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Standstill detection

Created by: Gordan at: 10/24/2012 3:27 PM (7 Replies)

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10/24/2012 3:27 PM	Rate (0)
Gordan Experienced Member Joined: 12/27/2011 Last visit: 4/24/2023 Posts: 7 Rating: (0)	Hello all, On our grinding machine we have a "GMN" high-frequency spindle (18000rpm) without encoder on it. However it has a proximity switch that provides 2 signals per rotation. I know there is GMN evaluation unit that process those signals, but we don't have it. Our question is can we somehow use those 2 signals per rotation to detect standstill state of spindle. We have Sinumerik 840d sl. Thanks Agostini Gordan

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10/25/2012 3:00 PM	Rate (0)
Pee El Sea Gold Member Joined: 1/19/2008 Last visit: 10/2/2024 Posts: 992 Rating: (64)	Hi, Can you program the plc ? Pee

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10/25/2012 3:28 PM	Rate (0)
Gordan Experienced Member Joined: 12/27/2011 Last visit: 4/24/2023 Posts: 7 Rating: (0)	Thanks for answering. Yes we can program PLC. Those 2 signal goes both to Sinumerik and PP 48/72 IO module.

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10/25/2012 7:04 PM	Rate (0)
Pee El Sea Gold Member Joined: 1/19/2008 Last visit: 10/2/2024 Posts: 992 Rating: (64)	Hi, Because of the response of the plc I would think when the spindle is rotating at high speed the input will look like a permanent true signal. If the spindle is stopped the signal will ususally be false unless you are unlucky enough for the spindle to stop exactly where the sensor is triggered then it will be true. I don't think a true stopped state is possible to detect. I would probably count the pulses and look for consecutive lower values and when the pulses stop in either state assume it had then stopped. There may be a signal from the drive to help confirm a stopped state. So much depends on how fast the spindle can decelerate and what the scan time of your plc is. Pee

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10/26/2012 6:47 AM	Rate (0)
Nanu_333 Bronze Member Joined: 5/19/2011 Last visit: 12/23/2024 Posts: 196 Rating: (5)	Dear Gordan, You can try this with high speed inputs available on IO card. Regards, Chetan

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10/26/2012 8:34 AM	Rate (0)
Gordan Experienced Member Joined: 12/27/2011 Last visit: 4/24/2023 Posts: 7 Rating: (0)	We tried to count impulses and it worked fine for slow rotations, but PLC went to stop state as the speed of rotation incereased. As I said we have a PP 48/72 IO module and we dont know does that module has fast inputs?

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10/26/2012 12:30 PM	Rate (0)
Pee El Sea Gold Member Joined: 1/19/2008 Last visit: 10/2/2024 Posts: 992 Rating: (64)	Hi, I don't see how you can use fast inputs. If the spindle is spinning at 18000 * 2 pulses per rev = 36000/60 = 600 interrupts per second. About one every 1.5msec. Thats a lot of work for the plc. Why did your plc go into stop when you were counting the inputs ?. I can't see any reason why it should crash just counting normal inputs. Pee

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10/26/2012 3:35 PM	Rate (0)
EmaMic Posts: 3 Rating: (0)	Hello, is the spindle driven bythe NC through aS120 drive ? If so, and assuming that at high speed the PLC sees the 2 input signals always high, in this situation you could alsocheck via PLC the parameter r0032 CO: Active power actual value smoothed of the drive module. You need NCVar selector for this. I expect that the value read will be higher when rotating at high speed than at standstill. Regards, EmaMic
EmaMic Posts: 3 Rating: (0)
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