AB IMC 2 Axis Motion Controller

Hi,
I am seeking some help on a rather old axis motion controller. The controller type is an AB IMC 400-232-R, Series J, 2 axis motion controller with a firmware revision 303003.5B. It has 2 RIO output cards attached using the outputs as directly wired inputs to a SLC 500 controller input card.

My problem is that the machine tries to reset the axes by homing both axes to their individual home sensors. It completes the movement as normal and then just sits at this point with a message on the HMI saying the axes reset is in progress. It seems as if the servo's and drives are all functional. There are no faults on drives or motion controller.

Looking in the PLC code this message is held on by an input which is fed from the RIO output card. I don't have the original GML file but I got online today and managed to upload the script file which makes little sense to me and I am struggling to get the information from the controller to see why it is not acknowledging that the axes have completed their reference. I can see data for each axis which indicates that neither axis is in fault and I see when the axis homing signal is on. When it reaches its home limit switch the homing then says locked so all seems to be registering. I can jog the axis from the GML software also. However I can't get the information I need which is the reference acknowledge which seems to be the command to turn off the output on the RIO. Is there anyway of figuring out what turns on and off the outputs on the RIO from monitoring the controller or the script file? I am suspect that the 400 controller is defective in some way but I don't have a spare at hand. Any help would be appreciated. Thanks.

I would check to see that the home limit switches are working correctly
both that switch activates the input and they are actually made when it is traveling
they usually don't drop out of homing node the program see's the switch

Hi Gary,
Thanks for the reply. I have checked the homing switches with a voltmeter and also I can monitor them in the GML axis o and 1 online. It indicates homing when moving up towards the zero point and then locked once it reaches the reference. However I don't seem to get whatever is required to send this signal to turn off the RIO output and hence the machine continues to think it is referencing and just sits there. I am assuming the RIO outputs have been programmed in the GML but I can't read the script file and the original GML file is unavailable from OEM. I am struggling to understand what is happening. Is there any other means of diagnosing the RIO outputs through the GML?

Denis

Are you sure the RIO is reading correctly I think it should be 2 block transfers read and write
if I remember correctly the home function on those is a caned program that should run even with out the RIO working once it's triggered it runs to completion
the last one I worked on the home function worked like this on home trigger the axis mover I a direction to the home and past. after it passes the home switch it stops and reverses at a very slow speed to the home switch the home is set at the leading edge of the switch. It will stop past the home switch.
I think I still have the IMC software if it will help.

Hi Gary,
You are correct with the homing sequence, it goes to the home LS and then backs off the switch very slowly until it loses the LS signal. This seems to work perfectly and the IMC controller shows homing when moving up to the LS and locked once homing is complete. Output zero on the RIO card goes to I:2/3 as a hard wire. I am interpreting this as a reference complete signal because it throws a message to the HMI as "Axes referencing in progress" when on, however even after homing is complete output zero on the RIO remains on. This is where I think I have issues...
I have the GML commander software but because I don't have the original GML program I can't see the graphical code but can only upload a script which does not make much sense to me. Therefore I am struggling to understand what turns on and off the RIO outputs as I am not very experienced with this type of controller and RIO arrangement. I contacted Rockwell support but they said the drives were quite old and he didn't know much about them either so I am hoping I can get more information here. Again I appreciate the help.

yes they are very old and not supported
it seams odd that both axis failed at the same time
On some systems the use switch + the next z channel pulse from the encoder for homing
if both axis did in fact fail at the same time I would look for something they have in common not likely software maybe low voltage on the switch power supply
in fact not likely software at all programs generally don't change.

Hi Gary,
I don't suspect a program issue, all code is fine has been running for years. I have been thinking about the RIO scanner communications between it and the drive as you suggested above. Perhaps I have an issue with the reading of information from the drive. I have no faults on the RIO scanner or the drive but perhaps I am not getting information from the drive read back into the PLC? What could I check to test this communications link is working ok?

I would start by cycling power to everything and see what comes up not working
also most RIO modules that use block transfer must have a valid write before you will get a valid read. It need to write the configuration first, some times they only write the configuration on the first power up the module retains it until the next power cycle.

Thanks Gary,
I will check both the drive and the RIO scanner and look at the mapping table to see what words are mapped across. If what you suggest is correct that "the reference cycle may complete even without the RIO communications functioning then this certainly would make sense why it maybe hanging up and waiting after the reset. I don't think I have a RIO scanner card to swap out but I will try and see if one can be got, I doubt they're very plentiful either as they are quite old also. Is there any configuration to be done to a RIO scanner card upon replacement, or is it just a download to the SLC processor?. I have only worked on devicenet scanner cards in the past using RSNetworx but I assume there is nothing like this for RIO? Thanks for the help. I will be back at work Monday and I can try these few options and I will let you know how it goes and what the solution turns out to be.

Without the manuals it's difficult to say what's going on or to check the configuration file
look in the ladder code for a block transfer that's triggered by the first scan bit. this would be the configuration block. sometimes they are only sent on the first scan. cycling power off and back on will rewrite the configuration.
as I said before if both axes are not completing the homing cycle then I would look as things they have in common
I hope that maybe somebody else has some other things to look at.

What conditions must be met for the homing to be complete? As Gary mentioned, typical homing sequence is return to home switch at fast homing speed, stop reverse direction and move at slow home speed until the first Z pulse after clearing the home switch. I have seen cases where the slow home speed is too slow to generate enough of a torque command to overcome static friction and start moving.
One thing that could cause both axes to fail at the same time might be that the machine got bumped by an errant fork truck. That could have knocked the axes out of alignment such that it takes more torque to move.

Good thought Steve I didn't think of somebody bumping the machine but it would make sense.

Guys,
Just an update to close this out. I was back working on this issue and got to the solution. There was no issue with the RIO communication as I originally suspected, also the ICM 400 drive was also working fine. The issue was with a rotary drive which was required to drive a line of rotary valves to position before the servo axis could move downwards. The rotary valve motor was faulty and all worked fine upon replacement. There is a new machine in the pipeline to be delivered in the coming months which will see an end to much of the obsolete controls which are no longer supported. Thanks for taking the time to give input, much appreciated.