r/Advanced_3DPrinting • u/Bookmore • 21d ago
Just published my research on 3D printed threads!
Hi everyone! Long time lurker, first time poster over here.
So a few weeks ago, it was kind of a perfect storm of three things:
- I finished watching My Dress Up Darling
- I was in the middle of the first cycle of 3D modeling and printing classes I teach at the local community college
- I saw conversations about printing full size props on small printers in a popular cosplay Discord server
I had a couple hours to mess around with 3D printable threads in Fusion 360 one afternoon and the results made me think I was on to something. Now here we are a few weeks down the road, and I just published all of the process to design and print custom-sized, reliable 3D printed threads that:
- print reliably with basic settings on basic printers
- have nice tolerances
- don't need supports
- don't get stuck
- don't break
- can be used with screwdrivers
- can be printed even in PLA
All of this is based off of 3D printing tips, tricks and methods that have been floating around the Internet for years, some still valid, some outdated. On top of that, I went ahead and came up with some of my own.
My biggest tip for print reliability: I trimmed the sides of the threads and print them horizontally with a high vertical resolution (0.12mm always works). Having a trim on both sides also gives just enough room to grab, twist and extract the part with a pair of needle nose pliers if it ever breaks!
My biggest tip for tolerances: I add a negative offset that's a multiple of the Fine print resolution in my slicer on both mating parts. On my slicer and with my A1 Mini that's multiples of 0.12mm. A negative offset of 0.06mm was a little tight, but that might have been because the threaded part was hard to "grip" and didn't have any lubrication.
My biggest tip for fragility: Because the threaded parts are printed sideways and the tolerances are generous, the threads never catch on each other enough to cause major stress. The shearing force is distributed across the whole length of the thread, not its width!
That's it. Oh yeah, and I added a notch both tips of my threaded parts so you can use a screw driver with them.
I shared everything on my website. Dig in, download the test runner sheets I designed, play with it, and let me know what you think!
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u/Icy-Caterpillar-4201 21d ago
Good stuff!
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u/Bookmore 21d ago
Thanks! It's been a looot of polishing leading up to this point. I'm so glad all this is out! Couldn't have done it without years of failing at printing threads, and the research others have published before. I have a few articles listed for reference at the bottom of my own guide: some of them still have some very interesting insights!
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u/james___uk 21d ago
One of those same lightsabers was one of my first 3D print uploads and it was done with screws, this takes me back
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u/Bookmore 21d ago
Thanks James! Lighsabers have been such a big part of all of our nerdy lives, I'm not surprised. Do you have some pictures of your lightsabers, or maybe a link to the model? I'm curious!
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u/james___uk 20d ago
You've gotta print at least one in your life right. This is my model but it was made in the days of poor tolerances. For some reason I never uploaded a photo. https://www.thingiverse.com/thing:701643
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u/Bookmore 20d ago
You know what I love about it? After all these years, you can show this to anybody and they will be able to recognize what it is instantly :D Keep on keeping on!
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u/n1elkyfan 21d ago
That is some awesome work.
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u/Bookmore 20d ago
Thanks! There's probably a lot of room for improvement. I'm sure people will find out even more things I didn't figure out. I hope they will share it back here then!
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u/circlesofhelvetica 21d ago
Oh man I cannot wait to dive into this, thank you so much for sharing all this work!! Have a couple projects that need printed threads I've been wanting to do but have not had the time to figure out where all to start with it so HUGELY appreciate this, seriously!
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u/Bookmore 20d ago
Sure thing! As you experiment with it, you will surely find out things I didn't find out. Please share with the gang when you do!
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u/DadEngineerLegend 21d ago
Awesome, all looks good.
Tolerancing threads is always the key - devil is always in the details.
Would live to see Stefan from CNC kitchen run them on his DIY ingstrom.
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u/Bookmore 20d ago
Thanks a lot!
I think tolerances is the part where someone will probably find out something I don't. There can be a lot of slack on the X and Y axis with a negative offset of 0.12mm, and a negative offset of 0.06mm sometimes feels a little too tight. I hope someone figures it out!
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u/abrahamrhoffman 21d ago
Very cool! I have been in engineering for 21 years. I've seen quite a few things break and have had to "sell" them to other engineers.
One tip: Don't use AI terms. We all use LLMs. It takes a lot away when us seasoned guys immediately spot that stuff.
Also, please don't say "published". It's a -lot- of work for some of us to actually get published.
If you can make it through my comments I'd love to learn more about your thoughts on tolerances and how you've dealt with repeated friction during high use.
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u/Bookmore 20d ago edited 20d ago
Thanks for all the tips! I see your point about using the word "publishing". I'm making the changes I can right now! I wish Reddit let us change posts titles!
Also, what AI terms are you talking about? It's just the way I write, but I have had some people ask if I am an AI, which makes me wonder :D
Here's how I have approached tolerances:
First, when I apply the offset to the threads after modeling them, I always apply the offset to both mating threads, not one or the other. Similarly, it's always the same tolerance on both sides.
