Need Help!- Circles are ovals

[uspl]

Hi all

Runnign a JGRO build with Mach 3 R3.042.040 in demo mode.
The machine is cutting fine and reasonably accurately so far; I am only doing test custs in MDF while I tune the new build.

As the title says, circles are being cut as ovals, stretched by about 10% along the X-Axis.

So far I have:

• Fixed a minor backlash issue on X
• Checked the alignment of X-Y are as true to 90 degrees as I can measure
• Tried the two IJ options for Inc or Abs in Mach 3
• Tried cutting a pure rectangle to check alignment; all corners cut square and the rectangle was true

The setup also cuts text fine, nice and straight and algined.

I'm stumped, any suggestions appreciated.

Thanks

David

[uspl]

It wasn't 10%, it was actually 20%.

As I said, rectangles and squares were perfect, only circles were a problem. I was doing some CAM tests and happen to order two rectangles, 100mm x 50mm. One was aligned to the X axis the other to the Y axis. Lo and behold, they came out different sizes !!

I checked my thread pitch on both axis and found that my supplier had sold me two different pitches on the two different days I shopped for parts !! X axis is 1.5, the Y axis is only 1.25. I changed my Config>Motor tuning and presto my circles are circles. I didn't pick it up when making the nuts as I used HDPE and the rod just cut it's own thread.

Just goes to show, never assume.

Cheers
David

[rowbare]

Mach has a calibration feature that allows you to dial in your steps per unit quite precisely. Hoss discusses it and has a video showing how it works in this post: http://www.cnczone.com/forums/showth...ach#post563707

bob

[neilw20]

David,

You are right!!
You can't assume.
It makes an ASS out of U and ME!

[john23]

i do agree on that ! Its such a big pain in the neck when my circles turns oval!! There would be a part where in which it is finished to size and a part which is undersize... In times like this i try changing cutters