Part Wear and Damage

A final consideration may be that the parts selector will overwork the parts oscillating and vibrating them and kicking many of them back for retry after retry. If the effectiveness is virtually 100 percent, it is possible to use the system efficiency to calculate the chances that a part will be tossed back k times before reaching an acceptable orientation. Thus, nearly one out of a hundred parts will be kicked back ten times before achieving an acceptable orientation. The automation engineer must decide whether or not this kind of treatment will damage the product. The average number of kickbacks for every pad entering the 100 percent effective selector system is also a function of efficiency.

Stainless steel stampings are used to jacket and support pulleys used in the assembly of blocks of various designs used on sailboats. The stainless steel has a polished appearance and the quality of the surface finish is a factor in the acceptability of this costly product. Suppose these stamping are oriented for subsequent assembly using a bowl feeder having an effectiveness of 100 percent and an efficiency of 50 percent. What are the chances that a given stamping will be tossed back into the bowl three times before a correct orientation will present it for assembly? What is the average number of times a typical stamping will be tossed back into the bowl for this operation?

Having completed a discussion of the rather precise ways in which a parts selector can be analyzed, it should be knowledge that the mechanization of parts handling and orientation is as much an art as it is a science. The fabrication of selector mechanisms and escape devices is usually done in a very experimental way in which the skilled artisan cuts and tries many different configurations until an effective design is perfected. Although many scientific principles govern the behavior of parts orientation and selection processes trial and error experimentation can be used to develop practical working systems without the science. The primary benefit of the analysis is to understand the dependence between successive steps in the orientation process and the importance of efficiency and effectiveness to the overall success of the automation project.