Messages

11

General Mach Discussion / Re: Creeping Y position. Anyone know something else I can try?

« on: August 06, 2008, 05:23:46 PM »

It's actually a belt drive CNC 45" X 18". It was originally driven by ACME screws but I was getting too much whip, which cause vibration. The belts run it very smoothly.

The speed reduction is 17:1 using cogged timing pulleys. The belt drive version did run accurately with Omikron drives, but kept cooking them - that's why I went to the Geckos. Same motors that I used with the Ohmikrons.

I believe the Gecko 203V's are 10 microsteps, but I don't actually know - it isn't listed on their website like it is with the 201 and 202.

Thanks!

Dave

12

General Mach Discussion / Re: Creeping Y position. Anyone know something else I can try?

« on: August 06, 2008, 05:04:55 PM »

Hi Hood,

I swapped the pins for X and Y as you suggested - the error is still on the Y axis (goes 0.016" +Y from X0Y.) Not sure what that signifies. X axis is unaffected.

I don'think it matters, but I have the same motors and same speed reduction on both X and Y, but the number of pulses for X is 4750, Y is 4100. It should still go back to the original X0Y0, but it seems odd that they wouldn't be the same.

Thanks for your help!

Dave
Saltspring

13

General Mach Discussion / Re: Creeping Y position. Anyone know something else I can try?

« on: August 06, 2008, 04:52:55 PM »

Thanks for the suggestions, Chip.

I tried them each one of them in turn, then all together..., restarting the program and reloading the G-code each time - still no difference. No change at all in fact, except when I set my pins for X & Y - yours pins are set to 3,2, with Y, Z, and A being at 4,5..., 6,7..., 8,9. The the Y doesn't move at all. Any reason the X pins are reversed in the screen capture?

Another thing that might mean something to someone smarter than me, is that my pulses per unit for X  are different than they are for Y. I'm guessing this has to do with my belt drives being different lengths, but I'm open to suggestions.

I appreciate the suggestions - please keep them coming! At this point, this machine purrs along beautifully, (much nicer than when I had it on ACM screws ). But isn't much use to me if it can't find it's way home after even small cuts!

Thanks again.

Dave
Saltspring

14

General Mach Discussion / Re: Creeping Y position. Anyone know something else I can try?

« on: August 06, 2008, 02:55:34 PM »

Thanks for the quick reply, Hood.

Yes, the error is accumulative - creeps each time the program is run. .

I switched drives as you suggested, and the error remains on Y. So that points to..., the stepper motor? Or the software configuration?

Thanks.

Dave
Saltspring Island

15

General Mach Discussion / Creeping Y position. Anyone know something else I can try?

« on: August 06, 2008, 02:18:58 PM »

Hi,

I'm hoping that someone more experienced than I am can suggest where to look to solve this problem.

I get a consistent creep of 0.016 on my +Y axis each time the following routine runs. That is, each time I go back to X0Y0, it is 0.016" from X0Y0, in the +Y direction. No problem with the X axis.

I've searched the archives, and I've adjusted the # of pulses on the Y axis, tried variations in Velocity and Accelaeration - haven't had any improvement so far.

I'm running Mach3, the Mini_Combo (steppers) from CandCNC.com, Gecko 203V's.

M3
G90
M98 P1000 L100
M30

O1000
G1 Z-0.125F20
G0 Z0.25
G1 X4Y4F120
G0 Z-0.125F20
G1 X8F120
G1 Y8
G1 X4
G1 Y4
G0 Z0.25
G0 X0Y0
M99

Any ideas?

Thanks!

Dave
Saltspring