Would you use a feed rate for rotary axes in mm/min (surface speed)?

tuxcnc wrote:

"G93 is fine for me" means nothing.

 

"G93 is fine for me" means

Inverse-time feedrate generated by CAM is sufficient for my needs.

The OP indicated a simple response would be sufficient.  I gave one of the requested responses.

If your provocative post was not directed at me, disregard.

And, as usual, thank you grandixximo for all the work on LCNC.

These are mathematical heresies

Sure, but as I noted, sometimes I forget to use G93 and happen to include an A move in something innocuous, and it would be nice if the resulting motion was at least within an order of magnitude of correct instead of the default of stupidly slow.
Also, my third option gave the machine the math it needed to calculate the correct speeds.

Problem is if "stupidly slow" was a behavior anyone relied upon, or already based something on, tuxcnc has a point there, there could be subs out there that fixed this issue in gcode, and we might not what to change their behavior with a new default, is just something we have to account for, we have enough users where these seemingly rare occurrences might bite quite a few ppl...
A new INI to force a sensible default, and leaving old configs unchanged seems the right balance.

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And replying "G93 works for me" is totally fine, this was more of a census to see how many users actually would use the feature, and who already had it covered, one doesn't detract from the other, but give me a rough idea of who looked at it, and who I can ping for testing once it's built

Just thinking about this a bit...

I wonder if a new non-modal gcode could be created that didn't use any INI settings, and simple calculated the appropriate angular feedrate based on the Z0 being at the center of rotation.

In my CAM I have to set A-axis CoR to Z0 for it to work properly, even for simple indexing work.  I wonder if other users are 'used to' programming a rotary axis - at least a 4th axis - with CoR as Z0?

I also wonder if this is going to be more complicated... what if the tool is not just cutting on the rotational axis centerline?  Will the new Gcode/Mcode change (or work with) the trajectory planner to determine the 'real' radius based on rotational axis offset, plus tool diameter?

Sounds like it might get interesting.

Yes, I will try to make the least assumptions as possible, you could be working from Z0 center, or not, you could be working on a lathe or a mill, the spindle could be spinning or the table, you might want the feed to match the tip the side or half way trough the shaft of a tool, I think we need some flexibility, but I'd also compare with what other controllers do, and what a CAM or someone hand writing a gcode would expect...