Hood, thanks for the replies. You always have good insight that gets me thinking.
My sense is that you have big machines, outside the capabilities of steppers. Beyond a certain point, steppers fall off the possibilities list and servos get stupidly expensive. I'm aware of this, but my focus is on my little baby mill, and at that level, (which seems to represents a very large percentage of MACH users), the pricing is very comperable. That's not my opinion, that's a contemprary fact.
I don't want to get into a servo/stepper debate , but I will say that in my opinion, it is not really reasonable to compare steppers and servos on a power basis as their characteristics are so vastly different. They really each have their own place. I think a lot of the criticism of steppers is the result of people not acknowledging (or not knowing) their limitations and using them in situations that really call for servos.
While I am a newbee to home grown CNC, I am quite familiar with industrial closed loop control schemes and one of your comments has me a little confused.
I am aware of how the Gecko servo drivers take step and direction pulses from MACH and keep track internally of the desired position and fault if 'x' deviation occurs.
My understanding at the moment is that MACH only sees the fault condition and has no awareness of the real time performance of the axis. i.e. the axis may be on the ragged edge for a long time and not fault, but MACH would be as unaware of this as it would be of missed steps in a stepper.
The differnece being the servo would catch up and not require rehoming.
The similarity being an out-of-tollerance ruined part.
Commercial/Industrial systems, from what I can gather so far, first off are all servo driven, and the system computers read the encoders directly and control the motors, so there is no 'translator' like the Geckjo 320/340 or eqiv. preventing the control system from knowing exactly what strain is on the system, if the axis are keeping pace, and if there needs to be some corrective aciton taken, even if that action is simply an operator warning.
While the significance of the effect is certainly debatable, the limitation in MACH either exists or it does not.
If I have it wrong, please explain where I've gone off the mark.
If I have it right, then it doesn't mean MACH is no good, it simply means that the system designer (including a rank ameteur like myself) should consider if this limitation would compromise the intended function of the machine. In my case, from what I have learned thus far, I would not consider it critcal and I would find the MACH/GECKO/SERO scheme adequate for my puposes. But that would be an informed decision.
Southern California machining center operator warning:
"Dude, we're bogus on Zed by 6, time to cruise the program, man. . . . hold it, chill . . . awesome, we're righteous again .. . . party on, Dude!!"