Odd behaviour in LinuxCNC running Fusion360 code

Hi all,

I've recently dipped my toe into F360 for a bit of simple modelling and CAM. It's got a few oddities, but by and large I'm very happy - it's kinda like having a new machine..!

There's one thing that happens which I can't quite get me head around. Here's the short version of what's going on:

1. Open LinuxCNC, home it (G53) then set workpiece origins (G54)
2. Load code generated in F360 and run code to find that Z axis hasn't cut down as far as it should have
3. Recheck Z zero position, it's slightly higher than what I zeroed it as (0.5mm)
4. Re zero my Z position and run the program again without re-loading it
5. Position of Z axis remains correct throughout

Now, when I load a program immediately afterwards that's been written by VCARVE, the reverse is true - ie. that program wants to cut down 0.5mm more.

Weird huh..?

Here's the pre-amble to an example of the g-code I'm outputting from F360:

%
(FSS)
(T1 D=4. CR=0. - ZMIN=-18. - FLAT END MILL)
N10 G90 G94 G17 G91.1
N15 G21
N20 G28 G91 Z0.
N25 G90
(ADAPTIVE1)
N30 M9
N35 T1 M6
N40 S10000 M3
N45 G54
N50 G0 X-17.892 Y-22.049
N55 G43 Z15. H1
N60 G0 Z5.
N65 Z-4.2
N70 G1 Z-4.6 F960.

I've tried this with the G28 Safe Retracts command both enabled and disabled - the only discernable difference is that with the G28 enabled there's a slight pause following the final retract before the machine retracts fully to the G53 zero.

Any ideas?

Wal.

Wal Have you tried using a G49 tool length cancel in the preamble N10 G90 G94 G17 G91.1

Hi Clive - just got in. Will try this as soon as I'm able. Will give you a call tomorrow.

Wal.