Use a
bubble level
to get the nozzles about right. Move your z-axis up a bit and put a bubble level against the nozzles. Adjust as necessary so it's exactly level. The nozzles should be level enough that the bubble stays in the middle.
Fine-tune it with a
business card
. When you home the z- axis, you should be able to just fit a business card under both nozzles with a moderate amount of resistance. Don't force the card. If sliding the business card under produces a different amount of resistance for one nozzle than for another, adjust the nozzle a
tiny
amount. You can also use an index card or playing card.
Once it passes the card test, try a test print. If it doesn't work, make sure your bed is level, your nozzle offset is correct in the slicing software, and try calibrating with an index card again. If the nozzles become way off, try the bubble level again.
As for physically adjusting the level, another answer suggests shims made from aluminum foil, which work well. Personally, my extruder was off-level by almost exactly 1mm, so a pair of washers worked nicely for that.
Happy printing!
Leveling with a bubble:


q:
I just received this printer and while it seems to talk to Makerbot Desktop software I'm not sure if I should be trying to update the firmware.

The printer comes with firmware v7.2 and while Makerbot Desktop offers an upgrade to v7.5 I'm not sure if it's a good idea with this non-Makerbot branded printer.

I've also seen information on upgrading this printer to Sailfish v7.5, is this the same thing as Makerbot firmware v7.5?

[A]
The Monoprice Architect is is a bare-bones FlashForge Creator that has been re-badged for Monoprice. The Creator line is a very popular set of printers, so there is lots of good advice out there. The FlashForge Google Group is a good community to join:
https://groups.google.com/forum/#!forum/flashforge
The entire FF Creator line, in turn, is cloned from the original Makerbot Replicator 1. So you can use Makerbot slicing profiles for the Replicator 1. Just keep in mind that Makerbot does not generally test new software revs with their older printers, and DEFINITELY does not test new software revs with competitor knock-offs. Sometimes they appear to break functionality for non-Makerbot machines on purpose. So recent versions of Makerbot Desktop may not "play nice" with your FlashForge.
The most recent "known good" free slicer you should use with this printer is Makerware 2.4.x. You can find links by searching the FF Google Group.
On that note, you may have received instructions to use ReplicatorG with your printer. But RepG is abandonware: development stopped years ago. It should only be used for firmware updates, not as a slicer. You should also only use the most recent version posted on the Sailfish page on Thingiverse:
http://www.thingiverse.com/thing:32084
Using older versions of RepG with newer firmware revs will corrupt your EEPROM! Only use the version downloaded from the link above.
The firmware that comes with the printer is FlashForge's slightly-customized build of either Sailfish or Makerbot's Replicator 1/2/2x firmware. But here's the trick: Makerbot's Rep1/2/2x firmware is just an old, out-of-date, slightly customized version of Sailfish. Makerbot stopped keeping up with bug-fixes and feature additions a long time ago.
Everything is Sailfish:
just different versions. You should use the most recent official release version listed at:
http://www.sailfishfirmware.com/
Follow the instructions in the Sailfish manual from the link above, and RepG will automatically pull the right builds from the official mirror and populate a list of printer options to choose. The trick here is which build to download. As of 1-21-16, there is not an official Monoprice Architect build yet. Which would mean editing a machine xml profile to avoid the firmware throwing warnings. I STRONGLY recommend getting used to the printer using factory firmware before trying to fight with custom machine profiles... But here is the basic process to pick a Sailfish firmware build when you're ready:
First: which Atmega processor version do you have? The large chip in the middle of the control board will either say 1280 or 2560. You need to know which version you have. Bad things happen if you load the wrong version.
Second: What is the tooth count on the X and Y drivetrain pulleys? To my knowledge, FF always uses 17-tooth pulleys, which matches the Replicator 1 and FF Creator profiles. The Rep2 and 2x use 18t pulleys, so only use those builds if you have those pulleys. People often mess this up and their prints end up with dimensions ~5% off in X and Y.
Third: The Architect has one extruder and no heatbed, so firmware builds that expect those to be connected (Rep 1 Dual, Creator, etc) will throw errors if loaded. You can fix this from the LCD screen or RepG, but that's a whole separate question. Do some printing and learn about the printer before attempting any firmware update so you'll know what to do if you pick a build with the wrong parts.
Fourth: This one is just for the sake of completeness. Some FF models were shipped with off-spec heatbeds that require special firmware builds to prevent drawing too much current and overheating / overloading the power supply. The Architect doesn't have that, but firmware builds for those printer models (eg I believe the FF Creator 2560) will under-power regular heatbeds. This is just something you need to know with the Architect if you decide to install a heatbed later. But it's a really critical safety warning for people with those off-spec heatbeds.
If this all seems complicated, that's because FlashForge (and in turn Monoprice) relies heavily on the open source Sailfish project to maintain the software ecosystem behind this line of printers. FlashForge has some internal builds that they use for flashing new bots, but these are not kept particularly up-to-date. Nor does FlashForge release the source files, so it's quite opaque where exactly the stock firmware differs from mainstream Sailfish. In the long run, you should install mainline Sailfish. But it's ok to stick with the factory firmware until you get used to the printer.
To summarize: Because there is not an existing Sailfish build, you're going to need to do some investigating and some experimenting to figure out which build will work. Don't try that until you're familiar with the printer. Post on the FlashForge Google Group when you're ready for help.

s: huggingface

c: devops

d: intermediate


q:
I found a story about someone 3D-printing equipment for their Lego minifig, using an Ultimaker. (Article is in Dutch, but accompanied by photographs).

I noticed that what they made weren't the actual connecting bricks, but the tools used by the minifig. And that even so, some filing and a dremel were needed afterwards to make them fit properly.

I'm told that to make something connect properly with real Lego, the machine needs to be tuned very precisely.

So, what resolution is needed to print bricks that will connect with normal Lego bricks?

[A]
It's really more about calibration than resolution -- a poorly calibrated printer will have dimension errors that prevent mating with true LEGO bricks or other printed bricks.
Also, "resolution" is an incredibly loaded term for 3d printers, because it can mean a lot of different things. But we don't need to get into that right now. There are really two big things to worry about: layer height and extrusion width.
Layer heights of 0.1mm or 0.2mm should be fine. Coarser layers may run into surface finish issues that make the bricks difficult to put together or take apart. There probably isn't much reason to go finer than 0.1mm for this application. Almost all FFF printers can do 0.1mm layer heights as long as it is reasonably well-tuned.
Any typical household FFF printer with a "normal" nozzle size can print fine enough for the bricks to work. It just needs to be tuned well.
The smallest "must have" feature in a standard lego brick is the 1.6mm thick wall around the sides. The typical minimum printable feature size for an FFF printer is 2x the extrusion width, because the slicer will place a path on the inside edge of the shape and the outside edge of the shape. (Some slicers will allow single-extrusion features, but this is not generally recommended because it makes weak parts.)
So, how wide is the extrusion width? It's adjustable, and different slicers auto-recommend different values, but as a safe rule of thumb it needs to be between 1x and 2x your nozzle size. There are some volume calculation quirks in different slicers that may encourage larger or smaller sizes, so sometimes people recommend [extrusion width = nozzle size + layer height] particularly with Slic3r. This is very system-specific.
Assuming you have the most common stock nozzle with a 0.4mm orifice, and also set the extrusion width to 0.4mm, the slicer should put four strands in the walls of the LEGO brick. That's good.
Where it gets tricky is if you have an extrusion width that does not evenly divide into 1.6mm. Say you are printing with an extrusion width of 0.6mm. There is enough room in the wall of the part to place two full 0.6mm perimeter strands... but then a gap 0.4mm wide will be left in the center. You can't put another 0.6mm strand into that 0.4mm gap. Different slicers handle this different ways. Some will leave an empty space between the walls, and you get a very weak print. Some will mash an excessive amount of plastic into the gap, causing poor print quality as excess material builds up more and more on each layer. Some will push a smaller-than-commanded strand to try to properly fill the volume.
So, the general advice with small features is to make sure your extrusion width goes into the part's minimum thickness a reasonable number of times.
[Feature size / extrusion width < 2] is BAD
[Feature size / extrusion width = 2] is GOOD
[2 < Feature size / extrusion width < 3] is BAD
[Feature size / extrusion width > 3] is GOOD
Although these will vary somewhat by slicer -- older slicers like Skeinforge tend to have more issues with this than newer slicers. What you should do in practice is check your slicer's print previewer to see whether it is leaving a gap between the strands. Then adjust extrusion width and perimeter/shell count to try to get an intelligent output. There's some trial and error involved.


q: I was just shopping for filament, and saw some glowing claims about PETG being as easy to work with as PLA, but as strong as ABS, and less brittle. Anyone know if that's actually true, or what the tradeoffs are?

[A]
PETG is great stuff to work with. It is stronger than ABS also. It prints slower than ABS and PLA. The formulas vary quite a bit from vendor to vendor. I have used 3 brands, and each of their properties vary.
From my experience you do have to be careful with moisture. You'll be able to tell you have moisture in your filament if you start hearing a slight hissing and popping and an increased number of structural zits on the object. Moisture will also increase the problem listed in Mark's post below regarding the accumulation of filament on the nozzle.


q: Stereolithography produces parts by projecting ultraviolet light on the top of a vat of liquid photopolymer, causing it to harden.  CLIP produces parts by projecting ultraviolet light through the bottom of a vat of liquid photopolymer, causing it to harden.  This seems like a minor difference, yet CLIP is reportedly much faster (I've seen numbers as high as 100x).  Why is this?

