M9 Fusion Code Trouble, Accessory Commands Beta

Hey, I set up two IOT relays for automatic control of both the spindle and vacuum, which the Xcontroller has separate outputs for. The spindle stays on, but the vacuum turns on, then quickly back off before it starts cutting. I activated the beta feature in Easel for enabling accessory commands M7, M8, and M9. I think it’s the Easel post processor I’m using with Fusion 360 to export tool paths. I examined a .nc file it produced and found there is a M9 before the code, which is “Coolant Off” and this deactivates the relay. I made sure flood coolant (M8) was enabled for the tool. I can’t seem to find anywhere discussing this issue.

Does anyone else have the curse of the M9’s? How do you activate coolant with Easel post processor?


M7 and M8 turn “mist” and “flood” on, but M9 turns them both off.

Yes, I need to somehow modify the post processor to not put a M9 until the very end of the code. Why would it put that at the beginning?

Some CAM programs insert a lot of “initial” stuff just to make sure that the proper environment is set up for the G-code that follows since several of the G-code commands are modal.

I don’t use Easel. I don’t know if they expose their post processor.

This is the state of the grbl modal commands at power up: (assuming you are set up for mm not inches).
G0 G54 G17 G21 G90 G94 M0 M5 M9 T0 F0. S0.

I used the Fusion 360 Easel PP and didn’t run into the issues with M8 and M9 that I can recall. I had enabled Flood coolant for the tool and it worked as expected.

What PP did you grab? I believe I followed the instructions here:


@PhilJohnson I use separate IOTs on separate outputs (SPINDLE for the Dewalt, M8/Flood for my shop vac) so I can manually turn on my vac if needed or, if I need to not use it, just remove the M8 command. Just more flexibility for controlling the stuff.

I posted this question to the HSMworks forum and got a quick answer on how to kill the M9. https://forums.autodesk.com/t5/hsm-post-processor-forum/no-coolant-control-w-easel-post-processor/m-p/6951438 I just had to comment out the line that turns off coolant during a tool change, I think…

Thanks for all the quick feedback, yalls posts on this forum have helped me out immensely!

I set my tools to manual change in Fusion 360 to avoid the tool change command potentially causing havoc in Easel or GRBL.

Glad you found the answer!