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Offline moxy

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accuracy problems
« on: April 28, 2011, 03:28:00 PM »
Hi All, I have just done a retrofit on a Standard Mill (Chinese knockoff of a Bridgeport) and am having problems getting the cals right on the Y axis. I finally got it set by the change and check method to the point that a 100mm move is consistantly within .01mm. When I run some gcode the result is somewhat erratic. Circles are slightly flattened in the y axis. I have tuned the motor down to 1500mm/minute  and it is the same. The x and y axes are capable of moving at 4000mm/min and 2500mm/mi respectively and sound very steady. I found that the bob 5v was very noisy when I enabled the motors and fixed that up by fitting a larger capacitor. This stopped the erratic motor movement that I was having. The noise on the 5v is now about 3 millivolts. The backlash on both axes is 0.02mm Is there anything in setting mach3 up that I may have missed?
Regards
Les

Offline Hood

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Re: accuracy problems
« Reply #1 on: April 29, 2011, 03:55:11 AM »
I would say that you have some lost motion, I know you said backlash was 0.02mm but that was likely checked with no force against the axis, add in some cutting forces and you may get some flex on a bearing mount or maybe a pulley slipping slightly.
Hood

Offline moxy

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Re: accuracy problems
« Reply #2 on: April 29, 2011, 09:03:25 AM »
Hi Hood, thanks for your reply, I found the problem this morning. When I enabled any of the Gecko drives the 5v supply became very noisy and therefore put noise on the step and direction signals to the drive. I added some more capacitance to the 5v supply and the machine is now cutting very accurately.
Best regards
Les

Offline Hood

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Re: accuracy problems
« Reply #3 on: April 29, 2011, 10:02:55 AM »
Good news :)
Hood