QTPlasmaC with fourth axis - rotary

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.

This run was with the G93 conversion, apart from a 2.7 second longer run time the numbers are almost identical to the standard G94 run.
 

EDIT: Changing the A axis to LINEAR made no difference to either the G94 or G93 figures.

I am convinced it is the lack of look ahead in the trajectory planner for axes other than X, Y, or Z.
This seems to gel with 3D printer configs using the Z axis for the extruder and the A axis for the cartesian Z axis.

The issue with the one line look ahead is usually jerky movement (the shorter the segments the jerkier). If your runtime with g93 is longer than with g94 then I would suspect something went wrong with the calculation of the F values.

If your runtime with g93 is longer than with g94 then I would suspect something went wrong with the calculation of the F values.

Actually, looking more closely at the original GCode using G94 it does indeed seem to adjust the feed rate in relation to the angular movement. So a conversion to G93 might not give the advantage that is seen with other Gcode.
The thing that I find a bit odd here is that with G93 code I never seem to have an issue with slow motion but more with jerky movements as the planner seems to accelerate/decelerate for (each?) segment. Given the rather large feed rates I wonder if maybe there is an issue with max acceleration of your axes.

On the sim I have tried accelerations for the A axis ranging from 1000 to 50000. 
In the second video when doing the second cut you should be able to hear the odd vibrations each time it moves the A axis around the corners of the tube.
Tomorrow I will do a comparison on the second cut with and without the A axis.

In the second video when doing the second cut you should be able to hear the odd vibrations each time it moves the A axis around the corners of the tube.

I presume you mean this one:


It is not clear to me why it is much faster up until 0:40 and then really slow after that. What changed in the GCode between the two cuts?

Yep, that is the one.
 I don’t think there is any real change. It may be there is less X motion in the second cut so the segment lengths are shorter?