Hi Azalin,
AFAIK that all looks good and I don't know why its not working.
Tweakie
Mach requires one pulse per rev, an index, to calculate and synchronise a thread. Mach assumes that the speed is constant even when the tool engages the
material and starts cutting. We all know that is never actually the case, the spindle always slows a little. Even with closed loop control a feedback of one pulse
per rev is not enough for a controller to maintain spindle speed accurately enough for threading.
Sorry Craig but this is not quite true - there are many lathe users threading this way.
My understanding is:
Mach assumes constant speed. If the speed slowed over one revolution as a result of the cutting forces then Mach would attempt to cut the thread but do so
inaccurately. With spindle speed averaging it will take Mach several revolutions before a more accurate estimate of speed is available. If the spindle has significant
inertia and/or power then the speed change will be slight and the thread cut fine. A lightweight or underpowered spindle and the speed change could be significant
and the thread inaccurate.
For situations where the spindle is marginally powered, which is the same as saying taking heavy cuts relative to its power, then a higher bandwidth control
loop makes the most of the power available.
To my knowledge no-one has repealed Nyquist's sampling theorem and the control bandwidth is inextricably linked to the number of pulses per rev.
Several months ago I bought a 1.8kW Allen Bradley servo and drive for a spindle motor. Its encoder is 2000 line or 8000 count per rev with a loop update rate
of 20kHz. It beats any other spindle motor for speed/position accuracy that I've ever come across. Had I not bought one and tried it for myself I would not have
believed how much superior a servo could be over an index pulsed motor.
Craig