Re: I made a bolt! (and a threading dial ;)


DJ Delorie
 

For anything that needs to take mechanical stress you should set it
to 100% in-fill.
I have trouble at 100% because any inaccuracy in the filament diameter
or print path causes an accumulation of bloat. 90% gives the print
some "breathing room". Other folks print in the 75-90% range for
strength parts.

But... this isn't a regular gear, this is a transposition gear. The
teeth are always 100% filled anyway, and most of the power is
transferred between the two rings of teeth, the shaft is "just" there
to keep it centered (unlike a metal gear, where the shaft/key
transfers all the power). So I need most of the strenth in the outer
portion of the gear, which is where there's the most plastic anyway.

The "failure mode" would be the two halves of the gear separating at a
print layer. If that happens, I'll design in some holes for pins or
something. My plan, though, is to print those key layers at 100%
infill.

Since your printer can print ABS, you should be able to adjust the
temperature to print nylon, which tends to have better layer adhesion.
I have some nylon but haven't tried it yet. ABS and nylon are at the
upper limit of the temperatures I can use so I don't know if it'll be
hot enough for a good print. I'll try it (and PLA, and maybe TGlase)
if the ABS gear breaks, but given that this is just to run the lead
screw, unless I make large pitch metric screws I don't think it will
be a problem. We'll see. For normal turning (power feed and imperial
threads) I can use the metal gears.

Google 3D printed gears and you'll find some folks who have printed
nylon gears for Atlas and 9x20 and some other lathes. On Thingiverse
there's at least one full set of Atlas change gear models to download.
On Thingiverse there's pretty much everything...

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