Electronics Assembly due to the number of components of large, as well as a variety of electronic features such as short product life cycle, pose great challenges for operations scheduling, multi-species, small batch, change batch has become the mainstream of electronic manufacturing production mode. In this mode, the switch between multiple species occupy an increasing proportion in the entire time.
High-speed SMT machines and multi-functional SMT machine. In fact, the entire PCB assembly line also includes sending machine, screen printing machine, dispensing machines, reflow and curing furnace, and machine and other equipment, these devices in series PCB Assembly, but such auxiliary equipment does not constitute the entire line of bottleneck processes, thus be omitted while modeling. Each chip can hold 20 feeding slots, each element occupies a delivery slot on the chip. In General, single PCB required number of components does not exceed the capacity of feeder, but many varieties of PCB required components of total number of species is often beyond the capacity of feeder.
PCB mounting in different varieties needed elements are placed in the feeding trough, take the stickers removed equipment from the feeding slot location specified on the component mounted to the PCB. According to a survey of empirical research data, high-speed SMT machines mean time to mount a component of 0.06s, average time to switch a feeding trough for 180s. Multi-function Mounter has two jobs, but only one work, another table is only used for large or special-shaped components, each table seat 10 for the trough, average, 0.18s mount a component, average time to switch a feeder for 220S. When you switch between the different varieties of PCB, SMT machine requires a certain amount of preparation time, usually a component for switching around 6 times times trough time, 1200s. This shows that the switching time in the electronics assembly process plays an important role.
In more variety and minor batch's environment, usually to group the PCB, PCB is divided into a group with similar characteristics, so that, in the same group, different varieties of PCB Assembly does not need to replace the feeders, also no need to switch the time; but when the PCB needs to be replaced when the feeder between the two groups, you need to take into account the switching time between them. According to PCB production scheduling problem is divided into two levels: the first level scheduling of called "Board" problem, namely the identification of a PCB the PCB within the Group's sequence; the second level scheduling of called "group" scheduling problems, namely the identification of PCB organization of production orders.
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