M6 tool change bit plunge

Hi Everyone,

New to the forum here, Just got my onefinity recently I am very happy with it but I encounter a small problem, i am wondering if anyone can shed me some light.

So I have am cutting some foam for a school project 2 inch thick, and I program two tool for this job both 1/4 shank one short 1 inch LOC and 1 long 2.25 LOC. Programmed in fusion 360 with m6 post processor enable.

Upon M6 tool change, I am suppose to flip the back of the probe and measure the Z offset (which the system prompt me to do), after i swap out the shorter bit to the longer big bit and perform the z probe procedure the machine would plunge into the probe after the bit make contact with the probe.

Luckly I am cutting foam so the long endmill press the probe into the foam which the foam absorb all the pressure so I didn’t ended with a broken endmill. Can someone tell me why this is happening? Is there something I missed?

I notice I use imperial (inches) for my cam and in the M6 tool change command it uses g21 (mm), should I change it to G20, if so should I change G38.2 Z-10 to another number?

Here is my original m6 tool change gcode

(Runs on M6, tool change)
M0 M6 (MSG, Change tool and attach probe)
(probe to minimum z soft limit, which is -10)
G38.2 Z-10
G92 Z15.4
g0 Z30
M0 (MSG, Remove probe, start spindle)


Seems like a connection issue with the probe. Does it work without the M6?

Good Morning,

The probe and machine perform normally if I execute “Probe XYZ”. This phenomenon of my Z axis pluging down with loose connection(possibly) only occur while during M6. It’s not a regular occurrence. The speed of the plunge is very fast it’s not the usual 35 or 75mm/s probe speed. I am trying to capture it on video and post it here if it happen again.

That’s what I am thinking its a connection issue, but it baffle me that even if the probe has a loose connection the Z axis shouldn’t pick up speed and plunge down (In this case my bit will push the probe down). Luckly i am cutting foam but if iam cutting any other material I can say bye bye to my bit, but this doesn’t give me confident about using the probe or m6 toolchange sequence if iam cutting harder material because i don’t want to break my bit since they are not cheap per pop.

The F100 in the above G-code sets the “feed rate” which in this case will control how fast the Z axis is lowered. You can reduce this value to something more to your liking.

i tried that , but it is still happening.

I made a new post with video to show how that happen.