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What are some conductive filaments that can be used in printing electronics?
I'm very new to 3D printing, and I am very interested in printing electronics. I want to be able to print out circuits, so I've been trying to find a conductive filament. What sorts of conductive filaments are available to the consumer (me) and are of acceptable quality
Edited for clarity: I am not seeking a product recommendation, but rather am looking to know what sort of variety I can expect and more specifically which filaments are useful for printing electronics.

Be warned that if you're trying to do anything with high speed signals, conductive filaments will cause you lots of problems due to the tight tolerances on impedance. And I might even say is not possible with current 3D printers though I haven't tried anything that crazy before to be honest. Low power/slow signals you should be golden,

I'm voting to close this question as primarily opinion-based, because it asks for a product recommendation. Moreover, what is "acceptable quality" to me may not be to you.

They are asking what filaments are available to a consumer, if the "acceptable quality" line is clarified then this is fairly easy to answer.

You're asking the question the wrong way round. Find a candidate material, spec it and your use case, ask something specific about your concerns.

I have not been impressed with the conductive filaments that I have seen. Have you considered printing circuitry with conductive inks or pastes instead of filaments?

You can do a lot also an other thing i found very interesting is that you can metal plate that filaments xd :) so why not be able to metal plate specific areas that you have with that filament after the print ;)

@TomvanderZanden hey Tom. This post is from a new member. It's not that bad. Yet you voted to close? How does that help us get closer to being out of beta? I understand the programmer style black white and brutal often seen on SO however I feel you could have tried to work with the user to improve their question and coached them on what we look for. I don't think you know how you come across. Voting to close is aggressive and improper. I think we can improve this question and maybe get a new user who will come back IF we are nice and helpful.

@StarWind I disagree. That is simply the way StackExchange works. It's not a chatroom or forum. This is not a good question, and on any "mature" StackExchange site it would be closed quickly. It doesn't list any requirements: Are they looking to print stuff that needs low resistance? Low parasitic capacitance for high-frequency applications? Very few StackExchange sites accept product recommendation questions at all, and the few that do have strict standards on how specific and detailed your question should be. "Recommend me a high-quality X" is, IMO, not a suitable question.

Well let's talk about this more in meta. I feel you missed the point. I just want to express it would help us as a group if everyone was nice and more willing to work with these newcomers. There are already topics about this. As you are number one for points you have a larger responsibility to embrace and shape a positive community. These are not all harden veterans of stack overflow. Also maybe go read a few other SO communities, preferably non hard science engineering etc. You might find many are squishy and most do not hold what you say is standard.

Also to be fair he or she is not asking for brands. What sorts of filament. I personally answered that question as the sort that is infused with carbon or graphine. But that's how I read the question. Remind me what is the suggestion on the flag page? Help improve?

@StarWind You are right, my comment could have been more helpful and friendly, and explain more clearly what should be improved. I'll take note of this for the future, but I still think this question isn't a very good one. As Sean also points out, it should state the application and requirements for the filament. Googling "conductive filament" would answer the current question much better than a StackExchange answer ever could. How to ask explicitly states "search thoroughly for an answer before asking" and "give us details and context".

@TomvanderZanden I think we are in agreement. I also agree the question needs a lot of work. It would make a good meta post on how we want to help these new users who do not even have the basic terminology.

At this point conductive filaments are a very new thing. All the filiments on the market are PLA based that have been infused with Carbon or Graphine
However I worry you over estimate what you can do with this. You will at most be able to 3d print a simple wire and power a LED. You will not be able to run a microcontroller, and honestly I would expect a complicated print to have too much or too little resistance, maybe burst into flames.

You really should look into the Voxle 8 and other printers. The printer is really the driving factor. Using a conductive filament will not be enough. Note this printer uses a syringe not PLA plastic.
Here is a Voxle8 print.


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What causes bubbles in extruded filament?
I've noticed this on almost ever print I've ever had. On the initial first line that clears the extruder nozzle tiny little bubbles/craters seem to form on the line. While I don't think these are causing any issue with my prints I'm curious to know the reason why they form at all.
Is this due to water absorption in my filament that turns to steam, which then bursts through the molten plastic? Is it due to air bubbles in the filament that are cause by the manufacturing process of the filament? Or is this more an indication that my nozzle is damaged or clogged in some way?

This image was made using ABS plastic and a heated build plate. I've noticed these same 'bubbles' appearing using PLA, and Nylon.
Edit: Nozzle temperature 240°C, build plate temperature 150°C, Nozzle diameter 0.4 mm, filament diameter (measured 1.75 mm) retraction distance 1.7 mm. Using the Makerbot Desktop Slicer.
The first line that my printer extrudes, where I'm seeing these 'bubbles' is a nearly full line. Makerbot starts from the right side of the image, extruding to the left.

Please provide the  head temperatures, feed rates, nozzle diam, etc.  What I see in the picture looks more like a startup problem of the nozzle feed "chamber" not being completely filled yet.  Try preheating the head and manually forcing the filament in so that a couple inches are extruded before initiating the print code.

The last 10 prints i've done seem to be looking like the 'bubbles' occur more often right at the beginning of the print/ first line. Would this be more indicative of a retraction setting issue do you think?

Oh yeah, that's simple. You are printing too hot and are literally boiling the plastic. Else you have water. However if it was water you would hear Crackling as it printed. If it is too hot you will not hear nearly as much. I am 87.341% sure you are printing too hot.
Looking at your printing temps you are without a doubt printing too hot.
From this link on 3d hubs.

PLA (Only on Replicator 2) Print temp: 210°C (at 100m/s) Notes: heated
bed optional between 40 and 60°C
ABS (Only on Replicator 2X) Print
temp: 230°C (at 100m/s) Notes: heated bed at 110°C

I'll give it a try at lower temps, (was at 240C for ABS). I've been raising the temp to try and improve the top layer/last layer thinking that I was running a bit cold. Might have to open another question on that instead now :)

In those cases you want to lower your solid infill speed. That way it goes slower on those layers and adheres better. Speed and Temp are always in opposition.

Very useful information. This is what was causing my bubbles so if the feedrateis too slow it will get too hot and be boiling.

In my experience, bubbles like this are caused by the filament absorbing moisture, which then cooks out at the high printing temperatures.
See: http://reprap.org/wiki/Print_Troubleshooting_Pictorial_Guide#Material_Handling.2C_Material_Contamination_01

Would you expect a new roll of filament to have water absorption? Or would you recommend cooking/drying out a new roll?

If the roll didn't arrive in an airtight bag, with desiccant, I would expect water to have been absorbed, yes.

Probably not water then, It's a new roll, air tight sealed with a desiccant in the bag.

I had a similar issue with my Prusa i3 mk2. In researching what could cause extrusion to be nonuniform, I found that it could be due to a number of things:

Nozzle height
Flow rate
Bed/Nozzle/Ambient Temperature
Improper bed leveling
Dirty reservoir or filament
Low quality filament
Hardware failure
etc...

For me, the problem happened to be a hardware failure where the screw that held the pulley in place on the extruder motor had stripped somehow and the pulley was slipping as the printer was trying to extrude. I temporarily fixed this by using a slightly bigger screw, but was able to get a new pulley/screw piece from Prusa Research to replace the part.

was retraction rate/distance one of the variables that fell under the etc. heading? I'm noticing that the bubbles occur predominantly at the beginning of the first extrusion line.

I have spent many hours testing my Anet A8 to resolve the popping issue. The symptoms are similar to yours, Diesel. Both ABS and PLA, different manufactures, good packaging, as well as various sizes of nozzle, are producing bubbles.
I was experimenting mainly with two variables: nozzle temperature and retraction length. Other related parameters I kept fixed:

Material: ABS
Nozzle size: 0.5 mm
Retraction speed: 45 mm/s
Travel speed: 50 mm/s
Print speed: 40 mm/s

Retraction length
Originally it was set to 4.5 mm. I found it to be impacting the amount of popping significantly, especially in the range of 0.5 mm to 2.5 mm. The optimal value appeared to be in my case 0.8 mm. A lower value would produce even better results in terms of surface quality, but would also start producing oozing.
One important side note is that at the retraction length of 4.5 mm, leaking of the material during idle moves was significant and was becoming even a bigger contributor into gaps in the print strikes (immediately following the idle moves), than popping. This observation is kind of contradictory, but I am making no mistake here. Too large of a retraction apparently may have the inverse effect on leaking/oozing.
Nozzle temperature
Originally was set to 250°C. 260°C produced significantly worse results. 240°C is where I stopped.
Based on some other research, including talking to my friend who successfully uses the same plastic at 260°C, I made the conclusion that the quality of my print head assembly is not perfect, and that it is the main cause of the problem. By finding the perfect retraction/temperature combination I simply mitigated the air sucking in the head, which could be not happening at all if I had used a better quality extruder and nozzle in the first place.

The temperature is too high or your keep your filament in open for days. So that filament observe water from air do the following steps:

pla 190-220
 abs 220-240
If temperature in range then bake your filament at 50-60 temp.

There is only one way to find out, which is by isolating any reasons, starting from the simplest one:

Firstly, clean and check, or change, your nozzle;
Secondly, if that does not work, then change the filament, or find a way to get it dry (some people, with some filaments, use an oven to get moisture out - careful, don't burn it);
Finally, change filament brand and get a better quality filament or another type of filament.

Another reason that it does not extrude consistently, is that what you mention as [appearing to be] bubbles maybe [intentional] gaps [in the print].

He said he's used 3 different materials.  I strongly doubt all of them had mosture problems.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

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No Z hop in Dual extruder, print getting disturbed at retraction point
I'm using a Lulzbot KITTAZ with V2 Dual extruder(0.5mm). When I'm printing anything, the front left side of the print is getting disturbed because whenever the tool head switches the action between the extruders, they stop at the front left point of the print. They are not performing the Z-hop and because they are hot they are disturbing the print at that point.
These are the settings that are currently set:

The print with the disturbance:

Sometimes the whole print is getting dragged to the extruders.

