Originally Posted by amishx64  Can't you just connect the motors in series or parallel? That's what I'd do. Then you wouldn't have any controller discrepancies, and you could run both just as you were running only one. |
It is absolutely BAD to connect the motors together electrically!
If you want to use two motors, do as ger21 said, sync them via the software.
My point was two motors synced isn't the optimum for high speed rapids. And it's both a mechanical issue as well as an electrical issue.
Mechanically:
I like to use extremes sometimes to make a point. Consider one screw is 10 tpi, the other is 11 tpi, they wont travel very far without binding. Now lets get more practice, realize that all screws have tolerances, one maybe 10.001 tpi, the other might be 9.998 tpi, then factor in that they aren't necessarily linear, one maybe 10.002 for the first foot, then 9.998 the next foot, and the other is opposite in non linearity. What you wind up with is along the length of the travel, mechanical inefficiency. As long as you have plenty of power, it's not a big deal. BUT steppers loose power significantly as you go up in rpm's. This mechanical inefficiency becomes an issue.
Electrically:
The step sequence of two different controllers isn't an issue, they will be precisely in sync. BUT, motors aren't mechanically perfect. One may move 1.82degrees for a given step the other 1.79 degrees for a given step, so they basically fight each other. At low rpm's it's not an issue, but as rpm's increase it becomes more of an issue. NOW add on to that the fact that steppers naturally resonate. The specific resonance points vary based on motor, rpm and drive methodology. Regardless of wether you have resonance compensation or not, they will fight each other some. Again at lower rpm's it isn't an issue.
Bottom line, as you go up in motor rpms two sync'd motors won't behave as well as one motor.
The question was
which is the best, not wether two motor would or wouldn't work. Two motors do work when synced via software, and work very well.
Last point is biggest bang for the buck:
One G203V is $150 one motor is $40, one good screw is $40 one good nut is $20 Total = $250
Two axis of a G540 is $145, two motors are $80, two good screws are $80 two good nuts are $40 = $345 not including the cost of a bigger power supply, extra coupler and asundry parts.
And the G203V with the one motor will win the rapids race.
BUT, if your mechanical arrangement is prone to racking, THEN you are better off with two motors.