control loop while motion.enable 0 ?

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22 Dec 2010 18:29 #6214 by nursum
Hi,
one small question: When I have an error on my machine, for example to less oil I put the "motion.enable pin" to "0" to swich off the machine. Is the control loop in this case activ to hold the position of the machine? Ingo

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22 Dec 2010 23:56 #6221 by BigJohnT
I'm pretty sure that will place the machine in the "off" state. I don't know if it can be resumed where it left off or not.

Is low lube that critical? I would turn on a bitch light for some time first before shutting down the machine for low lube.

John

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23 Dec 2010 07:50 #6224 by nursum
Hello John, with the lube was only an example I can also say the pressure of the hydraulic pump, which is critical for the tool change. My interest is the control loop in the machine off state. My Z axis could go down depending on its own weight ore movement when the control loop is off, also the whole machine behavior could be critical whithout control loops when an error occur which swiched the machine off! I'am talking about a 12 ton milling centre. It is very important for me to know how I can stop the machine in all modes (manual,mdi,automatic) with workin PID control loops! Ingo

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23 Dec 2010 23:07 #6227 by BigJohnT
Does your Z axis have a brake on the ball screw shaft? My little 3.25 ton VMC has a brake on the Z but the X and Y can be pushed around when powered down. How does your machine keep from drifting down when the power is off? When you put motion.enable to 0 motion stops, the machine is placed in the "machine off" state, and a message is displayed for the operator. Just doing a few tests on my plasma when I'm in the "machine off" state the axis drives are still on so no drift but they are steppers. Took a cover or two off my Hardinge lathe and when in "machine off" state the drives are off and I can move the axis. This is configured this way to prevent the servos from drifting when not commanded by the control loop. I found that in the "machine off" state the servos would drift unless I disabled the drives. The good thing about EMC is you can configure it to work almost any way you like.

John

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23 Dec 2010 23:17 #6229 by robh
is this a Hydrolic counterbalance with direct drive on screw?

or
a counter balance weight in the back of machine

from an Estop or other (power cut etc) the machine should be able to be placed into a "safe" state quickly and easy.
if its direct drive im sure there is a brake in motor or on the screw shaft so when u hit estop it should be applied right then.

realy there is very little info for any one to say what should happen safly but i cant see there being any problem...

rob

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24 Dec 2010 00:11 #6231 by nursum
Hi John , thanks for that information, so the PID's are not in use when the machine is off, in that case I have to activate my break! If the PID's are active at "machine off" and I swich on the break I would get problems.... so now its clear! Thanks a lot! Ingo

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24 Dec 2010 00:14 #6232 by nursum
Hi Rob, no there isn't any problem with the info that at "machine off" the PID's are also off! Then I use my break... Ingo

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24 Dec 2010 00:22 #6233 by andypugh
If you have a class of signals that you want to prevent motion but keep control, you could set the feed-hold pin.

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