Can not cut circle

My BT48 will not cut a round circle. I have tried all of the usual things, pinions, adjustments, etc. Even replaced the X axis pinion just for drill.

Recently I was cutting a circle in Corian. The first pass the bit ran smoothly around the circle. On the second pass and all those after that the bit jerks and makes lumpy parts to the circle. It always does this in the same places so that the pieces are very nicely cut out, just not the right shape.

I am just about to decide that the problem is in the software rather than the machine.

Has anyone else had this problem? I am kind of thinking of converting the machine to a rezurection control system but if I did I would like to use Mach 3 as my operating system. Any comments on that?

How fast and how deep are you cutting the Corian? Sounds to me like you are stalling and losing steps in the axis assigned to the moving table. Is this correct? Where is the deviation happening - in what direction?

-B

"I am just about to decide that the problem is in the software rather than the machine."

That decision would be incorrect. My guess is that the lumps and bumps are near the 1/8 and/or 1/4 points of the circles where one motor (or the other) reverses direction. This is backlash. Assuming the gearboxes are OK, it will be 1) rack to pinion adjustments 2) Z slide or lower Y car Vroller adjustments

Quote:

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Originally Posted by Gary Campbell

"I am just about to decide that the problem is in the software rather than the machine."

That decision would be incorrect. My guess is that the lumps and bumps are near the 1/8 and/or 1/4 points of the circles where one motor (or the other) reverses direction. This is backlash. Assuming the gearboxes are OK, it will be 1) rack to pinion adjustments 2) Z slide or lower Y car Vroller adjustments

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You called it! The lumps are right at that point. I will check as you suggested.

Guess I am gonna have to think up a better reason to but that box from you.

Quote:

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Originally Posted by tlempicke

You called it! The lumps are right at that point. I will check as you suggested.

Guess I am gonna have to think up a better reason to but that box from you.

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Did you get the issue fixed? I'm currently experiencing the same circle issue. Ordering new pinions tomorrow, it's been 5 years with the factory pinions. I am curious how your situation ended though...

Actually yes I have.

I put new motors on the machine and converted it to a Centroid controller. The difference in accuracy is remarkable. When one part needs to fit into another I use a clearance of .025 to .030 and get a good fit each and every time. All of the hand work that I used to do is for the most part gone.

It has taken a lot of the challenge and mystery out of the experience, but then I have teen age grand children that manage to take up the slack.