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Author Topic: help, my circles arn't round.  (Read 2690 times)

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help, my circles arn't round.
« on: November 26, 2006, 08:38:02 PM »
I converted my Bridgeport j-head mill to cnc some time ago. Use an original Dan Mauch servo system and a ball screw kit from Mcmaster Carr. I use Mach II for the controller.

I recently noticed contoured circles are not turning out round in the diagonal direction. They're the right size in x and y but an 1.500 one is about .020 small diagonally. My backlash is under .001 in both x and y.

I'm mystified and looking for suggestions.

BTW, I recently added 2-200lb x 16 inch gas springs to the knee of the bp, also from mcmaster carr. They allowed me to triple the z speed. 

Thanks,

Jim

Offline Graham Waterworth

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Re: help, my circles arn't round.
« Reply #1 on: November 26, 2006, 09:53:00 PM »
Have you checked to see if you have any movement in the gibbs :-

can you twist the table pulling it back and forth from the front of the machine.

People nearly always use the middle part of the X axis so it wears more in the middle.

This would not show up in a backlash test.

Graham.
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