[saabman]

I am having a world of trouble getting my servos tuned. My focus is on Y at the moment. With the servos powered off the pulley/ballscrew turns easily by hand. The servos are from IH (part of the kit). They run the saddle in choppy steps. With an occassional smooth inch or two. Gib is totaly loose.

Limiter when turned all the way off disables the servo. When turned to 55 or 100% the behavior is the same.

The choppiness is during continuous jog or GO/G1 gcode moves.

For grins, I hooked up a an electric drill to the ball screw shaft and it moves the saddle in and out smoothly. Servo just doesnt seem to spin very fast.

I measured input voltage to the Gecko and it was 76 volts (spot on).

I have read about tuning on this forum and the Mach forum. I just dont get it. Gecko faults at anything over 50 IPM. Another clue is Mach thinks the feed rate is near where it is set (based on its feed rate display). But timing it by hand shows it running much slower.

Chris

[saabman]

Found my frequency counter and it revealed what I believe is the problem. Pulse rate is rediculously low (even though driver test ranked it stable and high). So encoder and servos likely working, just getting pulsed to slow. More details to follow.

[Runner4404spd]

what kind of computer are you running it? you should set your mach 3 config to 45khz. make sure that you have tuned your motors in mach 3 first before attempting to tune the geckos. you should check your acceleration. also check your motor tuning specs...

i have my steps per set to 20000. and i run my pulse at 5.

[saabman]

I was using a laptop to do basic testing (2 ghz). Since discovering my poor pulse rate, I have focussed on putting together the rack mount computer that is the permanent driver for the mill. I expect that I will have that running today some time. All basic components installed, time to install the OS.

I saw the Gecko spec was 3.5 usec for the pulse so I had it set at 4 inside Mach.

I am very optimsitc that the new computer will solve the problem.

[saabman]

Things look promising. DriverTest reports 24999 pulses for a 25K kernel, and rates it excellent. This is on a 3 Ghz P4 running XP. I suspect the problem with the laptop is the mobile processors spin down the cpu to conserve power (I did not think they did this when plugged in but evidence suggests otherwise). A word to the wise, the current generation of I5 and I7 chips (non mobile) have power saving features like mobile devices. They throttle back their clocks. This might cause Mach heartburn.

[saabman]

Wow, what a difference the correct computer makes. X and Y (have not tried Z yet) are moving very smoothly now, servos are quiet, and they can switch direction on a dime. Now to check them for accuracy.

Chris