I'm having an issue with interpolation / feed around the A axis. What it appears to be is an issue with acceleration of the axis. I'm running in inverse time feed rate at a surface speed of 40ipm, When the axis starts, you can see it accelerate normally. During the run the axis changes speed as it should to cut around the part during the rotation (correct). But after a bit, the axis looks as if it suddenly jumps from 0 to 40 ipm without the normal acceleration / deceleration causing the stepper to stick in place (but you can hear the drive scream but no motion).  I thought first it was binding, but after days of messing around, I'm almost positive it's an acceleration calculation problem. Is this a known problem, or am I missing something in configuration?

I believe the issue is at line 442 where the inverse feed rate is at ~14000 for a tiny amount of rotation change from the previous position. I'm not sure if Mach3 is getting confused with such radical numbers as I have no way to confirm for sure.  I did set the max inverse rate to 9000 and will try again.

N433 X-0.5466 Z6.0789 A7109.945 F365.7418
N434 X-0.5903 Z6.0787 A7128.757 F191.3729
N435 X-0.7254 Z6.0784 A7147.183 F165.6427
N436 X-0.9663 Z6.0781 A7169.937 F116.0445
N437 X-1.1105 Z6.0779 A7188.619 F160.817
N438 X-1.1494 Z6.0777 A7206.604 F200.997
N439 X-1.1346 A7229.086 F164.0643
N440 X-1.1274 A7251.407 F165.4696
N441 X-1.1453 A7268.31 F216.961
N442 X-1.1445 A7268.562 F13940.0244
N443 X-1.1418 Z6.0781 A7296.452 F132.891
N444 X-1.1372 Z6.0784 A7317.124 F178.3766
N445 X-1.1263 Z6.0787 A7338.413 F173.0219
N446 X-1.1422 Z6.079 A7360.892 F163.7325
N447 X-1.1397 Z6.0792 A7382.293 F172.1525
N448 X-1.0564 Z6.0793 A7399.838 F192.0588
N449 X-0.8447 A7421.434 F126.6222

Thanks for anyone helping.

Personally I do not think that the IFR is dependable with the 4th axis involved. I would try programming without it as a reference.

(;-) TP