Zhong Hua Jiang Z-Axis Touch Probe

The Zhong Hua Jiang probe is the plain version of that tool. It comes from Huajiang, a Chinese maker of CNC routers, spindle motors and inverters founded in 2000, whose Zhong Hua Jiang brand also sells a 3018-PRO machine and matching limit switches.

• A conductive puck about 40 mm across and 20 mm tall that sits on the stock.
• A clip lead that goes on the bit or collet, completing the circuit when the bit touches the puck.
• A 2 m cable with a quick-wiring connector, long enough to reach from the board to any spot on a 3018 bed.
• Software support for Candle on GRBL and for Mach3.

A one-click Z zero changes more than setup time. It makes Z repeatable between tool changes, which matters for any job with more than one bit. A pocket cut with a flat end mill and finished with a V-bit only lines up if both bits share the same zero.

Where a probe sits in the order of upgrades is set out in 3018 upgrades.

1. Jog the bit over a flat part of the stock, 5–10 mm above it.
2. Place the puck under the bit.
3. Clip the lead to the bit's shank, not the flutes.
4. Run the probe command in Candle, or the Z-probe script in Mach3.
5. GRBL moves Z down slowly with a G38.2 move until contact, then records the height.
6. The software subtracts the puck height and sets Z zero at the stock surface.
7. Unclip, remove the puck and start the job.

Material habits:

• MDF and plywood. Blow dust off the spot before placing the puck. A layer of fibres adds its thickness to every reading.
• Acrylic. Decide whether to probe on the protective film or bare plastic, and do it the same way every time.
• Copper-clad PCB. The board surface itself conducts. A common trick is to clip the probe lead to the copper and touch the bit straight onto it, with no puck and no offset.
• Hardwood with a finish. Probe on bare wood; the puck sits flatter.

Starting feeds for these materials are gathered in what a 3018 cuts.

On a GRBL 3018-PRO:

1. Power down and plug the connector into the probe header.
2. Power up and connect Candle or UGS.
3. Touch the clip to the puck by hand. The status report should show the probe pin as triggered; GRBL 1.1 lists it as Pn:P.
4. Release, and the flag should clear.
5. Run one probe cycle on scrap with a spare bit.

If it misbehaves:

• Probe alarm at the start. GRBL sees the probe as already triggered. Check for a short in the lead, then the probe-invert value, setting 6.
• Bit drives into the puck. No signal is reaching the board: clip not attached, lead in the wrong header, or a dirty collet breaking the circuit.
• Readings wander. Resin or dust on the bit or collet adds resistance. Clean the shank where the clip bites.
• Z zero off by a fixed amount. The puck height in the software is wrong.

For Mach3, map the probe to the input used by the motion card and test it in the diagnostics screen before running the probe script. Sender choices for GRBL are compared in 3018 CNC software.

Before ordering, check:

• The board has a 2-pin probe input, and which pins it uses.
• The lead reaches from the board to the most distant bed corner.
• The sender software runs a probe routine; Candle, UGS and Mach3 all do.

On a generic 3018-PRO or a Zhong Hua Jiang machine, this probe is the simple, matched choice. The long lead is its practical edge over shorter-cabled rivals on frames where the board sits at the back.

A plate probe also teaches good habits. Clipping onto a clean shank, probing slowly and measuring the puck once are the same steps any tool setter needs, so moving to a pricier probe later means changing hardware, not relearning the routine.

Pair it with limit switches and homing, and the probe's Z zero can be saved as a work offset that survives a restart. Without homing, re-probe after every power cycle.

Store the puck in a clean box between jobs. A scratched or dusty face reads as extra height, and the error only shows when a V-carve comes out a shade too wide.