Success 3D printing Technic parts?

[aminnich]

I ordered a 3D printer this past week to experiment with on some other projects I have been working on.  I thought about printing Technic parts, but I figured the tight tolerance of the injection molding would be much higher than an additive approach of 3D printing.  I have read a bunch of the threads on here and watched videos on other people's experience with printing, but I do not seem to get a straight answer.  Is 3D printing Technic parts worth while??

I have read that axle holes do not print well and most of the time require some sanding or polishing to get the hole in size. @896gerard was clever to incorporate an official LEGO piece to supply the axle holes for his wheel sprocket.  https://www.eurobricks.com/forum/index.php?/forums/topic/172067-more-opinion-about-custom-3d-printed-technic-parts/  Has anyone had luck direct printing axle holes?

@efferman has an entire thread dedicated to custom parts and has them made by shapeways.  Does anyone know more about the process shapeways uses to print models?  Do you they classic printing, resin or other? 

For those of you that purchased from shapeways, were you happy with your parts?

For me, I have CAD software that I can model my own parts and I have a lot of experience with modeling.  I do not see that as an issue, I am just worried about the precision of the printing.  I ordered a Anycubic Chiron printer.  

If anyone has any advice or comments on the matter, please let me know. Thanks

 

[TechnicRCRacer]

I have two 3D printers (soon to be 3) and I have printed a few parts to experiment with. I tried Efferman’s 32 tooth gear in ABS plastic (do not recommend, dangerous fumes) and it didn’t require any post processing at all.

What you need to do in CAD is make every dimension slightly bigger (for my main printer I make every hole 0.1mm bigger). It depends on how you have your printer tuned. I tried 3L links and those were fine. I also made some helical gears and they mostly worked but were a little rough meshing.

One thing to keep in mind is that PLA plastic (the standard for 3D printing) scratches/deforms LEGO elements made of ABS to a small extent. I recommend Polymaker Polymax PLA due to its softer formula made for mechanical parts.

If something doesn’t fit right the first time, your sliver program will probably have a setting called “horizontal expansion”. It will make all holes slightly bigger or slightly smaller. Out of curiosity, what printer did you choose?

Good luck!

[All_About_Lego]

To answer one of your questions, I have successfully 3D printed my own Lego wheel designs multiple times - many of which have axle holes.

However, It is a pretty tricky process to get a perfect sized axle hole. You mentioned that you have experience using CAD, so I assume your familiar with tolerances and making designs slightly larger than they actually need to be.
The hardest part however is due to the nature of 3D printing, firstly, depending on the accuracy of the printer there is obviously a limit to how accurate your prints can be, it is also worth thinking about things like the thermal expansion - it is highly unlikely that the object you’ve printed is going to be the exact same size as the one you designed, as depending on the filament you’ve used the plastic will contract a certain amount when cooled - which usually means an axle won’t fit as you’d expect it too. 

Thermal expansion percentages can be calculated, but I usually print a ‘test axle hole’ (just a cylinder with an axle hole in it) a few times, adjusting the size of the design slightly every time it is printed until an axle fits perfectly.

Another thing to consider is seams - when the printer moves up a layer it often leaves a small ‘blob’ of filament visible from the outside of the print, these are known as seams. Seams can be a nightmare on the inside of axle holes as it will block an axle from sliding in, so make sure these are reduced or located elsewhere on the part if possible.

There is a lot of trial and error involved, but once you’ve perfected it you can definitely successfully (and repeatedly) print axle holes!

Also, are you planning on printing custom parts, or just copies of existing ones?

[aminnich]

8 minutes ago, TechnicRCRacer said:

I have two 3D printers (soon to be 3) and I have printed a few parts to experiment with. I tried Efferman’s 32 tooth gear in ABS plastic (do not recommend, dangerous fumes) and it didn’t require any post processing at all.

What you need to do in CAD is make every dimension slightly bigger (for my main printer I make every hole 0.1mm bigger). It depends on how you have your printer tuned. I tried 3L links and those were fine. I also made some helical gears and they mostly worked but were a little rough meshing.