It appears as though you are using (or used) an old version of Cura. More recent releases allow you to insert G-code commands on changing the extruder. You could insert a Z-hop in these sections.
Extruder End G-code: First set the extruder in a relative mode, move up 2 mm, set absolute again:
G91
G1 Z2
G90

Extruder Start G-code: First set the extruder in a relative mode, move down 2 mm, set absolute again:
G91
G1 Z-2
G90

You could even do filament retractions to prevent oozing or stringing!
Note that this assumes both hotends are on the same carriage!

An alternative you could try is to use a print server that is able to inject G-code scripts, an example is OctoPrint:

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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How can I make this rounded enclosure feasible to print?
TL;DR - What needs to be done to the following model to ensure a successful print?
As part of a father-son project we're trying to make an enclosure for a digital clock. The idea is to make a 3D printed model of a rocket with a hollow body to hold the electronics. The main body consists of two halves that will press-fit together with some integrated mounting locations for the display, micro-controller, etc.
Since this is our first 3D printing project, I would like to know what can be done to the following model to help ensure a successful first print. We have not chosen a material or supplier yet, but I suspect we'll go with PLA since it seems to be quite common, inexpensive, available in lots of colours, etc.

The model is not yet complete - there are several details missing, like additional mounting locations - but I was hoping to make corrections to what we already have before too much further, just in case it requires a complete restart.
Here are some possibly relevant details and goals:

The shell thickness is currently 2.5 mm.
We would like the shell to be translucent to allow a glowing effect from some internal LEDs.
The nose cone and thruster (not shown) will probably have pins that press-fit into the top and bottom of both halves of the shell to hold them together.
There is a 0.5 mm clearance between the lip on the front shell and the detent on the rear shell.
The rectangular window will possibly be removed, or made into a flip-open door.

There aren't a lot of hard requirements as this is just a learning project, so we're willing to change almost anything about the design, as long as we can fit in the existing clock parts.
The Fusion 360 model is available to view online if it helps: Rocket Concept 3

I'm not sure how good a fit the question is here, it might be rather opinion driven. Two ideas from me: Think about overhangs and orientation (support can be used, but results in a less accurate lower surface), and suggest using an M3 bolt to secure the parts (in addition to ridges for alignment)

@SeanHoulihane Thanks for the tips - I'll consider bolts and read about supports. How can I improve this question to be less opinion based? I am looking for 'facts' that will improve my chance of success - ex, what problems to look out for - but as a complete newbie to 3d printing I don't know the specific questions to ask yet.

With a couple of minor adjustments, that would print just fine standing up as it is.
Alternatively you could lay it down with the open side facing upwards and use a few supports (my least favourite method), or simply make a flat spot on the back to lay on the printer bed. Which is probably what I would do.
As far as shell thickness goes - 2.5 mm is pretty heavy duty. You also need to bear in mind that it's best to have a thickness as a factor of the thickness of your bead or your layer height (depends on printing orientation) - assuming you are going to print this yourself. So usually that would either be divisible by the bead width or by the layer height. If you want translucent - easy enough use translucent or clear filament. I'd probably go for 1.2 mm or 1.6 mm wall thickness.
I made an angel at Christmas with clear PLA and quite a thick wall (wasn't my model and I didn't bother measuring - but at least 2 mm) and an LED candle lit it up really well.
It's much easier doing this kind of thing after buying the printer. that way you learn much quicker what works and what doesn't.

Thanks, this is the kind of feedback I am looking for. I am planning to send this out to get printed, so I won't have an opportunity to experiment first, which is the main reason for posting the question here. I'll consider the bead thickness when sizing the features, and add some supports. Can you include any other rules-of-thumb that I should consider during the modeling process?


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Prusa i3 Stopping midprint
I am trying to print an earbud holder with my Prusa i3. About an hour though the 3-hour print I left the printer for about 20 minutes and when I came back the printer stopped printing. The printer didn't display any errors on the LCD. The extruder and printing bed all cooled down but the z-axis didn't raise so the nozzle was stuck to the print. What could cause the printer to stop printing?

There's really no telling why that happened if you weren't there to observe it.
A possibility is a temporary power outage, which would stop and reset the printer without any trace of it having happened. Even if there was not a power outage, maybe there was a temporary dip in power that caused the power supply to be unable to supply the required voltage (or perhaps the power supply was of poor quality to begin with and suffered some issue that caused the voltage to drop).
Another possibility is that you were printing via a computer, and the computer rebooted during the print. If this is not the case and you were printing via an SD card, maybe the SD card became corrupted and the printer read some invalid G-code and reset itself (though this latter case would probably come with some indication of a fault on the LCD).


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Motor driver chip install direction?
I got a new MKS 1.4 controller board and it came with A4988 driver chips.  But I can't figure out which way they install.  I found something saying to match the printing on the back of the chip to that on the board.  But I don't see anything that matches.  Suggestions?

You might be able to figure this out with a multimeter. The 1A/2A/1B/2B pins should have continuity to the connectors for the motors.

Thanks - I found a pin diagram last night that indicates the same.

In that case, consider writing an answer to your own question, so that the next person who finds this question via google actually finds an answer here.

Will do, as soon as I can confirm it.

If this is the same board as MKS GEN, then this page should help: http://reprap.org/wiki/MKS_GEN

If one of the answers solves your problem could you mark it as accepted, in order to remove your question from the Unanswered list. As SE 3D Printing is a beta site, one of the pre-requisites to full graduation is a short unanswered list. Thanks :-)

From A4988 Stepper Motor Driver Carrier, the rear of the breakout board, is identical to yours:

Note the two square pads for the GND, whereas the others are round. Now looking at the top side:

and note the position of the square GND pins/pads, in relation to the trim pot.
Now look at this hi-res photo of a populated MKS board

Again, looking at the position of the trim pots, one can see that the A4988 breakout boards need to be oriented such that the side with GND pins need to be nearest to the top of the board. That is to say the GND on the corner of the breakout board, needs to be pointing North East, as it were.
Here is a schematic of the MKS 1.4 as well, although it is not much use, from MKS Gen 1.4 circuit and pinouts:

I´ve seen some cards using A4988, and also I have designed my own cards and the most and useful pin arrangement is V Mot, GND, 2B 2A 1A 1B VDD GND, so stepper motor is conected close to 2B 2A 1A 1B.
Never place this pinout oposite side to stepper connectors. Stepper connector are marked as X, Y, Z, E0, E1.
The assembly picture from Ali express is correct.

The below image was taken from their AliExpress shop page.
Unfortunately, I don't manage to find the datasheet or schematic to give more technical advice.


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Why does my domed print have a thin shell?
I am making a "fun button", with a dome-shaped top. The vertical sides, top center, and raised lettering seem fine, but the more sloped outer parts of the dome are very thin, with some gaps and the infill pattern is quite visible. It's almost like the slicer isn't recognizing the sloped part as an exterior shell.
What is causing this, and how can I fix it?

The model was made in Fusion 360, sliced in Repetier with Slic3r, and printed on a Monoprice Maker Select Mini.
Edit: More information after checking values used and taking more photos.
This was my second attempt, after increasing the shell count already.
On my first print, I clearly had a low value for horizontal shells, top and bottom were both at the default of 3. I upped these  both to 8. (Layer height is 0.13125.)  The bottom of the button is now good. The "good" center area extends a little further out, so I think it's probably thicker up at the top of the dome. But the sloped sides are pretty much the same - this is why I'm thinking it's not being considered as a "horizontal shell".
Comparison:

There are some design iterations, but the top surface is the same shape.
Update:
I did a print using Cura, with 0.8 mm shells, and it looks great!

I cut the two bad prints with a hacksaw to see a cross-section. The bottom is clearly thicker. The top on the outer infill void is pretty much the same. The top on the other void is thicker most of the way across, but suddenly changes to thin.

Looks like theres just one top layer? You should use at least 3 top layers. If i'm not seeing it right, and it's more than one top layer, than I think its under extrusion... put the printing speed for top layers down...

I'm thinking I might try with Cura to see what the result is...

Well thats worth a try... isn't there the opportunity in slic3r to change 'solit top layers' maybe you just changed 'shells' and 'solid bottom layers'

The settings in Slic3r are in a box labeled "Horizontal shells", then Solid Layers, with a setting for Top and Bottom. With my first print, they were at the default of "3", for the second, they were changed to "8".

Well its curious that it prints just one top layer when slicing with slic3r... I cant explain why... But good that it's working with cura. I dont lice Slic3r very much. Symplify 3D is the best slicer from my point of view, but it'sa bit expensive...

Re the cross section images added: It may be an issue with the slicer determining to use your values for perimeters versus top solid layers when deciding how many layers to use for the slope; at some point, it may switch from perimeters to top layers when the angle passes a threshold.

Just for grins, I set Slicer to use high values for Solid Top Layers, varying from 15-30, and inspected the print preview. I could see that it was definitely making the center of the dome and areas under the text thicker, but even at 30, the outer edges still looked like only one layer would be printed! This looks like a Slic3r bug to me. Also I didn't mention it, but the print with Cura seemed much higher quality overall.

Slice with more solid top layers. I always use five with low-density infill.

Even with two layers, a sloped top shell may show gaps.

I realize the original question didn't have this information. My second attempt that prompted the question was printed with 8 solid top layers, and the print quality was nearly the same as with the first, using the default of 3 solid layers.

You can either increase the shells, or you can increase the infill density. In addition different fill patterns will help. I would do 4 minimum for such a print.


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Cooling for big layers
There is an option in Slic3r to disable cooling for layers that take more than n seconds.
What would be the disadvantages of having cooling on big layers ?

