A laser in the garage, and a gate before it fires

Early on we wrote down one rule that hasn’t moved: no laser in the cottage. It is an 1868 timber building shared with other businesses. A laser cutter is a fire source that makes smoke. It doesn’t belong there.

But a laser is very useful. Labels, jigs, engraved plywood, small cut parts for the furniture. So on 15 October a TwoTrees TTS-10 Pro came home to the garage: a 10 W blue diode laser with a 300 × 300 mm bed, inventory number EQP-0004. Today was the first day we talked to it.

Read before you write

The first thing we ran was a script that only reads. It asks the controller who it is and what its settings are, and changes nothing. That turned up one correction straight away: the board is an MKS DLC32, running GRBL 1.1h. Our own equipment notes had it down as something else. Better to find that out from a read-only check than from a setting that doesn’t exist.

Everything checked out, including the one that matters most: laser mode is on, which means the beam is off while the head travels between cuts.

Where is zero?

This machine has no limit switches. So there is no homing: wherever the head sits when the controller starts is 0,0. The procedure is to switch off, push the head gently to the front-left corner, switch on.

The gotcha we hit today: the USB cable powers the controller. With the cable plugged in, the power switch cuts the motors and the laser, but the brain stays on and remembers its old position. We pushed the head to the corner by hand and the controller still thought it was 50 mm up. Now the sending script refuses to start unless the controller reads exactly 0,0.

The burn gate

The second script sends jobs. It has one rule built in: any file that would turn the laser on is refused unless you add a flag that says the gear is ready. That flag is a statement, not a convenience. It means all of this is true:

• The fire kit is within reach: extinguisher, fire blanket, smoke alarm in the room.
• Everyone present is wearing OD6+ glasses rated for 445 nm. A blue diode laser can blind you from a reflection.
• Nothing burns unattended. Ever.
• No wood until there is air assist and an exhaust to the outside.

Stopping is built in too: Ctrl-C does a feed hold and a reset. Over Wi-Fi, if the network drops mid-job, the stop is the power switch. That is written on the machine’s profile, so nobody has to remember it.

Three tests, in order

1. Motion square, beam off. The head drew a square in the air and came back to 0,0. Twelve seconds, over USB, then the same again over Wi-Fi.
2. First light, on card. Four short marks at 1, 5, 10 and 20 % power. The 5, 10 and 20 % marks showed. The 1 % didn’t, which is what we expected. Power control works and the beam fires where it should.
3. Calibration plate for 12 mm ply. The file is ready: engrave only, 100 mm square. It won’t run until the air assist and the exhaust are in, because that is the rule.

Writing it down

The laser has its own profile in the handbook: what it is, how it is configured, how to talk to it, and a modification log. Every change gets a row: date, what changed, old value, new value, why, and how it was checked. One change at a time, with a settings dump before and after. It feels slow. It is how you end up with a machine you can still understand in a year.

Next: air assist, an exhaust to outside, a honeycomb bed. Then the first piece of plywood.

Les plans sont gratuits — the plans are free.