How to select a feeder

Part feeders come in many forms. These include vibratory bowls, inline feeders, centrifugal feeders, belt feeders and step feeders. All part feeders utilize common engineering principals to feed and orient parts which include part weight,center of gravity, part geometry and part velocity. Part feeders differ in the method with which each motivates or conveys parts past tooling. Tooling may be passive, like a simple rail with an elevation wiper, or more recently PLC controlled programmable active with sensor and a pneumatic or servo-electric to sort or orient parts. The later devices are often used to tend upstream machines as well.

1 Analyze the part
It always begins with the part. Consider the length, width, thickness, material weight and shape of the part. Parts generally have a natural bias. This is caused by basic geometry and by various features which might be included within the part’s design. These features should also be considered in relation to the centre of gravity and the general shape and size of the part. In combination features will determine the 'natural' feeding bias of the part. This is also called the parts “aspect ratio” and it defines how parts are fed, metered and ultimately oriented. In addition any outstanding feature may serve as a guide for orientation, such as; angles, grooves, flanges, bosses, projecting pins and convex or concave surfaces. In simplest terms part with good weight to surface are with few features to slow it feed best. Parts with a center of gravity or features which allow for simple, passive tooling are oriented in simple low cost feeder-orientors. How fragile the part of part surface is should also be a primary consideration. Some feeder designs work very well with robust or rough form parts but are likely to damage parts which require “gentle” handling. So a nut, bolt or screw may be appropriate for a vibratory bowl or step feeder which are excellent at metering part to tooling but are generally best suited for more robust parts while ceramic, powdered metal, high value packaging and machined parts are generally fair better in a linear feeder.Additionally, the part surface condition needs to be identified. When parts are dry the surface is not a limiting factor but when wet or oily the parts are best handled within a brushlon lined bowl or linear feeder which reduces part to machine surface adhesion.
Testing is generally required to determine how well it will feed and how simply the part is to orient but our skilled part handling engineers can generally provide initial guideance and suggestions with answers to a few simple questions, imagery or a few test parts.

2 How fast do you need the parts?
The second issue to consider is feed rate. Both bowl and linear vibratory feeders generally operate at a similar
maximum effective operating speed of not greater the 320 ipm. Belt feeders and centrifugal feeders can operate at much higher speeds but only on certain. Feed rate is affected by tooling efficiency. A simple part like a washer with random oriented part fed single layer x single file OD to OD has 2 in 2 tooling efficiency. If the part is being sorted for a feature like an ID chamfer then the efficiency drops to 1 in 2 It is important to understand that every feeder operates on an average feed rate so sufficient run out should be included in the discharge track or conveyor to maintain a supply of conforming parts available for your next operation.

3 What is your environment?
The third issue to consider is the environment where the feeder will be operating. Feeders are constructed for every industrial environment. It is critical the designer understands the requirements of the environment where the feeder is operating. The size of the feeder is effected by the size of the part and the part supply required to maintain the desired feed rate.

4 Part Supply?
The fourth issue to consider is where the part supply is coming from. The feed rate is a related issue since sufficient supply. Various floor level hoppers, table hoppers, horizontal hoppers, integrated bin dumpers, tote dumpers and “in line” part supplies are available to maintain part supplies to feeders. These supply devices are generally combined with simple part flow controls sensors so that parts are supplied to feeder “on demand”. This is often vital to the efficiency of a feeder since too few or too many parts within the feeder will negatively impacts the feeder performance.

5. Part Orientation?
Part orientation is affected by passing the part through a series of engineered obstructions or guides in the feeder track using standard modular tooling as well as custom tooling as needed. Parts lacking adequate aspect ratio, geometry or feature suitable for efficient feeding or passive tooling may be oriented using “active tooling”. Active tooling are sensors combined with an active orientation device such as a pneumatic pick/rotate/place device.

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