PLC Diagnostics

I am trying to develop a list of logical step by step diagnostics procedures for a machine controlled by a PLC for a friend who is a plant mechanic.

Something like

Is anything working, yes skip to step ...
no check power and fault lights on the PLC
...
stop the program from running by...
Check each input device to see if you are getting a signal light at the PLC card
etc.

If anyone has any ideas on this or places to look to get ideas I would greatly appreciate it.

TIA
John

We are an oem machine builder. Most of our machines contain valve actuated devices (air and hydraulic cylinders, grippers, etc.), rotary index tables and servo motors.

I would say that after a machine has been up and running for a few months, at least 75% of the support calls we receive are a direct result of a limit/prox switch either loosening up and moving out of the proper adjustment or an operator mis-adjusting said switch.

I'd say on an existing machine w/ a good history, "Start with the switches!"

Thanks, that makes sense to me. I have never had a failure in a PLC that you could not smell VBG when you opened the el cabinet...

What industry do you build machines for?

John

What industry do you build machines for?

Click to expand...

Mostly but not exclusively automotive type companies.

We deal mostly with dedicated production machinery with either multiple holes (drill/ream/tap etc.) or single pass honing applications. Manual and automatic load machinery.

Almost all our machines are one-of-a-kind and dedicated to one part or a similar family of parts. Recently have had some requests and success in 100% process gauging on machines.

One of my favorite machines I have worked on processed aluminum floor panels for use in clean rooms. These are the panels with holes in them for the air return. The panels were about 2 ft. square. Our machine drilled 1024 (One Thousand Twenty Four) holes in each panel with a cycle time of 26 seconds!

The panels were aluminum so punching was not an option. The back side blow out from punching left a fractured surface which would continue to release aluminum fines into the clean room...not good for the filters.

ndzied1 said:

Our machine drilled 1024 (One Thousand Twenty Four) holes in each panel with a cycle time of 26 seconds!

Click to expand...

I assume the holes were NOT drilled one at a time?...

beerchug

-Eric

If you are looking for information on how to troubleshoot the PLC end of things, here are a couple good references ...

PLC-5 Quick Reference Guide

PLC-5 Enhanced and Ethernet Processors

I assume the holes were NOT drilled one at a time?

Click to expand...

Good assumption! 64 at a time. Still, the machine looked more like a punch press than a drill