Troubleshooting CNC Controller Errors

When a CNC device makes an unexplained move or cut, how can you isolate the source of the glitch? September 3, 2010

We have a Mulitcam 5000 series that we have been very happy with. Recently we were doing a 3-D operation, (toolpathed and posted from Mastercam 9.1 and x2) and out of nowhere the machine, while being in the correct x and y axis, dipped down too far down in the z and cut about an inch - then lifted up and continued on. This does not show at all in the verification or backplot in Mastercam. Has anyone ever had a similar error? Can a file become corrupt all of a sudden? We have run numerous 3-D files in the past without any problem. Our z is a servo motor, not air assisted.

Forum Responses
(CNC Forum)
From contributor S:
Have you tried using the Multicam Job Previewer to find the exact point where this error occurred? The verify function would not see this as an error but by going line by line to the error point you will be able to see the Z axis output that the router received. This Z output would then tell you if it was a software output problem or the Multicam's.

From contributor V:
Maybe something in the geometry causes a glitch when posting out of Mastercam. Check to see if it's a post error, then you may be able to find out if there's a Z problem.

From contributor W:
Mastercam (and most CAM programs) backplot the source code for the program, not the code itself. If you open the actual code as a text file you should be able to isolate the exact location of the errant Z move.

This is either:

1. A post processor error.

2. The geometry of the 3-D drawing file was incorrect, the model had not been "swept" or the entities had a "break" that the post processor did not know how to interpret.

3. However you transfer code to machine , the DNC software may be corrupt. I would guess it is number two above.

From contributor M:
I've had a few similar occurrences from Mastercam. The first time I just blew it off as a one time thing. The second time it happened I noticed it and have been on the look for similar happenings since. It only happens on really intense 3-D work and I noticed that it occurs on items with less than ideal surfaces. When I see it now I just do a quick manual edit after I post and all is happy.

From contributor R:
Have you looked at the G-Code? It should tell you if the error is an issue with the translation from Mastercam or if there is a machine error.