Hi,

I have a warco mini mill which has recently been converted to CNC using cncfusion kit 4.
The machine works great with backlash <= 0.03mm and smooth table travel. But, I have a major problem.

When the machine was being used manually I never checked the squareness of the X and Y axis.
But now with the resulting resolution of the CNC I have noticed a major flaw:

1) When I machined a large circle (50mm plus) the resulting circle was not round. This is a classic backlash problem but proved to be not the case.
2) I machined an 'L' shape edge (200 by 70mm) into 3mm plastic and the resulting square edge was out by about 0.3mm on its longest side.
3) Because of the above I decided to measure the squareness of the X and Y axis using the following method:
a) Squared up a 400mm length of straight edge (25mm by 10mm profile +- 0.01mm over 300mm) along the X held in a vice.
My best effort achieved +- 0.03mm repeatability over 300mm which meant the X table travel was ok.
b) Made sure the vice was solid and replaced the bar with an engineers 150mm square held in the vice.
c) I now measured the Y axis movement along the right angle formed by the square. The results were alarming.
Over only 75mm in the Y direction the error was 0.32mm which means the Y axis was running at an angle to the X axis. This is hard to believe especially when the X and Y are running so smoothly under CNC control.

I repeated the above measurements by setting up to the Y axis first and then checking the squareness of the X . Same error found.


Any ideas how to resolve this problem.
Thanks