[A]
It's important to understand what specifically is being compared.
CLIP is much faster than bottom-up technologies that require a peel step between every layer.
For example, the Form1 galvo SLA printer tilts the resin vat to separate the transparent bottom from the print. That is, by far, the slowest part of SLA/DLP printing with most modern light sources. Where the speed comes in is that without a peel, a continuous "movie" can be used to cure the resin rather than a series of alternating images and peels.
Top-down printers can print dramatically faster than bottom-up-and-peel printers. CLIP is not necessarily faster than top-down. For example, the Gizmo 3D line of top-down printers are very similar in print speed to CLIP. (
http://www.gizmo3dprinters.com.au/
)
Most "consumer" SLA printers these days use bottom-up-and-peel techniques, because this has some practical advantages over top-down printers:
Way less resin is required to fill the printer when the part is pulled out as it builds rather than being lowered into the tank (along with the Z stage) as it builds. Resin is expensive. This also means bottom up printers can be smaller and have fewer mechanical parts such as leveling devices submerged in resin.
Standard resins contain an inhibitor chemical that prevents polymerization in the presence of oxygen, which causes the surface layer exposed to air (and low-level stray light) to not cure. So top-down printers must shoot light through a non-curing layer before reaching curable resin. This makes the tuning more sensitive and can somewhat reduce detail compared to a bottom-up printer curing right on the window.
Replacement vats or windows for bottom-up printers may be seen by manufacturers as a profit-generating consumable, since they have to be replaced somewhat frequently.
Top-down printers have to worry somewhat more about resin flow rates as the part is lowered. Air bubbles may be pulled into the resin or the fresh resin layer above the part may vary significantly in thickness if the part is submerged too fast for the resin viscosity. (Admittedly, bottom-up printers will experience excessive suction forces and potentially break off bits of the print at high peel speeds.)
CLIP is a bottom-up technique that doesn't require a peel step, because the vat creates an oxygen layer over the window that keeps the resin from curing directly on the surface and sticking. In that way, it arguably performs more like a top-down printer than a bottom-up printer.
Top-down printers that are designed to overcome the above issues and use high-intensity light sources can achieve exceptionally high print speeds. This includes similar "continuous" build techniques used as in CLIP.


q:
E3D-Online and Make Magazine have written about the potential damage printing carbon fiber and glow in the dark filaments can do to your printer's nozzle.

What I can't seem to find is what clues or warning signs to be on the look out for if your nozzle has taken a significant amount of wear. I've printed a few hundred grams of glow filament personally and have not noticed any change in print quality.

E3D says you may have "unpredictable erratic printing" with a worn nozzle. Can anyone explain or provide examples of what this actually means and when a replacement is necessary?

[A]
I believe the little experiment made by E3D - the same link you provide - answers your question very well. Several points about wear can be found in this article. After printing only 250 grams of ColorFabb XT-CF20 (carbon fiber filament):
The nozzle diameter had increased markedly
The inner walls of the orifice (opening) showed deep sharp ridges and grooves
The tip of the nozzle had become critically rounded, and shortened
All of these symptoms were found repeatedly for standard brass nozzles.
In particular, I believe the last of these symptoms may be the one most easily identifiable without accurate measuring equipment (and without observing print quality).
With regards to reduction in print quality, these symptoms could be simulated by:
Setting the nozzle diameter too big in your slicer
Leveling your bed too high (the rounded tip will also reduce the length of the tip)
Printing with a partial clog that interruptus normal filament flow (due to the grooves and ridges)
Exactly what this will look like on your printed part is hard to predict, but I would assume you could see blobs, under-extrusion, poor layer adhesion, as well as an irregular surface finish of your top layers.


q:
I need to do some post processing of my 3D-printed models that includes adding some holes. For each of PLA, ABS, PETG and other 3D-printing materials:

In what ways is drilling a hole in a model made from that material like or unlike drilling wood? Is it worth getting special "plastic drilling bits" that cost tons of money or can I use regular high speed drill bits? Do these plastics have grain that they will split on when drilled into, and if so, what are ways to avoid such splitting? Are higher speeds better, or lower speeds, or should I only use a finger-twirled bit holder?

Are some 3D-printing materials easier to drill than others?

What other methods also work for creating a hole in the different types of plastics?

[A]
I wouldn't recommend drilling a hole in a 3D printed part in a traditional sense like with wood. Instead, I would merely ream a 3D printed part.
I've done this quite a bit where I'll print my holes at a slightly smaller than nominal size and use a standard carbide drill to ream the hole.
Things to consider:
Printing the holes smaller than nominal will ensure your hole is not printed larger than nominal
Printing with a higher shell will ensure you can remove the material without exposing the infill
Note that drilling directly into (or thru) an infill area of the part could lead to cracking of the part later, depending on the hole's functionality. In general, a printed hole (even if reamed) will be significantly stronger than one drilled through an infill area.


q:
On one of the nozzles on my printer, the filament comes out at a 45 degree angle.  It seems that this causes problems with adhesion to the bed and overall quality.

What caused this problem?

How do I fix it?

How do I prevent it from
happening in the future?

[A]
If you're extruding into the air, it's actually quite normal for the filament to come out in seemingly random directions. This shouldn't cause problems because the filament should always be getting squished onto the bed/layer underneath (or during bridging, getting stretched). The way the filament comes out in free air doesn't reflect how it behaves during printing.
If you are experiencing troubles then perhaps the nozzle is clogged with a small piece of debris (or, unlikely) the nozzle is actually damaged. There's little you can do to prevent that apart from using high quality filament and being careful not to damage the nozzle.


q:
I"m considering making my own filament, with a device like the one at http://www.thingiverse.com/thing:380987. Partly because it's another machine to build, which is cool, but also to save money on filament.

Has anyone here tried to make their own filament? My main questions are:

Is the quality comparable to typical off-the-shelf filaments? Put another way, with reasonable tuning can one produce filament that's good enough to use without a lot of frustration?

Does it require a lot of attention to tuning, monitoring, or other details (which make it less worthwhile / more time-consuming)? Warning of pitfalls to avoid is also welcome.

Are there useful things one can do this way, that are hard to achieve with off-the-shelf filaments? For example, unusual materials; better control of diameter, density, etc; or mixing one's own colors?

[A]
You can basically use any machine that pulverizes your pellets into small pieces.
One guy on 3dhubs, explained it in details.
My conclusion is that you can recycle everything using this data gathered from research up in link there.
Also, you can use any plastic material and pulverize it into pellets (even from the bottles) and you can try to do this process. Only thing that matters is quality of product.
I was thinking about pellets from vinyl records. I bought one big collection before one year, and there was around 500-600 records that are completley useless. So, you can pulverize them and repeat the process, because process of making vinyl records and process of making bottles is completley different, and uses different kind of plastics.
So to draw a conslusion: everything depends on quality of pellets.
And to answer on your three questions:
Is the quality comparable to typical off-the-shelf filaments? Put
another way, with reasonable tuning can one produce filament that's
good enough to use without a lot of frustration?
No, it isn't Your filament would be lower quality if you don't get a great pellets.
Does it require a lot of attention to tuning, monitoring, or other
  details (which make it less worthwhile / more time-consuming)? Warning
  of pitfalls to avoid is also welcome.
Yes it does. Check the link up there.
Are there useful things one can do this way, that are hard to achieve
  with off-the-shelf filaments? For example, unusual materials; better
  control of diameter, density, etc; or mixing one's own colors?
Again, it all depends on type of filament you like to use. I wrote about plastic filaments.


q:
When installing and using a new hotend for the first time, which steps of action should be taken before. This will probably be more applicable to chinese clones than to authentic products (is the statement true?): Should a certain cleaning procedure be carried out (removing swarf/shavings for example)? Should mechanical precision be controlled and if necessary improved (de-edging and nozzle size are two things I could think of)?

I know the topic How should I clean my extruder when changing materials?, which is a nice addon read, but I am concerned about brand-new extruders.

[A]
I haven't done anything special to set up mine. But it's probably worth doing a general cleaning. I'd swab it off with alcohol, including running a q-tip or similar inside the fiber feed path. Then blow out the nozzle with compressed air to make sure it's clear.
You could measure the nozzle diameter by fitting fine drill bits in to see which is the largest one the passes through freely. Be sure to measure how much fiber your extruder
really
takes in when you ask it to extrude a certain length -- but that's about the extruder, not the hotend per se.
Finally, I'd check the insulation, if any. I got a couple hot ends that had big gaps in/around the insulation. I've found that "high-temperature gasket maker" is great for improving insulation (depends, of course, on the shape and design of the specific hot end.


q:
If I need to test out some of the components of a RAMPS 1.4 based 3D Printer, can I only plug some of them into the board (not all of them) and test them out?

I'd like to test out the NEMA 17 motors without testing the heated bed or extruder.  Is this safe and why?

[A]
Yes, you can. By leaving components unplugged you would simply have some pins powered that are not in use. But even with all your components plugged in, you would still have some unused, powered pins on your board, so I wouldn't think too hard about that. In some cases it might be needed to mount e.i. fans to cool your electronics while running, but for testing a few stepper motors, you will be just fine.
Exactly how you would address each individual motor depends on your setup, however. My best bet would be to simply rely on your "default" firmware (such as Marlin), and then run commands for testing through Pronterface/PrintRun or similar.
Alternatively, you could upload your own sketch/firmware to the Arduino, and manipulate each stepper driver individually. This is a somewhat more advanced option, though.


q:
This is in with my other question about components and the other question about electricity; how can I check to see how many amps are being pulled?  Can I check a component at a time to make sure I'm not going over the limit, and then just add them all in together once I've summed the amps to make sure it's safe to hook everything up.  The amps shouldn't change right?

What settings should my multimeter be set to?  And to check how much it's pulling, do I just put the multimeter's leads on the green terminals on RAMPS 1.4?

[A]
To measure amps (current), the meter has to be wired in series with the item to be measured (for this reason, ammeters are designed to have very low resistance).
This has the down-side that you have to disconnect the component to put the meter in line with it. That makes it hard to do the "check a component at a time" method you mentioned.
An ammeter measures
actual
current flow, so you really can't test a component for it in isolation. Components can have wildly different "current draw" depending on the situation. For example, motor current varies with torque and speed; current through a resistor varies with the voltage across it; and so on.
There are special "clamp-on" current meters that just clamp around a conductor and report the current by using induction. Very nice if you have one.
If you just want the total current the entire RAMPS board is pulling, put the ammeter between the power supply and the RAMPS power input connection(s). Be
very
sure not to have the meter set to read volts or ohms when you do this (it might or might not survive).


q:
There is a little circuit board, or breadboard or something in the diagram of the wiring for the i3.