One thing to keep in mind is that PLA plastic (the standard for 3D printing) scratches/deforms LEGO elements made of ABS to a small extent. I recommend Polymaker Polymax PLA due to its softer formula made for mechanical parts.

If something doesn’t fit right the first time, your sliver program will probably have a setting called “horizontal expansion”. It will make all holes slightly bigger or slightly smaller. Out of curiosity, what printer did you choose?

Good luck!

Thanks for the advice.  I knew that LEGO is made with ABS and the fumes are not something to mess with.  I was also looking into PETG because of its strength, but I am worried about it's possible lack of flexibility. Something to try out I guess.  The printer I ordered is an Anycubic Chiron. I will give the Polymaker filament a try, thanks for the suggestion. 

I read a little bit about the horizontal expansion.  I will need to look further into it to really get a feel for it.  

Thanks for all the helpful tips!

7 minutes ago, All_About_Lego said:

To answer one of your questions, I have successfully 3D printed my own Lego wheel designs multiple times - many of which have axle holes.

However, It is a pretty tricky process to get a perfect sized axle hole. You mentioned that you have experience using CAD, so I assume your familiar with tolerances and making designs slightly larger than they actually need to be.
The hardest part however is due to the nature of 3D printing, firstly, depending on the accuracy of the printer there is obviously a limit to how accurate your prints can be, it is also worth thinking about things like the thermal expansion - it is highly unlikely that the object you’ve printed is going to be the exact same size as the one you designed, as depending on the filament you’ve used the plastic will contract a certain amount when cooled - which usually means an axle won’t fit as you’d expect it too. 

Thermal expansion percentages can be calculated, but I usually print a ‘test axle hole’ (just a cylinder with an axle hole in it) a few times, adjusting the size of the design slightly every time it is printed until an axle fits perfectly.

Another thing to consider is seams - when the printer moves up a layer it often leaves a small ‘blob’ of filament visible from the outside of the print, these are known as seams. Seams can be a nightmare on the inside of axle holes as it will block an axle from sliding in, so make sure these are reduced or located elsewhere on the part if possible.

There is a lot of trial and error involved, but once you’ve perfected it you can definitely successfully (and repeatedly) print axle holes!

Also, are you planning on printing custom parts, or just copies of existing ones?

I am glad to see printing holes is not a huge issue, just takes some trial and error to get right.  Also nice to see once you get it dialed in, repeatability is there. 

I use CAD for my work and work closely with the machine shop.  I know all about tolerances and such.  I figured machining tolerances are going to be a bit different than on a 3D printer, so I was planning on making my own chart for reference.  This would be specifically for my printer, which by the way is a Anycubic Chiron.  It has a print accuracy of 0.05-0.3 mm with a 0.4mm nozzle head.  I may change that to a smaller nozzle if I get into higher precision stuff. 

How do you reduce the number of seams for a hole?  I would think the number of seams is minimized by the number of layers, not?

This printer would be used specifically for custom parts.  I do not see any reason to print existing parts when bricklink.com is a thing haha 

[TechnicRCRacer]

15 minutes ago, aminnich said:

It has a print accuracy of 0.05-0.3 mm with a 0.4mm nozzle head.

Remember that “print accuracy” in this case means vertical layer height, not tolerances. My new printer will come in January and I will be putting a 0.25mm nozzle on it. I will let you know how it goes!

I haven’t found a great way to minimize the Z-seam. You can see it in your slicer program under the “layers” view mode. It usually aligns with the sharpest corner, or you can set it to other settings like “randomize” if you want blobs all over your print  If you tune your retraction settings properly, the Z-seam should not be a problem.

[Josephiah]

We have a couple of Prusa i3 filament printers at work (used a lot for several years), and a new SL1 resin printer (not used much yet).

I haven't tried doing technic parts - as you say, the tolerances will be a challenge. I have had reasonable success with printing Duplo parts (well, actually, adaptor pieces from Duplo to Brio train tracks - worked really nicely with a bit of trial and error). I don't know if you might want to try a finer nozzle than the 0.4mm one many printers come with by default?

