Support Proportional laser power on M4 commands

[EasyTarget]

The popular and well-supported GRBL firmware(s) implement an alternative form of 'laser mode' using the otherwise redundant M4 'reverse spindle' gcode.
With this enabled they scale the laser power during (and only during) cut movements as a factor of the actual movement speed vs desired cut rate.

This is not really aimed at laser cutting; it's intended for those of us doing engraving activities; it prevents overburning artifacts during acceleration and corners; and protects the workpiece during travel moves.

So; I'd like to suggest that Duet implements a 2nd 'laser mode' that follows the behaviour of grbl1.1f+ in using M4 and pwm scaling.

• It's a valuable mode that produces real improvements to work quality, and is totally the sort of thing an advanced motion control system should provide.
• It brings instant compatibility with gcode produced by all the common free and hobby oriented engraving tools.

Note:
I had a search and saw this but cant find anything 'formal' here discussing this, so I thought I'd lob it at the Wishlist. I'm kinda hoping the answer is 'yawn; on the way; just wait for RRF3 to flesh out', but here goes anyway.

[dc42]

RRF2 already implements PWM scaling during the steady-speed phase of the movement. RRF3 implements it during the acceleration and deceleration phases too.

[infamous_panda]

In laser mode is there a difference between M3 and M4 in RRF?

[A Former User]

@infamous_panda M4 is CNC specific, what sort of software is generating M4 for laser cutting?