“Alarm 1 hard limit”

Hi there, new to the forum and new to my machine. I am trying to cut out just basic letters on a piece of 3/4 inch MDF and I’ve tried about 10 times now and it will cut for a few min-10 min then suddenly stops its course and hovers and I get an alert that says “alarm 1 hard limit” then says to press reset to continue but it doesn’t continue after doing these steps… anyone have any info that could help me through this. Me and my husband have been at this all day for something that should have taken 30 min to cut. Thanks so much in advance and so happy to have found this forum!

Where are you seeing this alarm?

Which controller do you have?

How are you running the job?

More data about your board and setup will help, but I’m guessing this is a grbl controller with limit switches enabled. Sounds like the warning I’d get when there was noise on my end stop wires. I ended up adding capacitors between the ground and signal line right at the connector on the control board end and it filtered out the noise.

Another option would be to disable hard limits with $21=0. Of course, that means no homing, but I’d try it as a test.

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Its a raspberry pi4 with a v1pi server. connected by USB to an imbedded arduino nano/GRBL board.

That makes sense. I think Tom has it right

Agreed with Tom here
I had the same problem, but for me it mostly happened during homing and caused the home cycle to fail.

I solved it by using shielded 2 core cable i had lying around for the end stop cables, and separated them from the stepper motor cables by a couple of cm, and that got rid of it.

Tom’s suggestion of a caps would also work (likely better then my solution)

Just to add…also using N/C (normally closed) switches for your limit switches (and associated options in the firmware $5=1) will reduce problems with electrical noise. Many people find limit switches more trouble than they are worth in the long run.

I tried changing to NC switches and still had noise problems. My cables are shielded, but they have 6 conductors and the switches are inside the shielding with the stepper motor lines, so the source of the noise isn’t any kind of mystery. I could probably run separate lines for the switches, but I like the clean look with the single cable. I literally slipped the capacitors into the cable connectors at the control board, so it was a really easy fix.