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

I'm deciding whether to work on a LinuxCNC feature and would like to know first whether anyone would actually use it.

Today, when a rotary axis moves together with X, Y or Z, F applies to the linear axes only, and a rotary move on its own runs at F in degrees per minute. On a 4th-axis wrap, where the surface of a cylinder is cut with X and A, the surface speed therefore doesn't match F. The usual workaround is inverse time (G93) from the CAM.

The idea is a reference radius for each rotary axis, set in the INI. For example, `[AXIS_A] FEED_RADIUS = 25` puts A in the feed calculation as if it were a length at 25 mm from its centre. A move of A alone at F100 would then run at 100 mm/min on the surface at that radius, and X with A would run at F along the combined path. Siemens (FGREF) and Fanuc (a parameter) do the same.

Questions:
1. Would you use this, or does G93 from your CAM already cover it for you?
2. What machine: 4th-axis wrap, rotary table, something else?
3. The useful radius is usually the stock radius, which changes per job. Is a fixed INI value good enough, or would you need to set it from G-code?

A short "yes, I'd use it", "no" or "G93 is fine" helps. If nobody needs it, I'll leave it.

 

grandixximo wrote:

The idea is a reference radius for each rotary axis, set in the INI. For example, `[AXIS_A] FEED_RADIUS = 25` 

This is a very bad idea, looks like it was captured from Mach3...
This is what LinuxCNC is good at, it doesn't have a thousand buttons that change the way it interprets g-codes.
Sharing settings between the ini file and the ngc file like this is bound to end in an accident at some point.
However, there are no contraindications to adding a new G or M code that will do what you write about. Then everything will be in one file and there will be no risk of running one program with the settings of another...

Yes got some mixed responses, G93 works for some. The ones who'd like to try, seem to want it as a G-code, which makes sense...