Thanks everybody for the suggestions.
Here is an update.
I got this info from the motor supplier:
" If you could increase your power supply to 28V that will help also. But the easiest thing is to reconfigure the stepper motor wires for center tap to end. This cuts the inductance by a factor of 4 increasing the speed. I would kick the xylotex board up to 2.5A
connect red to A
connect red/white to A#
connect black to B
connect black/white to B#
insulate the ends of the remaining wires but do not connect them to anything"
I tried this and was able to increase my speed from 12" per minute to 32" per minute and still get good torque. I am looking for a 28v/30v power supply as that would give me 15% more voltage.
Xylotex send me a similar response:
" Your motors have a very high inductance. This is the reason they
can be so powerful, yet only require 2 Amps. The problem you are
seeing is due to the time it takes to charge the coils in your
motor. The pulse width really isn't changing anything, except it is
allowing more time for the coils to charge. It thus makes it so you
can't step as fast.
The opitmal (maximum) motor size (torque vs. inductance) for the
Xylotex drive is around 250 oz.in. at around 2.3A to 2.7A per
phase. Higher torque at similar current will require more time to
charge, or a higher voltage.
Although only 2Amps, the inductance of your motor needs a voltage
around 40 to 60VDC to be effective (Gecko territory). You will get
the full rated *holding* torque with the drive, but as step rate
increases, torque drops. This isn't a problem with my drive (other
than not handling 60VDC), it's really a matter of physics."
The interesting point here is the recommend motor size of 250 ox-in max. for good speed performance. That's important to know when developing a DIY machine, (matching components for optimal performance.)
Marvin, thanks for your practical advise. Ignoring the issues with the larger motors, I was jogging and moving my machine at over 100" per minute with the 116oz-in motors no problem, but when I ran a program with lots of little steps I would see a definite loss of steps. I'll experiment some more before I switch over to the big motors entirely.
Trent  |