The string diagram is one of the industrial engineer's oldest tools, but still has application today. Use them regularly not just for product flows and material handling, but also for the movement of people around a cell, in changeover and in maintenance.

Begin with a scale diagram of the plant on a pin board. Select out a few major products, and trace their movement around the factory, showing the flowpath by means of coloured string and drawing pins. Then question, simplify, and quantify. The power of such a tool is its visual impact. For cost effectiveness, the string diagram is hard to beat.

On separate diagrams, trace the movements of operators doing regular work, doing changeover operations, and routine maintenance. Strangely, although material flows are often studied in detail, operator movements are sometimes ignored. What is the total distance moved to do a changeover? How many times does the operator go to and from a tool rack or walk around a machine during a changeover?

Vehicle movements can also be traced. Several studies have shown that the human eye and judgement is almost as effective as sophisticated routing algorithms, in sorting out shortest routes, provided there is a map showing the required visits.

So simple. So effective.