Homing is the process of moving a CNC machine to a known position, called the "home position". The home position is used as a stable reference for everything else in the machine, including the project location and the position of your BitSetter.
The homing process involves slowly moving the machine in the correct direction until it detects the home position. Shapeoko and Nomad machines use inductive switches to detect the home position.
Inductive switches can be thought of as small metal detectors. They turn on or off when metal is brought close to the face of the switch. The switches trigger with either steel or aluminum metal targets.
Inductive switches are "potted," meaning they're filled with epoxy after assembly making them a completely sealed unit. Because of the potting, they cannot be serviced or disassembled; they can only be replaced.
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Homing will fail on a machine if the axis is jammed, so it cannot move to the home position. In most cases, this is one of two things:
If either of these happens to you, make the fix and reinitialize the machine, and you should be back to work quickly.
The Shapeoko 5 Pro uses switches on each Y axis to resquare the machine whenever it homes. The Shapeoko 5 Pro can compensate for around 25mm of error in the initial squareness of the machine without any trouble. The homing process will fail if the machine is off by more than that before running the initialization routine.
If this happens to you, check that nothing is blocking the travel of your Y axis and reinitialize the machine. It should start from a better position after the first attempt, so it will likely succeed the next time.
We have seen failures where a switch failed to close because the metal target that triggers it was missing or out of position. This is usually fixed by repositioning the switch or target to get them in the correct position.
We have seen cases of switch failure that turned out to be metal chips from the CNC machine packed onto the surface of the switch, causing it to be constantly activated. This is not a failure of the switch, and the problem is quickly fixed by removing the chips.
Inductive switches are relatively simple devices and only fail in a couple of ways.
ESD / Electrostatic Discharge - It's possible to zap a switch with static electricity and kill it. This would most likely be static electricity from an ungrounded vacuum system in a CNC machine.
Wiring - The wires coming out of the switch can be pulled or crimped in a way that damages the internal circuit.
If none of the fixes above work for you, see the section below on testing the homing switches.
Like the switches themselves, the wiring and PCB in the machine is usually only damaged by physical abuse or ESD.
If your switches checked out OK, see the section below on testing the wiring and PCB.
Each inductive switch has a small LED light that lights up when they sense metal, making it easy to test the switch.
If everything above looks good, you must test the full signal path back to the main PCB.
Carbide Motion includes a debug panel that makes it easy to see if the main PCB can get the switch input signals.
If it doesn't work correctly, our support team can help you diagnose if it's a bad switch, wiring harness, or PCB.
When a switch fails, it's impossible to continue using the CNC machine, even though the homing switches are only used to initialize the machine. We have a process outlined below to continue using your machine while waiting for a replacement.
Note: You'll want to reset your project zero after a manual homing routing because the manual home position will likely be just slightly off from the one your machine uses.