Design of a High Reliability Transport Mechanism

High volume automated manufacturing lines often run at efficiencies as low as seventy percent-even for well-understood, mature products. Despite continuous improvement efforts over the last two decades that resulted in increased line speed, overall line efficiency (the actual number of parts produced divided by the maximum number of parts the line is capable of producing) has typically remained below eighty percent. It is argued in this thesis that increasing efficiency provides a greater financial return on investment than increasing line speed, yield, or flexibility, and should be the focus of future improvement efforts. Further studies of efficiency within disposable consumer goods manufacturing reveal that the key cause of downtime is not machine reliability, but transfer/transition point jams. Numerous transfer points between machines, feeders, and tracks can force efficiencies below sixty percent, even with reliabilities as high as 1 jam per 50,000 parts. Clearly, the most effective means of reducing transfer/transition points is to grab positively each part once and not let it go until it completes its route through the entire manufacturing process. This thesis describes the development, design and construction of a prototype transfer line in which parts are positively held and oriented as they are carried from one manufacturing operation to the next, greatly reducing the number of transfer/transition points and potentially raising efficiency dramatically. The prototype can operate at a rate of 840 parts per minute, and can be easily upgraded to 2500 parts per minute. This transfer line concept can theoretically operate efficiently at rates as high as several thousand parts per minute, but is in fact limited by current part feeding technologies.