Software limit

Is there a way to set up a software limit in usbcnc so that the spindle can not go any further than the set limit. I do not have homing switches on my machine and currently I'm running the machine in the middle of the bed so I have no fear of crashing into the x negative and positive limits. And no chance of hitting the y negative and positive limits as well. But because I have a 4 axis machine, my z axis gets hit on the negative (up) frequently because it only leaves me about 20 or 30 mm of travel from the top of the part. And that's a generous estimate.

Is there a way to set the software with a ceiling so it won't allow the z axis to go any higher than a certain height. I realise I may have to reset this limit each time I run a part but I'd rather do that than ruin expensive parts on my machine.

Yes I'm aware homing switches are cheap but I don't have the money to buy them right now and unless someone is sending me some free ones that won't work.

So I need a software based solution. Is there anything like that built into usbcnc or a workaround I can use to do it?

Thank you in advance.

Yes, you can set "Motor Limits" and/or "Motion Range".
https://www.cnczone.com/forums/attac...d=409502&stc=1

That's in plantcnc tng, I'm using usbcnc. Are they interchangeable. Is tng just the newest version or something. And can this be done in usbcnc or is this option only available in tng.


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Go to "Axes" in settings, specify the desired limits in "Limits" and activate the soft limits under "Soft Limits".
It is kind of self explanatory.

Thank you. And no it's not exactly self explanatory. To me a soft limit can be exceeded and a hard limit is one that could not be exceeded. That's what soft limit means. That's why I didn't check it. But even had I known that it wouldn't have helped because it's greyed out and I can't check it. So what do I have to do to get it to work?


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Originally Posted by cammel8

Thank you. And no it's not exactly self explanatory. To me a soft limit can be exceeded and a hard limit is one that could not be exceeded. That's what soft limit means. That's why I didn't check it. But even had I known that it wouldn't have helped because it's greyed out and I can't check it. So what do I have to do to get it to work?
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Not sure why greyed out. On my machine with MK2 and another one with MK3/4 the soft limit controls are active, even when the machine is not connected. Maybe Planet CNC has an explanation for that.

As for the "soft limit" definitions, I am under the assumption that only means "limit in software" (vs. hardware switches). But when activated, they are just limits and the machine is not allowed to go beyond them. You can also activate deceleration when approaching these limits to avoid step loss due to sudden stop. Another recommendation is to activate g-code check to get a warning if the soft limits will be exceeded before running the program and getting unexpectedly stopped in the middle of the run.

You probably have Chinese knock-off controller. They are based on our first Mk1 controller which an obsolete and not supported item. Many of their features are outdated and there is no software/firmware development.

Mk1 controller does not support soft limits.

Quote:

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Originally Posted by PlanetCNC

You probably have Chinese knock-off controller. They are based on our first Mk1 controller which an obsolete and not supported item. Many of their features are outdated and there is no software/firmware development.

Mk1 controller does not support soft limits.

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How do I find out what I have


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You do have Chinese knock-off controller unless you made it yourself.

It is a good chance that it is JP-382c:
https://planet-cnc.com/replacing-chi...rv-controller/