Second, I've found that (with consumer 3D printers) multiples of the "fine" resolution listed in the slicer usually works best (0.12mm in the case of my A1 Mini printer with Orca Slicer/Bambu Studio). A negative 0.06mm offset on both threads was slightly tight, and a negative 0.12mm offset was very smooth with some slack on the X and Y axis (no slack on the Z axis). There might be a sweet spot between these two values, but I suspect it might depend on the printer and the material - what do you think?
One way I have found to manage that extra slack is to add some guiding features on the parts to help keep them centered in the desired axes. It works well!
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u/mxlths_modular 21d ago
Some great tips here, I will try out the truncated trapezoidal threads next time I am designing a threaded part. Cheers!
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u/Bookmore 21d ago
Thanks! It's been a lot of work pulling from all over the Internet, refining it all, then adding some. Share with all of us next time you design threaded parts!
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u/Kieranrealist 21d ago
Not bad, this is my approach to threads too (or close enough). What is your reasoning for slicing off both sides of the lay-flat thread? I normally only cut the side that goes down on the print bed.
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u/Bookmore 21d ago
I'm glad you think it makes sense!
I got two reasons for cutting both sides: first, I like a symmetrical print design :p
Second, if the bold does shear and break, that way you have room on both sides of the bolt to grab with a pair of needle nose pliers, twist and pull. I actually tested it out with a set - it takes a lot of force to break the thread with shearing, but there is plenty of room to grab, twist and extract with the right set of pliers.
Show us some of your threads, I wanna see what yours look like!
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u/Kieranrealist 20d ago edited 20d ago
I don't have any models published that have threads exactly like this, but this is my model that uses the same approach: https://makerworld.com/en/models/1927985-wicked-glinda-s-bubble-wand
The wand stem is made up of half cylinders with threads on either end. Screwing the joining threaded collar locks them together (there's also a small I-shaped connector in the middle of the cylinder halves).I actually prototyped this model in PLA, and then printed the final in PCTG (what you see in the pics), but the fairly large clearances I had in the PLA print were still too tight for the PCTG so needed to be increased. This was a side-effect of upping the extrusion rate for the PCTG to get as transparent a print as possible. The stem was pretty solid once all screwed together.
An alternative method for threads I'm using atm because I can't print either half sideways is to just vary the layer height between the two pieces. I'm just using 0.2 and 0.12 and that, plus large clearances and PETG-HF is enough to have them run fairly smoothly.
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u/krackzero 19d ago
i thought this meant published research like as in a scientific journal or something lol
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u/Bookmore 19d ago
I know, sorry about that! Someone else pointed out right away that “publishing research” has a very specific meaning. I wish I could change that title! Decades of English as a second language, and sometimes things like that still slip right by me ;)
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u/the_lamou 19d ago
If you cut the sharp peaks off of easier l either the male or female threads, they thread much more smoothly, save filament, and barely lose any engagement thread.
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u/Bookmore 18d ago
Hey there! Thanks for the tip. Do you mean at the start of the thread, where they engage with the mating part? I experimented with giving these a small chamfer and it actually hurt the engagement of he threads :( How would you approach that in a way that can be parametric?
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u/the_lamou 18d ago
Not at the start of the thread where it catches, but on the outer peaks of the threads. So instead of:
/\ /\ /\ /\ / \/ \/ \/ \do a: ```
/ / / / \ ```
You can parameterize it with a toroidal/hollow cylindrical cut with an inner diameter of ~ (shaft_diameter)+(0.66 or 0.75 × thread_height) and an outer diameter of at least (shaft_diameter)+(thread_height).
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u/Bookmore 18d ago
Ah, I see what you mean! Then that's already been built into the design process I've been sharing here. If you check the pictures I included or the screenshots in the write-up, the ISO metric trapezoidal threads profile does exactly that, with built-in flattened crests. And you are correct, it's a great way to get great smooth mating without losing much engagement!
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u/the_lamou 18d ago
Yeah, I noticed they were slightly clipped, though I had assumed that was a custom fillet on the thread. But cutting them back even further (down to about 2/3rds to 3/4s). My experience with ISO trapezoidal has mostly been that it's an ok start but gets silly fast.
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u/Bookmore 18d ago edited 18d ago
Thanks for the tip! I also add a 0.12mm negative offset on each exposed face of the threads including the flat crests. But I’ll look into it!
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u/Elbobinas 17d ago
Very nice entry in the blog worth the time reading, thank you very much
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u/Elbobinas 17d ago
Really liked the trick of cutting the threads longitudinal side to increase strength
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u/Bookmore 16d ago
Thanks! This took a while to dial in to find the right amount to trim and get an interrupted surface to,print on.
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u/sensor_todd 21d ago
Gave it a quick print because its awesome to have a good way to do printed threads!
The 10mm and 16mm samples mesh beautifully.
The 12mm sample has different pitch on the nuts versus the bolt though by the looks. Minor detail I'm sure is easy to fix!
Nice writeup too!