And it's mentioned that the z-axis motors need to be wired in parallel but beyond that they don't give you much detail about parts or how the wires go in.

Can someone provide me with some more detail on this?

[A]
In the diagram, they do show the wires connecting together, which is right. You can accomplish that just about any way you like, so long as you pair up the wires correctly from one motor to the other.
I'm assuming both "Z" motors are the same type and have the same color-coding for their wires. If not, you'll need to figure out the correspondences first (you may want to post another question if you need a hand with that, since it's pretty specific and generally useful).
Many control boards have "headers" sticking up, with 4 bare pins for each motor. Connectors that plug right onto those are readily available, such as at
https://www.sparkfun.com/products/10364
.
Some ways you can wire the motors in parallel:
Some control boards, like my RAMPS 1.4, provide 2 sets of header pins next to the Z stepper driver board. In that case, just put a connector on each motor (if they're not there already), and plug them in next to each other.
If there's just one set of header pins (or one Z-motor socket of some other kind) on your controller, make a "Y-cord" by soldering the wires from one connector (that plugs to the controller) to
2
4 pin connectors, one to mate with each motor.
Or you can skip the 2 extra connectors entirely, and just solder the motor wires to the wires from the connector: 2 reds to red, 2 blacks to black, or whatever.
If your controller just has empty holes, either solder in header pins and do as above (preferred, IMHO), or wire directly into the holes, splicing the 2 sets of motor wires if there's only one set of holes.
Motor and connector wires are wildly inconsistent, so make sure you get them sorted out right if they aren't already. The first thing is to check continuity: find 2 pairs of wires, which are the ends of two separate coils. If your motors have more than 4 wires it's trickier.
With RAMPS (see handy diagram
RAMPS 1.4 RepRap Arduino Mega Pololu shield
),
the 4 pins are commonly labelled (starting from the one nearest the power-supply end of the RAMPS board):
```
```
2B 2A 1A 1B
```
```
It means coil 1 and coil 2, each of which has ends A and B. I find this unclear because it could just as well have been numbers for the coils, and letters for the ends (if you wire it that way it won't work). So be sure you have continuity (maybe 15 ohms or so) between the wires you connect to 2B and 2A, and between the wires you connect to 1A and 1B.
The
really good thing
about this pin order is that if a motor is running backwards all you have to do is power off and then turn the plug around. That's one reason I think it's important to keep connectors in there, rather than soldering directly.


q:
I'm thinking about buliding my own 3D printer from scratch.

Is it better to buy a starter DIY kit and try to build your printer around it, or to order separate parts for printer, and then to combine a printer?

[A]
From a general point of view, there are a few things to consider.
If you buy a kit
:
Pros:
You get some insurance that
you have all the parts that you need
to get a functional printer - all the electronics, structure, bolts, nuts, screws, washers, wires and so on.
Most likely, all the parts you get are made to
fit together
.
You will (usually) get a
manual
, often a community that can help you out, and sometimes even technical support.
Sometimes, it can be
cheaper
than buying each part separately (but it can also be more expensive)
Cons:
You have limited/no options to customize your printer to your own preferences without purchasing additional parts.
Some kits can be difficult to upgrade later or may be locked to some configuration or software.
My opinion:
The way I look at it, the better option for
you
depends on how you want to spend your time. That is:
If you get a kit, you can spend more time building.
If you collect all the parts yourself, you will have to spend time planning, ordering parts (possibly multiple times) in addition to actually building the printer. A possible lack of manuals could also increase the building difficulty.
If you don't already own a 3D printer, I would recommend getting a kit, simply because struggling with trivial things like parts not fitting together can take away the fun for many people.


q: How do I smooth 3D printed objects? What is the best / common method to do this?


q:
I have seen lots of printers that print chocolate using a syringe with molten chocolate. But, even cooler, would it be possible to print chocolate using some kind of feed system for continuous chocolate printing, so large objects and for a prolonged time, not only lasting the content of one syringe with molten chocolate ?

Things to consider are IMO:

How to keep the chocolate long enough in a molten, viscous state
enough to print ?

Chocolate needs a tempering temperature, which
means it needs to be around 32-37 degrees celsius, else it doesn't
shine but gets a dull look (or turns white after a while).

Chocolate
is food, so you need foodsave equipment in the whole chain that is in
contact with the chocolate.

Maybe a peristaltic pump that keeps pumping the molten chocolate to the extruder, which might be a valve that can be open/closed from G-code ?

[A]
Update: I found a nice article about chocolate printing:
https://all3dp.com/2/chocolate-3d-printer-all-you-need-to-know/
You are searching for chocolate extruder. I did not find one, which would fulfill all your requirements. You have to adapt each solution.
Zmorph3d Liquid paste extruder
https://zmorph3d.com/cake-and-chocolate-extruder/
According video on the page you insert chocolate in liquid form. That could be solved with heated chocolate container.
Syringe based extruders
http://www.open-electronics.org/3drag-is-now-printing-with-chocolate/
http://richrap.blogspot.de/2012/04/universal-paste-extruder-ceramic-food.html
http://www.instructables.com/id/Chocolate-Extruder-for-Ultimaker/
You can use a
2 liters syringe
. And if this is not enough then you can refill during print.
Convert pellet extruder
Printing from chocolate pellets is simpler then printing from plastic pellets. Therefore if you use foodsave parts to build such a extruder then this is useable for you.
https://www.youmagine.com/designs/universal-pellet-extruder-reprap-3d-printing
Cooling
3DRAG CHOCO (Chocolate 3d printer) Cooling system explained
Shop
by Open-Electronics
Extrude for chocolate
Syringe Heater for 3Drag chocolate printer


q:
I recently found out carbon fiber and glow in the dark PLA can damage the printer nozzle, now I'm suspicious of all the "exotic" filaments.

So, does wood filament cause damage to the nozzle? (under normal use, or at least what someone who only used PLA/ABS before would consider normal use)

Let's assume a normal quality brass nozzle - not some cheap stuff that didn't even came in the correct size to begin with and not some premium reinforeced nozzle - and reasonable quality filament.

[A]
If you haven't been to their site before, you should check out the forums on 3DHubs. There's a lot of how-to's. A quick Google search yields
this
link to a similar question.
The key thing to note is that in all technicalities, any material you run through the nozzle is going to cause
some
sort of wear on your nozzle.
How quickly
depends on the material or composition.
The answer to the question linked above relates it spot on to sandpaper. If you have sandpaper made out of metal (ie stainless pla), it will scratch your skin fairly easily. If you have sandpaper made out of tree bark (ie laywood pla), it probably won't scratch your skin as bad, but it'll still scratch. And just for poops and giggles, lets say you have sandpaper made out of pla; it'll take a while, but you could eventually make your skin raw if you rub the plastic against your arm long enough.
It is typically recommended to use one nozzle for each material type as to avoid cross-contamination of materials in your printing. With this idea in mind, if you are using many types of materials, you can also minimize failed prints due to clogging and other "damaged nozzle" type troubles.


q: In general 3D printers are compact and smaller than RP machines. That's ok. But, what's the difference? 3D printers can be used as RP machine too.

[A]
All rapid prototyping means is automatically producing a physical part from a cad model. 3D printing is a way to achieve rapid prototyping. There are 2 main methods of rapid prototyping: additive, and subtractive.
A 3D printer is additive- you add materials to an object layer by layer.
Usually, when people talk about a subtractive machine, they are talking about a CNC mill (or lathe), which tend to be extremely large (most are over one ton). You start with all the material there, and you subtract the material that you don't want. This might be what you are thinking of.


q:
I'm using Cura as my slicing/printing software and I just started using the BuildTak printing surface.

The BuildTak is damaged by pushing a hot nozzle into it and my printer's (Robo3D R1+) autoleveling feature works by pushing the nozzle into the build surface.

Is there a way to configure Cura so that it runs the Z probe first, then heat up the nozzle?

My first sheet of BuildTak already has 10 small holes in it (at the homing position and at the 9 leveling touch points)

[A]
In Cura (and Slic3r), you can 100% customize what the printer does before printing your actual model through custom
start/end g-code
.
If you navigate to the
```
Start/End-GCode tab in Cura
```
, then select
```
start.gcode
```
, you can see what operations are run before each print begins. Lines prefixed with
```
;
```
are comments, and does not affect the printing in any way.
Basically, we want to manually tell the printer to do the auto leveling
before
heating up the nozzle by editing the g-code in
```
start.gcode
```
.
G-Code generated with the default start.gcode:
If you try to slice some model with the default code found in
```
start.gcode
```
, you will get something like the following (depending on your printer):
```
```
; CURA AUTOMATICALLY INSERTS THESE TEMPERATURE CODES

M190 S70.000000 ; Set bed temperature to 70 degrees
M109 S210.000000 ; Set nozzle temperature to 210 degrees

; THESE ARE THE CODES FROM START.GCODE (for a ROBO 3D R1)

G28          ;move printer to endstops (the home position)
G92 E0       ;zero the extruded filament length
M565 Z-1     ;set z-probe offset
G1 Z5 F5000  ;move the printer 5mm above the bed
G29          ;run auto-leveling

; THE ACTUAL MODEL BEGINS HERE

;Layer count: 168
;LAYER:0
.
.
```
```
Analyzing the g-code output
At the top of this code snippet, we can see that Cura automatically inserts g-code for heating up the bed and nozzle to their respective temperatures with the
M190
and
M109
g-codes. This means the printer always will heat up the nozzle before reading the
```
start.gcode
```
s that we set. However, if we manually override
M109
code in
```
start.gcode
```
, the
M109
at the top will automagically disappear from the generated g-code output! (Thanks, @TomvanderZanden!)
We could therefore use the auto-leveling command
G29
before manually setting the nozzle temperature with
M109
; specifically, we want to add
```
M109 S{print_temperature}
```
, which reads the
```
Basic -> Print Temperature
```
-setting in Cura, and replace
```
{print_temperature}
```
with it automatically.
Manipulating start.gcode:
In order to postpone heating the hotend till after probing,
```
start.gcode
```
could be something like:
```
```
G28          ;move printer to endstops (the home position)
G92 E0       ;zero the extruded filament length
M565 Z-1     ;set z-probe offset     <-----   ( YOU HAVE TO ADJUST THIS, READ BELOW)
G1 Z5 F5000  ;move the printer 5mm above the bed
G29          ;run auto-leveling
M109 S{print_temperature}    ;set nozzle temperature, and wait for it heat up
```
```
And that's about it! You can then use these codes in your
```
start.gcode
```
. However, you probably will have to recalibrate your z-prove offset.
Adjust z-probe offset:
Normally, auto-leveling is done with the nozzle heated for a reason: when the nozzle is warm, it expands slightly, moving closer to the bed. You might therefore have to adjust your Z-probe offset with the
M565
command (as demonstrated in the snippet) to account for the increase in nozzle length when warm.
Remember:
Remember that when editing g-code in this manner, you will take full control of how the printer operates. You could therefore very well do something unintended, so keep the power switch close!


q:
I am wondering how people that use standalone 3D printers (printers that have the ability to print autonomously from SD Card) feed in filament, prime the printhead and/or change filaments without a laptop ?