Warping. Especially with materials like ABS, you want the plastic to cool down as gradually (and slowly) as possible, to prevent the print from warping as the cooling plastic contracts. On small layers, cooling is usually mandatory: with really small layers, you just end up with a big glob of molten plastic if the previous layer hasn't solidified enough before the next layer is put on top.
You want just enough cooling that the plastic holds its shape, but no more than that. On a large layer, the plastic cools enough naturally without help from a fan.


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I can not really connect successfully to my printer via USB
I have a Tronxy P802M (very similar to the Anet A8, but using a Melzi2.0V5 board) that seems to work fine (I just finished building, and axes movement and the integrated display work) but when I try to connect to the printer from my Simplify3D on Windows 10, I get the following:
[...]
  Connected to machine!
SENT: T0
READ: ok 0
READ: wait
SENT: M105
READ: ok 0
READ: T:24.44 /0 B:23.33 /0 B@:0 @:0
  Connection failed.

My other printers all connect fine.

Try doing this in Simplify3d and see if it works - Go to Tools --> Firmware Configuration and then click the Communication tab. Set the flow control to "Hardware flow control".

Nope, did not change much, except now the initial connect does not work. I also tried a different USB cable and using a direct USB port as well as suing a USB2 hub...

Operating system?

Windows 10 - sorry, forgot the details

Okay have you set the Baud rate? I know thats an issue with slic3r. Can you see the printer under devices?

Yes, Baud rate is set the same on both sides (otherwise there are different errors). The COM port shows up under devices.

This is more suited as a comment. Moreover, the fact that he's receiving something legible (like the "T:24.44" line), means the baud rate must be correct.

The Simplify3D support site mentions to disable the "wait for startup command" option in the firmware configuration for S3D.
This allows me to make a rudimentary connection to control the printer, however e.g. during the bed levelling wizard of S3D, the connection still breaks off.
It works reliably with Octoprint. I'll consider that good enough.

If you are using a USB 3 port to connect the printer to your PC, try connecting via a USB 2 hub.
My Vector 3 will not work on a USB 3 port, only on a USB 2 or lower.  The device correctly mounts and presents but serial communication fails.  One of my laptops only has USB 3 ports on it, so to work around the limitation I connect via a cheap USB 2 hub.
I have heard that many 3D printers use a similar USB to UART / serial connector chip and that they suffer from similar limitations as a result.

already tried that, did not change anything :(

The cheapest, and common, USB to Serial IC (i.e. an FTDI clone) in use, seems to be the CH340g

@Greenonline The CH340 is not an FTDI clone. Not every USB to Serial IC needs to be an FTDI clone. The CH340 happens to be an independent design.

@TomvanderZanden - OK, understood. :-) I guess I should have said substitute rather than clone.

Try changing your port in the control menu. By default, mine is set to COM 1 and I have to change it to COM 3.

I get a response from the printer: READ: T:24.44 /0 B:23.33 /0 B@:0 @:0. It just aborts the connection due to some timeouts. Looks like S3D is very strict when it comes to bad connections or slow boards


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Why are my prints so defective?
I received a Monoprice Maker Select v2 (I3 V2 clone) from my wife for Christmas.  The sample .gcode files that came with the printer generally print great with no noticeable defects.
However, when I try to print miniatures for use with table-top gaming (D&D, primarily), I tend to get a lot of oozing and stringing.  On top of that, bridge supports don't cool in time and tend to get fudged by the print nozzle, which results in oddities like arms being only half printed, sticking to the nozzle, and getting relocated to some other part of the print.  If I use full grid supports with the most modest fill settings (8%) they end up being stronger than the miniature and are a real pain to remove.
My printer is calibrated, as level as can be (the desk it's on is slightly warped but I've got the printer in the center of the warp; there is no wobble or lean) and squared.  The build plate is calibrated and set to the right height.
I'm using the version of Cura that came on the SD card with the printer (honestly not sure which one and I'm not at home to check).  I've fiddled with print speed, extruder temp (ranging from 185 to 210), layer cooling, retraction settings, and tried switching to Slic3r (didn't go over well -- couldn't even get past the first layer).
I'm using Hatchbox silver PLA filament (1.75mm +/- 0.05mm).  I don't have another filament I can test with to compare performance.
Even when I import the profile settings from one of the sample .gcode files I tend to end up with blobbing, pulling, and stringing all over the miniatures, in addition to missing or deformed parts.  Notably, arms and hands -- most often overhangs -- tend to stick to the hotend and get repositioned, sending the whole thing out of whack.
I end up with similar problems when I use the Novice mode settings in Cura (Normal Quality, High Quality, etc).
Is there something I'm missing that I can do to improve the quality of small, detailed prints, or is the I3, as an entry-level printer, simply not up to the task?  I'm especially interested in answers from users who have experience printing miniatures and their experiences in tuning for that type of print job.
A few things I've tried test printing:
Printer calibration test model v1
Printer calibration test model v3
Both of these came out very stringy, with lots of blobbing and layer pulling, especially towards the upper portions of the taller elements.
I have also tried printing these two models:
Knight with sword - high detail
Elf monk - high detail
All test prints of these two models had at least one missing hand due to it getting stuck to the hotend and pulling off the part, and both demonstrated lots of minor blobbing and pulling on otherwise smooth surfaces, with loss of detail in the more finely detailed areas.  Here's a sample of the output for the knight model.  Please ignore the fact that he has been dismembered, that was mostly my fiddling with it post-printing (I guess I don't know my own strength), though the left hand was not well-attached and fell off rather easily.  He was printed with both hands and feet/base intact, but you can see the blobbing and pulling pretty well.

Yeah you need to get the Slic3r / Ultimaker Cura profile from the manufacturer. Calibration print worked. We know the firmware works. We know the hardware works. That leaves your Slic3r settings. Post your Slic3r settings please. But I doubt we can do more than point out the way off settings. Google calibration guides and you should be all set.

Wow, that isn't how you imagine a thing to come out of a 3D printer... What layer height are you using?
I would try it with layer height 0.1 mm (because strong overhangs getting better printed).
Did you figure out the 'min time per layer' setting? I'd try to set this to about 15 seconds to try, if it works better than. Don't put the extruder temp to high, about 195 ºC.

I've not done much miniatures printing, but I have the same printer and I happen to have the exact same filament loaded.  Also, I've been doing a lot of tuning lately, including this z-brace mod which has improved my overall print quality, so I thought I'd take a pass at printing the Knight from your photos and sharing my findings.
First, I've posted a series of pictures to show my findings.  Overall, I'd say my print quality was better than what you showed in your photos, but still isn't good enough.  I sliced with Cura 15.04.6, and printed from SD card.  Here are my (Full) settings:
Layer height (mm)         : 0.1
Shell thickness (mm)      : 0.5
Enable retraction         : Yes
Bottom/Top thickness (mm) : 0.3
Fill Density (%)          : 20
Print Speed (mm/s)        : 20
Printing Temperature (C)  : 210
Bed Temperature (C)       : 67
Support Type              : Everywhere
Platform Adhesion         : None
Skirts                    : 3
Filament Diameter (mm)    : 1.75
Filament Flow (%)         : 100.0
Nozzle size (mm)          : 0.5

Retract Speed (mm/s)      : 40.0
Retract Distance (mm)     : 7
Initial Layer Thick (mm)  : 0.2
Initial Later width (%)   : 100
Cut off object bottom (mm): 0.0
Travel Speed (mm/s)       : 100
Bottom Layer Speed (mm/s) : 20
Infill speed (mm/s)       : 50
Top/bottom speed (mm/s)   : 20
Outer Shell speed (mm/s)  : 20
Inner Shell speed (mm/s)  : 20
Min. Layer Time (sec)     : 10
Enable cooling fan        : Yes

I do most of my printing with a later height of 0.2mm, but for a detailed mini, 0.1mm is probably the largest that will look good (and probably the smallest possible on this printer.  I normally set most of my speeds to 50 mm/s, with first layer at 20 mm/s; for this I slowed it all to 20 mm/s due to the fine details, and I think it helped.
Temps of 67˚C bed and 210˚C extruder are what I've found to work best on my machine for PLA, after much experimentation, but your machine may vary; I'm not sure how accurate the temperature measurements are on these machines.  67˚C gives me an observed bed temp of 60˚C, but that's at the top surface - I have PEI atop Borosilicate glass, adhered to the bare aluminum bed with silicone-based heat transfer pad.
I think I miscalculated the top/bottom heights and infill.  I'm not used to printing at 0.1mm layer height, but 3 top layers over 20% infill is clearly not enough - see the closeup of the mini's base in my linked gallery.  Next print, I'll either try 0.6mm top/bottom, or much higher infill.
The supports came off easily; I used a pair of sidecutters from my electronics bench.  A little more cleanup with a sharp hobby knife, combined with a better base top layer would probably produce an acceptable result.
There were two major flaws.  The first are the little blobs on many layers; see for example the inseam area on the picture of the knight's back.  Ed Nisley at Softsolder.com calls these "Reveral Zits", and I think the name is apt.  These happen when the print head needs to quickly reverse direction or stop-move-print, but filament continues to extrude.  I use fairly aggressive retraction settings, and I think my print shows smaller zits than yours, but still far too many.  Ed has explored this topic in some depth; it's possible my extruder stepper isn't keeping up with my settings due to mechanical limits.  This is an area I want to pursue, but I don't have time at the moment.  I plan to read Ed's work and try some experiments on my machine to see if I can get better results; I will update this answer if/when I do.  As it stands, most of them are quite small, and could probably be cleaned up with a knife; the worst are those around unsupported areas, such as the back of the shoulder guard.
The second major flaw is the helmet.  It's just... bad.  I'm not sure the printer has much hope of nailing those horns, but overall the head is just bad.  I'm not sure what can be done there.
To summarize:  @disc0ninja's advice on Bed Level and Print speed are certainly the right place to start; You might want to try my Cura settings to see if you get similar results.  Also, the Z-brace mod I linked to above has made a big difference for me; I rarely have to adjust my leveling anymore.  I also plan to try slicing with Slic3r, which I haven't used previously, but have been looking into.  You mentioned you couldn't print with Slic3r, was that USB or SD Card?  I'd suggest trying via SD if it failed during USB printing.
Update 30 Jan 2017:  It took a little doing, but I managed to slice and print this model via slic3r.  I had some issues with the original STL in slic3er, which I ended up fixing with a free trial at makeprintable.com.  I spent a lot of time fiddling with slic3r; it has a lot more knobs to turn than Cura, and I make no claims of having the best settings for this print.  There are so many settings that rather than transcribe them here, I've captured them in my pictures of the slic3er print.

