Hi Hood - Hopefully I've worded this carefully enough to avoid a good kicking from Terry - but here goes...
I kinda left it vague because it depends on what you want to do and what your THC can do. We can wax lyrical about speeds but ultimately you'll probably end up slowing Z down to match the capabilities of any (including mine) "budget" THC. Spend a few grand on one and the game changes entirely (so I'm told).
To give some perspective though, here's what the tables I've built in the past did (with my THC). I'm sure there are better (and worse) tables out there so I'm not saying this is good or bad - just what they were.
My THC samples at 1KHz. If it's set to do 1 step pulse per sample (which it is) then it can obviously drive the Z at 1000 pps. The Z was rack n pinion with a steps per of 42.44131816 steps/mm.
so Z moved at 1000 / 42.44131816 * 60 / 1000 m/min i.e. 1.4m/min.
Lets say then that it's cutting at 6m/min. It can therefore handle a slope of 6/1.4 = approx 13 degrees. I've yet to find this to be inadequate. Of course it means it couldn't cut corrugated - but it wasn't designed to - it was simply designed to cope with "typical" warpage.
Thanks for that Ian, not even sure what the sample rate of the THC I have is, so looks like whichever way I go it will be plenty fast.
One thing though, I wonder if I would maybe be better trying the built in THC of the CSMIO. I am not sure how it works but if it is totally internal to the CSMIO then it should be very fast. Will have to do some reading on it.
With the Z I see no problems in setting an extremely high accel with the setup I propose as there will be little mass to it and the servo should be more than capable of handling it even direct drive.
Remember with THC the Z accel is not used so it's irrelevant.
Yes I saw that mentioned earlier, what I was really getting at was I should be able to have a very fast acceleration with whichever scenario I choose for the motor/gearing/screw. So really there being no accel in Mach should not make a difference as the servo should be able to get to speed almost as quick as it is told to without falling foul of itself.
For example I have a motor hooked up here, I command a RPM of 6000 at an accel of 6000 revs/s/s and it quite happily does it. There will be error of course but it still does it easily. Also there is no load so that would change things but 6000 rpm to -6000rpm at acccel of 6000rpm/s/s is fairly aggressive
Hood