Safety first: Use the E-stop, unplug spindle/machine power before touching tools, switches or couplers, and keep hands out of axis travel. Never bypass a hard-limit switch to run a cutting job; do not loosen a powered spindle or jog an axis into its physical end.
Model and version covered
Genmitsu 3018-PROVer V2 with GRBL-compatible controller. Check board marking and firmware before applying GRBL commands; the older 3018-PROVer and V2 Lite do not necessarily have identical connectors.
Version check: Confirm controller, GRBL firmware and actual limit/probe connections before changing parameters or running automated motion.
DIAGNOSE THE CAUSE · APPLY THE FIX · CONFIRM THE RESULT
Find the cause and fix it
Jump to your symptom: 01 · Candle reports cannot open serial/COM port02 · Port exists but busy or communication garbled03 · COM device never enumerates on multiple PCs/cables
01
Candle reports cannot open serial/COM port
HOW TO CHECK & CORRECT THIS CAUSE
- Plug direct into PC with known-good data USB cable, install manual's CH340 driver, locate CH340 COM number in Device Manager and select it in Candle at 115200 baud.
How to tell it is fixed: Candle displays connected GRBL greeting/status.
02
Port exists but busy or communication garbled
HOW TO CHECK & CORRECT THIS CAUSE
- Disconnect offline controller and close other serial apps, avoid two programs owning same COM port and reconnect Candle.
How to tell it is fixed: Commands such as status query return coherent GRBL response.
03
COM device never enumerates on multiple PCs/cables
HOW TO CHECK & CORRECT THIS CAUSE
- Investigate USB connector/controller mainboard replacement matched for PROVer V2.
- Reinstalling software cannot fix broken USB hardware.
How to tell it is fixed: Stable COM enumeration and controlled jog after board repair.
Source and model restrictions
Technical baseline: Manufacturer guide or model manual ↗