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Old October 19th, 2018, 02:27 PM   #1
JohnnyQuanex
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Exclamation Motion (MAM) with (MCD) Allen Bradley Question

Hi again folks,

In advance, thank you for your extremely valuable input... LOL

I'm trying to use a MCD in conjunction with an MAM to vary the move speed...

When it cycles it will move to the specified position, but then won't (the MAM that is) go in .PC status. (Therefore, the logic won't move to the next state of my machine.)

I've confirmed my logic works by doing away with the MCD and putting a static speed value into the MAM. It works fine.

See snips of ladder for reference...

Any help?

Thanks,

John
Attached Images
File Type: jpg Snip MAM(2) Stuck, Actual Position Verified.JPG (58.7 KB, 17 views)
File Type: jpg Snip MCD for MAM(2).JPG (53.1 KB, 17 views)
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Old October 19th, 2018, 03:41 PM   #2
Ken Roach
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Taking a closer look; you are using the same Motion Control tag (Traverser_Axis_Ctrl.MI.MAM[2]) to control both the MAM and the MCD.

Each motion control instruction needs a unique backing tag.

Since yours are evidently part of a user-defined data type structure, browse through that structure to see if there's a Motion Control datatype element that is meant for use by an MCD.
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Old October 22nd, 2018, 08:16 AM   #3
JohnnyQuanex
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Ken Roach,

Much appreciated. Problem solved.

That is what I call a duh moment. I don't know why I put an MAM in there... LOL

Very, very much appreciated...

John
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Old October 23rd, 2018, 01:52 PM   #4
JohnnyQuanex
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Okay...

So now I seem to be having an issue... I am running the axis using a varying speed value in some MAM instructions, but in others I'm using a fixed speed--all on the same axis.

The MCD seems to be overriding SOME of my other MAM's that I've got setup with fixed speed values...

Any suggestions?

Thanks,

John
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Old October 23rd, 2018, 01:54 PM   #5
JohnnyQuanex
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I move the MCD to bottom of my ladder. That seems to have corrected the problem. Seems like you should be able to select specify instruction array numbers for MCD to function with so you can do more than one speed on an axis.

Thanks,

John
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Old October 23rd, 2018, 02:56 PM   #6
Ken Roach
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Quote:
do more than one speed on an axis.
Not all ControlLogix motion applications use an array of Motion Control tags, or a UDT full of them.

Remember that an axis only has one speed, even if the axis is sometimes controlled by different motion control instructions.

MCD changes the dynamics of an axis, usually the speed. That's all. It applies to the axis, not to the particular MAM or MAJ or MAG or whatever other command is controlling the axis and making it move.

So you need to set up conditions to run the MCD to only change the speed based on which MAM's need the variable speed. The In Process (IP) bit from each Motion Control control tag is a great way to distinguish between which of the MAM's are running.

I have a nice simple one-axis machine I do this on. When it's running in Auto Mode, it has to slow down half-way through the stroke. When it was started by a Manual Cycle button, it runs at a lower speed and does not change speed. I just use the Auto Mode bit as one of the conditions of my MCD, so it doesn't fire when I pass the position threshold during a manually-started move.
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