Hobbed Gear Sizing
The hobbed gears on my common extruder shaft of the MMU were not the same size, measuring their diameter at the thinnest point, I found I was introducing a 4% error in the feeding length, at 40 cm that's about 1.6 cm, and it was enough to keep two colors from working.
Diameter % error avg %error #C %error #B %error #A %error #D %error #E
A 6.15 1.85 2.84 1.15 0.00 4.41 0.99
B 6.08 0.70 1.67 0.00 1.14 3.23 0.16
C 5.98 0.96 0.00 1.64 2.76 1.53 1.81
D 5.89 2.45 1.51 3.13 4.23 0.00 3.28
E 6.09 0.86 1.84 0.16 0.98 3.40 0.00
avg 6.038 1.36 1.57 1.22 1.82 2.51 1.25
2.84 3.13 4.23 4.41 3.28
I've since rearranged the gears, selecting the 'most average' and picking for the smallest pairwise error. I believe I've gotten my error down to 2.8%, which is still kinda high - over a cm of difference. I could check the gear in my extruder but it's unclear if it would help, the error is still >1cm.
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Re: Hobbed Gear Sizing
Hmm, for retractions, could this be overcome by the FINDA?
ie, it tries to retract 41.6 cm due to error, but stops at 38cm because FINDA detects end of tip, then it retracts the final 5cm (or whatever length), where the 4% error would be less important?
For feeds into extruder, tries to feed 40cm, but falls short at 38.4 due to % error. As long as it reaches extruder gears, I would GUESS it wouldn't mater too much? Or would that 1.6cm error still be too short to reach extruder gears? Even if its short, the wipe tower would absorb any error... maybe?
Sorry if it sounds silly. This is pure speculation from a printing noob. So I'm not sure.
Re: Hobbed Gear Sizing
I like the idea of active control, but I'm not sure how you get there.
Perhaps you could watch the current on the lower bondtech's, and when you're driving them with the upper motor shoving filament through, have them take over.
My problem is on loading. Right now I have tip issues, and a tip cutter every pass sounds like a good idea, but I'm hoping it's something I can dial out.
I maintain an informal list of San Diego, CA 3D printing enthusiasts. PM me for details. If you include a contact email and I can add you to the informal mailing list.