Wednesday, 24 May 2006

Automatic Assembly (14/16)

Once it has been determined that a part can be fed by a bowl feeder, the remaining consideration is the maximum feed rate that can be obtained from the feeder.  The feed rate of the part must be within the cycle time of the complete assembly operation.  This rate, for a given conveying velocity, depends upon the physical size of the component and the features for orientation.  For parts symmetrical about all axes, e.g. cubes, spheres, every part will leave the feeder 'first time through', or 100% of the parts will leave the bowl because no tooling is required.  This 'first time through' rate is the measure of a part's efficiency at being fed automatically.  These parts will always be correctly orientated and ready for insertion.  Components having little symmetry have a much lower tooling efficiency and it can be difficult to achieve the required feed rate using one bowl feeder with passive tooling.

Parts feeding is the most difficult area of assembly automation.  If the part can be automatically fed and orientated to the workhead then it can usually be assembled.

The final parts forming stage can be used as a method for feeding difficult parts.  The parts are usually fed in bulk on strips and pressed or guillotined, before being fed to the workheads.  The strips are easy to handle and orientation can be better controlled.

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