Hello All,

I'm analyzing some PLC code for a bending machine and I came across a switch that prevents the PLC from reading a piece of feed data input.

The bending machine works by using two cylinders (one on the top and one on the bottom of a metal disc attached to a motor. Each cylinder is attached to a separate motor). There are 6 bending group inputs in the program and each group has variables such as angle and feed length that tell the machine how much to bend the metal and where to bend it, but the bend angle and feed length input for the top cylinder is different than the bottom cylinder.

The machine alternates between using the top cylinder while the bottom cylinder is fixed and vice versa to bend the metal around the cylinder. For groups 2 and 4, the feed data input of the bottom cylinder is blocked by some random switch that was inserted and left there.

The clients have complained of some inputs doing nothing, so I think there is some connection here. However, the machine still works fine, so I'm not sure if I should remove it or not. I checked the logic for all the other groups and they do not possess this switch, so the bottom spindle feed length data is fine.

Could anyone please spare some advice or wisdom that will guide me in the right direction?

In case it is relevant, I'm using Siemens TIA Portal V13 Service
Pack 1 to upgrade a program that was originally done in RS Logix 500.

Best,
AKA_knowledge23

 

I think you are making a basic mistake. You seem to be trying to reverse-engineer this machine from looking at the code and usually that's not a good idea because I found the code and he seems not very well written. Your best bet is to figure out how the machine has to work to do what it is supposed to do, and then figure out what it is the code is trying to do to support that.

 

>I think you are making a basic mistake...

Hello Bob,

I have seen the machine working and combined that insight with knowledge of the PLC code. Otherwise, I would not have been able to get this far. I'm going to be testing the machine soon and I'll post my results if I'm still having trouble.

Best,
AKA_knowledge23