Do the printers have a menu to arrange all these tasks ?
I often only see the options to preheat the head to a certain temperature, but not to load/unload filament, extrude a small amount etc.

I understand this differs from printer to printer, but still am wondering about this.

[A]
There are options for tablets. They are running software
(for example)
on some device that has internal storage, wifi, USB connection etc.
You can buy a new tablet, or reuse your old one just to be a controller.
Another great example is
this app
.
Apps have menus that can arrange everything for you, now it depends on what app do you use and what filament you use. It's very simple thing.


q:
I'm thinking of another extruder on my printer, and I'm curious about this one....

Is it necessary to have both hot ends on same height? Why yes / why not? (if there is not)

[A]
I don't have dual extruder printer myself, but to my understanding having both nozzles leveled at the same height is critical for getting successful prints.
For typical FDM printers, the lowest point of the end effector should always be the nozzle. If you, for instance, mount a fan lower than the tip of your nozzle, it will eventually collide with the printed object.
The effect of having unequally leveled nozzle tips for a dual extruder printer will be exactly the same: one of the nozzles will either drag against or collide with the model during print; or, one of the nozzles will be to far away from the model, giving poor layer adhesion. Either way, the result will be sub-optimal.
So, leveling both nozzles equally is probably a good idea. You might want to have a look at
this question
on some advice regarding how to do it.


q:
I have searched the internet and found various 3D printers with different advantages and materials which they can print - some even multi color.

However, I cannot seem to find a printer that can print multiple material with different properties; for instance, simultaneously printing PLA and metal. Is there currently such a printer available or in development?

[A]
Yes and no.
for instance simultanious printing of plas plastic and lets say metal. Is such a printer available or in development ?
Practically speaking, no.  Metal printing requires significantly higher temperatures than plastic, and the two processes are so incompatible that there is currently no good solutions that would allow one printer to print both in the same print. Whether extruding filament, laser sintering, or curing resins, the materials involved have to be fairly similar in processing environment to print adjacent to each other without issue.
There are many printers that are intended to print multiple materials by changing the print head.  You might, for instance, use a ceramic paste extruder, then change the head for the next print using plastic.
There have been efforts in the past, and some efforts are ongoing, to resolve this.  For instance wood's metal, a low temperature alloy, can be poured at temperatures compatible with plastics, so it's possible to create a printer that prints plastic, leaving troughs or voids in the plastic, then the same printer during this print would pour molten woods metal into these areas, which then solidifies into an internal metal structure.  These are intended for circuitry and electrical use, however significant problems still exist because the thermal expansion differences in these materials lead to stress and result in poor reliability.
So while some of these processes are being developed, this is still just in the experimental stage and there are significant problems to overcome before printers can print widely different materials in a single printing session.
Of course you can find plastics with such a wide range of characteristics that they can be seen as printing different materials.  Plastics imbued with wood fibers, printing next to conductive plastics with graphite, printing next to flexible plastics, etc, etc are now possible, and depending on your requirements they may meet your needs.


q: Is there a good method or tool to level the bed of 3D printers? I find myself making small adjustments a lot and it's mostly just trial-and-error. A normal bubble level is of limited help and trying to figure out if the head is the thickness of a sheet of paper from the bed in all corners is beyond the capability of my vision.

[A]
The easiest way I know of (unless your printer has a Z-probe and automatic leveling), is to bring the nozzle(s) down fairly close to the bed (maybe 1/4" or so), and then move it around while watching for anyplace that doesn't look even. Adjust the bed until it seems even. You can just eyeball it, or use a ruler or object to measure.
Then bring the nozzle down closer, and repeat. Each time you move it closer, you'll be able to eyeball more accurately.
Once you're quite close, pull out a 3x5 card, or business card, or similar, and move the nozzle up or down until the card just fits between the nozzle and the bed (with no great pressure, but no space either). Again, move the head all around the bed, and do any remaining (tiny) adjustments so it's the same everywhere.
Of course if the bed is at all warped this will be much harder, or even impossible. So before starting, put a good-quality straightedge along it to make sure it's actually flat.


q:
Occasionally, while printing, my y axis will slip and the layer will, from that point forward, be shifted, ruining the print.

What might be the causes of an axis slipping? I have tried cooling the motor which seemed to have been getting warm, and the belts are not too tight.

This does not happen with every print, and seems to be an intermittent problem.

My printer is a MendelMax RepRap, and the y axis is my moving bed.

[A]
From what I've experienced, there could be three potential reasons.
Your belt(s) could be loose. Simply loosen your Y-Axis motor and pull the motor until the belt is slightly more than taught (it will relax into a taught position). Then, tighten the motor securely in its place.
One of your axis endstops could be triggered mid-print. If you have a larger print, you run the risk of hitting an endstop, which could cause the machine to lose its coordinate system.
I found on my machine, if you run your program via USB (on MakerWare specifically, possibly others) there might be some sort of lag in the serial connection that could cause the entire program or coordinate system to shift. I repeated this issue multiple time using a USB connection and fixed it (repeatedly) by either running off of an SD card, using a different slicer (in my case the Cura plugin for OctoPi), or trying an earlier version of your software (this was my long term solution).
The latter worked best for me. I tried running MakerBot Desktop on my Dual Replicator 1, but ran into the same exact issue as you. In fact, I encountered this issue around firmware 5.0 on the Replicator as well (7.? is the latest). Finally I switched back to using MakerWare 2.4.? and everything worked fine.


q:
From what I understand, it takes a really long time for the heated bed to heat up using an MK2a heated bed.  I've heard some people suggest that using Polyisocyanurate (PIR) foam (insulation that takes quite a bit of heat to catch on fire) can be used under the headed bed to make it heat up faster.

Now of course there are other methods for doing this too, for instance using a larger power supply, but at this point I'd rather just use the parts that I have without re-soldering many of the components on the RAMPS board.

I was wondering what a proper way to attach this to the bed would be for instance, should the springs go on the bottom or on the top of the bed?  Do I need some extra parts?  Are there any other considerations for doing this?

[A]
If you use a seperate powersupply for your bed (or if your controller has a built in voltage regulator so it doesn't damage at higher voltages) you can sometimes find an small potentiometer near the connection terminals of your powersupply, turning this potentiometer up can raise the outputvoltage of your powersupply by a few volts max. In my case the potentiometer was orange and allowed me to turn up the voltage by almost 2Volts!
If your printcontroller is running from the same powersupply and is critical about input DON'T do this since it will damage the electronics.
Better option then is to find a higher voltage powersupply and power the bed Seperately.
A buddy of mine runs his MARK2a bed on 19V and it heats up very fast. (he uses an obscure 15V powersupply that was able to be cranked up to 19V). And he doesn't use insulation at all!


q:
Glass is always level, easy to clean, easy to work with.

Aluminium allows for the addition of automatic bed leveling with an inductive sensor and distributes heat a little more evenly.

When printing mostly ABS and PLA, which one is better?

[A]
I believe printing directly on aluminium is unwise, simply because it will expand when heated, typically giving the bed a concave or convex shape. Glass, on the other hand, does not (at least not significantly).
As pointed out in the comments below, the heat expansion of aluminium could potentially be mitigated by increasing the thickness of the bed, as well as heating it evenly. Also, a common solution is to place a glass plate on top of an aluminium bed, at the cost of a slightly longer heat-up time.
In my experience, printing directly on heated glass can be very practical and give a nice surface finish for some PLA variants and other materials that support it. I don't know if printing directly on aluminium can give similar benefits.


q:
I currently print with a .4mm nozzle on my extruder, and my prints seem to come out fairly accurate; would I see much of a difference if I went to a .3mm?

What are the pros and cons of larger and smaller nozzle sizes?

[A] My understanding is that the only difference is your range that your layer height can be. For example, the optimal layer heights for a 0.4mm nozzle fall between 0.1-0.3mm. So, we can assume a smaller nozzle will yield a lower range. Keep in mind that varying sizes in the nozzle could produce complications more prominently than with a standard size. Things such as ooze, clogging, and filament backup may occur with a smaller nozzle size if your slicing engine is not setup correctly.


q:
Some electronics come as a single PCB. They have CPU and everything on just one board.

Other electronics are a shield for an Arduino. So these are always two boards. The Arduino and the other PCB.

You probably don't want to exchange the Arduino unless it is broken. Does it break that often or are the two boards just the predecessors of the one board solution?

What are the benefits/downsides to having one/two boards?

