Generating GCode moves Z Axis starting point.

[raptessmistfyre]

Hey folks, I am very new to Fusion 360 but I have run into a couple problems that I cannot seem to correct.

Whenever I create a design for my CNC, I then go to 'Manufacture' and go through the process of setting up the cutting sequence etc at which point everything looks good in Fusion 360.

I then post the GCode as a .tap file for use with my CNC machine, only to find out when I run the gcode on my CNC the Z Axis Zero Point has been auto adjusted, resulting in the cutting process taking place around 10mm+ above the surface of the stock material.

For instance:

I load up the .tap file into Mach3, set all my Zero points on the machine, press 'Start' and the machine raises the Z axis to +15 (clearance5+Retract5+Feed Height5), starts the spindle and moves to X-Y entry points, the Z axis begins to lower into position, but then stops and it begins the cutting process at Z+10 instead of dropping down to Z-1.

When I test the GCode in a CNC Simulator (CAMotics) everything looks to be good. It's only when I run the GCode on my CNC that the problem happens.

The other program I use for CNC designs (Carbide Create) does not have this issue, however it's a lot more difficult to generate 3D models / paths.

I have included both the .tap / .dxf files for inspection if anyone has the time to assist. Would be great to know if I am doing something wrong or not.

[raptessmistfyre]

I've been exploring the possibility of a G command changing the Z zero point during the startup, but unfortunately as I am such a beginner I don't fully understand some of them ..

This is the start of the .tap gcode for my drilling process, is there any G commands here that could change the Z zero point on the fly ?

(DRILL 3MM HOLES)
(MACHINE)
( VENDOR AUTODESK)
( MODEL CNCEST)
( DESCRIPTION GENERIC 3-AXIS)
(T1 D=6. CR=0. - ZMIN=-4. - FLAT END MILL)
G90 G94 G91.1 G40 G49 G17
G21
G28 G91 Z0.
G90

(DRILL1)
M5
T1 M6
S12000 M3
G54
G0 X14.5 Y19.5
G43 Z15. H1
Z5.
G98 G81 X14.5 Y19.5 Z-4. R1. F796.
X64.5
X114.5

[raptessmistfyre · Accepted solution]

Although there has been no response, I wanted to say thank you to all that had a look into the code.

With many trials, I managed to figure it out without any headaches to follow ..

It was a combination of GCode (G54) & Mach3 settings, where for some unknown reason the Z Axis points for Tools 1-12 were all set to a Z Axis +7 Offset in Mach3. Every time the G54 command was issued, it would reset the Z Axis to +7mm higher.

I honestly have no clue as to how / why the defaults were Offset by +7, but once I removed this Offset from the Mach3 settings, everything is now working 100% spot on.

Leaving this here just in case anyone else runs into the same / similar problem 🙂

[brent2XUZQ]

Having this issue on my Maverick CNC, glad I found this thread. Going to explore if I have the same issue. Thanks again.