Re: [CAD_CAM_EDM_DRO] Re: Max feedrate

On Tuesday 18 February 2003 09:38, CL wrote:

> I am pretty convinced that I would have a hard time watching a
> machine like a Sherline conduct rapids at 30ipm or so ( someone tell me
> what they do hit ).... I think I would bolt the thing down, and shoot
> for 100ipm with larger motors and Faster screws. You could certainly get
> close, if your target resolution was kept in the neighborhood of .0005,
> instead of what they must be getting with those fine screws and 10
> microstep drivers.

I actually did some tests of this very thing the other day. I tried to
determine the maximum feedrate of a Sherline 5400 Mill's X axis, powered by a
Sherline provided stepper motor (http://www.sherline.com/67127pg.htm). The
motor was mounted direct drive (naturally), and the acceleration setting was
(IIRC) 0.5 inches/second/second. I determined the maximum reliable feedrate
by jogging the axis back and forth repeatedly at increasing feedrates until
the motor stalled. I then backed off the feedrate until the axis would jog
repeatedly (maybe 20 times) without stalling (although I could certainly have
lost a step or two without noticing). For a real machine I'd test with a dial
indicator and derate these figues by 5%-20%. All tests were done with the
drives in half-step mode, and with idle current limiting enabled.

Drive: Microkinetics Unodrive
Motor Hookup: Full Coil
Power Supply Voltage: 40Vdc
Drive Current Setting: 1.6A
Absolute Max Reliable Feedrate: 13IPM
Motor Temperature: Cool
Notes:

Drive: Microkinetics Unodrive
Motor Hookup: Half Coil
Power Supply Voltage: 40Vdc
Drive Current Setting: 1.6A (that's the max for this drive)
Absolute Max Reliable Feedrate: 12IPM
Motor Temperature: Lukewarm
Notes: Much less holding torque than full coil.

Drive: Geckodrive G210
Motor Hookup: Full Coil
Power Supply Voltage: 75Vdc
Drive Current Setting: 1.0A
Absolute Max Reliable Feedrate: 21IPM
Motor Temperature: Hot
Notes:

Drive: Geckodrive G210
Motor Hookup: Half Coil
Power Supply Voltage: 75Vdc
Drive Current Setting: 2.0A
Absolute Max Reliable Feedrate: 30IPM
Motor Temperature: Hotter 'n ____
Notes: PWM frequency audible.

I'd love to hear more results. Here's a handy form for reporting them:

Machine: <make_and_model>
Leadscrew Pitch: <distance/turn>
Reduction Ratio: <motor_turns:leadscrew_turns>
Motor: <make_and_model>
Motor Hookup: <full_coil | half_coil | parallel_coils | servo>
Encoder Resolution: <counts/inch | counts/mm> (if applicable)
Drive: <make_and_model>
Power Supply Voltage: <volts_dc>
Drive Current Setting: <amps_dc>
Drive Step Setting: <full | half | eighth | 10u_step | whatever>
Acceleration: <inches/second/second | mm/sec/sec>
Absolute Max Reliable Feedrate: <inches/minute | mm/min>
Motor Temperature: <cool | warm | hot | very_hot>
Notes: <meaningful_observations>

Thanks,
Matt