Benchtop Pro Mach 3 Z Crash

I was wondering if somebody could look at this G-Code Fusion 360 generated as part of the stock avid CNC squaring test code.

I was able to zero the Z to the work surface using the Z touch plate fine.

The code successfully etched the corner diagonals for me, then it got to the home to zero commands and things went bad. The spindle dove the bit all the way through the work piece, into the aluminum then broke the bit.

I don’t see any reason for this to have happened except I don’t fully understand why fusion generated the final G-Code commands.
If the M5 command indeed stopped the spindle, it proceeded to dive the bit into the table before it lost momentum until it sunk into the aluminum. Then it tried to move into the final x,y relative homing coordinate and snapped the now overheated bit seized into the aluminum.

Is my Warp 9 ethernet controller thing just flaking out? Or is fusion generating unsafe commands. I’ve noticed it doing weird things periodically like instead of it going to the calibrated surface when telling it to go to zero it will press the bit into the surface.

This is the G-Code.

(SQURECHECK)
(T4 D=0.25 CR=0. - ZMIN=-0.0394 - FLAT END MILL)
G90 G94 G91.1 G40 G49 G17
G20
G28 G91 Z0.
G90

(TRACE1)
T4 M6
S20000 M3
G17 G90 G94
G54
M8
G0 X-8.2209 Y6.8067
G43 Z0.5512 H4
G0 Z0.1181
G1 Z-0.0394 F250.
X-6.8066 Y8.2209 F450.
Z0.1181 F250.
G0 Z0.1575
X6.8067
Z0.1181
G1 Z-0.0394 F250.
X8.2209 Y6.8067 F450.
Z0.1181 F250.
G0 Z0.1575
X6.8067 Y-8.2209
Z0.1181
G1 Z-0.0394 F250.
X8.2209 Y-6.8066 F450.
Z0.1181 F250.
G0 Z0.1575
X-8.2209
Z0.1181
G1 Z-0.0394 F250.
X-6.8066 Y-8.2209 F450.
Z0.1181 F250.
G0 Z0.5512

M9
M5
G28 G91 Z0.
G90
G28 G91 X0. Y0.
G90
M30

It’s gotta be your G28 home position; maybe you reset it in mach 4. When you go to a G28 in MDI (and be careful when you do it), where does it go?

I think I had it set to the xy limits with the z at the old 1" spoil board surface. But now I need to double check. If that’s the case it shouldn’t have drilled all the way through the current piece I’m using for the square check so it’s a little confusing what happened; however, the 1/4" bit is longer than the 1/8" bits I had been using.
G28 is the REF ALL HOME? values?

I’ll have to verify that, but why the hell would Fusion 360 Assume I wanted to REF ALL HOME by default especially putting the BIT at the spoil board surface first? Sounds like a recipe for crashing into clamps and work pieces.

My understanding of G28 is to go “home”, which (I think) you can customize a particular position to be. It shouldn’t hit bits; it first goes to Z0, then X0/Y0, so it should clear anything.

Most Fusion post processors have this as an option…check your settings in Fusion and uncheck it if you don’t want it to do this.


REF ALL HOME works as expected Moving to Max Z height, then Full forward Y and Full Left X.

Unfortunately this is not where the G28 Home is defaulted. I will set it to 8" and see if it gives desired behavior. I would think that homing to work space might be generally better or just lifting to max Z .

Setting to 8 for z works.

That said I have begun to loath Fusion 360.
I’m using the AVID CNC Gantry Square and Traming Calibration file.

The simulation has everything cutting in the proper places.
For the Tangential Trace it generates G-Code which navigates with respect to the specified zero as the center point between all of the tangents.

Then the next part of the G-Code is generating the paths for the squaring holes with respect to the center point acting like it’s the X0, Y0 left front coordinate meaning the hold drill coordinates are displaced diagonally from the tangent cuts by 50% And causing the machine to think it must travel beyond its soft limits to make the square holes.

WTH this is the file supplied by AVID CNC. Why is the zero screwed up so bad?

I never used Mach 3, and I don’t have Mach 4 anymore (Centroid now), so I don’t really know what is wrong or how it is supposed to be. I’m not sure how the z value are supposed to be set. Usually up is positive, down is negative, so the limits seem strange, but…I don’t know how it is supposed to be.

It sounds like your origin in the Setup is not the same as what your physical zero’ed out origin on the machine is.

Fusion is great and one of the best CAD/CAM’s out there! Stick with it and you’l be happy.