"How to automate any process."
August 11th, 2006 by Mike StrawbridgeWith process automation technologies, any repetitive task can be automated. Often the process of designing an automation system will enhance the quality of the process as each variable in the process is identified.
At Westvaco, I led a team that designed one of the first automated batch distillation columns for recovering printing solvents. This project was done back when a Modicon 484 PLC was the state of the art PLC controller. Not only did we have to discover what steps where to be done when, we had to work around the limitations of the controller with seems crude by modern standards. Years later we converted this control scheme to run on an Allen Bradley plc programming. At the same time, we updated the process automation technology to match the way the column was operated at the time.
Neither process automation project would have been possible without a thorough understanding of the workings of the process.
Over the years I did lots more plc programming, managed plc training and worked with different plc manufacturers. So what does PLC stand for? Programmable Logic Controller. They are now the staple of process automation technology. We used them for everything from running distillation columns to opening doors to controlling conveyors to a sophisticated defect rejection system.
The most challenging automation project that I managed at Westvaco was a real challenge to even the best process automation technologies available to us at the time. We designed a speed control system that would locate a break in a product stream and alternately switch product form one conveyor to another at very high speed. The alternator had to not only match the changing sped of the conveyor but also hit the exact break between the materials. Precise motor control was required with a feedback system to correct for any errors. Using process control technology originally designed for our CompuRally rally computer system, we were able to develop an error correcting algorithm to precisely hit the tiny gap in the product streams. The error correcting routine proved so robust that it changed the way the machine was started up. The lengthy phasing routine was eliminated and the machine was simply started up and the error corrector allowed to find the phase angle. This new method resulted in much less waste than the original manual stand still phasing. Later we found that by recording the error correction value, and reentering it on similar jobs, the start up waste was reduced even further.
Contact Mike to discuss your process automation technology challenges.
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Mike Strawbridge August 11, 2006
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