Tuesday, May 16, 2006


Godzilla vs the Siemens gearmotor...

I sometimes wonder where innovation would have got in the past forty years without duct tape. I did a quick lashup of the Siemens gearmotor (designed for automobile electric windows) to the horizontal z-axis on Godzilla and fed it 12v dc.

The Siemens gearmotor cranks 57,600 gm-cm of design torque vs the NEMA 17's 3,240. While I was having to constantly adjust the z-axis positioning stage with the NEMA stepper to get it to work at all, it was all that I could do to keep the thrust rod from unscrewing itself from the positioning stage with the Siemens motor running using about the same amount of current.

The "load" of the positioning stage, such as it is, made no difference to the design spec'ed 55 rpm for the motor at 12v. That motor speed gives me, 0.87 rps on the z-axis positioning stage, about what we're currently getting with the NEMA 17.

It seems kind of silly to gear the Siemens motor down to 55 rpm and then gear it back up to maybe 12-1400 rpm so that I can push that threaded drive rod at 15-20 cm/sec, but hey... these motors are cheap, efficient and tough. :-)

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