Manual milling using a CNC mill & MPG question.

I know this thread is a little old, but thought I'd chime in anyway.
I have a VistaCNC pendant and use it for manual cutting on my CNC mill quite often for simple things especially like squaring or surfacing a part or edge.
I simply set the slow jog speed in mach 3 to match my desired cut speed and use continuous mode. It will move at the slow jog speed as long as the wheel is rotated. The speed the pendant wheel is rotated doesn't matter and the cut speed doesn't vary and is consistent as long as the wheel is turning no matter how fast or slow. As soon as I stop turning the wheel, movement stops. Rotate clockwise for axis positive movement and counterclockwise for negative movement. Select which axis to move by the press/selection of a button. I can fine tune position by selecting step mode. Set any step amount (hundreth, thou, 10 thou etc) in Mach3 and select step mode and it will move one step each wheel detent very precisely. Most models have a LCD that shows the "DRO" position of the selected axis without having to even look at the computer screen. All in all really handy... like a DRO and powerfeed on steriods. I'm not affiliated with Vistacnc in any way but I highly recommend their pendants. Once you use one a bit it becomes pretty much second nature to quickly do "manual" milling on a CNC mill.
 
Wreck™Wreck said:
Servo or stepper machine?
Click to expand...

If the question is meant for my me and last post, my mill has steppers but I doubt as far as the pendant goes its an issue one way or another. Cut speeds are so slow compared to the machines max feed rate capabilities that torque isn't an issue nor lost steps. Also, most of what I machine is aluminum. A servo driven closed loop/encoder setup would be best I suppose.
 
The servo vs. stepper question, while always interesting, is not really applicable to the OP's question. Either drive system will accelerate, move a certain distance, and decelerate when used with a 'dumb' MPG in step mode resulting in the not very smooth motion he was experiencing.

The difference in drive systems might only become obvious when a stepper system drive is set to full-steps (no micro-stepping) and moved very slowly at a constant rate. The magnetic poles would then cause some 'clunking' at very low speeds, and a 'throbbing' at slightly higher speeds, especially if they're direct drive on the ball screws. Enabling micro-stepping should smooth things out, as does switching to 3-pole steppers, or the rare stepper that has more than 200 steps per rev.
 
I used to use jog dials for manual machining, but I now find manual data input much easier. I don't use Mach 3, but in my machine, an "up arrow" runs through previous commands so repeating a move is very easy - do a pass, drop z 0.05" with the dial, then repeat the x move that's already in the manual data window.


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