Pro 5 homing error: cycle failed to clear limit switch

Suddenly my machine won’t initialize. I’m getting a GRBL Alarm 8: Homing fail: Cycle failed to clear limit switch when pulling off.

I saw other threads about loose ball screws, and i indeed did have a very loose on on the right y axis, i’ve tightened it up but still getting the error.

Here is the log:

N0 M5
Grbl 1.1h [‘$’ for help]
[MSG:‘$H’|‘$X’ to unlock]
Grbl 1.1h [‘$’ for help]
[MSG:‘$H’|‘$X’ to unlock]
[MSG:Caution: Unlocked]
N0 M5

Usually this is electronic: bad homing switch or loose connection, or mechanical: something prevents or interferes with machine motion — write in to

Sure thing, left a vmail and sent in an email with a screenshot. Thanks. Hopefully simple fix, it was working this morning, then I spun my machine 180 (the cart it’s on) and loaded a sheet of plywood to run a program.

I checked all the wiring and everything looks fine, so not sure what happened. Checked all the rest of the ball screws and motors as well.

This particular message means that the limit switch is stuck ON. Carbide Motion can show you the Inputs, from that you can tell which switch is stuck, and you can see if something has shifted and is triggering the switch.

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I wasn’t clear on where in motion you can see the switch status?
EDIT: finally figured that out

I might have tweaked something loading the 4x8 sheet, I’m gonna take it off and check square again.

So looks like my Y2 sensor is bad, it will show red when i test it but i’m not seeing it register.

I’m trying to follow the instructions to bypass it, however i cannot access the jog screen.

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 just slightly off from the one your machine uses.

Furthermore i’ve traced the issue down to the control board, i checked the wiring harness for continuity all the back to the main connector harness plugged into the board.

Hopefully i hear from support tomorrow. I have a bunch of projects stacked up now!

I am experiencing a similar issue right now and looking forward to try your homing override method to get it running while waiting. My “X” homing fails. I have a new sensor in hand but did not take care of the issue. I am suspecting control board failure also.

G28.3 works, you have to disable bitsetter.

Trying to figure out if i can find a way to run my projects so i don’t get behind this week until parts show up.

I got my replacement board and wiring harness on Friday. Was able to run a job Saturday with tool changes. Hopefully no more issues.

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