RE: [CAD_CAM_EDM_DRO] Re: Servo hardware

>What I like about closed loop to the computer is I can hit feed hold at any

time and the machine stops immediately. Then to >restart just hit the green
run button and off it goes with absolutely no loss of position.



You don't need a closed loop system for that functionality. Since the
controller is well, in control, when you hit feed hold it simply decelerates
and stops, hit start and your off and running. If you hit EStop though all
bets are off as the axis are not decelerated by the controller.



A lot of hype is associated with 'closed loop back to the controller', where
its real utility lies is with the control program being able to coordinate
all axis movement with one that is running 'slow', avoiding a servo fault
and potentially scrapped part. This coordinated motion between axis is also
very useful in other cases, such as threading, etc.



In my experience when you hit EStop when the machine is running or have a
servo fault it is because something bad was happening. It is completely
unimportant if your encoder maintained power and thinks it knows where an
axis is at because odds are your fixturing, or tool, or even an axis has
slipped (think large gantry machine.) (Just as Tim said). If you don't
re-home and re-indicate to your work your being foolish.



Jeff Birt

Soigeneris.com



From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of timgoldstein
Sent: Tuesday, December 28, 2010 11:20 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: Servo hardware

> --- In CAD_CAM_EDM_DRO@yahoogroups.com

<mailto:CAD_CAM_EDM_DRO%40yahoogroups.com> , "grd750" <grd750@> wrote:

> Usually if a servo faults it already has lost position. The control

software is in charge of knowing where the toolpath is SUPPOSED to be but if
the error is great enough to fault, do you really want to restart from the
wrong position? The best thing is to determine what caused the fault in the
first place (or it will just do it again) and then reestablish table zero
and restart the cut from an accurate position.

>
> TOM caudle

For me, I could care less about what happens if the servo faults. At that
point the part is probably scrap, the tool is ruined, and the setup is
likely mucked up. At least this is the result when we fault an axis on the
Haas, but it has 2000 lbs of thrust at fault.

I agree with you Tom, a fault is telling me I really messed up something and
need to reprogram or if the part was sucked out the the vise/fixture that I
need to improve my work holding.

What I like about closed loop to the computer is I can hit feed hold at any
time and the machine stops immediately. Then to restart just hit the green
run button and off it goes with absolutely no loss of position.

Tim Goldstein
A2Z Corp
A2Z CNC division
3955 S Mariposa St
Englewood CO 80110
720 833-9300
Toll Free 877 754-7465

www.A2ZCorp.us/store
USA made accessories for desktop mills & lathes.





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