Limit switches are tripping randomly during machine operation

[Gary Campbell]

I agree with most everything in that article, and this one also from 2002: https://www.amazon.com/Woodshop-Dust-Co ... 1561584991

That said, neither apply, nor do they mention CNC requirements. They are geared at the possibility of explosion in a home shop dust collection system, which is very low or nonexistent. Simple test: Remove the dust collection hose from the CNC machine and rerun the file

[slodat]

It has been running for 54 minutes since last trip. It’s not the dust collection (I think). It has done it (once I recall for sure) without dust collection.

[slodat]

Ran the last program without incident. I looked at the error log and there are many entries for the limit switch trip. It shows all three. Has me thinking there's something common to them, but I'm not sure what's up with that yet. Report and config photo attached.

[mick41zxr]

Check with Keith,
I think there is an issue with home/limitOk setup at moment. I had an issue where home/limit kept re-tripping on axis 1 across a variety of switch types.
Only happened in first axis. Changed setup to home all & problem went away, just used soft limits after that.
Regards,
Michael

[slodat]

Michael,

So I can switch the inputs to be home only and then use travel limits to handle the limit piece..? Hadn't thought of that. Hopefully Keith will weigh in.

Thank you!

[mick41zxr]

Yes,
Wire them in series to one input, set it to HomeAll & control travels with soft limits.
Regards,
Michael

[cncman172]

slodat,

Another options is to make your limit switches use 24V logic. Use a 24V relay and have the 24V flow through the NC contacts of the limit switches to and to 24V power supply. When the limit switch or all the limit switches if you choose to wire them all in series are NC not being touched at any extreme, the 24V power will energize a 24V relay. Not the 24V relay on the Acorn board a stand alone relay. The contacts of that relay will be wired to the input on Acorn selected for limits. This will keep all the limits well above the noise level and you will not see any limits firing with dust collection or anything else. This is a common practice on many commercial machines.

Russ

[slodat]

I changed the inputs to HomeOk for each of the three axis.

[slodat]

Keith?

[cnckeith]

hello.
we do not recommend using NO switches as they are susceptible to noise. use NC switches and 24 vdc.