Don't bother with ABS (it's ubiquity in the 3d printing world was largely a matter of just being there first) - PETG is my go-to material at the moment - it's stronger than PLA, and less brittle - it has a bit of flex to it. Friends recommend ASA as well, though I haven't tried it myself.

One of the biggest challenges with 3d printing is getting the directionality right for any given part - you really have to think through what direction the stresses will be going through the part - if the forces on it are in a direction that makes the layers want to separate, then consider printing in with the layers in a different direction. And sometimes the best solution for a particular part is to print in two halves (to get a nice flat plane to put on the printed) then glue together. With a bit of trial and error you can even peg/glue parts together with short pieces of raw filament.

My limited experience with resin printing so far suggests great surface finish, detail and appearance, but with a tendency to sag/warp in the printer if not supported well enough (so we've often found the dimensional accuracy worse than our filament printers), and the materials tend to be a little more brittle.

In terms of the mail-order services, we've had good results from Materialise (both the full on commercial (expensive!) service for work, and the more accessibly-priced consumer version); haven't tried Shapeways, so would be interested to hear people's impressions.

Have fun experimenting - will be interested to see how you get on.

[All_About_Lego]

1 hour ago, aminnich said:

 

How do you reduce the number of seams for a hole?  I would think the number of seams is minimized by the number of layers, not?

 

The best way to reduce seams is to play around with retraction settings when performing a layer change (i.e. the speed and distance of a retraction move), the 'blobs' which cause the seams are due to a pressure build up inside the nozzle caused from the extruder pushing out filament during printing, which then forces excess plastic out of the nozzle each layer change (as the print head is not moving this plastic has no where else to go).

By changing these settings, you can minimise seams - but it is pretty hard to completely remove them, so I would still suggest that the best thing to do is ensure that the seam is positioned somewhere else on the part so that it doesn't effect any axle holes - there is usually a setting in your slicing software called 'seam position' which should help.

Your chart idea sounds like a good plan by the way!

And yes, that's what I was going to say - there is no point printing non-custom parts

O

[aminnich]

4 hours ago, TechnicRCRacer said:

Remember that “print accuracy” in this case means vertical layer height, not tolerances. My new printer will come in January and I will be putting a 0.25mm nozzle on it. I will let you know how it goes!

I haven’t found a great way to minimize the Z-seam. You can see it in your slicer program under the “layers” view mode. It usually aligns with the sharpest corner, or you can set it to other settings like “randomize” if you want blobs all over your print  If you tune your retraction settings properly, the Z-seam should not be a problem.

So printers dont supply a print tolerance?  That sucks.  Would be nice to know that for modeling a component. Ya well 

4 hours ago, Josephiah said:

We have a couple of Prusa i3 filament printers at work (used a lot for several years), and a new SL1 resin printer (not used much yet).

I haven't tried doing technic parts - as you say, the tolerances will be a challenge. I have had reasonable success with printing Duplo parts (well, actually, adaptor pieces from Duplo to Brio train tracks - worked really nicely with a bit of trial and error). I don't know if you might want to try a finer nozzle than the 0.4mm one many printers come with by default?

Don't bother with ABS (it's ubiquity in the 3d printing world was largely a matter of just being there first) - PETG is my go-to material at the moment - it's stronger than PLA, and less brittle - it has a bit of flex to it. Friends recommend ASA as well, though I haven't tried it myself.

One of the biggest challenges with 3d printing is getting the directionality right for any given part - you really have to think through what direction the stresses will be going through the part - if the forces on it are in a direction that makes the layers want to separate, then consider printing in with the layers in a different direction. And sometimes the best solution for a particular part is to print in two halves (to get a nice flat plane to put on the printed) then glue together. With a bit of trial and error you can even peg/glue parts together with short pieces of raw filament.

