Cutting deeper in areas???

[alboy]

The machine is set to have a safe distance of 10mm above home position so when you home to the workspace the end of the bit will be 10mm from the workpiece surface. I set the machine to go from home position to work position and it seems to be accurate each time. I tested the gap with a piece of 10mm thick aly.
I set up a job to drill 10 6mm holes 0.2mm deep in a line across the x axis over a distance of 600mm. and as the holes are being drilled left to right, the far left hole seems correct but the holes get gradually shallower along the right of the axis. Machine bed spoil board seems nice and flat.

Al

[JAZZCNC]

Ok well if your sure it's returning to WC-Zero (forget MC-Z) after the job as finished and no steps are being lost then it must be the table or machine frame. (provided tool is secure in spindle)

The bed may look flat but if it's not exactly parallel to the cutter across the whole area then you'll get this issue. That's why you should surface the bed to be sure.
If you still have issues after surfacing then I'd be looking at the machine frame and if it's twisted etc.!

[Clive S]

The machine is set to have a safe distance of 10mm above home position so when you home to the workspace the end of the bit will be 10mm from the workpiece surface. I set the machine to go from home position to work position and it seems to be accurate each time. I tested the gap with a piece of 10mm thick aly.
I set up a job to drill 10 6mm holes 0.2mm deep in a line across the x axis over a distance of 600mm. and as the holes are being drilled left to right, the far left hole seems correct but the holes get gradually shallower along the right of the axis. Machine bed spoil board seems nice and flat.

Al

Ok first drill holes are not ideal as they will have a tapered bottom an end mill would be better as it will leave you with a flat bottom and you can could measure it better. Now you say the spoil board is flat, have you checked that with a 10mm spacer across the bed where the holes are drilled? If you have a DTI check to see if you have any end float in the Z axis. ..Clive

[alboy]

Cheers Guys

I will surface the spoil board again just to be sure but it does seem flat when i test the difference between the end of the bit and the surface using the 10mm block. I do not have a DTI but I have ordere one today so hopefully will be able to check things with better accuracy. Will let you know how it goes.

Al