Overview
My company had recently commissioned a closed die press. I was originally tasked with going to the site and installing a remote connection device (a Netbiter).
Whilst I was on site, the customer reported they were having continuous crashing issues, whereby they had to recycle power to the entire press, sometimes 15 times in a day. This would cause a great loss in productivity.
Task
I was not tasked with solving this issue but took it upon myself to help the customer. I set myself the task to diagnose the reason for the crash and fix it.
My Work
- Discovered that the reported fault was indeed occurring by analysing data of the remote connection device.
- Found the solution to the problem by analysing the diagnostics buffer.
- Changed the safety settings on the Siemens safety cards to allow more time for the detection of the inputs.
- Improved HMI design to fix issues operators complained about around motor starting.
- Created a detailed report of my proposed resolutions to fix the PLC crashing.
The holdup valve discrepancy time was changed from 50ms to 200ms. This allows the switch more time to switch, which will greatly reduce the false flags. All other safety discrepancy times were also increased to 200ms.
Three error handling blocks were also added to the program to prevent the PLC from freezing upon finding a fault.
Outcome
The maintenance staff and management were left happy after my visit and my work afterwards led to the uncovering of a serious fault with an easy fix.