Overall, I feel like the quality is higher.  The "reversal zits" are hardly noticeable; but the big remaining problem is one I didn't fully diagnose in the original Cura print - lack of support for areas such as the shoulders.  Slic3r added more support than Cura, but it's also harder to separate from the base.  The head isn't great, but much better than the Cura print; I don't think my photos show it as well as it looks.  This print has convinced me that there's plenty of quality still to be wrung from this printer; I hope to make time to do some more slic3r prints of this model while tweaking the params to see what's possible.  If I make any big leaps in quality I will update this answer.

This is an excellent answer. I've taken the liberty of adding the images to the SE imgur, just in case the external link died in the future. I've inlined the images, although it might be better just to have links to them. Some inlined images of the model and supports would be good too but I got tired of adding images :-)

@Greenonline brilliant, thanks for the improvements!  I really need to get that printer up and running again.  I never quite finished a mod to replace the Z-axis limit switch with a proximity sensor.   Re-reading this old thread is a great motivation.

I have an Alunar(Anet) Prusa i3 printer I bought from amazon 7 months ago. I have not done much for ultra high detail prints, but it does seem to print everything I've thrown at it quite well. It took sometime for me to get it dialed in. I've found that Bed Level, Z-axis height, and Print Speed are usually what makes the most difference.
I have only used Inland PLA (Microcenter brand) and can get good quality prints.
I would recommend double checking bed level, z-axis, and going through print quality trouble shooting. Re-measure your PLA thickness and make sure your print multiplier is adjusted appropriately, and try to slow down your print speed.
If you could post a link to a sample file that you're trying to print It may be helpful?
Simplify 3D has a wonderful trouble shooting guide you can check out here

I posted a few links to files that I've failed to print well, as well as an image of one of my failed miniature prints.

I downloaded the knight and elf models and will try and get them to print nicely and take note of the adjustments I have to make, so I can suggest them. Have you tried adjusting Extra Restart Distance ? I have read that a negative value can help reduce blobbing, by not pushing as much filament immediately after retractions.

I'm not even sure that's an option in the version of Cura that I'm using.  I'll have to check when I get home.

I downloaded Cura 2.3.1 and (at least in this version) The setting I mentioned earlier is called Retraction Extra Prime Amount and I had to enable its visibility in Preferences => Settings => Material It also only accepts positive values in cura,  but I think it works the same. Eg. Retraction Extra Prime Amount = 0.2mm Will push .8mm of filament after a retraction (if the retraction distance was 1mm) which counteracts filament oozing. I could be wrong, but that's my understanding of how it works


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How important is the dimensional accuracy of filament relative to the detail of a print?
In this answer user Barafu says,

Yet I manage to keep my tolerances +- 0.05 mm which is enough for everything but miniature printing.

I have asked for clarification on that answer regarding what is meant by "miniature printing" but in the meantime, I want to ask the general question.
What impact does dimensional accuracy of filament have on final print quality, and why?  Does it vary between different filament types?

Dimensional accuracy is not as important as dimensional uniformity. I can print with undersized (or oversized) filament, adjusting the flow appropriately, provided the filament has a consistent diameter. When creating filament in-house, without expensive equipment, it is difficult to maintain the same diameter throughout the entire extrusion. It is likely this extrusion diameter (when creating filament, rather than the output of the actual print head) to which Barafu is referring when he mentions his tolerances: +/- 0.05 mm in diameter. Which is reasonable.
The "miniature printing" comment likely refers to printing miniature models for tabletop gaming.
If the source filament becomes wider than expected, the output will have overflow, or more material than desired will be deposited, and this will certainly affect the quality of the piece.

Perhaps I should adjust the question, then? I see most PLA filaments advertised as 1.75 mm (+/-0.05 mm).  Does this mean a variance of 0.05 mm in the diameter throughout the filament?  Or that the diameter is uniform, and it's within 0.05 mm of the advertised diameter?

It could mean either, but most likely the first option. Your print head is likely tuned to accept a certain (small) range of filament diameters.

@LegendaryDude - it means the first of the two (variance throughout the filament).  That number does not give you a degree of certainty but a degree of uncertainty.  The cases where the filament may be constantly +0.05 mm or -0.05 mm from its nominal value are just "special cases" of the more general one.

Put it simply: they say 1.75 mm with a ± error of 0.05 mm.   Which means your flow may vary ±2.9 % while you are printing creating blobs and such.
The smaller the filament tolerance, the more expensive the production costs.

I'm curious how you arrived at 2.9% when I calculate +-5.7%.  The difference in surface area between maximum and minimum allowable diameter is 2.54 - 2.27 = 0.27mm^2.   Which is 11.4% maximum variance in extrusion volume or ~+-5.7% from nominal.  Have I done something wrong?  This is why I buy +-0.03 or +-0.02 filament.  They have 6.9% & 4.6% max variance respectively.  If I've done something wrong I may be paying more for less benefit than I think.


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What is the best material for printing an anatomic bone model?
What is the best medium/material for printing an anatomic model for educational or study purposes? Specifically, I'm interested in printing intricate head and neck bony anatomy that requires fine detail to look at important holes and "cracks"/fissures.

I think a possibly better wording would be "What are appropriate types of printers for printing an....". It may not be the desired definitive question, but it stays away from "best"-type questions. Also, in this case you will be most limited by the style/capabilities of the 3D printer type.

The Stack Exchange discourages "best" type questions, as any answers are going to be opinion based. There are going to be more opinions than types of materials and types of printing.
Your question regarding specifics is more on the mark, however, and has less to do with material than with method.
Consider that resin based printing, especially SLA printers will provide extremely fine detail at extremely fine prices. SLA printers are more commonly used for smaller models such as jewelry and dental applications.
SLS, Selective Laser Sintering is capable of nearly as detailed work as SLA and is better suited for larger models. One can contract for SLS work on the major 3D printing services. Pricing for SLS is also "up there." Use The Google to locate 3D printer services for a suitable resource.
In the FDM world, you'll find lower costs and lower resolution. My printer is capable of 0.100 mm layer thickness, which means barely visible layer lines, but they are still quite obvious, especially on sloped or slanted surfaces.
I suggest that you find a small scale or segment of the part you wish to have printed and send it off for sample returns in the above formats.
As an option, once you have the parts, you could consider to use them to create molds and cast in resin as many copies as you would need.

Also when you print white with FDM. even at 0.3 mm+ layers it is hardly noticeable


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Melzi v3b firmware flash
I'm trying to flash the repetier Firmware to my Prusa i3 3D Printer, which uses Melzi 2.0 board. I uploaded it successfully 2 days ago with same settings but now is failing always.
@avrdude -p m1284p -b57600 -c arduino -P COM%x% -e -U flash:w:%filename%.hex
avrdude: AVR device initialized and ready to accept instructions
Reading | ################################################## | 100% 0.02s
avrdude: Device signature = 0x1e9705 (probably m1284p)
avrdude: erasing chip
avrdude: reading input file "newa.hex"
avrdude: input file newa.hex auto detected as Intel Hex
avrdude: writing flash (114266 bytes):
Writing |                                                    | 0% 0.00s
avrdude: stk500_paged_write(): (a) protocol error, expect=0x14, resp=0x64
avrdude: stk500_recv(): programmer is not responding

How do I solve this problem?

I have had trouble before not using spacing between arguments. I think no spacing between -b and 57600 is causing the problem. Try
avrdude -p m1284p -b 57600 -c arduino -P COM%x% -e -U flash:w:%filename%.hex

authors: Натали Осипова


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Weight Reducing Design Change for Extruder Driver
I'm considering removing the driver motor from the extruder assembly, and placing it on a stationary mount point instead, and then using a flex-shaft type connector from the motor to the extruder assembly to actually drive the extruder. The motivation for this change is to reduce the overall weight of the extruder driver and hot end assembly, allowing for quicker movement of the carriage on it's associated axis(one of X,Y).
Would it be better to run a pair of drivers (one for each direction) to manage reversing the filament pressure or would it be better to use just one driver and reverse the motor as usual?

The configuration you suggest is in place and called Flex3Drive. A quick search will present many links to the same web site for this product. I cannot vouch for the product, having cancelled my delivery.

Very cool idea,
One motor would definitely be more than capable of producing the required torques even through a flexshaft connector. For any normal sized 3D-printer the torques required, and the speeds you'll need for rapid response are well within the capabilities of any off-the-shelf stepper motor.
Just a note on the idea though, with a normal, 'rigid', connection there is essentially no winding or unwinding, and only the backlash between the gears and the filament to consider, and that is effectively zero. With a flex-shaft though, the stack-up of twists and flexing will be much greater. The system will require more rotations at the source to effect the same amount of torque at the end effector as the flex shaft flexes and bends under the load. For tiny torques with short flex shafts, this wont be an issue as filament pressure is pretty minimal. But if you scale up this project or start working at much higher speeds, you may run into some issues with this design.
I have no idea how big or fast you'd need to be working at for this to begin to become a problem. I'm imagining pretty big though. Just something you might want to keep in mind if you try turning this into a huge, super fast 3D-printer.

Some 3D printing software can compensate for backlash using Oozebane aka Retraction Tuning aka deprime.

