Servo Purchase Recommendations, Yaskawa?

@Arvi, sorry, all i recall is that he did something regarding this and that topic is loooong.

yer all a bunch of jerks.



anyhow, when i say the issue of jerk control goes away with pulse drives i mean YOUR issues with misbehaving servos. obviously the problem is still there, however dumb (stepper) and advanced servo systems alike simply manage to deal with it better than linuxcnc's analogue system does (in my experience, on old slow drives).

people tend to only use analogue when they are trying to repurpose the existing drives. i dont hear of anyone buying brand new drives and trying to run analogue.

as it happens, i have the kit here to do both analgoue and step (mesa 7i77 and 7i76), although my machine is not assembled right now. it is a light weight machine with a high pitch screw (130kg moving mass, 2525 screw), so i would expect it to beave very badly in analogue mode if it had the old sanyo drives from the brother. the drive though is a much newer sanyo rs1 with a 1khz loop, and the motor is 2048 lines/8192 pulses per turn.

if noone else shows me anything interesting by the time im ready to assemble it, i may give analogue mode a go and see if it indeed behaves.

this was as good as i ever got my x and y.
this is an adaptive clearing program, with g64 on. 400ipm. 0.5G acceleration. it tends to behave well in the g64 moves, but "bangs" around on exact stop moves. you can sorta hear it in the video, in real life it was super apparent - and of course you could see it on the scope. there's nothing wrong with the tracking, it never deviated much more than a few encoder pulses, but the direction reversals i think would both leave marks on a part and damage the machine. the Z you'll note doesn't do much, that's cause i never got it anywhere close to tuned, it would resonate bad.

compare to the original control




ive asked before, but if controls from the 80's running on intel 8088's had jerk control, what is the hold up with linuxcnc? even $200 3d printed have jerk control (although i think thats not a live trajectory).

pure straight g64 path, smooth as butter.

Is the issue specific to analog? I would imagine it would also be a problem for closed loop pulse control.