Hi, I recently got great bipolar drives (4wires) and upgraded my fixed gantry router with 100oz-in unipolars motors (from 90oz-in unipolars) ran as bipolars serial and to 40v power supply (from 18v).
Now I reach rapids above 96IPM (from 36IPM) (on a MDF machine with roller blade bearings!) using ACME 1/2"-10 at quite nice accelerations. Repeatability with no load seems limit (+- 0.005) at this speed but I know that this is too fast for the actual motors. Just a max speed test. It must drop some steps here and there, but impact is limited since those are microsteps drives (10:1) so a step there is not much...
If I start engraving a picture at 60IPM, the table vibrate so much I had to lower my start speed and acceleration all around... down to 25IPM! At this speed, the engraving (0 degrees angle toolpath) does not go sideway. If I go above 30IPM, the picture left top corner end-up being between 5 and 30 degress to the left when starting at the lower left corner... So the top left corner end up at around y-0.25 or so after a few inches of X travel when engraving at 0.02 inch per line.
Now, I use a Pentium75 with TurboCNC on there. I don't seem to have a step problem but when running at hight speed, the motors are set with this config:
ACCEL: 22000
START SPEED: 2000
MAX SPEED: 24000
runing at 0.0005" per step.
Which may be WAY above what the PC can deliver and would cause the missed step problems when trying to move all axis to these speeds... I do understand you can jog 1 motor at 25khz but when all 3 try to go at 20khz this seems a bit too much for the pc... Or something's wrong?
I really need to make those 4 hours jobs faster, what are your tought on this?
I may have some stepper coupler slip because of the acceleration. Rubber hoses are fine but not on twisted shafts... To this end, I'll have to make bushings to slip and lock on the motor shafts THEN use the rubber hose. Diameter of the shaft is probably too small to handle the forces involved as well (a bit less than 1/4).
I understand a couple things there. My motors being plugged as bipolar serial are set at half amps on the drives to deal with inductance. The power supply should go to 70v pretty soon, as soon as I can find the appropriate transfo.
The motors are probably too weak OR I'm just driving em past their torque curve available at 40v OR I have coupler slip OR all of this...
Comments?
Note that I would'nt be there at all was'nt it for this board. Thanks guys...
Para