Old CNC tripping up on it’s Z-Axis

CAD/CAM/CNC
1

I’m working with an old Biesse Rover 346.
When doing a side drilling operation a couple of times i realized the holes aren’t getting drilled in the center anymore, but rather too high.
The problem persists when doing milling or drilling vertical holes. So it seems it’s the whole “carriage” is misbehaving.

First time running a program it runs correct, but if I restart the same program it will have moved the Z-Axis 1-2mm up.
The DRO still reads the correct value, but the cutting bit is not at the right Z-Height.

Any help getting me in the right direction would be greatly appreciated!

Ps: new to the industry and terminology, and not natively speaking English :slight_smile:

2

This is a good one… The DRO is not measuring any difference in height but you know that the tool is higher?

Is the tool pushing up in the holder?
Is the machine changing the tool height offset on its own?

Machines absolutely WILL change G54 location when shut down and turned back on. Are you restarting the machine between the cycles?

Only way it will be off on tool hight if the DRO is saying your good is if G54 changed in Z, tool height offset gets Changed, or the tool is actually moving into the holder or out.

Besides massive failure of Z axis is broken.

What have you found this far?

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