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Geared stepper? Torque, resolution, heat, etc

Posted by 3dp_dude 
Geared stepper? Torque, resolution, heat, etc
June 10, 2011 10:02AM
Hi all,

We (myself and a few high-schoolers) are building an extruder of our own design, but using design ideas from Mendel and others. Thinking we can simplify the build if we use a geared stepper such as this Kysan geared stepper. However, I need to know if this will work...

Torque: Stated as 210mN.m, which translates to 29.7 oz-in, which is apparently at the motor, so with the 10:1 gear ratio, that's 297 oz-in at the output shaft (that the filament sees). This is much higher than Adrian's extruder at 107 oz-in, or Wade's at 244 oz-in. For the latter two, I'm calculating based on the specified gear ratios.

Speed: The 10:1 gear ratio is slower than others, but no where have I seen that motor speed is an issue.

Heat: By eliminating the gears, we plan to knurl the end of the output shaft, and with the metal gears and housing wondering if heat would be an issue where it touches the filament? We will probably have a fan to help cool the upper part of the extruder (filament feed, etc).

Drop size: Using 3mm filament, the 10:1 gear ratio and 0.9-deg steps will mean finer steps, so that's 0.444mm3, before any microstepping. Using 1/8 microstepping, that's about 0.056 mm3 per "drop".

Any thoughts on these, or any other thing we need to be concerned about? We have drivers to support this.

Re: Geared stepper? Torque, resolution, heat, etc
June 10, 2011 10:33AM
Well, you aren't eliminating the gears, but replacing replicated parts with industry manufactured ones. I think the chances this will work are good, even if this isn't an advantage in the sense of the Rep-licating Rap-id prototyper.

Generation 7 Electronics Teacup Firmware RepRap DIY
Re: Geared stepper? Torque, resolution, heat, etc
June 10, 2011 11:20AM
Ha ha... never really saw the point in replicating itself, especially when ours is made of metal. Being able to make parts for other things is where it's at. This is ours, btw...
2-axis test

BTW, also just found this motor, which has 5.18:1 gear ratio instead...
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