Resetting Rotary Axis to Zero

After completing a program that involves multiple turns of the rotary axis, I'd like to return to my start position for the next cycle. I want this to happen without having to "unwind" the rotary axis, rather just have it return to the nearest zero equivalent position.

I know that WRAPPED_ROTARY=1 is one way to accomplish this, but using this would mean that I'd need to write all of my combined motion in incremental mode, which I do not want to do for more than a few reasons.

I also know that I can put values into the axis position registers using G10 L20 Pn B0. I see that G10 L2 is supposed to write a value to the coordinate system regisiter but when I do this the position changes accordingly. I'm not able to reset both of these. If I don't, I will have an accumulating offset every time a cycle is run.

I want the equivalent of homing - where I tell it "this is zero", period. Is there a good way to accomplish this from G code?

After reading the details for G92 I wonder if this wouldn't have the same effect as G10 L20. It uses an offset to zero the current position, so if my position was always some positive number when the program completes then the absolute offset would be increasing by that amount every cycle. Some might argue this isn't a problem because the number is so big, but because it's so big it's also hard to test what happens when the number overflows.

This is all speculation though, as I haven't tried it yet. I will do so. Thanks for suggesting another option.

I use this to prevent unwind A-axis:

G10 L20 P#5220 A[#5423 MOD 360]

MaHa wrote:

I use this to prevent unwind A-axis:

G10 L20 P#5220 A[#5423 MOD 360]

This is much more clever than just using G10 L20 P1 A0 like I was. Yours accounts for different coordinate systems in effect and "rewinds" to the same angle but in the 0 -> 359.999 range.

However, it still has the issue of an increasing offset every time you do it. For most people this won't become an issue, but this machine will be running the same program over and over day after day, week after week. I don't want to leave this to chance.

Yes, this does seem to be the standard answer. Although it strikes me as being too similar to the Y2K fiasco, and not at all an elegant solution. It is, however, a workable solution and the one I've settled on so as not to be sidetracked by something that isn't an immediate problem.

I haven't tried this yet but I assume it will work and be of great benefit to my particular situation. My question is why/how does it work? I've looked the DOCs and googled it but its still as clear as mud to me.

So I tried it in a sub-routine at the end of a sub-path and it works! It seems to mathematically take away all full 360 degree rotations and leaves the remainder, a big help. I like to get back to zero so I can visually make sure nothing wonky happened since I don't fully trust my mechanics, so I just add "G0 A0" to the sub-routine and it essentially homes. Fantastic! and Thanks!

MaHa wrote:

I use this to prevent unwind A-axis:

G10 L20 P#5220 A[#5423 MOD 360]

This is excellent. Thank you. For fusion users, just add -
/* Set to A0 and prevent unnecessary unwind */
writeBlock(
gMotionModal.format(0),
conditional(abcFormat.format(abc.x) == 0, "G10 L20 P#5220 A[#5423 MOD 360]")
);

Cheers