If you're talking about a common 3D printer stepper motor and driver, then one driver is perfectly capable of driving the motor both forward and backward.
The flex tube setup you describe sounds like a Bowden extruder.

What he described is not a bowden extruder, but something more similar to the Flex3Drive as noted by fred.

@TomvanderZanden Ah, I understand now. Thanks for pointing that out.

But the Bowden is an approach that solves the same problem in a similar but different way. Moving the motor off the printhead, and connecting a "thing that transmits force", (the filament captured in the tube, for the Bowden), to the printhead from where the force is generated at the motor. I suspect the Bowden is lighter, based on flex-shaft tools I have owned.


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Reprap variants with servo motors rather than stepper motors?
In a discussion about motors with a friend who used to work in the robotics industry, he told me that he despised stepper motor systems, as every stepper based system he had worked on required a bunch of hacky software fixes to make the system perform to the required level.
He said that servo motor based systems had their own foibles, but at least they could generally be tuned out and you always knew that if the encoder said you were in a given place then you would be (to within the constraints of the backlash compensation).
Because of this, I was wondering if there were any options for using brushless DC motors + encoders + drive electronics instead of steppers + drive electronics.

Given that there are robotic servo arms that are used for 3d printing. What you really want is a DC motor with an encoder.

You can get "stepper replacement" servo drives that supposedly put all the needed control in the drive, and accept ordinary stepper inputs. Those should make the servo-drive a "drop-in" option on anything that uses stepper drives.
That said, I've seen an affordable CNC router system based on steppers turned into a much more expensive system based on servos, and I still have the "obsolete" stepper version, as the servo based system is MUCH more expensive and I could not keep up with the "upgrades" and never would have bought it at the price it now goes for. I'm in fact considering changing that to a reprap control system (still as a router, not as a printer, as I currently think.)
Given some practical limits to printhead speed in additive 3D printing based on the material solidifying, there may not be a lot of benefit in the considerable added expense of servos. They can move faster, but how much of that will translate to actually printing faster? How fast can you melt and pump plastic and have it stay where you put it?

I think using these technologies is possible, and may be better than stepper motors, but by using these you loose the main advantages of the steppers : the simplicity and the cost.
When you use steppers, you assume your motors are strong enough to don't loose any step, and you "just" command them. Steppers are not so expensive and are compacts, so your 3D printer is "simple".
If you use separated motors and encoders, you can do better job, but your 3D printer will be a lot more expensive, harder to tune, and harder to program.

I wouldn't agree with "harder to program" -- you just need a different driver.

Yeah, by "harder to program" I mean the control engineering part. With steppers, you don't even think about it, you just suppose the motors follow the command.

The question is "[are there] any options for using brushless DC motors + encoders + drive electronics instead of steppers + drive electronics?". You're giving your own opinion of why steppers are more commonly used rather than servos, but this does not answer the question of whether there exist any servo-based 3D printers (they might very well exist even if you think a stepper-based system is better).


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My anet a2 auto-homes incorrectly
I just made my anet a2, and when I hit auto-home it goes off the board makes a loud clacking sound going down a bit (under the heat bed but off to the side). Any suggestions?

Your limit switches are not working properly - they should always hit.
Do the following steps:

Move axis in all possible directions, both positive and negative;
Check limit switch wiring;
Limit switch output.


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Which is more durable to sunlight/weather - PLA, ABS or PETG
The backstory: I'm installing a pigeon net in my home. Because of the shape of the opening I'm installing the net in and the material on the sides it's difficult to anchor the net using the normal means but I can print clips that will hold the net in place.
The clips will be outside and will be exposed to the weather and direct sunlight, the weather here is relatively hot (up to 30C) with a lot of sun most of the year and rain in the winter.
I only have PLA, ABS and PETG available, anything else will take too long to arrive.
I don't care about the parts changing color and mostly I don't care about them deforming a little bit - only about breaking.
If the parts have to be replaced after a year I'm ok with it, less then that will be annoying, longer will be better.
So, under those conditions, which of the 3 materials is more durable?

Ok, I tried all 3 materials.
PLA failed after less then one day, I believe it deformed from the constant pressure and fell out (I didn't find the part but I didn't really search for it, there's some tall grass below the window)
ABS lasted about a year, it fell strait down and I found the part, it looks ok if probably deformed by just a few mm so it doesn't pressure fit anymore.
PETG still going strong as I write this

PLA is not ice to desappear in one day, I have parts printed two years ago an still is working in good shape. Also "nice" testing if you loose one testing part and don't try to find it, what kind of proof is that?

@FernandoBaltazar - those parts are pressure-fit on the outside of a ledge on the 3rd floor and hold a tight pigeon net, the most likely failure mode is that the part deforms just enough to not hold the ledge any more and is then shot into the street below by the tension of the net. it makes sense PLA does not work for this specific case because it involves constant pressure and PLA is known for deforming under pressure, the direct sun and heat probably doesn't help - this isn't proof that PLA isn't good for outdoor use but it does show PLA doesn't work for my specific use

Well, all depends on kind of testing and robustness of the parts involved. I have parts as supports for antenna for repetiers directly to sun exposed with no shadow during the whole day. Of course some parts need to be for stronger material like ABS and some polycarbonates, but as a hobbie we will use the material available on the market.

Very interesting that PETG outperformed ABS, as ABS has a higher Tg temperature. I'm curious what filament colors you used? That might have made a difference.

@Blossoming_Flower - Both ABS and PETG are completely solid at any outdoor temperature anywhere on earth, so the Tg temperature is kind of irrelevant here. I used cheap Chinese "natural" PETG (also, natural ABS from the same supplier)

@Nir then any clue why the ABS deformed and the PETG didn't?

@Blossoming_Flower - I don't know, all I know it was pressure-fit into place outside and it fell down after about a year, it didn't break and without measuring it looked like it kept it's shape, I assume it deformed because otherwise it didn't have a reason for falling, it could be any combination of UV from the sun, water from rain, temperature changes, wind, or anything else, for all I know a bird might have pulled it our intentionally. I'm not a material scientist, chemist, or anyone who has any business talking about this but if I had to guess I would go with UV as the dominant factor

(Late to the party) With luck, you will have figured out by now that it really doesn't matter much which filament chemistry you use, as long as you PAINT IT. Paint blocks the UV and prevents moisture intrusion, stabilizing the object. Recommendation: prime with shellac, then paint with "aluminum" colored paint.

I can confirm this, i printed a 3D dragon with separated fit parts, they fit perfectly yesterday. I've sprayed prime into the pieces and let they cure through the day and now i cant connect any of the parts ahahah
Gonna need to sand all the pieces a lot because of one day into the sun.

PLA would be a non-starter for outdoor use as it's biodegradable and can breakdown in sunlight. Albeit slowly, but won't be useful for long term project.
ABS would be a good choice for longevity, as it can last in outdoor situations for quite a while. Its glass transition temperature is above 100 degrees celsius so it'll last in most climates. As for strength ABS is one of the better choices out there, also it's slightly softer than PLA meaning it will flex before breaking, PLA is much more likely to shatter. ABS is well known for warping while printing though. Not a huge problem though, if you're used to printing with it.
PETG not a bad choice either. It has a glass transition temperature around 80-90°C. So if you're building in a hot place with direct sunlight with some reflection, you could have deformation issues, though not that likely. It is stronger than ABS and it's also easier to print (less warping issues). PETG is also supposedly 'food safe' meaning if the outdoor animals start pecking at it, it'll probably not kill them... I wouldn't recommend trying to taste it though. Finally PETG is a bit closer to PLA in terms of brittleness so it may shatter before flexing. ABS is less brittle than PETG.
If it were me I'd go with ABS despite its issues with warping while printing. If you're newer to printing, then probably better to go with PETG.

I do not think PLA is more susceptible to breaking down from sunlight than any other plastic. Biodegradation of PLA will not take place if it's only sitting outside - you need a carefully controlled commercial composting facility to get it to do anything.

According to this article: http://www.emerginginvestigators.org/2013/11/the-effect-of-uv-treatment-on-the-degradation-of-compostable-polylactic-acid/     Degradation of PLA is  significantly increased with exposure to UV light.

They were specifically trying to get PLA to degrade. According to that article "The specific type of light used in this experiment is UVC [...] UVC light is not commonly found in sunlight because the ozone layer of the atmosphere absorbs most UVC light.".

Another benefit of ABS: if you vaporsmooth the surface. This does prevent moisture from creeping in through the layer boundries.

Prints over time do handle well: https://www.youtube.com/watch?v=qqNfa_zExRU

I might be late to the party, but I have a suggestion. Why not use ASA filament, it's the kind of plastic used in car cup holders, lawn rakes and sprinkler heads, it is both heat and cold resistant, as well as solar stable and weatherproof. As far as printing with it it is similar to printing in ABS as far as I am aware, I might be wrong though. I personally am surprised how often this kind of question pops up and literally No One mentions ASA filament. I think I might buy some because I like the idea of printing something that can be left outside.

ASA needs a print temperature of 250+ °C, which most printers with lined hotends can't reach without destroying the liner. Some ASA filament (3DXMax) even wants 270-290 °C. Heated bed is mandatory and ask for 80 to 110 °C. It also is best printed in an enclosure, which all are facts that make it a nieche product. It's fumes from the printing from printing also are likely to be toxic (research pending), and is one of those notorious hard to print filaments as it has severe layer adhesion problems and answers to those with splitting.

In addition to what @Trish said, ASA is also relatively hard to get (unless you live in amazon-prime-free-shipping-land, sometimes referred to as the USA), I don't know of any filament supplier in my entire country that sells ASA

I wouldn't be so quick to dismiss this suggestion. I didn't know about ASA, yet I have an enclosed, air filtered printer with a 300ºC+ extruder w/ heated bed. Looking it up, dozens of choices available next day on Amazon Prime for me - I live in Scotland.

