GRBL configuration

Walk through the GRBL settings that matter most for laser work. Set them once, write to EEPROM, move on.

For laser engraving on a GRBL machine, a small handful of $ settings determine whether the machine behaves correctly. This guide walks through them in priority order.

For the exhaustive list, see $ settings reference. For the underlying concepts, see GRBL essentials.

What you need

The machine connected.
The Console panel open.

Steps

1. Dump current settings

In the Console panel, send:

$$

GRBL responds with every $ setting and its current value. Read them. Take a screenshot or save the output, useful baseline before changes.

2. Set laser mode

$32=1

Enables laser mode. With it on, GRBL synchronizes laser power with motion (dim during deceleration, full during cruise) so fills come out evenly. Non-negotiable for engraving.

3. Set the max S value

$30=1000

(Or whatever your firmware uses, common values are 1000 or 255.) This is the maximum value of S (power) that the firmware understands. The Device Settings S-value Max should match.

4. Set max rates

$110=6000
$111=6000

Max travel speeds in mm/min for X and Y. Set these to your machine's safe max, going beyond will stall motors.

5. Set acceleration

$120=3000
$121=3000

Max acceleration in mm/sec² for X and Y. Higher values mean tighter cornering but more stress on the mechanics. Reasonable starting point for diode lasers: 1000-3000. For CO2 gantries with heavier heads: 500-1500.

6. Set steps/mm

$100=80
$101=80

The motor steps required to move 1 mm in X and Y. Specific to your motor / pulley / belt combination. See Steps per millimeter for how to compute and verify.

7. (Optional) Set up homing

If your machine has limit switches, enable homing:

$22=1
$23=3

$22 enables; $23 selects which corner is home (varies by machine).

8. Apply to Beam Bench profile

After changes, open Device Settings → GRBL Settings tab and click Apply to Active Profile. This copies the live values into your machine profile so they survive across sessions.

Verify it worked

$$ shows your new values.
A test rectangle cuts at the right size.
A fill engraves uniformly (no banding at start / end).
Jogging feels responsive but does not stall.

Common mistakes

Forgot $32=1: engravings are noticeably darker / lighter at the start and end of each line. Set $32=1.
$30 mismatch: laser fires at the wrong intensity. Make sure Beam Bench's S-value Max matches.
Steps/mm wrong: cuts come out a percentage off. Re-measure and update.

GRBL configuration

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