Rotary axis limits

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12 Oct 2020 08:09 - 12 Oct 2020 08:10 #185809 by JetForMe
Rotary axis limits was created by JetForMe
I just added a rotary axis to my AvidCNC-based gantry CNC router. The servo, like all the others, is a Teknic SDSK, and it's driven by the Mesa 7i76e card driving everything else. So far so good.

I just tried posting a non-trivial rotary toolpath from Fusion 360, and it commands A to 93240. I know I can constrain Fusion to limit angles, but I'm wondering what the right configuration is for the machine itself. My yet-to-be optimized INI has my A axis arbitrarily limited to [-9999, 9999].

Should I increase that limit? Is there a way to tell LinuxCNC it's virtually unbounded? There is a count limit internal to the SDSK's encoder, I don't know what it is or what happens if it's exceeded.

Or is it better to constrain Fusion 360? I feel like I'd rather not constrain it unnecessarily. I can see machining results being better if it never has to stop rotating to reverse direction.

Also, it seems LinuxCNC didn't warn me that the loaded NC file exceeded the rotary axis position limits (in the same way it warns me for linear axes). At least, not until it hit the limit while running the NC program.
Last edit: 12 Oct 2020 08:10 by JetForMe.

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12 Oct 2020 12:40 #185825 by andypugh
Replied by andypugh on topic Rotary axis limits
I think that I just put in some very big numbers.
You could look at WRAPPED_ROTARY but that only works if the CAM system understands it.

There isn't a simple option (like setting the limits both to zero) as 0 is a perfectly valid max or min limit.

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12 Oct 2020 19:45 #185869 by andypugh
Replied by andypugh on topic Rotary axis limits
I just accidentally found the answer, looking for something else.

If you leave out the MAX_LIMIT and MIN_LIMIR for a rotary joint then no (practical) limit are enforced.

linuxcnc.org/docs/2.8/html/config/ini-co...t__lt_num_gt_section
The following user(s) said Thank You: Aciera

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15 Oct 2020 09:02 #186170 by JetForMe
Replied by JetForMe on topic Rotary axis limits
Ah, thanks. Sets it to +/- 1e99. Which is not as good as actually ignoring limits, but better than nothing.

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