Troubleshooting Out-of-Level Machining on a CNC Router

Problems with a mis-alignment between the CNC gantry and the table. February 12, 2010

I own a small CNC router (1000 x 800mm) and I noticed that the machining height across the whole machining area is not uniform. If I machined some material to a depth of say 1mm, as the cutter is travelling and machining down the length of the table the engraved depth will decrease until about 2/3 down the table the cutter will miss the material all together.

Can this problem be corrected easily? I'm wondering if this can be resolved within the machining operating software I am using (maybe the settings are out slightly) or something physically on the table can be adjusted.

Forum Responses
(CNC Forum)
From contributor T:
Obviously your table top is not level and parallel with your router motor gantry. If you are using a spoil board, just machine it down until your cutting the same amount off all areas. Is this a machine you set up yourself? If not the manufacturers set up crew should have taken care of this. As far as I know there is no way of programming something like this out.

From contributor J:
What drivers are you using? Is the z loss consistent and is it more obvious in 3d vs. 2d? I have had a drive go weak that has caused this set your z at 1" off the table and check the four corners and several other points by simply moving xy it the depth remains constant it probably is not gantry to table dimension issue.

From contributor B:
If itís not a leveling issue you could have a gasket not bed down correctly (folded), or debris under your spoil-board. Like said, it might be a slight inconsistent depth thickness in your spoil board if you donít fly-cut both sides of the MDF.

From contributor J:
I would recommend using a dial indicator and check all the locations of your tables to make sure it is not an issue. The tables should be right on the same number anyplace you set your dial indicator. Just remember before doing this to make sure you base is perfectly level. I had a machine in Denver twist due to being anchored down as it should be but the concrete slabs had moved and pulled the machine off causing an issue similar to this.