I've been using ASA and I'm pretty happy with it. Agreed that you need some high temps, I think I have to print at 270 which is the absolute tops of what my printer does, and bed, and enclosed, and mind the fumes, but if you happen to have that tech, it's easier to print than either PETG or ABS. Few colors. Supply in the USA is easy, multiple vendors, don't need amazon to get it.

We use PLA in an outdoor environment, non-direct sunlight.  PLA seems to be just as strong as day one. It has been about six months now.
Of course, you must seal coat to protect from moisture.

I have some PLA parts outside since about 18 months now with no protection whatsoever. Except for some discoloration the parts are as strong as the first day. Of course the climate of your region plays a role in this too. I'm in Belgium, not in Arizona!

I'm in California, 30 degrees Fahrenheit up to 110.

Good watch in this regard: https://www.youtube.com/watch?v=qqNfa_zExRU

What colour was your PLA? PLA will soften around 60C and a dark colour will easily get hotter than that in direct sun on a 30C day.  Clear PLA seems to have much, much better temperature resistance, but any sort of PETG will kick it's butt in that regard.


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Is there any reason *not* to use a steel nozzle for printing all materials?
I know that for printing some materials like the carbon-fiber filled PLA it's recommenced to use a steel nozzle since it'll wear-out a standard brass nozzle quickly. Is there any reason to prefer using a brass nozzle for 'simple' plastic-only filaments instead of just printing everything with steel?

Thermal conductivity of brass is approximately twice as better than steel (not stainless). Given that the size of nozzle is relatively small, it should be able to transfer enough heat for a medium-speed prints at least.
I have printed PLA and ABS using "steel" nozzle (brand of steel unknown) at the speed around 80 mm/s without any visible differences compared to brass.
However, an ideal nozzle (I see) is made of tempered bronze with polished inner channels. Bronze is known to have better friction coefficient and tempered one should be enough to resist carbon-type filaments more efficiently.

One caveat about brass nozzles, is that most have some small percentage of lead in them. IFF you're printing something that i meant for food, water, gardening etc, there could be some transfer to the printed part.

Keyword is "small" here. Typical lead presence in brass alloys is not more than 3%. Let's say nozzle looses 1% of its weight per 1kg of plastic (very pessimistic view on brass). Nozzle weight is about 2.5g. This results in transfer of 0.0025 * 0.01 * 0.03 = 0.00000075 kg of lead per 1kg of plastic.

Agreed, miniscule percentages. But for making food grade products some people still want to know that there is a non-zero transfer..even if you're almost  better off measuring number if atoms transfered.

@MikhailZ, according to https://www.cdc.gov/nceh/lead/tips/water.htm, Lead concentrations in drinking water should be below the EPA action level of 15 parts per billion. That puts your (very extreme) estimates at 50x concentration of "safe" drinking water. Now, you also need to get the lead back OUT of the print into the food, and similar figures would apply - i doubt you would lose (and comsume!) 1/50th of the print per time that you consume from a print that weighs the same as the food being served!


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How to join pieces automatically using interlocking or similar?
I have a piece, which I need to cut into two different pieces, see image 1.
Image 1

Then I need to make interlocking joints or similar, see image 2.
Image 2

How can I do that automatically, using Solidworks or another program?
It's an *.STL file so I can easily manipulate all parts without any errors.

I'm not qualified to advise regarding Solidworks, but can suggest a process and concept from which you may be able to adapt to your software.
As you have the two pieces currently in STL form, it makes things only slightly more difficult. Consider to align them parametrically so the faces contact and the edges are coincidental. The block STL will appear as a single cube, in the example you've provided.
Create and place a mating cylinder piece in the desired position as you've shown in the second image. It is a common feature of many 3D modeling programs to be able to perform a subtraction of one part from another. It is equally common to be able to merge two parts into a single manifold part.
Save the file containing the three parts.
Select either block and the cylinder. You can delete or otherwise hide or deselect the unused block. Perform a subtraction on the remaining pair. Save this file under a different name.
Reload the three parts file.
Select the other block and cylinder, perform a union of the pair. Save this file under a different name.
Rather than saving the three parts in a file, one can frequently save the joined or subtracted part and perform an undo until the three parts return. This is a faster more convenient method.
I have performed the above steps in Meshmixer and know that it can be done in Blender, if one is skilled in these programs.
I've performed an internet search for "perform boolean subtraction solidworks" and found multiple results for this process. One link references the "cavity" feature for subtraction. I did not search for boolean union and leave this as an exercise for the reader.
Consider also to plan for this activity in the future by leaving the block intact, unsliced, place the cylinder, perform the boolean action, then slice it as desired. The sequence of saves and/or undo actions will be different from above, but may be easier than re-aligning a previously sliced "block" or item.


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FDM layer bonding strength
I'm looking for some advice, rules of thumb, or models for how to design parts for layer bonding strength.
As an example part, lets assume a circular beam in bending (tall cylinder). Depending on how the part is setup on the build platform (tube axis aligned parallel to Z, or setup to lay in the X-Y plane) the layers and internal structure will then be different depending on the orientation chosen at the time of building. Does/has anyone done any investigation to what roles these factors will play on simple shapes like a solid cylinder?
Ideally, with a CNC'd, injection molded part the total strength of a solid part is quite easy to model (mathematically) for strength and flexibility. However, with a 3D printed part the orientation makes the isotropic material properties effectively anisotropic, as layers don't bond perfectly, different cooling rates, and a host of other reasons.
Ideally I'd love to find a 'simplified' model that can be applied to hand-calculations to come up with rough approximations to part strength and bending. My guess is that these parts would be modeled something similar to an ABD matrix, similar to composite materials, but that's just a guess.

I have not been able to find a simple model for FDM part strength.  FDM parts are pretty complicated as they have a LOT more things that affect their strength than just layer adhesion.  Since any "solid" part will have infill, the part can't really be modeled as a laminant.  There are so many settings you can play with in the slicer that effects part strength, the model would have to have tens (if not hundreds) of parameters.  Also, you would likely have to establish them for your own printer since lots of things can affect them (like room temp, ventilation, humidity, material, material storage, ...)
One empirical example discussing the affects of FDM choices on part strength is a video done by Angus at Marker's Muse.  In the video he discussed how orientation and wall thickness affects strength.  Angus is not a math/ME guy (by his own admission).  FEA or other modeling would not be his approach; but, you can get some insight from his experience.
On the modeling front, I have seen one company that did create an FEA model to test whether their product would be strong enough if they produced it using FDM.  Here is the publication they wrote showing their analysis approach.  It will give you some insight on how they approached what I think you want to do.
Note: They do offer a service where you can pay to have your part analyzed for a considerable amount of money.  I have no idea how much money; but, based on jobs I have quoted in the past, I would expect it would be a least a few hundreds dollars.
As for me, I really enjoy basing my decisions on models and understanding how a part/process works. In this case; however, an empirical/experimental approach might be more cost effective.  If you really want to take an analytical approach (and have the time to spend doing it), I would recommend choosing several key parameters and run an analysis using DOE (Design of Experiments).
If you come up with something, I would love to see it posted here.
Good luck and happy printing.


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Is there a technique for turning an image into a 2d model?
The overall goal is to create a print of the liberty bell.  No clapper is needed.  The support beam is not needed.  I am just looking to mimic the outside shape of the bell.  After an application of Google-fu I found this image.  It has been cleaned up and cropped a bit.

In OpenScad the surface function was applied to the png to generate a height model.   I subtracted out a few cubes, and eventually got it down to a layer of about .1 height.
My Evil (pun intended) plan is to get it down to a 2d model.  Then by shifting a copy of model from itself, and subtracting the two.  That should leave just the curve.  Then rotate_extrude the curve to generate the actual bell at the desired thickness.
I see the problem coming. If the model is layered down to zero height it will vanish. Leaving me nothing to rotate.
So on to the question.
Is there any tool or technique to turn the image into a 2d openscad object or failing that is there another way to approach the problem?

The direction that fred pointed me at is viable. I didn't use the actual image shown here, but a manually generated one from OpenScad.  As a proof of concept the technique works well.

This sounds like what you're asking for is a 2D drawing file of a 3D part in a given plane? If so, Solidworks, Solid Edge, and Autocad are all fantastic at this, not sure about OpenSCAD though.

As you are already familiar with OpenSCAD, consider to use the projection() function to accomplish your goal.
If you allow for an interpretation that one can cast a shadow of the part on a surface below, it becomes a 2D representation of the part. This is effectively how projection works in OpenSCAD.
Note that the part image below is centered in x, y, z and the cut/projection action takes place at the z = 0 plane:

When the function is applied to this model, the result is a non-contiguous 2d image:

When the cut parameter is ignored or set to false, the image which results is effectively an orthogonal shadow of the entire object, rather than a selected slice:

It gets better, of course. In OpenSCAD, the translate, rotate and scale functions apply. One can tip a model over, resize it, spin it around, combine with the cut parameter and get any combination of 2d image from the original model:

It's important to note that OpenSCAD does provide non-zero thickness to these projections when rendered, or maybe when previewed. I always get those two swapped around. As your objective is a 2D result, you may be able to select from PNG (save as image) or Export as DXF or SVG.
Re-reading your post, I also missed part of a more useful answer. Once you have the profile you desire, you can use the rotate_extrude function on the profile you generate. Despite the non-zero thickness, it uses the zero-thickness aspect to create the model from that function.
That aspect of the answer is left as an exercise for the reader, as the options are many and results can be complex.

Clearly it is time to review all of the open scad functions.

Two options:

Use TRACE2SCAD (http://aggregate.org/MAKE/TRACE2SCAD)
For the more adventurous: Dig up the old pull-request for the suggested trace() module: https://github.com/openscad/openscad/pull/1110

Thank you Marius.  I will be taking a look at trace2scad as another arrow in my quiver.

