Production preparation and numerical control in PCB assembly

In this article, we analyze numerical control problems arising in a component insertion line for printed circuit board mounting. Such a line consists of a number of fully automated placement machines, connected by an automated, carrierless conveyor system. At each machine, the placement device consists of an arm equipped with a number of placement heads. Each head may serve certain component types; there is some freedom in the choice of equipment for each head. Components are supplied to each machine by tape feeders (each containing components of only one type) which are placed at certain feeder positions along the machine. Before actually operating such a line, a careful production preparation phase has to be completed, specifying for each printed circuit board type the exact way in which such a board should be mounted. Problems arising in this production preparation phase include: the choice of heads to be mounted on the placement arm of each machine, the choice of components to be placed at each machine (workload balancing), an assignment of feeders to feeder positions on each machine, clustering of components to be placed in one pick-and-place move, and the sequencing of component insertions at one machine. Formulations and solutions for all these problems are given and numerical results for some industrial examples are given. The numerical control system developed has been tested and implemented and has resulted in software, which is in use at several sites of Philips' Electronics