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Hacking the Solarbotics GM2

Posted by Forrest Higgs 
Hacking the Solarbotics GM2
April 04, 2007 11:12AM
For those of you who are using Solarbotics gearmotors coupled with shaft encoders to power their xyz axes Solarbotics has published a hack on their GM2 that may be of interest to you.


The big problem with both steppers and gearmotors driving threaded rod-driven axes is that the motor speeds tend to be rather low which translates out as very slow traverse speeds on the axes and very low print productivity. The GM2 would ordinarily run at about 38 rpm. The hack changes the 224:1 gear ratio to 14:1. That gives you about 530 rpm. Using a 3/8-16 threaded rod that gives you a top traverse speed of about 15 mm/sec. Using metric studding with a pitch of 1 turn/mm that gives you a top traverse speed of about 8 mm/sec.

What remains to be seen is whether there is enough torque to run an axis at that much higher speed. As well, assuming that there is enough torque there is the question of just how much friction will reduce that top theoretical speed.

All the same, this is good news. I intend to buy a few GM2's and try them out in this mode in the next month or two. If they don't provide the needed torque I can always use them to drive extruders.

Edited 1 time(s). Last edit at 04/04/2007 11:13AM by Forrest Higgs.
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