Troubleshooting Homing

Introduction

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.

Support Videos

For those who prefer video to text, we have this, which might help out.

Common Causes of Homing Failure

Jammed Axis

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:

1. Cutting debris is packed into the axis and blocking any motion. Cleaning everything out can quickly fix this.
2. The vacuum hose is draped over an axis so that it blocks any motion. The vacuum hose should never rest on the machine; it should be suspended over the machine.

If either of these happens to you, make the fix and reinitialize the machine, and you should be back to work quickly.

The Machine is Out of Square (Shapeoko 5 Pro only)

The Shapeoko 5 Pro uses switches on each Y axis to resquare the machine whenever it homes. The Shapeoko 5 Pro can compensate for approximately 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.

Switch Targets Missing

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.

Metal Debris on the Switch

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 Switch Failures

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.

Wiring or PCB Failures

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.

Homing Error Codes

Starting in Carbide Motion 623, the homing error codes were changed to be Carbide-specific, so we can add more meaningful information about the nature of any homing problem that occurs. Below is a list of the error codes that you may encounter.

HM001: The machine could not pull off the homing switches

At the start of the homing process, Carbide Motion checks the state of the homing switches to see if they’re already closed. Carbide Motion will attempt to move the machine away from any currently active homing switches if they are. This may fail for a number of reasons:

1. The machine’s axis is jammed, either mechanically by something like a vacuum hose or by dust and chips jammed in the axis.
2. The homing switch is bad, causing it to light up even when there is no metal target in front of it. (Click here to test)
3. If the main electronics module is bad, Carbide Motion may register the switch as being active, even when it’s not. (Click here to test)

HM006: The controller was reset during homing

HM006 is equivalent to GRBL Alarm 6, meaning that the machine’s controller reset itself in the middle of the homing process. This should never happen in everyday use.

The best course of action is to restart the machine and redo the initialization process in Carbide Motion. If the problem persists, it’s likely a bad electronics module, but the support team can help you troubleshoot to verify that.

HM007: The safety door was opened during homing

HM007 is equivalent to GRBL Alarm 7, meaning that the safety door was opened in the middle of the homing process. This should never happen on a Shapeoko (which doesn’t have that code enabled), only on a Nomad.

If this happens, you’ll need to close the door and redo the initialization process.

HM008: The machine could not pull off the homing switches

HM008 is equivalent to GRBL Alarm 8. After the switches are found, your machine will back off from the switch and approach them again more slowly to more accurately find the homing position.

Because Carbide Motion does a number of checks before beginning the homing process, this error is very rare.

This error could be caused by:

1. The machine’s axis is jammed, either mechanically by something like a vacuum hose or by dust and chips jammed in the axis.
2. The homing switch is bad, causing it to light up even when there is no metal target in front of it. (Click here to test)
3. If the main electronics module is bad, Carbide Motion may register the switch as being active, even when it’s not. (Click here to test)

HM009: The machine could not find the homing switches

HM009 is equivalent to GRBL Alarm 9, meaning that the machine was not able to find the homing switch within the search distance. When this happens, the machine will typically crash into the end stop and vibrate until the distance limit is reached.

This could be caused by:

1. The machine’s axis is jammed, either mechanically by something like a vacuum hose or by dust and chips jammed in the axis.
2. The homing switch is bad, causing it not to light up even when there is a metal target in front of it. (Click here to test)
3. If the main electronics module is bad, Carbide Motion may not register the switch as being active, even when it’s lit up. (Click here to test)

HM010: The machine could not find the Y2 homing switch

HM010 is equivalent to GRBL Alarm 10 and should only occur on the Shapeoko 5 Pro.

When homing a machine with dual Y switches, the machine first homes the right side and then the left to bring the machine into square if it’s not already there. There are a few reasons that the Y2 switch may not be found:

1. The machine’s axis is jammed, either mechanically by something like a vacuum hose or by dust and chips jammed in the axis.
2. The homing switch is bad, causing it to light up even when there is no metal target in front of it. (Click here to test)
3. If the main electronics module is bad, Carbide Motion may register the switch as being active, even when it’s not. (Click here to test)
4. The search distance for the Y2 switch is fairly small to ensure that the machine is not damaged in the case of a bad Y2 switch. If the machine starts too far out of the square, the machine may not be able to find the Y2 switch in a single homing cycle, so you’ll need to redo the initialization process again to bring it into a square. (This generally only happens the first time a machine is run)

Testing Homing Switches

Each inductive switch has a small LED light that lights up when it senses metal, making it easy to test the switch.

1. Power on the machine.
2. Ensure the machine axis is more than an inch away from the switch.
3. Ensure the LED is off. If it's not, you likely have a broken switch.
4. Put a piece of metal in front of the switch. Ensure the LED is on. If not, you have a bad switch or a broken wiring harness.

If everything above looks good, you must test the full signal path back to the main PCB.

Testing the Wiring and PCB

Carbide Motion includes a debug panel that makes it easy to see if the main PCB can get the switch input signals.

1. Open Carbide Motion
2. Connect to your machine
3. Go to Settings
4. At the bottom of the pane, you'll see an active switch panel with X, Y, and Z (For the Shapeoko 5 Pro, you'll also have a Y2)
5. Test the switches as you did above and see that the matching signal activates and deactivates when you put a piece of metal in front of the switch.

If it doesn't work correctly, our support team can help you diagnose if it's a bad switch, wiring harness, or PCB.

Bypassing Homing Switches

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.

1. Connect to your machine in Carbide Motion.
2. Go to the MDI screen.
3. Enter G28.3 and send it to the machine. This will cause your machine to set itself as "homed" with the current position being the home position.
4. Go to the Jog screen.
5. Jog your machine all the way to the back right, and lift the Z to the maximum height.
6. Go to the MDI screen.
7. Enter G28.3 and send it to the machine. This sets the current position as home, which should be very close to the real home position.

Note: You'll want to reset your project zero after a manual homing routing because the manual home position will likely be slightly off from the one your machine uses.