Electronics assembly due to the large number and variety of its components and characteristics of electronic product life cycle is short, to the production operation scheduling
By high-speed placement machine and multi-function strips into a unit.
In fact, the whole PCB assembly lines include machine, screen printing machine, glue machine, reflow soldering, and curing furnace, machine equipment, these devices together of PCB assembly lines, but this does not constitute the whole production line auxiliary equipment bottleneck process, thus will be omitted during the modeling.
Every SMT machine can accommodate 20 feed slot, each element occupies patch on a feed slot.
In general, the single PCB components needed to several kinds of no more than the capacity of the feeder, but many kinds of PCB components needed for the total number of species is usually beyond the capacity of the feeder.
Different varieties of PCB in SMT process required components are placed on the feeding trough, take device is removed from the feed trough components attached to the location specified on the PCB.
According to the survey data for empirical research object, a high-speed placement machine, on average, pasted on the element of time is 0.
6 s, the average switching a feeding trough time of 180 s.
Multi-function placement machine has two table, but only one workbench work, another workbench is used only for large or alien elements, each workbench accommodate 10 feeding trough, average pasted on a component to 0.
18 s, an average of one feeder switch time of 220 s.
When switching between different varieties of PCB, SMT machine needs to be certain to switch time, usually for a switch component feed trough time about 6 times, the 1200 s.
Switch time, therefore, has a pivotal position in the process of electronic products assembly.
In many varieties and small batch environment, usually for grouping PCB first, will have similar characteristics of PCB is divided into a set of, so, in the same group, between different varieties of PCB assembly do not need to change feeder, also do not need to switch time;
But when two groups between the PCB need change the feeder, you need to consider the switching time between them.
On the basis of PCB production scheduling problem was divided into two levels: first level scheduling problem known as the 'board' scheduling problem, namely to determine a PCB group between the PCB production order;
At the second level of scheduling problem is known as 'group level' scheduling problem, which determine PCB production order between the groups.
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