Doesbot GRBL 1.1 Controller Board

Many stock 3018 boards follow the same pattern under their cases. That makes this one a direct stand-in when the original board fails, and a cheap starting point for a machine built from parts.

• Brain: a Nano-based motion controller running GRBL 1.1, the firmware every 3018 sender speaks.
• Drivers: three A4988 modules in sockets, with a fourth in the box as a spare.
• Supply: 12 to 24V DC into the board, with the polarity marked and worth checking twice.
• Outputs: a spindle output, plus a laser output for 12V or 5V heads with or without a TTL input.
• Inputs: limit switches on all three axes, a probe pin, and a header for an optional offline controller.

The board comes bare. There is no case, no fan and no power switch, so it needs mounting on standoffs and, for long jobs, some airflow across the driver heatsinks.

GRBL 1.1 on a Nano is the classic 8-bit setup. It streams at 115200 baud and handles three axes, which is all a 3018 uses. Senders such as Candle, UGS and LaserGRBL connect without drivers beyond the USB-serial chip, as the software entry explains.

Microstepping splits each 1.8° motor step into smaller moves. The A4988 goes down to one-sixteenth steps, which gives finer motion and quieter running. The DRV8825, which drops into the same sockets, goes to one-thirty-second and handles a little more current.

Steps per millimetre follow from the lead screw. On a T8 screw with an 8 mm lead, a 200-step motor at 1/16 microstepping needs 400 steps per mm; at 1/32 it needs 800.

1. Set the microstep jumpers under each driver socket the same way on every axis you want matched.
2. Turn the trim pot to set current just below the motor's rating, measured at the driver's reference pin.
3. Enter the steps per mm in GRBL settings 100, 101 and 102 for X, Y and Z.
4. Jog 100 mm and measure; adjust the setting if the real move is off.

Motors that whine and skip usually have too little current; motors that are too hot to touch have too much.

The XYY setting clones the Y driver's step and direction to a second motor. That suits larger gantry builds where the Y axis has a motor on each side, and it is also how many hobby laser frames drive both sides of a wide bed. A 3018 uses one Y motor, so it stays in the plain XYZ mode.

• XYZ: the normal 3018 layout, three motors, three drivers.
• XYY: two Y motors moving together, no Z; common on laser-only frames.
• Laser: 12V heads with a three-pin lead, or 5V heads taking a TTL power signal.
• Spindle: the output runs a small DC motor such as a 775; a 300–500W spindle needs its own supply and controller.

Laser work on GRBL also needs laser mode switched on. With GRBL setting 32 at 1, the board changes power without stopping at each move, so corners do not burn darker than straight lines.

The probe pin makes Z zeroing quick. A touch plate on the pin and a clip on the bit let the sender lower the tool until contact, then set Z automatically. Limit switches on the three limit inputs make homing possible, which lets the machine find the same origin every session.

The SainSmart Z-axis touch probe is a common partner for that probe input, since it works with Candle's probing routine.

The Doesbot is the most open of them. It suits someone happy to set jumpers and trim pots, and it doubles as a controller for a plotter or a laser built from scratch. The trade is polish: the Genmitsu board arrives in a case and the MKS with a screen, while this one arrives as a bare circuit board with loose driver modules.

For a Genmitsu 3018-PRO, the Genmitsu board is the plug-for-plug match, with the connectors in the places the looms expect. The Doesbot suits other brands and scratch builds, where a little rewiring is part of the job anyway.

1. Photograph the old board's wiring before unplugging anything.
2. Note the connector types on the motor and switch leads; some boards use XH2.54 plugs, others screw terminals.
3. Record the old GRBL settings with the $$ command in the sender, so feed and travel limits carry over.
4. Confirm the supply voltage matches the board's 12–24V range and the laser's own voltage.

A new board is also the moment to add what the old one lacked. The upgrade order entry puts limit switches and an E-stop early in the list for that reason.