Estimating the Production Rate and Machine Utilization of an Automated Component Insertion Line - Part I.

Many shops such as the D5 line in Merrimack Valley, the AIM line in North Carolina and the CIM lines in Oklahoma City assemble circuit packs using highly automated insertion equipment and the inline manufacturing concept. More new shops, the DDM1000 line in North Carolina for example, are being built. In these lines, relatively small buffers are assigned between workstations in order to guarantee a small manufacturing interval and quick feedback in the event of process failure to make acceptable product. These small buffers could lead to a noticeable loss of insertion capacity due to the phenomenon of blocking and starvation. In this memorandum, we show by means of simple examples how the buffer sizes, the mix of codes and the sequence in which the codes are produced significantly affect the throughput of the line. A method is then developed to estimate the insertion capacity for a given configuration of machines and buffer sizes and for a given code mix and sequence. The method also gives the expected machine utilizations, the time machines are blocked/starved and, more importantly, the reason for this lost insertion capacity. By judiciously interpreting this information, we show, via examples, how one can take one or more of the following steps to improve the insertion rate : (a) change the sequence, (b) increase the buffer space selectively, (c) make codes in smaller or larger lots and (d) add new machines.