You could have done that with OpenSCAD, there are instructions for extruding.
Personally, I'd just do a 1 altitude copy with
Image 2 STL 2 Heightmap Mesh Converter Generator, then rotate in OpenSCAD. It's called rotate_extrude() and is used for seashells.
In MeshLab you can use Laplacian Smooth to depixelate/antialias it.

interesting.  I did the whole thing in openscad.


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Filament material for chemical application
I am doing laboratory experiments and need to print some components.
I am working with different aqueous (water) solutions containing sulphuric acid (H2SO4), hydrochloric acid (HCl), and hydrogen peroxide (H2O2), separately and in combination. The pH of the solutions are in the range 0 to 7. Temperatures don't exceed 40° Celsius.
In another application we have aqueous solutions containing high concentrations of FeCl3, HCl and in some cases H2O2 at temperatures of up to 180° Celsius.
Which 3D printing filament materials can you recommend for these applications?

Why are you looking for filament materials? You can print with liquids and gels.

for 180 you may consider a silicon mould using caulk silicon as in YT guide and make copies using resin epoxies same stuff as circuit boards that go to 250. highest plastics are usable at about 230, peek-tm is cnc'd it is at 280 max.

@Davo: The printer that I am using uses filament materials.

There are two issues you have here, one is temperature stability and the other is chemical reactivity of plastics. I can't help you with the chemistry side, but I can help with the temperature.
Application 1 (Temp < 40 °C)
Any FDM plastic will perform reasonably well under these temperatures. I would suggest trying a Nylon, PETG or a PolyCarbonate filament as I know these are more resistant to acids than PLA or ABS. As far as strength of the parts, all FDM plastics will work well
Application 2 (Temp > 180 °C)
This temperature range is above the glass transition temperature of the PLA, ABS, PETG and Nylon are all well below 180 °C and therefore aren't worth considering. Your best option is PolyCarbonate, or PolyCarbonate-ABS which are both fairly high (roughly 140-150 °C). However, are both below your minimum temperature threshold.
My conclusion is to try a polycarbonate sample and see how it reacts to the chemicals you're working with, though it doesn't look hopeful.
For Chemical reactivity, I did some Google-fu and found a few links that look helpful for PolyCarbonate:

Chemical resistance polycarbonate

Polycarbonate Chemical Compatibility Chart

A "glass transition temperature" only applies to cross-linked resins (like epoxy, many acrylics...).  Printed plastics are almost always linear and not cross linked (non cross linked can melt, cross linked cannot).

standard aliphatic resins like polyethylene, polybutylene, and substituted one like Teflon or PVC should be resistant to attack (but the last two are unlikely to be printable) check the melt temperatures.

Admittedly this is not my area of expertise, however, using Matweb (my goto for material properties), all plastics I mentioned have rated Glass Transition temperatures, cross-linked or not. As I understand it, Tg is defined by the temperature where the molecular chains are able to slide past each other. Above which the room temperature Younges modulus  would no longer be valid. The Melting temperature is the point at which the material changes phase from solid to pure liquid (in steady state), at which point you'd be concerned about fluid mechanics not solid mechanics.

You have a good point.  Non cross linked polymers will likely deform after the glass transition temperature.  Cross-linked ones will just become slightly weaker.  On the molecular scale, with cross-linked resins the chains can't slide past each other freely, "long scale segmental motion" is possible but free translation is unlikely.

@DanS for 3D printing, TG is pretty much the start where the model will start to deform under stress and the absolute maximum operation temperature for bearing stress.

Polyoxymethylene (POM) filament (known as Delrin or acetal) is suited to applications involving chemicals: it is chemically resistant to solvents, hydrocarbons, and neutral chemicals.


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Difficulty getting good precision
I have a reprap printer with 0.3mm nozzle. It prints quite well, I am really surprised with quality of all the surfaces and the general precision of the parts printed. BUT I HAVE a problem: when making (for example) a 10mm x 10mm x 10mm cube with a 2.8mm diameter hole from top to bottom (to fit a screw) after I print it gets a size of 3mm diameter.
I know this is related to extrusion width but cant the slicer software (I am using s3d) know that it is using a specific extrusion width and compensate for that in order to get the diamter right?
OBS: this printer is supposed to get 0.05mm precision.

You may need to double check this, but last time I looked at getting a new printer the precision that is rated is in reference to the position precision of the nozzle, while the part precision will be substantially worse than that.  TO get the precision of the final part I had to call the manufacturers directly and get them to fess up to what they were claiming

It's a generally accepted fact that FDM/FFF printers will have deviations when it comes to holes and perimeters. Typically, holes print smaller than designed and external surfaces end up larger than designed.
In your case, it seems to be the opposite: the hole is too big. It could be that you're just printing too big overall. You might want to make sure that your printer is printing the 10mm X/Y dimension in you example correctly. If it's too big, part of it may be just the typical oversized perimeter, but some of it might be due to incorrect firmware X/Y 'steps/mm' or extrusion like you mentioned.
See also: "Are you printing undersized holes?"

This is a common problem with many different types of 3d printers. When ever you print something the physical object will never be the exact same size as it is in the computer. However, you can get it to be very close to what you need. By tweaking certain things you can get the sizes almost perfect. It could be something slight like your stepper motors are mis-calibrated even a little bit. The distance between the build plate and the extruder could be off causing your print sizes to vary. Also the temperature of your extruder and your build plate could be affecting your overall size after printing. How long your print takes to cool and what temperature it is at at when it prints can affect sizes of your print.
This link could be of some assistance:
https://ultimaker.com/en/community/11526-problem-with-correct-size

If you include a link in your answer, please summarize the linked content, so we know what to expect at the linked site and your answer doesn't depend on the external source (i.e. the key information is contained in your answer and your answer remains useful, even if the external site becomes unavailable). Also, you can use markdown to format your answer (and include a link like this).

Simplify3D has a feature that makes holes a little bigger or smaller (for adjusting tolerances).
I don't remember what it's called, I think it's something-offset (if someone can help me with this in the comments I'll update the answer).
It's possible your silcer is set to enlarge the holes and the printer is just fine.

For one thing, the entire part generally shrinks, as it's printed (at whatever precision of nozzle location) as molten plastic, and then cools and solidifies.
Given that you are getting a bigger hole in the finished part, I'd start by measuring the part's actual overall outside size, as printed (is that 10mm, or might it be 10.5 or 11mm?), and suspect some calibration tweaks are needed.
If the outside of the cube is actually 10mm, then you may simply need to find the right fudge-factor for hole sizing - if 2.8 is becoming 3, you might need 2.65 to get 2.8 as printed - or 2.63, or...
Alternatively, plan for drilling when a precision hole is needed, and print a deliberately undersized hole with a thick shell so it can be drilled out precisely.


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What do the pink colors in Slic3r preview signify? If it signifies a problem, how do I fix it?
What does the pink color in Slic3r preview mean? Yellow is my model, green is support, and pink is..?
If the pink color is some kind of warning, how do I fix it?

In slic3r preview, salmon (pink) represents infill, yellow represents perimeters, and green represents support material, including skirt and brim.

Having had direct experience with Slic3r, I can offer up this information. Your model is composed of bottom layers, top layers, outside layers, infill, rafts, brims and perhaps something I've missed.
The program provides for color coding of these features. In the case of your image, the pink represents a top layer, but may also represent a type of infill, depending on "context."
Consider to slice the model, select the preview tab, which you have showing here, then using the slider control to the right of the image window. As you move it from bottom to top, you can observe the construction of the model and each feature as it appears, layer by layer.


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Anet A6's filament not feeding through the nozzle
Whenever I try putting the filament through the nozzle it does not go through. I have searched everywhere online and have found nothing.

What have(n't) you done and please elaborate on what is going on.

Many printers have a problem with inserting filament into the extruder. Cutting it at an angle is a huge help. It is also very possible that you have a cog or a bad extruder nozzle.
This link could be of some help: Extruder is not feeding.

It would be wise to summarize key points from that link to keep the information in case the link is no longer valid.

From How do I write a good answer?: Provide context for links - Links to external resources are encouraged, but please add context around the link so your fellow users will have some idea what it is and why it’s there. Always quote the most relevant part of an important link, in case the target site is unreachable or goes permanently offline.

My first step would be to cut the filament at a bit of an angle.  This will help the filament enter the extruder correctly.
If you're still having trouble, you may have a clogged nozzle.  This article by Lifewire -3D Printer Extruder Nozzle Clogged? Here Is How To Unclog It has some good info.
I've also heard stories about the Bowden Tube (the PTFE tube that guides the filament from the extruder to the hotend) becoming warped or melted in cases where the printer's temperature control went awry.  This is rare as PTFE doesn't melt until 320°C.

As @tjb1 states above: It would be wise to summarize key points from that link to keep the information in case the link is no longer valid.

From How do I write a good answer?: Provide context for links - Links to external resources are encouraged, but please add context around the link so your fellow users will have some idea what it is and why it’s there. Always quote the most relevant part of an important link, in case the target site is unreachable or goes permanently offline.

