Broken Limit Switch IDK why?

I was milling a 3 inch tall piece of wood with a 4 inch end mill. Had plenty of clearance when zeroing then I paused the operation and the HDZ went straight to the roof and broke the limit switch?
What did I do wrong?
Just ordered 10 at 4 dollars a piece. Wont leave me stranded in the middle of a project again!

what was your retract height set to in the design/toolpath ?
with such a long endmill and depending on how high/low your router is in the mount, it is possible that the retract height made the HDZ travel up to the limit, but…the limit switch should have stopped the movement then. Did it grind (i.e. not detect the limit switch at all) or did it contact & stop the movement, but left your switch damaged next time you started to home?

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It just went up and crashed and broke the switch locating pin right off and pushed the switch up. They have the switch positioned so if the HDZ hits the roof it breaks the switch. My retract was .4. Might have just been the switch broke on the previous homing? I had no indication of a problem.
I have had it for about a month now I am guessing probably 75-100 homings.

email support and in my experience they are no fuss and will just send a new one out instantly

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I ordered 10 overnight, should be here tomorrow so no need to bother them. There is nothing worse then being in the middle of a project and being shut down though! I feel like it would be preemptive to stock up on all breakable parts for future mishaps.
I found the wiki page that lists all the Shapeoko parts but I could not find any information on steel belts which I am guessing will probably need to be replaced first.

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The steel belts are a new development. Not sure where they’re being sourced from.

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@BubbyDog Are you using Carbide Motion? Are you sure it happened on a pause and not during a retract as @Julien mentioned? On a feedhold (pause) the Z should retract to 5mm below the Z limit. It’s doubtful the HDZ lost steps. Why did you pause?
Unfortunately, unless you have hard limits enabled (disabled by default), the switches don’t have any effect except during homing.

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I was using Carbide Motion and paused. The clearance was set to .4 with fusion 360 but I was using a very long end mill Amana 46590 - a 4 inch with 2.75 reach to carve out a 3 inch thick block on top of 1/2 inch spoilboard on top of 1/2 aluminum base.
It looked too close to probe just z but I was able to to a 3 axis probe no problem. On pause it just crashed into the top and stuttered while I hit the off switch. On inspection limit switch locating pin was broken and switch rotated up and plunger is broken which I tested.
My only explanation is I broke the limit switch during probing and did not notice? Seems too much of a coincidence?
Can you explain why hard limits are disabled? I would like to prevent this from happening again.

Man, it’s been so long since I last crashed at the top of my Z that I KEEP forgetting that the default Shapeoko config is like that. I’ll have to go and read related posts again to figure out if there is a really good reason not to enable hard limits. I seem to remember one reason being that “noisy switches” could generate false positives and stop a job midrun, but to me that is not the right answer (hardware or software noise filtering could be implemented)

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I think I would much rather stop a job, not sure how a noisy switch would send a false positive. It is a on/off switch yes?

Yes, the switches are NO, and need shielded wiring to reduce false positives.

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I think, it’s a safer position for Carbide3D to disable hard limits by default, because they have hundreds of users out there, and the machine is potentially susceptible to EMI (as @WillAdams noted, unshielded cables to the switches…), so there is a X% chance that the switches may false-trigger during runs, causing a job failure (very much like EMI-related disconnects), and then people would complain loudly.

But if you, on your machine, want to give hard limits a try, it’s as simple as setting $21=1 in the GRBL console.

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I ordered some steel belts off eBay, couldn’t really find many options. Ordered them Nov 24th and still waiting for them to leave the origin country. But it is a 10 meter roll so should be good for quite awhile once it arrives.

Wow talk about a long wait! Can I get a link please?

Thank you Julien, I really appreciate the help!

Take a look at this thread

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Yeah, especially since I ordered my proximity switches at the same time and got those a couple weeks back.

The link says 6mm, but there is a width option on there.

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https://reprapworld.com/products/mechanical/timing_belts/gt2x9_mm_steel_reinforced_timing_belt_per_meter/

is another place, they ship from europe, took about a week for me

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Thank you Adam, they are on the way! On a really slow boat from China I guess…

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One minute too slow haha Ok they are cheap so I ordered from both companys.

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