My limited experience with resin printing so far suggests great surface finish, detail and appearance, but with a tendency to sag/warp in the printer if not supported well enough (so we've often found the dimensional accuracy worse than our filament printers), and the materials tend to be a little more brittle.

In terms of the mail-order services, we've had good results from Materialise (both the full on commercial (expensive!) service for work, and the more accessibly-priced consumer version); haven't tried Shapeways, so would be interested to hear people's impressions.

Have fun experimenting - will be interested to see how you get on.

I had looked at resin printers, but I read that they smell awful and did not want that in my house haha.

I am hoping that I do not need to print my models in half and glue together, that sounds like it could be a challenge to get right.  

Thanks for the tips!

3 hours ago, All_About_Lego said:

The best way to reduce seams is to play around with retraction settings when performing a layer change (i.e. the speed and distance of a retraction move), the 'blobs' which cause the seams are due to a pressure build up inside the nozzle caused from the extruder pushing out filament during printing, which then forces excess plastic out of the nozzle each layer change (as the print head is not moving this plastic has no where else to go).

By changing these settings, you can minimise seams - but it is pretty hard to completely remove them, so I would still suggest that the best thing to do is ensure that the seam is positioned somewhere else on the part so that it doesn't effect any axle holes - there is usually a setting in your slicing software called 'seam position' which should help.

Your chart idea sounds like a good plan by the way!

And yes, that's what I was going to say - there is no point printing non-custom parts

O

I wonder if there is a way to reduce that pressure when a layer is done being printed?  Would reduce the amount of "blob" and help reduce the seam buildup.  I will for sure look into moving the seam to a desired location when starting to print. Thanks!

[dr_spock]

I can get usable parts out of my cheapy kit printer like PU and PF connectors to make adapter cables.

I print ABS in the bathroom.  The bathroom's exhaust fan vents the ABS fumes to outside.  Acetone vapour smoothing can be used on ABS prints.

You can also play with the scaling function in your 3D printer slicer program to get the print to the right size. It's a lot of trial and error.  Have fun.

[TechnicRCRacer]

2 hours ago, aminnich said:

So printers dont supply a print tolerance?

Nope, but it can be improved in your settings. When you get the printer, consider this test model which will determine how dimensionally accurate your printer is with current settings.

[Bartybum]

I absolutely recommend FDM 3D printing Lego (assuming you already have a 3D printer; don’t buy one with the sole purpose of printing Lego). If there’s an expensive piece you’re looking for, such as a rotary catch, it’s often much more economical to just design and print one.

I’m currently printing custom rims for Technic cars and it’s totally fine.

It can be hard finding the right orientation in which to print stuff though

[All_About_Lego]

11 hours ago, aminnich said:

I wonder if there is a way to reduce that pressure when a layer is done being printed?  Would reduce the amount of "blob" and help reduce the seam buildup.  I will for sure look into moving the seam to a desired location when starting to print. Thanks!

This is actually one of the reasons retraction is used, the extruder motor pulls back some of the filament out of the nozzle, hence reducing the pressure inside the nozzle, but it is still pretty tricky to get a ‘seamless’ print, especially as you don’t want too much retraction which will likely give you other printing problems!

Good luck! And have fun experimenting

[Bartybum]

4 minutes ago, All_About_Lego said:

This is actually one of the reasons retraction is used

Retraction doesn't solve the issue entirely. I'm pretty sure coasting was actually the solution developed to tackle this, although it's a difficult thing to do. An alternate method is available through some slicers, for example Cura, which allow you to choose to begin layers at a sharpest point, so for pinholes you can artificially introduce a sharp corner/notch somewhere in the geometry to force the walls to begin there.

[All_About_Lego]

43 minutes ago, Bartybum said:

Retraction doesn't solve the issue entirely. I'm pretty sure coasting was actually the solution developed to tackle this, although it's a difficult thing to do.

You're right - as I said retraction alone is unlikely to give a 'seamless print', coasting was developed to solve this by simply moving the print head by X amount without actually pushing any more filament through the extruder. The build up of pressure is enough to force excess filament out onto the print.

