Need help with printing tiny parts

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Toby
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Re: Need help with printing tiny parts

Post by Toby » Sun Jun 08, 2014 5:25 am

Amazingly, the gear printed even better than my larger test case:
gear7mm.JPG
gear7mm.JPG (40.62 KiB) Viewed 3278 times
The ruler marks at the bottom are in mm, so the diameter is about 6 mm, and each tooth is under a mm.

I seem to remember little gears like that from some kit or other when I was a kid. Looks and feels exactly like them.

Edit: I just realized, you said the gear was 7mm across, and it shows up as 6 3/4 in S3D, but as printed it really is under 6 mm. That suggests it might be helpful to scale it up by 10% or so in X and Y before printing.

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Tim
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Re: Need help with printing tiny parts

Post by Tim » Sun Jun 08, 2014 2:57 pm

That's so small that every movement of the machine counts---for instance, the seam at the right side makes one gear tooth significantly larger than the others. But then the piece is so small that the total number of instructions in the gcode is small enough that the gcode can be tweaked by hand. It's one thing to say that the gear looks nice, but it's quite another thing to put it on an axle and try to reliably engage another gear with it.

Toby
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Re: Need help with printing tiny parts

Post by Toby » Sun Jun 08, 2014 6:30 pm

Tim, I see your point. I hadn't noticed that bulge. Unfortunately I don't have the mechanical intuition to know if it would work as a gear or not.

I tweaked the settings a bit in an attempt to improve it. I tried to trick the nozzle into behaving like a smaller one by setting the nozzle diameter to .25 and the extrusion width to .25. Also, I turned on random start points for the perimeter. Here's what I got:
gearTweak.1.JPG
gearTweak.1.JPG (21.17 KiB) Viewed 3268 times
This is 10x actual size. I scaled the original model by 5% trying to compensate for whatever was making it print smaller. This one came out about .5mm shy, which I think is mostly just missing tips of the teeth.

The gear is too small to test by hand, but rotating two of my slightly larger gears against each other they appear to mesh well:
gearTweak.2.JPG
gearTweak.2.JPG (23.06 KiB) Viewed 3268 times
Attached is the latest .factory file, which includes my test gear, the scaled 7mm gear, and the new settings for PLA.
Attachments
gearTweak.zip
(14.87 KiB) Downloaded 130 times

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boxermegan
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Re: Need help with printing tiny parts

Post by boxermegan » Sun Jun 08, 2014 7:27 pm

That looks great Toby. Can't wait to try it. Ultimately, I am going to buy a 0.25 nozzle for this.

The epoxy worked for the extruder mount, but now the electronics case fan won't come on. :(
I was able to print a new extruder mount in ABS though by using an external fan blowing on the electronics case. I realized that this problem with the mount has gotten progressively worse. The print came out so clean and straight with no pitting or defects. Just like when the printer was new. It happened slowly enough that I didn't notice it until it cracked all the way through. Now I know what to watch out for.

megan

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