I can post the updated code if DonMilne is okay with that.
That's fine. There's nothing proprietary in what I sent you, I just made a few test calls to TrevM's library.
If OpenSCAD is displacing the threads outwards by 0.4mm then that would certainly explain why the body of my bolt now has threads protruding through. And if the threads are unsupported, then certainly that could cause blobby prints.
Oh, when when you talk about "achieving the same effect" by increasing the body diameter, I assume the effect aimed for was to obscure the threads. So in other words you're saying that this M6 thread actually has a diameter of 6.2mm? Houston, we have a problem! (unless he's trying to compensate for shrinkage?).
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Okay, so DonMilne sent me his original files, so I did some comparisons.
Using his settings from is gcode file, and slicing his original STL in Cura, the threads look like they would work.
Even regenerating the STL from the SCAD and slicing it seems to be correct. So definitely the older ISOThread_20120823 library works properly.
I then tried updating his origial Thread Test SCAD to use the new library. I can post the updated code if DonMilne is okay with that. Otherwise PM me. What I changed was the following:
This looks like my other previous failures. So I think the new library is the source of the issue, perhaps regardless of $fn value.
After this, looking really closely at the model in OpenSCAD, it seems that the old library puts the thread segments right against, touching, the shaft cylinder; but the new library leave a very small space. The threads are not actually touching the shaft! :(
I think that is the problem. I think that might also explain the seemingly wider threads that required the widening of the plain cylinder. I do not know if changed to $fn impacts or Cura's slicing here or not. Maybe higher $fn is fine, but the thread seperation from the shaft is the issue.
I don't yet know why the new library puts that extra space, but I think it is a mistake. I will look at it more closely tomorrow.
... I wonder maybe it is an incompatiblity with OpenSCAD 15.03, which I have, versus 14,xx. Hmm...
Anyway, this is what I have figured out so far. I hope it helps. I will continue this adventure tomorrow.
Thanks very much DonMilne for all your help. You rock!
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