[A]
Many 3d printer motherboards are based on Arduino/Atmega microcontroller and just add some stepper motor drivers, MOSFETs and such in a single board. That explains why you use the Arduino IDE to update or modify their firmware.
Now why you would want to use an Arduino + an Arduino shield board like RAMPS? Well if you're not good at electronics, are happy with the cost of your own board, don't care much about upgrades/modding beyond what is possible with your board, maybe you shouldn't, it might be overwhelming.
There are several advantages with using Arduino with a shield for your 3d printer, "two boards are not just the predecessors of the one board solution", no.
1) It is moddable/exandable/upgradable/has replacable parts.
If your printer came with its own motherboard that doesn't have additional or enough pins to add more fans, enclosure lights, a second extruder, an LCD and you want to, it sucks. RAMPS can do that, it has plenty of extra pins.
It is upgradable. You want to replace the stepper drivers with a new one? Or you accidentally damaged the one you have? Fear not, you can just replace that instead of the whole motherboard.
Think if it like other motherboards being PCs on which you can't change the CPU, RAM and GPU.
2) It is here for a long time, you will be able to acquire one for a long time.
There isn't just one company making RAMPS or similar sheilds. Sometimes 3d printing companies go out of business or stop producing your particular motherboard. RAMPS is likely here to stay. Because Arduino is very likely here to stay.
3) As said above, not just one company owns or makes RAMPS or other Arduino shields. Besides the possibility of your motherboard not being produced anymore, there's also the advantage of not being at the mercy of one companies pricing and shipping policies. This is true for some other boards as well though.
4) It is possibly cheaper than what have you. I don't want to post a link, but one company right now is selling their derivative of Printrboard for like $180. Check the cost of Arduino Mega, stepper drivers and a RAMPS board yourself, quite a difference. That said, there are some boards which are close in price.
5) It's an Arduino. Why is this a good thing by itself? Because many people who have a 3d printer are tinkerers/makers and they already use Arduino for other projects. It is open source with a rich library to control many things. The modding and upgrades for your 3d printer which can be done with Arduino is another level higher. Or it can be a good learning experience for your future Arduino projects. If on the other hand you already use Arduino and are experienced with it, you might use it just because you know how to control it/fix it better than some specialized board you haven't seen before. Plus for a guy like you your 3d printer's motherboard will be an "off-the-shelf" part, that's nice, right?
Video on RAMPS:
https://www.youtube.com/watch?v=FYJn6FuWOv4


q:
My printer has an auto-leveling feature that works by touching the build plate with the tip of the nozzle.

I started using a BuildTak surface and BuildTak is damaged when you push a hot nozzle into it.

So I edited the start G-code to run the auto-leveling before heating up the hotend

But ABS doesn't stick to the build surface unless I pre-heat the hotend and wait about a minute.

So now I'm looking for a G-code command to put at the end of the start G-code that will make the printer wait a minute before printing

The sequence I'm looking for is:

Heat up the bed

Auto level

Raise the hotend a little bit so it doesn't touch the build plate

Heat up the hotend

Wait a minute (that's the only part that is missing, everything else works)

Start printing

Any way to insert a delay into the G-code?

I'm using Cura to slice/print, my printer is Robo3D R1+

[A]
An alternative solution to using a hard delay with the
G4 dwell command
, is to increase the time that the temperature set with
M109
has to be held before it continues with the next command.
In Marlin, this setting is named
```
TEMP_RESIDENCY_TIME
```
, and can be found around line 150 in
```
Configuration.h
```
. By default, this is set to 5 seconds, which looks like:
```
```
// Actual temperature must be close to target for this long before M109 returns success
#define TEMP_RESIDENCY_TIME 5  // (seconds)
```
```
If increasing this setting solves your exact problem, I cannot say, but it could be worth looking into.


q:
Most electronics use micro-controllers like an AVR, but I'm seeing ARM chips in new electronics. ARM chips are said to be more powerful, but in what areas related to 3D printing could this help?  What are the features that the AVR struggles with and where an ARM could be better?

High Speed movement? Delta printers? Graphic display?

And is the AVR really the limitation there?

[A]
Generally, AVR is in fact less powerful than many ARM cores used today. Most printers with AVRs don't have floating-point coprocessors, although a lot of the step and movement control can be done in integer-only math (except for G2/G3). Marlin can interrupt for step handling
up to 10000 times per second
on AVR, translating to 40000 steps per second. This isn't particularly useful without mechanical components that can move at those speeds and still print meaningful results (or are far more precise and have a far higher step-count-per-mm at a similar speed).
Graphic display isn't a particularly taxing thing to do at
low
speeds--high speeds or weird interfaces might require a bit more power or a dedicated interrupt.
The times when ARM might be important are for more math-heavy and especially floating-point-heavy setups such as delta, where every move requires many floating-point and trig operations, and navigation in menus on a 16MHz AVR (atmega2560)
is described as
"painfully slow", but Marlin does succeed in printing meaningful results on delta-style printers.
Clearly, an ARM core that is either faster at performing soft floating-point, or supports hardfloat (hardware that does floating point operations very efficiently) will see a benefit for such processes.


q:
I  was wondering if this printer(daVinci 1.0) had the ability to print very small objects, like insects, coins, or small nuts. (About the size of 1 -2 cubic centimeters)

Here is a link to the printer on the website.

The reason I ask is someone asked me if it was able to, but I have not been able to access the actual 3-D printer for use at this time, just manuals which I have looked through.

So if the 3-D printer was able to print small objects, would a novice be able to do such a thing?

Please let me know if any additional details are needed.

[A]
1) If we're talking about FFF/FDM printers:
Accuracy of the electronics and motors allows it, yes.
But how FDM printers work it might be very hard to lay down layers of molten plastic so small as to preserve little details in the X and Y axis, not much of a problem doing 20 micron layer height though (Z resolution).
Check this answer to find out what the X and Y resolution is and what it depends on:
https://3dprinting.stackexchange.com/a/509/381
You'll need both a small enough nozzle, as well as somehow cool the plastic because since the printed objects are so tiny the nozzle keeps contact with the surface surrounding it and heats it longer, which might melt the whole object or even char it.
I've seen very few people do tiny prints with success. And the smallest nozzles I know are 250 micron.
Not trying to dscourage you, just letting you know. If it was easy to do I think more people would be doing it and more companies would be advertising their printers as capable of such a thing
So you'll have around 20 micron Z resolution and around maybe 200 in the X/Y.
If that's enough for you, then you could try. Calibrating it all won't be easy, tiniest backlash will be noticeable.
2) It's a lot easier with curing resin 3d printers (SLA or DLP). Most of them actually have trouble printing larger objects, ironically (trouble sticking to the bed and cracking of the 3d print).
Even here badly calibrated lasers would prevent you from doing this and even many Form 1 users have reported their lasers being assembled poorly resulting in poor beam profile.
Size of the laser beam profile (aka laser "spot size") is what determines the X/Y resolution for SLA 3d printers. With the Form 2 its 140 micron, unless you'll get a badly calibrated printer.
For DLP printers it's easier, it's the resolution of the DLP projector divided from the size of the print area.


q:
I have a Printrbot Simple Metal. The extruder is getting clogged all the time. I went through the process demonstrated here multiple times already. Heatting the extruder and pushing different tools all the way through to make sure it is completely clear.
Every time I get a clear flow of PLA, and after a few minutes the extruder motor starts clicking again. At that point, it is even hard to push in the filament by hand.

I replaced the tip already, but this didn't make any difference. I also tried few different filaments, all of them worked perfectly before.

It feels like stopping the flow even for about 30 seconds would cause it to jam.

[A]
I'm not sure if this is particularly the issue for you right now, but I have encountered the tension on my drive gear being too high.
Before I upgraded my extruder to the spring loaded mechanism, my extruder used a Delrin plunger to provide tension against the filament towards the drive gear. This plunger used copper washers to help adjust the tension required. Many people ended up upgrading their assemblies to the spring loaded mechanism as the plunger would either put too much or too little tension against the drive gear. Too little and the filament will not be driven into the hotend. Too much and the filament will grind against the drive gear and the drive gear may begin to "eat" away at the filament (especially when the filament becomes hotter). Obviously, if the drive gear is no longer able to catch on the filament, the nozzle will get clogged.
However, even with a spring mechanism, your tension can become too high. Most of these mechanisms allow you to adjust the tension by tightening/loosening the screw holding down the spring. The "sweet spot" for me is just past when the filament can be successfully driven into the hotend. You can test this if you have control over your extrusion motor by removing the extrusion motor from its mount, leaving the spring mechanism installed on the face of the motor. Then, turn your motor on and try feeding the filament through the mechanism. Starting with no tension on the spring, begin slowly increasing tension by tightening the screw on your mechanism until the drive gear is successfully able to guide the filament through. I might even complete another half turn on the screw to account for varying diameters and plasticity states of the filament as it becomes hot.
Hopefully this helps and please keep us updated on anything else you find.


q:
On a Cartesian printer movements are really simple. If we assume the printer has 100 steps/mm on each axis, then a move of 10mm on a axis is just 1000 Steps on that axis.

Movements that are not aligned with one axis are also simple. Moving from x,y = 0,0 to 10,10 would be 1000 steps on x and y.

On deltas even for simple moves more than one motor has to move. And just calculating the amount of steps on each axis needed to reach the destination probably gives a curved move.

So what is the algorithm to calculate the steps for a given move for a delta printer?

[A]
I am describing how this is done in the Marlin firmware.
The first step is to split a linear movement from (x, y, z) to (x', y', z') into many discrete segments. To this end, the amount of time the move would take at a given speed is calculated, and the value
delta_segments_per_second
is used to calculate the number of segments used.
This is done in the function
prepare_move_delta
in the file Marlin_main.cpp. The endpoints of each of these segments is then passed to the function
calculate_delta
:
```
```
void calculate_delta(float cartesian[3]) {
    //reverse kinematics.
    // Perform reversed kinematics, and place results in delta[3]
    // The maths and first version has been done by QHARLEY . Integrated into masterbranch 06/2014 and slightly restructured by Joachim Cerny in June 2014

    float SCARA_pos[2];
    static float SCARA_C2, SCARA_S2, SCARA_K1, SCARA_K2, SCARA_theta, SCARA_psi;

    SCARA_pos[X_AXIS] = cartesian[X_AXIS] * axis_scaling[X_AXIS] - SCARA_offset_x;  //Translate SCARA to standard X Y
    SCARA_pos[Y_AXIS] = cartesian[Y_AXIS] * axis_scaling[Y_AXIS] - SCARA_offset_y;  // With scaling factor.

