View Full Version : UCCNC post processor - weird move G0 G53 X0 on start?

02-13-2018, 05:35 AM

I am new to CNC, so maybe I have some misunderstanding.

My CNC mill is setup with Z-Axis counting upwards, Z-endstop mounted so home-position is UP and is at 0(mm). Soft-limits are set to 0.1mm (upper) and -130.1mm (lower). So in fact I am working with negative Z heights.

I am using Fusion 360 with its integrated CAM and the UCCNC post from the autodesk website (latest).

All my GCode-files start with:

G0 G53 Z0.

later in the program, it happens that

G0 Z15
is set, so hitting the softlimit (and endstop).

I could set Z home postion to 130 and work with positive Z heights.

Yet what makes me wonder is the "G53". From my understanding it forces the machine to zero Z in its MCS, which makes absolutely no sense to me. From my understanding, I jog the machine to the desired zero-position and zero XYZ in the WCS. Then the programm uses the WCS exclusively. Why is there a reference to the MCS? It makes the machine move away from my desired Z height!

Best regards,

02-13-2018, 06:53 AM
Whoever wrote the post thought it was a good idea??

02-13-2018, 07:24 AM
Is this a statement or a question?

Sometimes I assume that in fact other people do something by intend. In this case, I would assume that the "G53" is perfectly right under the assumption that my setup is somehow not properly set up or at least in some unusual way. Not I am looking for feedback in a way that either a) I can align my setup to the standard or b) somebody tells me its perfectly ok to alter the post as the G53 is unusual there.

Best regards,

02-13-2018, 07:32 AM
In a number of CNC controls that I am familiar with numerous actions have the G53 Z0 associated to them.

This is simply lifting the Z to its max height, "0" using the MCS. It should not matter if you are using the MCS or any of the WCS offsets. I would expect this is normal on all machines with a z homing switch and unusual on those that do not.