Logix5000 Motion (Technique Ok?)

Hi,
The current application I am working is a 3axis machine, with 2 of the axis 'slaved' to the master.
When I say slaved, they can only move relative to a certain position on the master, that is it. All they need to do is move xx amount as fast as possible when the Master reaches the set position. No interpolation or camming required, IMO anyway. This is an indexing machine. Adjustment of the move start position is a nice feature to maintain though.

What I have done, is setup a MAW for the master axis with the move start position as the Watch Point. I then have an Event task that triggers when the MAW activates.
The Event task then enables the slave axis via a MAM. The problem I encountered, was that the MAM needs to see a transition, so would only activate on the initial Event entry.
To solve this, & this is the point for discussion, I unlatched the MAM.EN bit when the MAW.PC bit was set. Does anyone see any issues with this.?
My other thought to try tomorrow, is to just unlatch the MAM.EN bits on the first rung of the Event task, that way there will be always a transition when the MAM is executed.

Whilst this worked & did everything that I wanted it to do, I am not sure if this is a good technique or not?

Cheers
LC

Hi LC

I always unlatch the .PC . EN and the .ER. Bits before I request a mam move for the same reason you have.
I have this in a lot of programs and I have had no issues.
The motion in Ab is edge triggered so you are correct. I would not use a separate task that is triggered like you have but again this is only my choice and I can not see anything wrong with it


Donnchadh

Thanks Donnchadh,
Good to know that what I'm doing is done elsewhere.
This is my first time with the AB motion gear, but is pretty straight forward. Had everything setup & working with 2hours, with no major issues which was a real bonus based on other systems recently!

Out of interest, how would you trigger a move based a position? The previous control system used a form of camming I guess. The slaves moved at the same speed as the master, so I the master was slowed down, the slaves did as well.

personally I find that when I need to reset the .EN etc I do not have the program right - I am missing something in my understanding of how to use the instructions or the drive interface.

Usually I have a mini sequencer that triggers the MAM and the conditions that feed the sequencer ensure that the MAM is event triggered
I can also then catch the errors and take corrective action if required

Most of my systems use the PCAM (position CAM) instruction and MAG (Gear)

easiest way to learn is to play using a virtual axis and emulator - enormous amounts of testing can be done this way.

Hi

There is camming in logix 5000 and it works very well.
Or you could just look at the position of the axis using a LIM instruction and then start mam from this it really depends on your requirement

Donnchadh

+1 on the camming. It's going to be even faster and more accurate than even an event task.

I would only do the MAW/Event task thing if you didn't want the slave to move at a speed relative to the master.

Thanks for the replies chaps,
This is my first Logix Motion project, so still doing the learning.
What I have is working, but is yet to be put through the pace's to see if/where the limitations are.
We have another identical machine that is going to have a brick in it with pulse train, so the idea is to use the same code structure with a few minor tweaks.

bmacattack33 said:

+1 on the camming. It's going to be even faster and more accurate than even an event task.

I would only do the MAW/Event task thing if you didn't want the slave to move at a speed relative to the master.

Click to expand...

How much faster/more accurate though?
The last machines the slaves moved relative to the master, but fundamentally this machine does not really need to.
If I get time I will look at using the camming instructions to see how that functions as well.

For the experts, this application has an axis that rotates 360 deg repeatedly, the no of cycles depends on the product recipe.
The slave axis need to move within certain angles of this axis, that is all. There are zones when it is safe to move, zones when it is not safe..

So say there were 2x zones, each one 180 deg. During the first 180 degrees, no slave motion is required, the second 180 motion is.
How would I set this up with a Cam instruction? The only type of profile that it is is start/end position..?

Hi

This actually sounds perfect for camming right down to the 360 degree as this is how a lot if machine builders think and talk.
Now in logix look up MCCP and also type camming in. Set it up a 0 to 360 for the master axis and then just draw the curve above the line to advance your servo basses on the master and below the line the retract it.
I learned it by setting up the two servos on the bench and just trying out with different number of points and making the Slave stay still for x degrees , going forward then back and so on until I understood how the graph worked

Donnchadh

lostcontrol said:

...
This is my first time with the AB motion gear, but is pretty straight forward. Had everything setup & working with 2hours, with no major issues...

Click to expand...

Nice!
I'm usually flopping around like a fish on deck after just 2 hours.