CNCTOPBAOS Limit Switch & E-Stop Kit

• Six micro limit switches. Two per axis, one at each end of travel. Each has NC, NO and C terminals, with NO and C pre-wired to an 80 cm 2-pin lead.
• One emergency stop. A push button rated AC 250V 3 A and DC 30V 5 A, released by turning it clockwise until it pops up.
• Fixing hardware. Mounting screws and hex wrenches sized for 3018-series frames.

Six switches rather than three is a deliberate choice. Homing needs only one switch per axis, at the home end. The second switch on each axis guards the far end as a hard limit, so a jog in the wrong direction or a job larger than the bed stops at the switch instead of the frame.

The 80 cm leads are long enough to reach from the controller at the back of a 3018 to the far end of the X gantry. That is the length where short leads usually fall short, and where many owners end up splicing.

Compared with a PROVer switch set, the difference is the connector. These are plain 2-pin switches with no indicator LED and no power wire, matching the 2-pin limit headers on 3018-PRO-family boards.

Jobs where that repeatability pays off:

• Two-sided carving. Flip a walnut blank on dowel pins located from machine zero and the back lines up with the front.
• Double-sided PCBs. Top and bottom copper need registration within a fraction of a millimetre.
• Batches. A jig fixed to the spoilboard stays at the same machine coordinates, so the tenth coaster starts where the first did.
• Recovery. After an E-stop or a power cut, homing restores the reference and saved work offsets become valid again.

GRBL's settings make the switches useful. The numbers below are GRBL setting numbers, entered in the console:

Soft limits are the quiet win. With the travel set, GRBL rejects a job that would run off the bed before the spindle turns, which saves a plywood blank and a bit. Enable the settings in that order, testing each before the next: homing, then hard limits, then soft limits. Setting details for each sender are in 3018 CNC software.

1. Power down and unplug the machine.
2. Fit one switch at each end of X, Y and Z, lever facing the moving part.
3. Jog each axis by hand toward each switch and confirm it clicks before any metal touches.
4. Route the 80 cm leads along the frame, clear of the lead screws and gantry.
5. Plug the pair of switches for each axis into that axis's limit port.
6. Plug the E-stop into its port.
7. Power up and press each switch by hand; the sender's status should show the pin change.

GRBL on 3018-class boards reads one limit input per axis. Both switches on an axis share that input: in parallel when wired normally open, as supplied, or in series when rewired normally closed.

Test before trusting:

• Run a homing cycle at a slow seek rate with a hand on the E-stop.
• Confirm each axis stops and backs off its switch.
• Press the E-stop mid-jog and check the board halts, then turn it clockwise to release and reset.

Before ordering, check:

• The controller has limit ports for X, Y and Z and an E-stop port, all 2-pin.
• The frame is a 3018-PRO, Pro-Max, Plus or 1610-PRO pattern, so the holes line up.
• The GRBL version on the board supports homing; any 1.1 board does.

For a CNCTOPBAOS or RATTMMOTOR machine, this kit is the matched set. It adds the stop button and the homing hardware in one order, and the long leads spare the splicing. The rest of the upgrade order is in 3018 upgrades.

A plastic-bodied switch is fine on a 3018. Loads are tiny, the switches only carry a logic signal, and the lever takes a light carriage touch rather than a crash. Keep them clear of chip piles, though: MDF dust packed under a lever can hold a switch closed, and GRBL reads that as a tripped limit on the next job.

One kit covers the whole machine. Nothing else is needed except, perhaps, a few cable clips to keep the 80 cm leads away from the lead screws.