[HuFlungDung]

Marc,

I don't believe the application to steppers over servos is unique. The crux of the issue is this for both kinds of motors: an accel/decel ramp must exist.

This may not seem evident at first, but it is there all the time.

Thus, the motion card needs to be told at what rate to accel/decel for every move. And, if the move is truly going to end, then you must tell it to decelerate, and not just "end motion", which is like a command to decelerate at an infinite rate. This causes the amplifier to send or receive a huge pulse which causes nuisance tripping of the overload detector.

The advantage of the Galil/Camsoft setup, is that it is possible to eliminate this accel/decel between feed commands when you choose to. When this is the case, then all the movement vectors are just downloaded into the card one after the other, with never any thought given to accel/decel. This is what creates smmmoooth machine motion when running short segment nc code, at a high rate. Regular cnc's lacking this capability tend to get into a vibrating, shaking mode when trying to execute hundreds of blocks per second, because the accel/decel is always trying to cut back in between the movements, because the processor is taking too long to send the next move, and there is a miniscule pause, which allows decel to begin, then accel to be applied immediately when the next movement is read.

I have seen the effect of "smooth on" while running my Camsoft lathe. I was turning a very long slender shaft, for which I had to create a special curved toolpath for, to compensate for the deflection of the part. This resulted in several intersections in the cut length, from one end to the other. With "smooth off", there would be just the tiniest toolmark at each intersection, as the next move was read, and the decelstop was applied. With "smooth on", there were absolutely no toolmarks at any intersections, because the whole profile executed with only a single accel at the start and a decel at the other end of it.