Genmitsu Micro Limit Switches (6-pack)

The details that set this set apart from bare micro switches:

• A blue LED on each switch. It lights when the switch closes, so a glance shows whether the lever is pressed.
• Pre-made 1 m 3-pin cables. No crimping; each lead plugs into the switch and into the board.
• Plug-in fit on Genmitsu boards. The GC3D3-V2.1, MC3D3-V2.1 and MC5D3-V3.3 accept them directly.
• A full set. Six switches cover the minimum and maximum of every axis, or give three spares for a homing-only setup.

Each switch is 18 × 27 × 14 mm with 3.0 mm mounting holes, normally open and momentary, and weighs 11 g. The 125 VAC, 1 A rating is far above the few volts a CNC board puts through a limit input, so the contacts are never the weak point.

For anyone cutting oak drawer fronts or acrylic panels in repeat batches, homing is what makes the second batch land where the first one did.

Where homing earns its keep:

• Repeat batches of oak coasters or acrylic tags from a saved work offset.
• Two-sided jobs, where the flipped part must line up with the first side.
• Recovering after a power cut or an emergency stop without guessing the zero.
• Fixtures screwed to the spoilboard at a known machine position.

Homing also changes how a shop works. Instead of zeroing on a pencil mark each session, the machine homes, and the work offset from last time is still valid.

The limits of limit switches:

• They protect only at the ends of travel. A bit plunging too deep into the stock is not a limit-switch problem.
• Electrical noise from spindle leads can trigger false alarms if switch cables run alongside them.
• Dust and chips can hold a lever down or stop it closing. The LED shows which.

1. Power down and unplug the machine.
2. Remove the old switch, noting which way its lever faces.
3. Screw the new switch to the same mount through its 3.0 mm holes, lever toward the moving part.
4. Plug the 3-pin cable into the switch and the matching port on the board.
5. Route the cable along the frame, clear of the spindle leads, with slack for the axis's full travel.
6. Power up and press each lever by hand: its LED should light.

Then check the board sees it. GRBL 1.1 reports triggered inputs in its status line as a Pn: field, followed by the letters of any pins that are active. Press the X switch and an X should appear; release it and the X should go.

Wiring to other boards:

• Genmitsu notes that non-Genmitsu boards may define the pins differently.
• Check which pin is signal, which is power for the LED and which is ground before plugging in.
• Swap the order in the connector if needed, rather than forcing a mismatched plug.

Run the first homing cycle with a hand on the stop. Start it with each carriage mid-travel, and confirm every axis moves toward its own switch and backs off after touching it.

If the board reads every switch as pressed when none is, GRBL's invert-limit-pins setting is the usual fix. Homing and limit settings are covered on the 3018 software page and the PROVer V2 entry.

Owners of an original PROVer who plan to keep it for years often buy this set before anything breaks. The switches sit where chips fall, the levers are thin, and a single bent lever stops homing on that axis until it is replaced. Having the part in a drawer turns a stalled weekend into a ten-minute swap.

For machines with no switches at all, the job is bigger than buying a pack: mounts must be printed or bought, and the board needs spare limit inputs. That is worth pricing before starting.

The fit comes down to three details:

• The machine name and board model; direct plug-in fit is for GC3D3-V2.1, MC3D3-V2.1 and MC5D3-V3.3.
• How many switches are needed: three for homing only, six for homing plus hard limits at both ends.
• That the board has free limit ports for every switch being added.

Switches and a stop button sit early in the upgrade order, after a probe and workholding; the sequence is on 3018 upgrades. At 11 g each, a spare set weighs nothing in a drawer and saves a stalled project when one lever snaps.