Claude,
I have exaclty the same issue with my mill. I'm using the latest lockdown vn...40. I am cutting a profile using X axis and Z axis with a round part in the A axis. The X axis moves along the part and Z goes up and down to give the right profile on the part. A then rotates half a degree for the next part of the profile and x moves back the other way.
I have 0.05mm backlash in X and Z that is not normally an issue but for this part it is, so I turned on backlash comp and set up each axis distance, shuttle time and velocity and all is fine with each axis.
BUT, as you say, when one axis is moving along smoothly (x) at 0.3M/min and then the other (z) changes direction the X axis suddenly stops to wait for the Z axis to complete its compensation, then suddenly X carries on at the same rate.
From what I have read in other threads, this sudden stop is possibly because the backlash comp is not within the Mach3 "trajectory planner" - it just stops motion, adds the compensation regarding the adjustments set and starts it up again. This is very hard for stepper motors as, with a heavy X axis, it will possibly/probably loose steps. There is no respect for the (de)acceleration or any other setting for the axis that is having to wait for the other axis compensation.
So, it is possible to adjust the way the compensated axis behaves (as Rich explains well) and to get that smooth and not loose steps but other axis are abruptly interupted. Luckily my mill is small and it just about copes with it, but it is painful to watch and I'm sure will loose steps under heavy load one day.
Rich, Hood, Brian, Art, may I ask if my understanding is correct or have I missed a magic setting somewhere? If correct, are there any plans to get backlash inside the trajectory planner so it can work with all axes smoothly and be more stepper friendly?
Or, any advise to improve the situation for the "not compensated" axis motion?
Thanks!
Woody.