How do I adapt my existing post-processor to support the Laser Module?

Old router-style laser posts will not work correctly with the Laser Module; they used spindle workarounds. Adapting a post takes four changes. For general editing mechanics, see the post-processor editing entry.

1. Add a POWER variable

Define how the 1 to 100 percent power value is written for your controller:

VAR POWER = [P|C|S|1.0|10.0] (GRBL example)

In order: P is the placeholder used elsewhere in the file, C means only output when the value changes, S is the G-code letter (GRBL reuses spindle speed S), 1.0 formats as a whole number, and 10.0 multiplies 1 to 100 up to GRBL's 1 to 1000 scale.

2. Add three laser blocks

• begin JET_TOOL_ON with "M4[P]": fires the laser at the set power.
• begin JET_TOOL_POWER with "[P]": outputs power changes mid-cut.
• begin JET_TOOL_OFF with "M5": shuts the beam off.

(M4/M5 are the GRBL commands; substitute your controller's.)

3. Fix the motion blocks

Append [P] to every feed move, for example begin FEED_MOVE outputting "G1[X][Y][Z][P]". The C flag keeps files clean by only writing power when it changes.

Then separate spindle startup from plunge moves. Routers spin up during the plunge, but a laser powered during a positioning move overburns the material. Give spindle startup its own SPINDLE_ON block ("[S]M3") and strip spindle commands out of PLUNGE_MOVE ("G1[X][Y][Z][F]"), so laser strategies can reach Z height with the beam off.

4. Declare laser support

Add LASER_SUPPORT = "YES" to the global section of the file. Only then does the post appear as selectable for laser toolpaths. Add it last, after testing everything else.

Pro tips

• Copy your working spindle post and adapt the copy; you keep a known-good router post.
• Test on scrap watching for overburn at plunge points; that is the symptom of step 3 done wrong.
• Official documentation: Adapting a post-processor for lasers