Parul Engineering

They are used as part of many processes, including conveying, screening, and packaging.

Principles

• Like all vibrating feeders, an electromagnetic vibrating feeder moves product by making the feeder tray vibrate.
• The product sits in the tray. When the tray vibrates, the product moves in a series of small hops. This series of hops combine to create the constant motion of the product.
• The direction of movement is determined by the angle of the springs. The product will move up from the tray, perpendicular to the angle of the springs.

• The vibration of an electromagnetically driven feeder is generated as the alternating electrical current moves back and forward through the wires of the coil.
• The magnet (attached to the feeder tray) is held a few millimetres away from the coil by the flat springs. As the current moves in one direction, the coil attracts the magnet and adds tension to the springs.
• When the current switches direction the magnet is released, and the potential energy stored as tension in the springs is used to move the tray. This action throws any product in the tray forward creating the hop.

Components

Achieving the correct relationship between the vibratory feeder tray and springs isn't quite as simple as it might seem.

An electromagnetic drive will operate at a set frequency.

(Important Note: It is possible to alter the frequency of the drives with an inverter control system; this is discussed further under the Feeder Control Systems section below)

It is important to try and set up the system so that the natural frequency with which the tray would oscillate on the springs matches the frequency of the electromagnetic drive. This will reduce stresses in the feeder tray and encourage product to flow as quickly and efficiently as possible.

The natural frequency of the oscillation is determined by the relationship between the combined total stiffness of the springs in the system and the mass of the feeder tray plus any product in the tray.

As the feeder tray and mass of product is largely determined by the application, and the electromagnetic drive (minus variable controls) will operate at the frequency of the alternating input (e.g. mains supply at 50Hz), the design variable is the springs.

Increasing the number of springs, and the width and thickness of the spring will increase the spring stiffness. The length of the spring is also a factor; longer springs are less stiff.

The main purpose of the feeder tray is to channel the product being fed to where it needs to go.

To achieve this, aside from being shaped to contain the product and prevent spillage, the tray needs to transfer as much of the energy generated by the drive, into the product as possible.

This is achieved by having a rigid feeder tray, which is determined by the design of the tray.

A tray which is not rigid will lead to areas of the tray vibrating at different frequencies, called secondary vibrations. These areas create anomalies in the flow of product, meaning product can slow, stop, or even run backwards.

As a vibrating feeder is a relatively simple piece of equipment, the control requirements are small.

Once a feeder is set up to perform its intended function, control requirements are usually limited to stop and start.

This type of control is common when the feeder is controlling the flow of product into a process further down the production line.