pocket wizard

[lotusman]

Can anyone help me?
I'm having trouble getting the pocket wizard to cut the right size.

I have checked my machine & it is moving the right distance in the X & Y, but when I try to cut a circle it is undersized.

Thanks
Butch

[Hood]

Is your cutter the right size for what you are telling the wizard it is?
Hood

[Tweakie.CNC]

Hi Lotusman,

Welcome to the forum.

I can't help much with the pocket wizard but It would be great if you could post some pictures of your CNC table addition to your manual knee mill, please. 

Tweakie.

[lotusman]

I measured the cutter @ 6.3mm.
I believe the problem is the motors are not big enough (NEMA 23 235 oz-in with a 2/1 gear reduction) to hold position while cutting. If I move the table using MDI, then plunge with the same end mill, measure between the holes, it is right on the money. Anyone have some suggestions for motor size? I was thinking 600 oz-in.

[RICH]

You don't say how much smaller the pocket comes out nor do you say if there is any difference in the diameter depending on where it is measured.
Are your steps per based on a calculated value or from actual verification? There can be small differences if one were to refine them but only after testing.

Motor size is relavent to a number of things and holding requirements is only one part of the it all.
A finish cut post roughing cuts will give more precise tolerances. You can deliberately cut undersize,then measure,  and then use a modified value for cutter od for the finish cut based on what you measured.

RICH

[lotusman]

Rich,
All of the holes that I have tried come out 0.3mm undersized. I can adjust for the difference by telling the wizard my endmill is 6.15mm & it cuts the pocket to the right size. I don't want to have to do this every time. I should be able to measure the endmill & type in the number & it should be right.

This is what I have tried since my last post.
1. Swapped my stepper drive for a Gecko G540 that a friend had. Works the same as my 3-axis drive.
2. Posted a circle frame tool path created in Master CAM & it does the same thing.
3. Looked everywhere in Mach for some settting that would cause both axis to be offset.

It just doesn't make any sense that I can move to a distance in both axis to within 0.0005" repeatedly but it won't cut a circle.

Any other ideas?

Thanks.

[Hood]

Do a circular pocket, is it round ? Could it be backlash?
Hood

[lotusman]

The pocket is round, near as I can measure.

[RICH]

Can you post the code used to cut the circle?
RICH