Hard & soft limits to keep Shapeoko from crashing

I just upgraded my 2015 Shapeoko to an XXL (I had upgraded it to an XL in 2017) and went to surface a top wasteboard. I set the size in Carbide Create to 32" x 32" ands started in the front left corner, forgetting the XXL was actually only about 30.5" deep from that point. Even though my homing switches seemed to work perfectly, the machine crashed into the back rail repeatedly for the final few passes.

I was surprised Carbide Motion didn’t prevent the Shapeoko from crashing into the back rail, and also surprised to see that both hard and soft limits are turned off by default. Why wouldn’t one or both of these be enabled? I’m assuming the answer is because CM is supposed to prevent this kind of crash automatically? I’m using build 4.0.428 on a 16" MacBook Pro running macOS 10.15.2.

Thanks for any help!

Soft limits aren’t enabled because false positives are difficult to troubleshoot. Hard limits because the homing switches are only at one corner and use unshielded wiring which can result in false positives.

See https://wiki.shapeoko.com/index.php/SO3_Function_Test#XXL for notes on how far the machine can move in what direction (note that those numbers may need to be updated for newer versions of Carbide Motion).


Thanks, Will! But am I wrong that Carbide Motion used to prevent crashes? If I zero the machine near the back or right rail and then tell it to move at 200 ipm to the right or back, I thought CM4 automatically stopped that. But maybe it never did and I’ve just been more careful before not. It wasn’t a big deal, I just was surprised that the hard or soft limits weren’t on by default because I remember turning them on manually years ago when the limit switches first became available as an upgrade.

Carbide Motion implements soft limits when jogging.

Right. I think when I first installed the limit switches as an optional upgrade almost four years ago, the instructions were to manually turn on either soft or hard limits ($20=1 if I recall), so I think that’s what I was remembering.

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