A specialty media print company was having issues with one of their tape coating lines. The line had obsolete equipment as far as the eye could see. As problems with the line arose over the years, the issues were resolved with a quick fix rather than fixing the root cause. This triggered a loss in functionality of the line which ultimately led to automatic functions being controlled manually for the last decade.
As with most customers, there was a major concern with the amount of downtime that the upgrades would cause. The decision was made to split the system into two separate projects, to be able to break the downtime into more manageable chunks along with spreading the cost over a greater period of time.
The customer finally decided that they could no longer run the line the way it was. Long down times due to compounding problems were losing up to half a day in production. With minimal diagnostic information, inexperienced operators could spend hours trying to fix a simple issue.
The line was plagued with constant tension control problems as each of the 20-year-old drives had their own self-contained PID loop. The system was controlled by two separate controllers trying to work together to run the same line, which added to the unnecessary complexity of the line. Overcoming these issues became the target of the first project.
As this project was the first of two projects completed on the same line, EDC had to do more upfront planning. The upgrades completed in this project had to work with the equipment that was remaining on the line.
SOLUTION & BENEFITS
Since only some of the components were being replaced in this project, EDC could not build and test the full system offsite. The new equipment was prepped before installation so that it could be installed next to the existing components that were remaining. The prep work completed offsite ensured that the deadlines for the installation could be met on time.
EDC simplified the controls of the line by replacing the dual PLC controllers with a single Allen Bradley GuardLogix L81 PLC. This allowed for a single controller to run everything with integrated safety. EDC was then able to add in run permissive messages and safety alarms to ensure that operators had a clear understanding of what steps needed to be taken to get the line back up and running.
A full mechanical retrofit was completed for all of the motors. New AC Powerflex 525 and 755 drives replaced the existing DC drives. The tension control which was originally controlled in each drive individually, was centralized into the new PLC. With the updates in technology over the last 20 years, the amount of time to calculate the tension requirements in the PLC and transmit the speeds over ethernet to the vector drives was a fast and robust solution.
The amount of downtime of the system has been significantly reduced. The run permissive messages and safety alarms allow the operators, at all levels of experience, be able to diagnose the issue and recover the system at a much faster rate.
With the upgrades to the PLC and the tension control, the unwind tension is now an automatic process again for the first time in over a decade. This has also helped to reduce the overall runtime of the machine, as the operators do not have to manually step through the process.
The line now runs better than it has in a long time. EDC was able to use their extensive experience with these types of lines to understand what needs to be done and what resources need to be available in order to get production running again in a timely fashion.