Standard XYZ Trunnion A and B rotary.

If I cut in indexed 5 axis mode, cuts perfect.

If I cut in 5x simultaneous mode, my B axis is off at end of program.  I don't use homing, I just use center of trunnion and make sure A is flat an B is square to X axis.

I'm 99% sure B isn't loosing steps, it's not a backlash problem.

One weird phenomenon is after program ends, I type Z10 in mdi, then X0Y0A0 in mdi and it moves at f50 which is what previous program calls. When I type B0 it's feedrate is like f1.... so type f50 B0 to return that to 0 position.

What should I be looking for?

You need to find out if its lost steps or a calibration issue.

Add a line at the end of the program to return to the start position.

e.g. G00 G90 X0 Y0 Z10. A0 B0

Run the program as normal and if the table is back to the exact same point its a calibration issue if not its lost steps.

Thanks for tip. I'll if I have time to try that tomorrow

My post processor uses inverse time feed G93.

I know it's not a backlash problem.

It may be loosing steps because of acceleration issues changing direction? I know it's not loosing steps because of cutting forces or binding

Still trying to figure this out.

I believe 3.042 version. Not buy machine for a few days.

Backlash is disabled for B axis. B axis doesn't need Backlash compensation. I have tried it both ways, Backlash comp on and off .same problem.

A word Mach3 issue. A axis is zeroed. A axis has Backlash comp on. If Backlash window is opened,  then closed... the A axis will show half the Backlash setting steps in DRO with no movement or anything done.

Could my issue be a bug in my version of Mach?

R3.043.062 is my version of Mach3

thank you for tip

Maybe I should ask this question.

Has anybody used Mach3 in a 5 axis trunnion setup, and it's worked exactly as intended?

i have it figured out, but don't know how to fix it.

I have toolpaths that are inverse feed and standard indexed moves in same program.

i get this error when I try to jog after program is run "F word is missing with inverse time g1 move , block = G91G1 A0.0010"

The rotary axis only moves in a jog if I spin pendant fast. So, during program run I think when feedrate is low it doesn't move when it's supposed too.

When it switches back and forth it wrecks havoc on toolpath moves and loses and or gains steps.