I think my PTFE shaft is in reverse when it was assembled and sent out. One side is the metal shaft only the other side the PTFE inner shaft.  I read about filament shavings from poor feeding, so it wouldn't make sense initial feeder takes on hard metal where it might shave it and obstruct ease, also the nozzle and the filament must need well heat so it doesn't make sense the PTFE is screwed in nearest the nozzle, rather the metal should conduct against it.  Thus also the thermal reading would be off from it not applied to the actual filament just around it.  In bike breaks it's to prevent the scraping of the metal chord against the metal housing upon where it exists the housing.  One of the video's suggested using twisty ties for the belt as well, with four extra pieces same as two which are used on the track at the bed, a non one time use disposable clamp can be made with extra screws, for each instead of the twisty ties, so it stands to reason likely however it maybe the sales/distribution form manufacture has poor communication or not at all instructions is how these discrepancies arrive.  IN MY OPINION.  Reverse the shaft from extrude to the nozzle if you don't see Teflon at the extrude part, I have not tested it myself yet, but I'm going to.  My unit as well seems poor ability to print at all.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

authors: เจ' หลังศูนย์


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Snap-in clamp geometry
I apologize if this is in the wrong section, but it seems relevant.
I am an absolute noob at 3D printing, but recently my need for a specific, small part intersected with access to a 3D printer at work (Zortrax M200), so I figured now was a good opportunity to get into printing.
I am designing a clamp for smaller can capacitors that will hold them upright from a mounting surface.  I would like the capacitors to snap into the clamp, but I am struggling to find information on how wide the opening to the clamp should be.  It clearly needs to be smaller than the diameter of the clamp, but I'm not sure how much smaller it can be without snapping the clamp arms.
Is there a rule of thumb or general guideline for this type of geometry?  I am using Z-ULTRAT, which is some proprietary filament made by Zortrax.  It seems to be similar to ABS in terms of strength properties, but stiffer.
I don't have an image at the moment, but I can provide one tomorrow when I have access to the part files.  The best analog I can think of is a LEGO figure's hands.
Thanks.
Edit: Per requests for additional information:

I am not sure what is considered a "thin" wall; currently, the clamp walls are 2mm thick at the thinnest point (where the push-in opening is).
I would like the walls to be just flexible enough to allow the cap to be seated without breaking - it is more critical that the cap is not loose in the socket.
The clamp is not going to be subject to repeated stress cycles - by the time the cap needs replacing, it's likely I'll need to print a new clamp as well.
With my estimations for cooling, I do not expect the clamp to see temperatures above 100C.

Edit 2:
Based on the link in the comments below, I came up with the following design:

The little nubbins in the back fit into the "neck" at the bottom of the capacitor to provide some positive lock.  220 degrees of surround with 4mm thick arms - I think this should work.

please taka a look here https://3dprinting.stackexchange.com/questions/771/designing-clips-that-wont-break/911#911

Thank you!  I must have missed that post when I was searching through the site.

I think your clamps are hanging in the air. It's feasible (to print in the air as same as to print with support material) but I'm sure it can be redesigned to not hang :)

I don't understand what you mean by "hanging in the air".  Do you mean the clamp arms are unsupported from below, and thus difficult/impossible to print in that orientation?  Would it be better to lay the clamp on its "back" (which will have to be flattened - not impossible) and print it that way?

yes - i was refering to unsupported clamps but no - definitely orientation of your detail is proper (potential issues described in link above). please take a closer look on the design in the link - there are clamps which are self-supported

If your solution, that you proposed in your EDIT 2 actually fixed your problem, then you could post EDIT 2 (text and image) as an answer (whilst also removing EDIT 2 remove your question, and then accept that answer as the correct solution. That way, your question will be removed from the Unanswered Question list. Thanks.

Yes, I apologize.

Based on the links and insights provided, I was able to adjust my design to that shown in Edit 2.  I opted to instead have it professionally printed via Sculpteo for a very reasonable price, and can say that the design works as intended.

I am sure someone much smarter will be able to point you towards datasheets and maths equations that will tell you exactly what you could/can't do, however, I would say it depends on a few things:

Material - some materials have more give/flexibility, others have less. Depending how hot you expect the caps/surrounding components to get may also influence choices.
Wall thickness - Are you just after a 'thin walled' print, or something more solid. Thinner walls tend to be more flexible.
Reusability - are you going to snap the cap in once or twice, or thousands of times?

I would hazard a guess that about 210-220 degrees of "surrounding" would be enough.
Can you try it and see? Or do you only have one shot?

see edits.  I'm not limited to one shot, but I'm trying to minimize the number of print jobs I have so I'm not occupying the printer needlessly.

As stated, not an engineer or other kind of material scientist, but your design looks like it should work!


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Embedding nuts and washers into print
I am creating a 3D printed part which will act as an attachment between a plate (actually a strain gauge) with two M2.5 bolts and a 2kg load with a single M4 bolt. I wouldn't be happy with tapping a screw thread into the print itself so I want to try embedding the nuts into the print itself - so I'll pause the print at the right layer and then insert the nut and, hopefully, the print will resume.
I'm wondering is it worth also including washers? It's a major pain because, while a nut can be captive in a hex space, a washer is circular. So it needs to be glued down on insertion in case it rotates while the printer is printing on top of it.
For a 2kg load I don't believe the nut will attempt to pull through the part but there isn't a whole lot of support between the bore hole and the edge of an M2.5 nut though, only about 1mm.
Edit: I'll add an image of my initial design. The strain gauge is one of a set pulled out of a weighing scales (from Lidl, €5.99. You can buy each separately on the internet for 20 euro, so I saved 74 euro!). The gauge itself is mounted on the narrow "neck" of the gauge. The whole block will drop into a holder that grabs the outer edge of the gauge.

Why does it matter if a washer rotates while printing?

@tjb1 I guess that not only would the washer rotate, the plastic that was deposited on top of it would rotate with it. I can certainly see that being undesirable.

@TomvanderZanden but the printer doesn't know it's printing on something, to the printer it is effectively bridging a gap and once the plastic touches the other side of the gap it's solid and the rotation of a washer caused by vibration isn't going to move it.

@tjb1 I think it matters when you have a nut on top of it, where the surrounding plastic is smaller than the washer diameter. If the first thing the printer does is try to draw a hexagon on top of the washer, where the hexagon doesn't meet the edges, that wouldn't be good. However if you arrange it such that the inner shells, done first, touch the previous layer, I think you'd get away with it.

What you could do is design in a single layer which is a rectangle with the short edges safely within the design and the long edges bridging the gap across the edges of washer. The long edges would be spaced by the distance across flats on the nuts + a bit for clearance. This would then be the situation that tjb1 mentions but is a bit annoying to have to do :-)

I'm not sure about the strength, but why not use a heat-set threaded insert?

@ChrisM. I guess I wasn't convinced about their pull out strength although they are a good bit better than bare threads.

@ChrisM. I've found some test links (eg: http://blog.capinc.com/2015/03/advantages-of-using-brass-inserts-in-3d-printed-parts/) and, although they are testing with solid infill, they are getting 50 kg pull out forces on M3 bare threads and three times that on the inserts. Which really surprised me. The advantage of embedded nuts are that they are cheap. The disadvantage is that they are tricky to place. I think I should do some more tests :-)

@carveone I found the same link at nearly the same time, I think.  :)  It all comes down to time vs money at that point (although 100 for $15 isn't terrible from my POV).

It could depend on how well your printer-filament type combination can bridge.  If you can generate bridges wider than the washer diameter, then print not only the hex recess but a disc recess for the washer, then print over both.
However,  my preference would be to redesign the part so that the washer&hex nut are on the far side of the part so that you don't need to deal with printing over&around them. This has the added advantage that you can replace the nut if it ever gets worn or stripped.

I think I see what you mean but the main issue there is that a wider recess puts you in a tricky position. If the sides of the hex recess are too wide, the nut will rotate in the recess making it impossible to screw a bolt into it. If they are the right size, you can't put a washer in.
I agree with your preference to redesign so I don't have to do this at all. I worry about smashing the extruder nozzle into the side of a badly inserted metal nut on a new €3000 printer!

@carveone  my hope was that the washer recess was "above" the nut recess so that you could print each to fit.

Ah! I'm not sure why I didn't see that ;-) As the M4 bolt will be topmost in the print, that should work fine. I don't have to bridge the washer as a whole - I can print on top of it as long as it doesn't rotate too much. Which it won't if I glue the washer to the nut before insertion. Sure, that works! It's only if the washer is to be placed before the nut that things get difficult but perhaps I can make slots in the side of the print to place the nuts and washers afterwards. I'll see how that works out...

I think I'll redesign. Now that I've actually done some basic testing and read some tests done by others (see OP comments), I can see that for my specific loading requirements, I was overly pessimistic as to the design strength of properly infilled ABS. I will have flexure issues long before I have pullout issues. I'll mark this post as the answer (although other posts were helpfull too, thank you).

I've had good luck with just leaving a hex-shaped hole in the print, and press-fitting in the nut afterwards. You'll want the axis of the bolt to be along the z-axis, and to use a fair amount of infill and shells. I usually use PLA, so YMMV slightly.
You may also want to consider your strain gauge setup carefully. If you're doing something like making a hook out of the ABS and the plate is acting as a lever arm, you need to make sure the lever arm length is the same every time, or your calibration will be wrong.

I thought it would be useful to add an image of my design (very slowly, thanks to Fusion 360 deciding right now was a good time to update itself!). I did a small test with an M3 bolt and nut. If, as you say, the shells and infill are adequate, I don't need a washer. I just need the hole tolerance to be tight enough that the nut won't slip into the hole. So an M3 bolt needs a 3.2mm hole (as printed) - I tried and I can't even begin to pull it through (by hand at least). As my load is 4kg max I think I can do without. Interestingly, I can flex the ABS at 4mm so that's suddenly more important!

@carveone it probably depends on your design more than anything else. My experience suggests that it's workable in many cases. My feeling from looking at your design is that it would work fine for the yellow part, and that the red part will have more trouble with the flat parts deforming than with the bolts coming out.

Luckily the red part is the metal strain gauge itself and deforming is what I'd like it do ;-)

There isn't any structural issue with having it allowed to rotate. If you were to print the part without the washer embedded and then put it on afterwards the washer would still be free to rotate. Friction from clamping would hold it in place.
Ideally you want your washer to be in contact with your nut to properly spread out the loading of the bolt compression to a larger area (the purpose of a washer). If you put the part between the nut and the washer then the washer is effectively acting as a spacer and your part is being loaded only where the nut contacts it.

If your nut will be exposed, you can simply insert it into the printed cavity and then seat it in place by heating it with a soldering iron.

That's my favorite way to fasten 3D printed parts, using metal threaded inserts from mcMaster or ebay and a soldering iron. Like this https://www.youtube.com/watch?v=nU06915NJ30