Threads In FORM 3

Hello everyone!

Im facing a problem with printing my threads, I use a FORM3 and at this moment I´m printing using clear resine. As I suppose, when we buy a new printer we all run into the same problem with the threads, the females are smaller than it should, and the males are bigger.

I´ve been reading some post and articles in which the people share their experiencies or solutions to this problems, but I´m not not getting to solve the problem with the advice they give.

How have you solved this problem?
Until I solve the problem, the impressions will not be functional since the threads are essential for me.

I use solid edge 2021 to create my designs and I tried to use some tools to modificate the sketchess, such as project a sketch or similar.

Thank you all for your time and help!

Hello @IMOPAC ,

Threads are particularly challenging for SLA printing due to the overhang risk and the amount of touchpoints needed to adequately support these overhanging pieces as they print; as such, we recently updated one of our articles about designing threaded parts for SLA. This should hopefully contain some information that will assist in your future endeavors; best of luck!

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@IMOPAC The Form printers are pretty susceptible to… I don’t know what the proper word is here… but I call it blooming. Imagine the laser is tracing the proper path of your thread, but the laser itself has a thickness to it. The laser is ultimately going to cure a little bit outside of the line, like tracing a fine line with a crayon. This makes it incredibly challenging to create mating parts. I don’t know solid edge, but try reducing the tolerances of the thread so they appear like a really sloppy fit in CAD, but when printed, they should be ok. If both parts are 3D printed, it may be easier to keep either the male thread or the female thread fixed so you only need to adjust one at a time. The other thing you could try is to print nominally, but before curing, chase the thread with a metal nut and/or screw to open them up. The print should still be soft enough to shave off the excess - but this is also assuming you’re printing nominal threads.

Also, you can’t just shrink the part by x% because you would also be shrinking the pitch as well, you have to reduce just the tolerance/XY dimension. Once you get that dialed in, it should be pretty consistent across prints in the same resin. Though this “blooming” effect is different on any given resin, so you’ll have to calibrate for each material. I with Formlabs would give us an option in preform to adjust the laser offset so we didn’t have to go back and make all of these changes in CAD.

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I’ll be following this “thread” with interest!

All of our parts have threaded features on them that have to mate with other parts, some printed some not. What I have been experimenting with is modeling the flanks of the thread closer together so as the create more clearance between them. I usually model the female thread to its nominal diameter and then make the diameter of the male one about 1-1.5% smaller.

The orientation of the print makes a big difference also. Having the threaded feature parallel withe the build plate will give the best “roundness” but the flanks that face the build platform will suffer from bulging/sag, thus the extra clearance required. Having the feature normal to the build plate will give better thread geometry but the roundness will suffer and may require greater diametrical clearance.

Location of the supports is our greatest issue that we’re having. Putting them on the crests is best for post-processing but it’s a laborious process to do. And it’s impossible to control the opposite end of the support in Preform. We’re experimenting with Fusion 360 to build supports.

Hope this helps, I’ll post some images when I’m back at work.

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Ive had some success designing threads with “flats” on either side. If you looked at injection molded parts, the threads using have a flat spot near the parting line. you can kind of use this technique to keep the threads orientated the best way, and then the flats get the support material.

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