Same design - 2 software pkgs - different results

Cutting 1/8" lite ply. 5 passes @100% power and 4mm/sec. Using same parameters in both programs.

Vendor provided software cut all the way through.

With LB cuts half the thickness. That was after 7 passes.

My gut tells me that somehow the power settings from LB do not match the actual laser 100% power. Since I am using the same hardware and different software, can’t draw any more conclusions at this time

I read some postings on here that alluded to the controller not putting out all power when set to 100%.

Any ideas.

Cut settings

Could you please enlighten us as to what machine you have, as I am not familiar with any laser called “U”.


It is a Universal Engraver. The laser is like this


0.25 inches / sec is not 4mm/sec, it’s 6.35mm/sec. So, are you sure you’re using the same parameters in both programs?

  • What are the firmware speed limits in your controller? ($110 and $111 settings)
  • What is the $30 setting in your controller?
  • What is the S-value Max setting in Edit > Device Settings in LightBurn?

Waiting for connection…

Waiting for connection…


Grbl 1.0b [’$’ for help]


error: Setting disabled

$0=10 (step pulse, usec) $1=25 (step idle delay, msec) $2=0 (step port invert mask:00000000) $3=0 (dir port invert mask:00000000) $4=0 (step enable invert, bool) $5=0 (limit pins invert, bool) $6=0 (probe pin invert, bool) $10=2 (status report mask:00000010) $11=0.010 (junction deviation, mm) $12=0.002 (arc tolerance, mm) $13=0 (report inches, bool) $20=0 (soft limits, bool) $21=0 (hard limits, bool) $22=0 (homing cycle, bool) $23=0 (homing dir invert mask:00000000) $24=25.000 (homing feed, mm/min) $25=500.000 (homing seek, mm/min) $26=250 (homing debounce, msec) $27=1.000 (homing pull-off, mm) $30=1000. (rpm max) $31=0. (rpm min) $32=1 (motor lock bool) $33=7 (motor mode mask:00000111) $100=80.000 (x, step/mm) $101=80.000 (y, step/mm) $102=80.000 (z, step/mm) $110=10000.000 (x max rate, mm/min) $111=10000.000 (y max rate, mm/min) $112=10000.000 (z max rate, mm/min) $120=250.000 (x accel, mm/sec^2) $121=250.000 (y accel, mm/sec^2) $122=250.000 (z accel, mm/sec^2) $130=500.000 (x max travel, mm) $131=500.000 (y max travel, mm) $132=500.000 (z max travel, mm) ok S-value = 1000

I believe your S value should be 255 - you’re using a relatively old version of GRBL that doesn’t support laser mode. I’m not very familiar with the 1.0b version, but changing that setting is worth a try.

Made S=255 and speed .15in/sec. Seem to do a lot better. Perhaps I should upgrade the firmware.

Prior to 1.1f, GRBL would pause with every power or mode change, which makes engravings stop constantly, and 1.1f or later will also reduce overburn when you slow for corners. It’s an improvement.

Can’t upgrade firmware. Found out it is not compatible with laser module. Anyway, seems it is working better now. Thinking the S=255 is the real difference.

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