Feeding Options for High Speed, 100% Inspection

Feeding parts for any application is critical to the efficiency of the process, including high speed inspection. The proper feeding of parts can optimize an inspection machine’s performance and enhance its inspection rates, while improper feeding will adversely affect inspections and decrease machine capability. Part handling, orientation, and changeover capabilities are all critical features of a feeder system. Feeders come in many different forms, functions, and capabilities including centrifugal feeders, vibratory bowls, step feeders and pick/place robotics. Selecting the correct one to fit the application can be challenging.  

A centrifugal feeder consists of a center “disk” that is mounted on an angle and an outer disk that rotate independently. The centrifugal force during rotation brings the parts to the edges of the center disc and carries the parts to the highest section, it delivers them onto the outer disk, which then has simple tooling which organizes the parts in a single lane to the conveyor and metering mechanism. Centrifugal feeders can be quiet and are gentle on parts while achieving very high parts per minute rates.  These systems can be expensive and need specific tooling and external controls to get proper part orientation, when required.

Vibratory feeders are “created” through a process of twisting and turning metal in somewhat of an artform, more so than a scientific process. These feeders use electromagnetic vibration to get parts to feed from bottom up in a multi-level stainless steel bowl. If the vibratory bowl is dedicated to a single part it can be very simple, achieve fast feed rates and easy to maintain. However, the more part configurations required the more complex the feeder bowl will be to changeover, you will see reduced feed rates and face challenges maintaining. Vibratory feeders can be very loud (depending on the size) but can be placed in a sound enclosure to perform under required decibel levels. The complexity of the bowl will determine the cost and for gentle part handling vibratory feeders are not an option.

Step feeders use staggered levels set up like stairs that move up from the well to advance parts vertically to a conveyor inline. If parts are stacked or overlapping, they fall off and back into the well. The line of parts that make it up to the top are then placed onto the conveyer for inspection. The step feeder is limited by capacity and is a slower feeder compared to the other feeder options. It does offer quiet and gentle operation, but pricing is high and flexibility is often the biggest challenge. 

Pick and Place Automation includes utilizing some form of multi-axis robot(s) placed between a pick conveyor and the inspection machine(s). The robots are guided by sensors to identify, pick, orient, and present parts. As with most feeder options, the more parts added to the mix, the more complex the system becomes. Custom grippers can be added to the robot arms to accommodate multiple part configurations. This form of automation can be very expensive, have slower feed rates, but offer flexibility that other feeder systems cannot offer. If gentle part handling is required, this is a great solution. As technology advances, pricing will become more competitive.

Part handling in the feeder process is very important, below are some of the most important details to consider when deciding which type fits your applications:

Gentle handling: Delicate parts can get easily damaged with the wrong feeder type

Orientation: Parts must be oriented a certain way to properly go through the inspection machine. Standard orientation of parts is very important and can be achieved through two different techniques: mechanically and visually.

Flexibility: For manufacturers who produce a wide range of part sizes, having easy and quick part to part changeover is essential. These changeovers can be accomplished in different ways such as mechanical tooling, rails and confinements for each specific part size. Or through sensor guided automation.

Parts Per Minute: What are the yearly volumes of each part, how many hours of operation per year will determine the rate required from the feeder system.

Each application offers unique challenges so creating specifications per application is critical to the development of the proper feeder system.  There are several options for feeder systems and it’s a challenge to select the correct type. But, by defining the parts per minute, required flexibility (all parts included plus any required part orientations), handling requirements (gentle?) up front will allow for an accurate price quote and more importantly a system that will perform to the desired results.