    #if (Linkage_1 == Linkage_2)
      SCARA_C2 = ((sq(SCARA_pos[X_AXIS]) + sq(SCARA_pos[Y_AXIS])) / (2 * (float)L1_2)) - 1;
    #else
      SCARA_C2 = (sq(SCARA_pos[X_AXIS]) + sq(SCARA_pos[Y_AXIS]) - (float)L1_2 - (float)L2_2) / 45000;
    #endif

    SCARA_S2 = sqrt(1 - sq(SCARA_C2));

    SCARA_K1 = Linkage_1 + Linkage_2 * SCARA_C2;
    SCARA_K2 = Linkage_2 * SCARA_S2;

    SCARA_theta = (atan2(SCARA_pos[X_AXIS], SCARA_pos[Y_AXIS]) - atan2(SCARA_K1, SCARA_K2)) * -1;
    SCARA_psi = atan2(SCARA_S2, SCARA_C2);

    delta[X_AXIS] = SCARA_theta * SCARA_RAD2DEG;  // Multiply by 180/Pi  -  theta is support arm angle
    delta[Y_AXIS] = (SCARA_theta + SCARA_psi) * SCARA_RAD2DEG;  //       -  equal to sub arm angle (inverted motor)
    delta[Z_AXIS] = cartesian[Z_AXIS];
}
```
```
This function takes care of the delta geometry and calculations needed to convert the (x,y,z) coordinates of the segment endpoints to corresponding positions for the carriages. The translated coordinates are then passed to
plan_buffer_line
, which calculates the steps needed for each stepper motor and actually makes these steps happen.
The exact kinematics used in this function are explained in much more detail at the
Marlin github
.
What is important to note is that plan_buffer_line moves the carriages linearly, and the printhead thus describes an arc and not a straight line. A straight line move is thus approximated by many small arcs.


q:
Is there a definitive scalable 3D printer?

I've seen examples of Chinese companies printing entire houses, and I'm curious as to printers / filaments that are intended (or at least able) be scaled up for (very) large print jobs.

Since most hobby printers can take hundreds of hours for something that can still be held in our hands, so I'm curious if there are any designs for printers that are meant to extrude material efficiently with a easily scalable printing area.

Open sourced / free is preferable; though I'm interested in any designs that exist, commercial included.

[A]
If I understand your question correctly, it sounds like you're looking somewhere within the
RepRap
realm. The RepRap community is mostly responsible for the boom in consumer 3D printing in the past 10 years, and that's most likely because it's
open source
. RepRap designs are mostly dynamic (and most parts can be 3D printed), so you could theoretically build a larger frame for your machine and use a slicing engine that allows you to set the build volume. I believe
Slic3r
allows you to customize the build space, I'm not sure though.


q:
When you cut or break a PLA model (for example to remove support) it often leaves an ugly while mark where the removed piece was connected.

Sanding also tend to leave dull white scratches on the sanded surface.

What can I do to restore the white areas to the original filament color?

[A]
A quick blast from a heat gun will very slightly reflow the surface texture and eliminate white marks.
However, it's important to avoid over-heating the perimeter layers or you'll see them soften and sag into the infill. So wait for the heat gun to get fully hot and then use a short duration of high heat. Let the part cool between attempts if you don't get it all the first time, or need to clean up a large area.
Incidentally, the heat gun will also help clean up strings from travel moves.


q: Cura does not seem let the full print area to be used. My printer is a Lulzbot Mini. The design illustrated below can be found here.

[A]
Cura is likely factoring in your skirt. Change the skirt lines to 0 and you might be able to print (
```
Expert
```
->
```
Switch to full settings
```
, then click the options button next to "platform adhesion type."). Cura also seems to have an in-built build size offset of about 2 mm. I can't seem to get rid of it in any way other than to change the build size.


q: In Cura, when you enable "Print support structure", is there a way to see what it will look like?

[A] Select the View Modes Button in the upper right hand corner, and select Layers.


q: I have seen some lasers attached to the RepRap platform for cutting but most seem to be cutting paper, balsa wood, or merely etching.  If I were wanting to build a platform for cutting wood, similar to the wood framed or boxed 3D printers on the market, what power laser would I need for that?  I assume that a lower powered laser would have to travel slower but going too slow would add the possibility of catching the wood on fire (not good).

[A]
Please do not go down this road. First, not all lasers are equally absorbed by the material and the energy converted to heat to vaporize the material. The light not absorbed is reflected right back into your eyes. This is especially dangerous because it doesn't make you go blind instantly, fooling you into thinking there is no harm. You got the other part right, the lower the laser power, the less turned to heat, the longer it takes to cut, the longer you risk exposure to your eyes. That's right, a low powered laser is MORE dangerous than a big one. Next, the only way to properly cut is with air assist. This means a stream of air blows away the vaporized material so the laser can keep cutting deeper. This also prevents fires. The thing we haven't even touched is a proper safety enclosure, proper bed design to not reflect the laser beam back into the laser killing it and your eyes, and finally smoke/particle exhaust.
Simply put, these cheapo DIY lasers are dangerous, and are also illegal.


q:
Using an FDM printer and PLA or ABS, without adding support material. What modifications can I make to improve how steep an overhang my printer can print before it starts having problems?

The obvious first answer is to add a cooling fan, increasing the airflow over the freshly-extruded material ensuring it solidifies. What other things can improve it?

Does lowing the temperature help? Raising it?

Does speeding up or slowing down the print head help?

Does increasing/decreasing the extrusion diameter, or layer height help?

[A]
There's an answer
here
that holds some of the same concepts. Regarding your questions:
Does lowering the temperature help? Raising it?
: Yes, lowering the temperature can help. I've found that it is best to stay closer to the lower end of the material's melting point and just a bit above the point. Not only does this help with potential over extrusion, but also shortens the time it takes for the material to cool (refer to the link above).
However
, this could cause clogging if your temperature is too low. Keep an eye on your drive gear to see if there is too much friction while at lower temperatures. Increasing may keep the drive gear from "eating" your filament.
Does speeding up or slowing down the print head help?
: I prefer to print slower, most of the time, to allow the material to cool a bit more to avoid curling/warping (I primarily print with ABS, so it matters more). You might be able to give and take between temperature and speed. Consider if your nozzle is cooler and your speed is up, bridging gaps might yield the same results as if you proportionately swap these two values. This concept may only matter if you are in a pinch to get the part done. Again, I prefer slowing my machine down as it allows current/previous layers to cool more before continuing. This can be especially helpful with overhangs when paired with lowering your nozzle temperature.
Does increasing/decreasing the extrusion diameter, or layer height help
- I assume that extrusion diameter equals layer height (not difference in nozzle diameter, aka swapping nozzles). I'm not completely sure, but I think this depends on the part as well as slicing engine settings. For me, MakerWare is pretty good about proportionately adjusting extrusion steps with layer height, so I see an equal change in the width of the extrusion. I would think that in general, a larger layer height would yield a larger extrusion width. This would be helpful when printing overhangs, but may not be helpful when printing bridges (a larger strand will retain heat longer than a smaller one).
Hopefully this helps, please comment if you need more information/clarification.


q:
I would like to secure my hotend thermistor in a more reliable way (now it is just thermistor plugged in the hotend :D). I want to have a stainless steel tip for it to fix it inside hotend with a screw (The same approach as used for the heating cartridge). I have thermistors, but I cannot find any tips to buy separately.

Maybe you have some links for this kind of stainless-steel tips? Or some keywords I can use to search them?


q: I have recently bought a spool of eSun PETG. So far I really like the filament. My only complaint is, I get lumps of charred filament deposited on my object. The slicer I used is Craft Ware and I have played with the Far Travel -> Elevation settings. I have noticed that this helps but then I have little to no adhesion to the print surface and my supports do not stick to the raft. Does any one know how to mitigated PETG from collecting on the extruder?

[A]
Different brands and blends of PET filaments seem to do this to different degrees. Esun's PETG is definitely one that tends to glob onto the nozzle. Basically, the nozzle plows through the top surface of the filament and lifts up some plastic, much like the bow of a ship lifting up some water at high speeds. PET's viscosity and stickiness seem to amplify this effect more than other filaments.
Some things you can do to minimize the globbing:
Calibrate extrusion volume on the low end of what you'd normally use for other filaments (how you do this depends on your slicer)
Use your slicer's "Z-hop" or "avoid perimeters" feature so you don't do travel moves across printed surfaces
Invest in an anti-stick coated nozzle, such as are sold by
Micro Swiss
or
Performance 3-d
(these don't eliminate globbing, but they do reduce it and make the nozzle much easier to clean)
Play with slicer settings such as extrusion width, layer height, and infill/perimeter overlap to reduce the amount of "excess material" that sticks above the print surface
Again, this is a common problem with PET blend filaments. Anecdotally, some brands seem to glob more or less than others, so switching to a different vendor may be worth trying if you want to do a lot of PETG prints.


q:
I have a z-axis which follows schematically the same principle as the makerbot one's (threaded rod and two leading rods with linear ball bearings carrying a level). It is from an old experimental lab doing physics or chemistry.

The axis move gorgeously about 5 cm, but then it get's stuck on either sides of this way. Both driving threaded rod and the leading rods seem perfectly fine and should be able to allow for further movement. This is as far as I can see by eye.

Where should I look to find further issues and how could I improve the performance? Do I need to take the construction apart?

[A]
There could be a few issues at play.
The smooth rods are not parallel which is causing the bearings to bind the further you go up.
Part of the thread is damaged not allowing it to pass through the nut.
The threaded rod is bent significantly to where it either doesn't pass through the nut or bind the assembly. (Is the end of the threaded rod opposite the motor constrained?)
Even less likely is that the motor could be damaged.  Since you said it moved 5mm I would have to assume that is several revolutions of the motor so this is unlikely but possible.
The easiest way to find the problem would be to unhook/remove the threaded rod and see if you can move the carriage up and down the rods by hand, if so you just narrowed the problem down significantly.


q:
Some RepRap models use only a single motor for the Z axis, others use two.

