By John Henry, www.changeover.com
Packaging machine speed is easy to calculate. Just count products out, divide by time, and you have instantaneous speed per minute. In theory, you should be able to multiply by 480 to get output per shift. In reality, that instantaneous speed probably doesn't match shift output. During the shift, the machine may have stopped. That may be because the operators went to lunch, because the upstream or downstream machine stopped, because it had its own problems, or a host of other reasons. What you are really interested in is output: how many pallets can you get on the truck at the end of the day? This is related to speed, but is not the same thing.
A typical line might consist of a filler, capper, labeler, and case packer. The filler can run 175ppm (products per minute), the capper, labeler, and case packer can run 150ppm. What is the theoretical line speed? It's not 175ppm because the filler can run no faster than the capper. It is not even 150ppm because the labeler must be stopped every 45 minutes for 3 minutes to replace the label roll. That makes the labeler speed not 150ppm but 140ppm. That is the fastest the line can ever run.