It is important to note that minor changes to either part or feeder geometries may result in markedly different behavior. As a result, designing feeders remains largely a black art, heavily dependent on labor intensive trial and error. Given the infinite number possible, a wide variety of feeder geometries have been developed for use in vibratory bowl feeders. The underlying function of parts feeding, however, may be expressed concisely in terms of the motions that parts make through a feeder. Figure 2 illustrates the function of a feeder represented as a filter on the motions of parts passing through the feeder.
Parts enter the filter in a finite number of stable orientations.
The path corresponding to those parts moving in the desired orientation passes through the filter. The remaining paths exit the filter, corresponding to parts falling off the feeder track. Though conceptually simple, the filter representation in Figure 2 lacks the necessary detail for analysis and design of a feeder for a specific part. Figure 3 shows an intermediate representation, one that captures the filter-like characteristics of Figure 2 in terms of motion constraints, and yet preserves the necessary detailed geometric information for analysis and design. Space limitations preclude a detailed explanation here.