Kinetix 6500 Download Bug

Hi Everyone!

I have another head-scratcher that I'd like your feedback on. I was recently asked to troubleshoot a problem with a Kinetix 6500 system.

First off, the details of the system:

Two axis flying beam saw, using two rotary PM motors. One is a 1.45 kW Catalog Number MPM-B1153F-M(Track1) and the other is a 7.9 kW Catalog Number MPL-B580J-M(Saw1). Each are using motor mounted feedback through the Hiperface, 1024 Feedback Cycles/Rev and 2048 Counts per Cycle. The Kinetix Modules are 2094-EN02D-M01-S0's. The PLC is a new generation CompactLogix 5069-L320ERM.

The motion is basically a matching speed cut where the Track1 axis matches the speed of product to be cut, and then Saw1 traverses across the product to cut it. This allows the plant to cut individual pieces out of one long piece while in continuous production. Saw 1 is MAG'd as a slave axis to Track1, and Track 1 matches speed of the product using a 3rd axis that is basically a measuring wheel from which Track1 gets its matching speed reference.

The problem: This system works perfectly under all circumstances except 1. Every time a new program has to be downloaded to the PLC, the ActualPosition tag for Track 1 randomly jumps from its normal home position of 226.5 to random numbers ranging from 650 to 690. There is no logic whatsoever in the program that sends this number to Track1, yet every time I download, it happens. It apparently happened to the OEM as well because he created a tag that moves this value into a random static tag so he probably was monitoring as well then just gave up and hoped nobody would come behind him and find this. At this point, the axis now thinks it's out of position. When an operator tries to run the MAH command, since it's trying to go to 226 and it thinks it's at 650-690, Track1 runs out to the overtravel prox where it then faults out. The only way I can fix this is to use motion direct commands to move it back to the home prox and then run the MAH command where it then sees the prox and writes the correct home position back to Track1. ActualPosition. This phenomenon doesn't happen to the Saw1 axis, and I can do online edits without causing this problem.

Any suggestions?

I am pretty sure that you can set a checkmark in the Axis configuration, to keep the servo position after a PLC download.

Why is it going to the overtravel prox and not the home prox, when you home the axis ?
You should be able to make a "homing routine" where you disable software travel limits and then jog the axis to the home prox, before executing the MAH instruction and then re-enable the soft travel limits.

Even though you make the servo remember its position after a download, you might still find yourself in a situation where you will need the homing routine... Etc. after a motor- or drive replacement.

Jobbe9000 said:

I am pretty sure that you can set a checkmark in the Axis configuration, to keep the servo position after a PLC download.

Why is it going to the overtravel prox and not the home prox, when you home the axis ?
You should be able to make a "homing routine" where you disable software travel limits and then jog the axis to the home prox, before executing the MAH instruction and then re-enable the soft travel limits.

Even though you make the servo remember its position after a download, you might still find yourself in a situation where you will need the homing routine... Etc. after a motor- or drive replacement.

Click to expand...

Due to the position of the home prox relative to this new ghost position, the axis tries to travel from 690 to 226.5 when homing which is away from the home prox and toward the negative overtravel prox

I will look for this check box you mentioned. I was hoping to not have to write logic to fix this issue, but yes ultimately it may lead to that if I can't prevent this post-download bug.

Thanks!

There was some bugish firmware that came on some kinetix around that time frame. Make sure that you’re running the latest version. But as you know, this can solve one problem and create another.

Update: After searching through forums and tech notes, I think I may have found something.

Looking through a tech note about a 6500 losing home position after power up lead me to look at the AxisHomed and ARPFault bits. Supposedly if you move the axis to its known home position, MSF it then MAH it, it will store its current position as a predefined home position somewhere in the drive itself.

When this is done, the AxisHomed bit will be set to and remain at 1 as long as there are no ARPFaults. The axis in question is the only one that does not have this bit set to 1, so maybe there is a specific bug related to this that affects download-only axis position being lost? Gonna try this when I can get some time on the line and will keep you all updated on the results.

Thanks

CLanford said:

Update: After searching through forums and tech notes, I think I may have found something.

Looking through a tech note about a 6500 losing home position after power up lead me to look at the AxisHomed and ARPFault bits. Supposedly if you move the axis to its known home position, MSF it then MAH it, it will store its current position as a predefined home position somewhere in the drive itself.

When this is done, the AxisHomed bit will be set to and remain at 1 as long as there are no ARPFaults. The axis in question is the only one that does not have this bit set to 1, so maybe there is a specific bug related to this that affects download-only axis position being lost? Gonna try this when I can get some time on the line and will keep you all updated on the results.

Thanks

Click to expand...

Kindly, did you try it on the line ? Did it work ?
Thank you

Kataeb said:

Kindly, did you try it on the line ? Did it work ?
Thank you

Click to expand...

Hi Kataeb,

Yes this procedure did work for me! But for some odd reason I had to manually (like literally manually) move the machine to its position, then MSF and MAH it. The AxisHomed bit then set to 1 and I lost the ARPFault bit. I tested this by making a small offline change then downloading to the controller, and the problem was resolved!

Note: I mention above that I literally manually moved the machine because when I tried to use the motion force commands to move it where I wanted and then did the above procedure, it did not work. I have no idea why manually moving the machine mattered, but it did. Good luck!