For example, there is the 3drag that has only one motor and a smooth rod on the other side. There are modifications that add a threaded rod on the other side that is connected to the motor axis with a belt - which seems to be a really good solution.

Other printers, like the Prusa i3 or the Mendel90 have two Z motors. And after playing around with a two motor model, I find it pretty annoying when they get out of sync and I need to calibrate the axis and the print bed again. So two motors seem more like an disadvantage to me.

Could someone please shed some light on why most RepRaps have two Z motors (nowadays)?

[A]
The general concept is to provide additional stability during the print. In the case of the 3drag machine you mentioned, you could run the risk of the -X- axis sagging due to the weight of the print head and/or additional wear on the rod or bearings on the one side (smooth side) as a result of the off balance weight. However, you may find "hacks" like
this
can potentially help reduce the affects by providing a bit more stability.
Having two -Z- axis motors with the threaded rods can help ensure stability of the -X- axis during print and can, overall, reduce wear on the mechanical components.


q:
What software is best for the basest of n00bs when it comes to 3D parts creation?

I have a heavy math background and know how to create explicit functions of volume, surface area, center of mass, etc. Ideally, I'd like a program that uses those strengths but I realize that most n00bs have a crippling math phobia so I'm not holding my breath.

I tried freeCAD once and made some headway but the next time I turned my computer on, it refused to open. It was just a weakling netbook that I don't even have in my possession anymore but the computer I'm currently using is rather slow and doesn't seem to have much memory left either, so I still need something lightweight.

tl;dr: Seeking a free, lightweight program to create .stl files that is good for n00bs that are not afraid of math.

[A]
I don't have a heavy math background, but enjoy using such skills when applicable.
If you've not yet explored
OpenSCAD
, you may find that it meets your qualifications. It's more or less a scripting/descriptive language "compiler" that takes ordinary text and converts it to your model design. I use quotes, because I'm not skilled enough to qualify it as a true compiler, although it works in a similar manner and may indeed be a compiler.
It meets another qualification of yours in that it's free and there's quite a supportive mailing list/forum for any questions or difficulties that arise. If you look on Thingiverse using OpenSCAD as a search term, you'll find others' code available for examination and integration into your own models.
For the folks who are not so much into the math and text and logic, there's a GUI of sorts for OpenSCAD called
BlocksCAD
that allows drag and drop of various modules in a manner akin to Scratch programming.
I'd been using OpenSCAD long enough that I found BlocksCAD to overly complicate the creation of models by obscuring details. It may be better suited for younger model makers in that respect.
Syntax and punctuation errors would be eliminated with BlocksCAD, while it's far too easy to create such errors in the editor for OpenSCAD. One gets used to it and error count quickly is reduced.


q:
I have some design diagrams only on paper. Scanning them to bitmaps is easy, but I've had no luck getting useful vectors out of them. I've tried vectorizers in programs like gimp, and a few online services. Generally, I end up with enormous numbers of spurious vectors (from dust, dotted lines, text on the  diagram, slightly variations in scanning contrast, etc).

What tools and/or techniques can I use to get a more useful vector result, that I can then modify in a normal CAD tool without spending absurd amounts of time cleaning it all up first?

[A]
There is the capable but somewhat expensive
Scan2CAD
.
Otherwise, if you're happy with outlines and not centre lines, scan b&w, aggressively clean up macules, mask off text, and then vectorize in potrace, autotrace, etc. Alternatively, load the bitmap at the correct resolution into a drawing package as a raster layer and draw the lines/objects you want over it. This avoids the horrors of dotted lines.
Both ways are quite a bit of work, sadly.


q:
I'm building a 3D printer and I've been looking around for materials suitable to make the frame.

I have occasional access to a laser cutter which I could use to manufacture a ply box-type (UltiMaker) enclosure, but I like the ease of adjustment provided by the T-slot beam kits.

I don't have any metal-cutting machine tools. Can aluminium beam be cut by hand with a hacksaw to a good degree of accuracy? How does one finish the cut end?

[A]
Aluminum of almost every grade is very easy to cut with a hacksaw. I would suggest to mark clearly the cut line and to wrap masking tape at the edge of the cut. Consider to allow for about 2-3 millimeters (1/16") extra material for final finishing. Cut across the line, rotate the part ninety degrees and cut again. Once you have the guide cuts in place, you should be able to manage a square cut by following those guides
You will want to have a clamping mechanism available, such as a vise or workbench type device.
After the cut is done, use a sharp file to make final adjustments to the length and appearance. Push the file, do not drag it backwards. Push forward, lift away from the work piece as you return, then push again. Pick up a file card, which is a fine metal-tooth brush used to clear the teeth of the file.
It is very easy to remove material with a hand file, perhaps three or four strokes to remove 1/16".
Your accuracy will depend on the measurement of the lines you create and how carefully you file to the edge of those lines.


q:
PLA is flammable, but a good case can protect the main board from dirt.

Is it worthwhile to protect a circuit board with a 3d printed case?

[A]
It depends.
Protecting your electronics from being touched by random bits of conductive material which would short and fry them is always a good idea.
If it's something that will be visible, then a pleasant printed casing might go well. You might just as well use any other casing though, there's no requirement it be 3D printed.
For a very small circuitboard (an inch or less) heatshrink tubing might be a better form of protection. Or just insulating tape.
If you never intend to access the circuitry again and heat dissipation isn't a big issue, then just putting the whole lot in potting compound may work best for you - complete waterproofing and environmental protection.
Or you could just tape a bit of plastic from a 2l coke bottle over it, and get 99% of the protection you'll ever need, and still keep the circuit visible and accessible.
Ultimately, it boils down to: Do you want it to be covered? If so, by what? If you would prefer a 3D printed case, then do you want it enough that it is worth the time and effort to you?


q:
Backstory

I've had issues in the past with my drive gear "eating" my filament. It seemed that the filament quit extruding for one reason or another and the drive gear would slowly eat away at the side of the filament.

I eventually assumed it was the plastic filament guides causing unnecessary tension that the drive gear couldn't compete with, ultimately keeping the filament from moving forward. Thusly, allowing the drive gear to continue "trying".

My solution was to hang my spools above the machine to avoid using the filament guides feeding from the back of the machine up through the top.

Question

Can the plastic filament guides really cause that much drag? What other variables can I expect to look out for?

Machine: MakerBot Replicator Dual (1st Generation)

[A]
I have a few hundred printing hours on a Monoprice Dual Extrusion, which is essentially the same thing.  I've had a couple random issues that lead to filament stripping by the extruder motor:
Clogs (either a buildup of material over time, or from over-retraction)
Filament kinks around the spool holder
Some other restriction of the spool's rotation
I suspected the guides early on, but the grips on the rotor are actually fairly strong and the guide tubes are smooth enough to not cause a problem by themselves; I'd recommend looking at the other ends of the assembly first, as they're more likely to cause a problem.  If you preheat the nozzle, open the tensioner on the extruder stepper, and can't push the filament into the nozzle with your fingers, the motor won't be able to do it either.


q:
I would like to make custom insoles for my wife.

This company makes a flexible filament that will be soft to stand on:
http://recreus.com/en/

I do not currently own a printer.

How can I measure her feet and transfer the measurements to the printer?
(one of these comes to mind: http://www.eggheadtoys.com/pin-art/)

How can I measure the inside of the shoe?

What kind of printer can print with the flexible filament?

[A]
Many questions in one post, but I'll address only the first. Consider to use a shoe with a flat insole, perhaps even what is commonly called a flip-flop. If your objective is to perfectly match the curve of her foot bottom, this should work. Apply a layer of polymer modeling clay, plasticine or similar material. It should be warm enough to permit her foot/feet to settle in and push enough material away to remove any voids. If voids appear, one could then add a few blobs and repeat the pressure.
Obviously some will ooze from the sides, which will have to be trimmed away. Trim a sufficient amount to fit her regular shoes and you'll have a reasonable match of the necessary fit.
The resulting shape can then be scanned with a 3d scanner and converted to a 3d model. Even if the clay is excessively thick, the typical 3d model editor can slice away the excess, although one would have to make an almost arbitrary judgement for the location of the slicing plane.
Another option comes to mind. There are various silicone molding products. I've used one from makeyourownmolds.com that is of a consistency of frosting. When mixed together and applied, it makes a perfect duplicate of the item, in reverse. Another product sold at the local HobbyLobby is a similar molding compound that is more akin to the modeling clay.
Both compounds will release easily from skin, are non-toxic and would provide a more durable model from which to scan.
I think one difficulty you may have is how to determine the correct foot pressure and posture to achieve the desired results. The modeling clay would give you more support and probably be more accurate. If your objective is to provide the same support as a bare foot, the silicone molding method would be more accurate.
If you stretch the concept even further, once you have the silicone or clay mold, you would be able to use the pin-art concept. The idea of measuring each tiny pin is mind-boggling, though.


q:
If you already have a 3D printer, would you say that you have saved money on buying the printer, buying models and then printing the models, compared to buying something alike in retail?

Would you say that saving money is an argument to buy a 3D printer?

[A]
Yes and No.
There are two sides of this,
yes
and
no
. Why I say
yes
is because there are little things that the 3D Printer can come in use for, like creating charger holders or just little household objects. The
no
side of this for me would be because of the cost of the filament in general and the maximum object size you can create with your 3D Printer. I know they have bigger ones out there, but you aren't going to make anything too big. Another reason it's a
no
is because of duration of time. It may save you money, but your going to be spending a lot more time and possibly more money the bigger your objects get, which is the only reason I'm not trying to get one at the moment. I'm choosing to wait until technologies advance to get my personal one, where it doesn't take over an hour to print out a keychain tag.
So
yes
, you probably could save money in the long run, depending on what you create with it based on size and how much filament you use, but I'm also going to say
no
because of the disadvantages the 3D Printer has. I personally would wait for technology to advance in the next 5-15 years before buying one that has a lot more power than these, as the one's currently in the market are expensive.
EDIT:
As I stated in my reasoning, I currently do not own a 3D Printer, but I do use one at my school for educational purposes and I do know the hassle on time and money for creating products that are relatively small in size.


q:
E3D mentions on their own wiki:

Excessively long retractions will cause issues by dragging soft filament into cold areas. [...] for bowden systems you might want to go up to 2 mm. Retraction beyond 2 mm is likely to cause issues.

