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Old January 14th, 2021, 01:34 PM   #1
PreLC
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Kinetix 5500 Active homing - using PLC tag instead of hardwired inputs?

Hello PLCs.net!

I have a kinetix 5500 drive connected to a gantry, I was wondering if there is a way to do active homing using a PLC tag?
At this moment, the AOP asked me to just go into the digital inputs tab and reassign one of the inputs as a homing input, currently the digital inputs 1&2 are used for positive and negative overtravel, so no spares.

Has anyone done homing through a PLC tag?
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-PreLC
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Old January 14th, 2021, 01:36 PM   #2
dmroeder
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It is possible. There is a technote, I'll find it in a bit. It involves sending a message to change one of the over travels to a home input. So basically, when you know you need to home, you MSG to change the negative over travel (for example) to a home input, issue a MAH, when complete, you MSG to change the input back to an overtravel.

KB: QA28637, techconnect level

Last edited by dmroeder; January 14th, 2021 at 01:44 PM.
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Old January 14th, 2021, 06:33 PM   #3
PreLC
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Quote:
Originally Posted by dmroeder View Post
It is possible. There is a technote, I'll find it in a bit. It involves sending a message to change one of the over travels to a home input. So basically, when you know you need to home, you MSG to change the negative over travel (for example) to a home input, issue a MAH, when complete, you MSG to change the input back to an overtravel.

KB: QA28637, techconnect level
Hmm. I guess we just need it wired to the drive itself.

Crazy question, for homing, have you used prox switches rather than actial limit switches?
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Old January 14th, 2021, 06:42 PM   #4
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Quote:
Originally Posted by PreLC View Post
Crazy question, for homing, have you used prox switches rather than actial limit switches?
Sure, I can't think of a time where we have ever used limit switches. We will generally use a prox or a photocell, depending on the application.
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Old January 14th, 2021, 06:52 PM   #5
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Quote:
Originally Posted by dmroeder View Post
Sure, I can't think of a time where we have ever used limit switches. We will generally use a prox or a photocell, depending on the application.
Thanks for the help DM, always appreciate it.
Huh. We just ordered a precision limit switch in order to home a table for a position-critical drilling machine. Haven't installed it yet, but it does have existing overtravel sensors. Do you think we should try active homing with those first? Also, what type of active homing would you recommend?
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Old January 14th, 2021, 07:22 PM   #6
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Quote:
Originally Posted by PreLC View Post
Thanks for the help DM, always appreciate it.
Huh. We just ordered a precision limit switch in order to home a table for a position-critical drilling machine. Haven't installed it yet, but it does have existing overtravel sensors. Do you think we should try active homing with those first? Also, what type of active homing would you recommend?
I'll defer to someone smarter than me, the stuff we are doing isn't super precise. Speed, power is generally what we are after, precision is a bonus.
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Old January 14th, 2021, 08:36 PM   #7
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For homing to a switch I like:
1. Move to actuate the home switch.
2. Reverse direction at very low speed until clear of the home switch.
3. Stop at the next encoder marker pulse and set the current axis position to be the home position including any offset.

The existence of step 3 allows for some variation in the actuation positions of the home switch each time you perform a homing routine. The final stopping position will be consistent.
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