QTPlasmaC with fourth axis - rotary

I think we need to test this on a machine with a decently fast fourth axis. Marius, it's probably up to you for this.

Phill, just out of interest how do the A axis velocities compare to the first cut?

I found Mach3 works more smoothly with the rotary axis configured for 1 unit per rev instead of 360 units/rev. Do you think this would help here?

LesNewell wrote:

Phill, just out of interest how do the A axis velocities compare to the first cut?

I didn't plot those, I can do tomorrow.

I found Mach3 works more smoothly with the rotary axis configured for 1 unit per rev instead of 360 units/rev. Do you think this would help here?

TBH I don't know if that is possible, I assumed angular joints/axes needed to be degrees.

This is from the docs:

phillc54 wrote:

1. My little rotary table is only capable of 150°/sec which is 25rpm
2. LinuxCNC has poor path planning for axes other than X, Y, or Z

Would inverse time (G93) help with #2 at all? I know it's common on mills to use G93 with 4/5th axis moves.

TBH I don't know if that is possible, I assumed angular joints/axes needed to be degrees.

I generally recommend that the 4th axis is defined as a linear axis rather than angular. I'm not sure about LinuxCNC but some other controls treat rotary axes differently to linear axes. Functions such as rotary axis diameter compensation or 360 degree rollover can cause all sorts of unexpected issues.

LesNewell wrote:

just out of interest how do the A axis velocities compare to the first cut?

Interestingly it is a little faster but still a long way from what it should be. Rapid moves are fine but coordinated moves are ordinary to say the least.
 

I will try to set up a Linear A axis next.

Here is a short video showing what I mean by G93. Perhaps sheetcam already exports code this way, I am not sure. But if nothing else, he has a good explanation of the problem and the solution.