However, I'm not sure if you've experienced the same, but I've never really had much luck with coasting - I found it to be unreliable and it caused too many issues elsewhere in prints to justify using it.

[Bartybum]

2 minutes ago, All_About_Lego said:

However, I'm not sure if you've experienced the same, but I've never really had much luck with coasting - I found it to be unreliable and it caused too many issues elsewhere in prints to justify using it.

I tried it once on a large shell-style print and it was awful; I assume there's some manner of tuning that needs to be done, because I sure as hell just enabled it and let it go

[All_About_Lego]

Just now, Bartybum said:

it was awful; I assume there's some manner of tuning that needs to be done, because I sure as hell just enabled it and let it go

It doesn't hurt to just press 'print' and see what happens!

There is some tuning that can be done - but as you said previously, its still pretty hard to master it!

[TechnicRCRacer]

I used advanced retraction settings to practically eliminate the blob. Cura has a “retraction extra prime amount” hidden in the settings panel that changes whether the retraction extrudes further or shorter after it retracts. Works for me!

[aminnich]

Looks like I have a lot of settings to mess around with when the printer is delivered.  I better schedule a week off from work so I have time to dial in the machine 

[ixodie]

Following...

 

[aminnich]

So I bought the printer in March and decided to mess with printing custom-ish LEGO this past week.  I printed part number 6571 without the extra ball joint.  I modeled it in SolidWorks and printed on my Prusa MK3s+ using Hatchbox filament.  After printing a batch of 20 "good" parts... I found a mistake and will be reprinting.  

    

[2GodBDGlory]

For a while I've thought to myself that someday it would be nice to get a 3D printer for a variety of purposes, like printing Lego, printing parts for generic things I'm trying to fix, or other trinkets, but I always figured I would wait until the technology got cheaper/better. On a whim I started looking at articles on "best budget 3D printers," and was surprised by how cheap they have gotten. I have been looking at this very cheap ($159 USD, https://www.amazon.com/Voxelab-Removable-Printing-Function-8-66x8-66x9-84in/dp/B08SPXYND4/ref=sr_1_3?dchild=1&keywords=Voxelab+Aquila&qid=1635789034&sr=8-3) one that was recommended in these articles as a good (or at least decent) entry-level printer. Do any of you with some experience 3D printing know if this machine would have tolerable precision for printing Technic parts? Maybe for that I'd have to step up to something above this bargain basement printer, but I'm cheap and don't really need one, so I'm not really interested in getting anything much more expensive.

[aminnich]

I have no experience with the cheap 3D printers on the market today. I have read some good reviews about them, but I have no idea what kind of print tolerance it gives. 
 

Mine is a mid grade printer, cost about $850. It prints really nice, but it did struggle on the small LEGO stuff. I have to mess with the program and settings to try for a better print in the future. 
 

If you are looking to print really high tolerance parts, I don’t know that I would recommend a cheap printer. 

[TechnicRCRacer]

@2GodBDGloryMy $400 Prusa Mini can create usable Technic parts. Prusa’s machines, quality control, and customer service are FANTASTIC. For parts with thin details like tow balls, printing will be very difficult no matter what printer you buy. Parts like beams and gears work well. I was able to print a differential I found online and it worked fine.

[2GodBDGlory]

Thanks for the feedback, guys! I'm probably not looking for stuff with great tolerances; I just want to print basic stuff that is usable. (Like the mythic 32T gear!)

I'm not sure yet what I'll do, but I appreciate your advice.

[dr_spock]

That Voxelab has a heated bed.  It should be able to print ABS.  Although, you may have to make or get an enclosure for it if you have issues with ABS warping. 

I bought a $200CAD kit printer a few years ago. With some tuning and mods it can print decent custom LEGO parts like PU connectors and train wheels. I think the lower the price, the more effort you'll have to put into it.  But once I have it dialed in, it works great.

For tiny detailed parts, a SLA resin printer would produce in finer resolution than a FFM printer.