E-Stop Sequence
- electrosteam
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10 Nov 2010 09:43 #5194
by electrosteam
E-Stop Sequence was created by electrosteam
I am new to CNC and have acquired a knee mill with stepper motors without any external E-Stop buttons.
As part of my re-commisoning, I want to add E-Stop buttons but I need to understand the sequence of events when an E-Stop occurs.
I have made an effort to discover the answers to my questions, but it alludes me.
I am sure the data is there, but where should I have looked ?
When F1 is operated to initiate E-Stop what happens to any drives then currently in motion ?
- instantaneous removal of pulsing ?
- drives ramped down to stop at the maximum allowable rate, then pulses removed ?
In the above, when does the E-Stop output via the parallel port get asserted ?
- instantaneously ?
- after the drives have stopped ?
Is an external E-Stop detected via the parallel port input treated exactly the same as an F1 operation ?
John.
As part of my re-commisoning, I want to add E-Stop buttons but I need to understand the sequence of events when an E-Stop occurs.
I have made an effort to discover the answers to my questions, but it alludes me.
I am sure the data is there, but where should I have looked ?
When F1 is operated to initiate E-Stop what happens to any drives then currently in motion ?
- instantaneous removal of pulsing ?
- drives ramped down to stop at the maximum allowable rate, then pulses removed ?
In the above, when does the E-Stop output via the parallel port get asserted ?
- instantaneously ?
- after the drives have stopped ?
Is an external E-Stop detected via the parallel port input treated exactly the same as an F1 operation ?
John.
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10 Nov 2010 11:15 #5195
by andypugh
Replied by andypugh on topic Re:E-Stop Sequence
Ideally the e-stop button would kill all power to the motors independent of software, and tell the software that is what has happened.
It is not ideal to have EMC2 in the e-stop loop (That "E" is "Emergency" not "Oops")
If your E-stop reports activation to EMC2 via IO (P-Port or whatever) then the software shutdown will be equivalent to F1. However that should be a consequence of the E-Stop, not the first part of the chain. (What if the problem is that EMC2 has crashed?)
It might be best to consider what you _want_ to happen, then figure out how to get EMC2 and the rest of the system to do that. I can imagine that F1 might be controlled stop at max decel, but external E-stop would kill all power to motors and drives and also set the EMC2 E-stop input.
It is not ideal to have EMC2 in the e-stop loop (That "E" is "Emergency" not "Oops")
If your E-stop reports activation to EMC2 via IO (P-Port or whatever) then the software shutdown will be equivalent to F1. However that should be a consequence of the E-Stop, not the first part of the chain. (What if the problem is that EMC2 has crashed?)
It might be best to consider what you _want_ to happen, then figure out how to get EMC2 and the rest of the system to do that. I can imagine that F1 might be controlled stop at max decel, but external E-stop would kill all power to motors and drives and also set the EMC2 E-stop input.
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10 Nov 2010 11:32 #5196
by BigJohnT
Replied by BigJohnT on topic Re:E-Stop Sequence
In addition to what Andy said and I agree 100% that the physical E-Stop button should interrupt the power and as a bounus let EMC know.
EMC has E-Stop interface via halui.
www.linuxcnc.org/docview/html//man/man1/halui.1.html
For some reason that I can not think of at this time in the morning it is just a bit tricky to get it all working...
One of my machines uses program pause and resume for normal "I don't think that is right" situations along with several "Oh Sh_t" buttons wired in a loop using normally closed contacts at strategic places that break the power buss to the drives.
John
EMC has E-Stop interface via halui.
www.linuxcnc.org/docview/html//man/man1/halui.1.html
For some reason that I can not think of at this time in the morning it is just a bit tricky to get it all working...
One of my machines uses program pause and resume for normal "I don't think that is right" situations along with several "Oh Sh_t" buttons wired in a loop using normally closed contacts at strategic places that break the power buss to the drives.
John
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- electrosteam
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11 Nov 2010 09:08 #5213
by electrosteam
Replied by electrosteam on topic Re:E-Stop Sequence
Andy and BigJohnT,
I agree with the absolute power removal under E-Stop conditions requiring a manual reset (depressed button etc) to regain power.
The external buttons will do this, but, should we allow a short time ( 1 sec ?) for EMC to ramp the drives to stop before removing the power ?
The delay could be provided by a timing relay or a small timing module independent of the computer.
A Bridgeport sized machine with a heavy set-up travelling at full speed in the X direction could coast for some time if the pulsing is just removed.
I am not sure what the Leadshine MD882 drivers do if not receiving pulse data.
Presumably the stepper coils are energised continuously with holding level current.
What level of retardation would this provide to a coasting table ?
I will get the mill into operation with simple E-Stop buttons, then set up some tests to see how much coast could occur.
John.
I agree with the absolute power removal under E-Stop conditions requiring a manual reset (depressed button etc) to regain power.
The external buttons will do this, but, should we allow a short time ( 1 sec ?) for EMC to ramp the drives to stop before removing the power ?
The delay could be provided by a timing relay or a small timing module independent of the computer.
A Bridgeport sized machine with a heavy set-up travelling at full speed in the X direction could coast for some time if the pulsing is just removed.
I am not sure what the Leadshine MD882 drivers do if not receiving pulse data.
Presumably the stepper coils are energised continuously with holding level current.
What level of retardation would this provide to a coasting table ?
I will get the mill into operation with simple E-Stop buttons, then set up some tests to see how much coast could occur.
John.
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11 Nov 2010 11:17 #5223
by andypugh
Replied by andypugh on topic Re:E-Stop Sequence
You might find that when EMC2 stops sending velocity data the boards stop the motors anyway. It takes some time for the stored energy in the capacitors to dissipate.
I would _not_ kill the logic power supply to the drives by the way. If you have braking resistors you might well find that with no velocity signal, no DC bus power but with logic the drives go into crash stop.
I would _not_ kill the logic power supply to the drives by the way. If you have braking resistors you might well find that with no velocity signal, no DC bus power but with logic the drives go into crash stop.
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11 Nov 2010 12:42 #5227
by BigJohnT
Replied by BigJohnT on topic Re:E-Stop Sequence
I should have been more clear on my E-Stop setup. It does not interrupt power to the PC or the logic side of the drivers only the power side of everything. If only I could type what I think...
John
John
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