I have retraction set to the recommended maximum of 2 mm, but I still get a lot of stringing and blobs. My printer is set up with a relatively long Bowden tube (500-600 mm). I wonder if I need to push my retraction setting slightly beyond 2 mm to take up some of the slack. Is the 2 mm a conservative rating (I guess they don't want dissatisfied customers with clogging problems) or is it really the maximum? Is there anything else I can do to improve retraction performance? (I already have a small coasting distance of 0.1 mm set.)

[A]
Yes, you can increase retraction past E3D's max 2 mm recommendation to compensate for Bowden tube stretch and slop. The reason for the recommendation is that jams will occur with most all-metal hot ends if you pull molten filament up into the cold zone. Any molten filament that enters the cold zone rapidly cools and hardens and sticks to the walls, very often forming a jam.
So, the requirement is to keep your retraction distance
at the extruder
less than 2 mm. Additional retraction travel that is absorbed by the Bowden tube and not seen at the extruder is fine. I personally run 2.5 mm retraction on an E3Dv6 Bowden system without any issues.


q:
I am encountering a problem with this ID3 printer using ABS -- at some point during the print the print head displaces on the y-axis by 2-3 centimeters. I cannot pinpoint how or why it is doing this. It has displaced in the positive Y direction and in the negative Y direction on separate runs of the same piece (which is just a poker chip I found on Thingiverse).

Is this a software issue (Simplify3D) or a hardware issue? Can anybody suggest a fix?

See the following photos:

[A]
It seems unlikely this is a software or G-code issue, instead it appears your Y-motor is occasionally missing some steps. There are two possible causes for this:
The current limit for the stepper driver is set too low, limiting the amount of torque the motor can generate. When the printhead encounters some resistance (for instance due to running into a blob on your model) the motor skips steps, resulting in a displaced model.
The current limit for the stepper driver is set too high. The stepper driver will overheat and thermal protection will shut it down temporarily. Some steps are lost while it is shut down.
There are various ways to calculate the ideal current for a motor and set it using a multimeter, but a simpler approach is to turn it way down, and then slowly turn it up. Turn it up just beyond the point where the axis moves reliably.


q: I have a long 8 mm smooth steel rod of about 55 cm long. This rods bend easily due to the length. If I replace them with 8mm solid carbon fiber rods, will the bending reduce? Will the bearings wear off the carbon fiber rod? I couldn't find too much information about this.

[A]
Steel is the best material for a linear rod when you have a fixed cross-section. It will have the least flex of any rod (aside from some exotic metals) of the same size.
Carbon fiber's material properties might seem superior at first sight, but the stiffness is very anisotropic -- it's very stiff along the grain and not very stiff across the grain. So multi-axis stresses like bending aren't necessarily going to perform up to the theoretical specs. Carbon fiber has exceptional stiffness-to-weight ratio, but the stiffness-per-area isn't necessarily superior in this application.
People do occasionally use carbon fiber for linear rods/rails, but only in much larger sizes than 8 mm. Think >25 mm.
And that's really the problem here. 8 mm diameter at 550 mm long is well outside what's reasonable for bending stiffness. Bending deflection increases with the CUBE of length, and this is simply far too long for the size of rod. The general rule of thumb for precision motion applications is length < 25*diameter. That's a conservative rule, but it's the right ballpark. You really shouldn't be going over 200-250 mm or so with an 8 mm rod.


q:
My printer will feature LM8UU bearings/threaded rods for the z-axis and bronze sinter bushings on the x- and y-Axis.

As also, but not only, written here http://reprap.org/wiki/Lubrication, I know that one should:

 - use machine oil for sinter bearings, if anything at all,

 - grease on the 'more fluid' side for the linear bearings so that the lubricant stays eqally with balls on the upper and lower side

 - and probably PTFE grease for the threaded rods (as for example provided by the Ultimaker UM2)

Is there a way to unify this or at least only use two lubricants?

I do not have the slightest idea about lubricants, I would not know what to actually buy if the combination would e.g. be machine oil and low viscosity grease. Do you have specific recommendations of what to avoid?

[A]
A mid-weight PTFE grease like the popular Superlube will work in all the cases you mention (bearings, screws, and sintered bushings). 3D printer service conditions are quite light-duty as far as lubricants are concerned. You really just need to keep everything a little bit "wet" with oil or grease and performance will be adequate.
The main downside to using grease with sintered bushings is that they will likely stop being "self-lubricating" after the first exposure. The grease tends to clog the pores that allow the sintered bushings' factory oil impregnation to maintain a nice oil film on the sliding surfaces. So the bushings will forever-after require regular re-greasing, just like the ball bearings and threaded rod.
In comparison, a light machine oil like 3-in-one will maintain the sintered bushings' self-lubricating properties, but if used in ball bearings and screws will require very frequent replenishment. And that is certainly an option -- oil DOES work on bearings and screws -- but odds are good that you'll eventually over-oil the bearings, get drips on the build plate, and bang your head against a wall trying to figure out why your prints won't stick all of a sudden. Grease doesn't need to be applied as often, and it tends to stay where you put it rather than dripping. So grease is generally preferred to oil if you have to pick just one lubricant.
Again, the most important thing is to keep sliding and rolling surfaces wet with
something
. You'll just have various maintenance trade-offs with different options.


q:
I began printing the parts for the Ultrascope DIY telescope designed by the Open Space Agency.  See http://www.openspaceagency.com/ultrascope.

All of the STL files for the 3D printable parts are canted 45 degrees.  Brackets, tubes, everything I have seen so far.  Is there a reason for this?  I printed one part last night and simply rotated the part so it would lay flat because I didn't want to deal with supports.  I am relatively new to 3D printing -- Am I missing something I should know?  Is this a thing?

[A]
The orientation of the part in the STL file depends on the Software that creates the file. I had a software that would export the parts standing upright instead of laying flat. Depending on the CAD software it can be beneficial for the creator of the model to create in in a different orientation as the one you want to use for printing. Also not all CAD Engineers know (or care) about the best orientation for printing a part.
So my guess is that this is an issue of file export/ STL file creation.
It is totally normal to rotate the parts into a position that is best for printing.


q:
I can download a file from Tinkercad as any of these:

.STL
.OBJ
.X3D
.VRML

Is there a way to convert any of those file types to .DWG?

[A]
In short, I don't think printing the full tetrahedral honeycomb design is a good approach considering the application of the part. Here are few things to note when attempting to 3D print the tetrahedral honeycomb:
I wouldn't recommend trying to 3D print this with a an FDM/FFF printer as you will most likely need supports and there would not be enough strength laterally. You may be able to
print
the design using SLA, but handling would be very difficult before post-processing as the part is very brittle post-print until a heat treat or curing process is done to chemically solidify. The post-process of the SLA could determine how strong the part is (ie. stainless steel powder, infused with bronze in a heat treat process would be good for such a part).
While SLS may be the best method for 3D printing this type of design, for that size part (30x30x10cm) you're looking at an expensive print regardless of whether or not you print it yourself.
Instead, I would highly recommend finding (or designing your own) a joint connector that would allow you to join wood/plastic dowels in the tetrahedral honeycomb shape. Not only will this be cheaper for you in the long run (easier to replace a few broken segments than an entire 3D printed model), but it could provide more structural strength for something that could potentially get banged around, like a tricopter.
For example,
this model
on Thingiverse (not my model) shows an example of how you can utilize 3D printing complex or custom joints that allow you to connect dowels in the shape you're looking for. It'd kind of be like building with
K'Nex
.
As far as designing said joint, you could model a single "inner" joint that has 18 connectors (8 on XY plane, 6 on YZ plane, and 4 on XZ plane). Below is a crude example of what I mean drawn in Google SketchUp:


q: I am new to 3D printing and need to know if I use steel in printing, do I get the same strength (compression and shear) as steel profiles manufactured in a factory?

[A]
A laser sintered part typically uses what could be described as surface bonding, as it does not melt particularly deeply into the powder. It would not have the same strength characteristics as machined steel or otherwise processed metal. A part constructed from 3d printing using feed metal/welding methods would have more strength, but would not necessarily have un-modified steel strength, due to the heat applied during the process.
Using a metal which responds to post processing, as in tempering, will likely improve the strength, but I believe that one is unlikely to reach the same values as "ordinary" steel. Compression along the lines of the construction layers would be reasonably strong, but forces applied in other directions are likely to match only the characteristics of the bond. The same consideration applies to shear strength.


q: I've been asked to prepare a 3D model for 3D printing in sandstone. I've been told that it needs to be 3" tall and the walls have to be at least 2 mm thick. It's an absolute pain in the neck having to make sure everything is the right thickness. So, I was wondering, can the whole model just be printed as a solid object, with 100% infill, and does that work for sandstone?

[A] Yes, you can just print it solid. However, it might be significantly more expensive to print your object entirely solid. For instance, Shapeways charges \$0.75 per cm³ of material for their full-color sandstone. A solid cube of 5x5x5 cm would cost \$96 to print, whereas it would only cost around \$6 if you printed it hollow with 2mm walls.


q: Is there a way to make all your prints seamless?? I know there was this program that printed a vase constantly changing the z axis making it seamless. Why cant this be done with regular prints?

[A]
If you ever seen 3d printouts on your own and you did keep it in hand then you probably felt layers. Most printouts contains 3 main "components"
bottom and top component (floor and ceiling)
outline (perimeters)
infill (inside supporting structure)
It is almost imposible (and for sure sensless) to create all these components with one continues line as it would be very complex and sophisticated line.
Second reason. It would be very often that printer would cross outlines (perimeters) so it would destroy good looking external surface.
And third reason. Objects can have "islands". Imagine printed elephant which is standing on 4 legs. How to draw leg leyers with one line if these legs are separated (at the floor level).
That's why "round vase" is the only option to print seamless. :)