3018 Micro Limit Switch Kit

These switches are small PCB modules rather than bare levers:

• Normally open, momentary contacts rated 125V AC at 2 A, far more than a 5V logic signal needs.
• A blue LED on each board that lights when the switch closes, so each one can be checked by eye.
• A 3-pin connector and a 1 m 3-pin cable per switch. The third wire powers the LED.
• 18 × 26 × 11 mm bodies weighing 11 g, with 3.0 mm mounting holes.

They come from Huajiang's Zhong Hua Jiang brand and are matched to its own 3018-PRO. The maker names three boards that take them with no rewiring: GC3D3-V2.1, MC3D3-V2.1 and MC5D3-V3.3.

What homing adds in practice: soft limits that refuse a job too big for the bed, a hard stop if a jog overruns, and a machine zero that makes saved work offsets valid after a restart. How limit switches fit the wider upgrade order is set out in 3018 upgrades.

1. Power down the machine.
2. Choose the home corner. Many 3018s home to the back-left or front-left, with Z homing up.
3. Fit the home switches first, one per axis, using the 3.0 mm holes and small brackets or printed mounts.
4. Fit the far-end switches on X and Y, and a bottom switch on Z if wanted.
5. Push each axis by hand toward each switch and watch the LED light before any metal meets metal.
6. Route each 1 m cable along the frame to the board, away from lead screws and the spindle.

Habits that keep switches working in a dusty machine:

• Point levers down or sideways. MDF and plywood dust settles on upward-facing switches and can hold a lever half-pressed.
• Keep them out of the chip path. The Y switches at the front of the bed catch the most debris.
• Leave travel after the trigger. The switch should close with a few millimetres to spare so a fast jog does not hit the frame.
• Glance at the LEDs. An LED that stays on with nothing touching points to dust or a bent lever.

Two switches on one axis share a single GRBL input, because GRBL on 3018-class boards reads one limit pin per axis. Normally open switches join in parallel on that input.

Before plugging in on an unknown board:

1. Find the limit header's silkscreen or pin chart: it should mark 5V (or VCC), GND and the signal pin (often S, X, Y or Z).
2. Look at the switch board's own markings for the same three pins.
3. If the order differs, lift the crimped pins out of the plastic housing with a pin or small screwdriver and reorder them.
4. Plug in one switch, power up, press it and confirm both the LED and the controller's pin state change.
5. Repeat for the others.

GRBL settings once all six read correctly:

• Setting 5 inverts the limit pins. If Candle reports a limit as triggered with nothing touching, flip it.
• Setting 22 enables homing; 21 hard limits; 20 soft limits after homing works.
• Settings 130–132 hold travel: about 300, 180 and 45 mm on a standard 3018-PRO.
• Setting 27 sets the pull-off distance after homing; a few millimetres keeps the switch released.

On Genmitsu PROVer and MX3 boards, the PROVer-labelled versions of this kit or Genmitsu's own six-pack match the headers directly. The meaning of every GRBL setting is covered in 3018 CNC software.

Against the other switch sets:

• CNCTOPBAOS kit: plain 2-pin switches, 80 cm leads and an E-stop, for CNCTOPBAOS and RATTMMOTOR boards.
• Genmitsu six-pack: 3-pin, 1 m, for PROVer and MX3.
• Genmitsu Essential Accessories Kit: six switches plus a probe and a stop button.

Check before ordering: the pin count on the board's limit headers, the pin order, and whether an E-stop is already fitted. For a board with 3-pin headers and a known pinout, the six-LED version is the tidy choice, and the lights make fault-finding quick.

Budget an afternoon for the fit. Mounting takes an hour; the rest goes on routing cables tidily, checking pin order and walking through the GRBL settings one at a time. The first successful homing cycle, all three axes backing off their switches in turn, is the moment the machine starts to feel like a tool rather than a kit.