In case of single coil vibratory bowl feeders, the coil is mounted centrally (either one coil or else two coils). The advantage is that one requires only a single coil, thus reducing the cost and secondly, the coil can be made powerful enough so that the same one can be used across models. However, there are certain major disadvantages of having a single or even two central coils. It leads to excessive vibrations at the centre, which reduce as the part moves away from the bowl centre. This results in a huge wastage of energy. Due to the eccentric and powerful load, there are possibilities of the springs and bolts breaking on a regular basis. To offset the extra load, the bowl needs to be made heavy or else extra counter weights need to be added to the bowl to balance it, further making the bowl needlessly heavy. The vibrations too are abnormal and heavy, resulting in damage to the parts being fed or resulting in a wrongly oriented part coming out. The bowl life too reduces due to this.
In case of multiple coil vibratory bowl feeders, the coils are mounted on the periphery of the vibratory bowl feeder (three or four coils). However, for this the coils need to be correctly designed for each and every model. But the advantages are that firstly there is no extra energy wasted, thus saving on energy costs and secondly, the coils being on the periphery of the vibratory feeder, the vibrations are equally transferred to the bowl, leading to better performance of the vibratory bowl feeder. Secondly, being on the periphery, one can design the bowl having a slightly bigger diameter, which is not possible in case of a centrally mounted powerful coil. Further the chances of the springs and bolts breaking are drastically reduced, especially in the case of full wave vibratory bowl feeders. The bowl can be designed to be light weight and cast aluminium bowls can also be used. The life of the vibratory feeders and the bowl too is much more in case of multiple coils mounted at the periphery of the vibratory feeder.