Automation 101: Learning the Language

What is operating frequency?

The frequencies at which the vibratory feeders operate are 50 and 60Hz.  The standard feeder operates at 60Hz, meaning it has 7200 vibrations per minute on AC (full wave) power and 3600vpm on RC (rectified half wave).  At 50Hz, the feeder has 6000 and 3000vpm for AC and RC, respectively.

What is rectified power?

Rectified power is a modified version of AC power.  AC power is represented as a sine wave.  Rectified power takes away the bottom half the AC sine wave and removes it, leaving a series of positive (DC) pulses.  When applied to a vibratory feeder, the rectified power energizes the magnet pulling the spring mounted trough back and down, and then de-energizes the magnet, springing the trough up and forward.

Air gap adjustment?

Air gap adjustment is the process of adjusting the air gap between the coil and armature of a vibratory feeder.  This is done by taking gage plates of known thicknesses and using them to adjust the air gap.  If the gap is too small, the armature will strike the coil, possibly damaging it.  If the air gap is too large, the coil won’t have enough pull on the armature, resulting in little or no feeding.  The larger the air gap, the higher the current and the lower the stroke.  The smaller the air gap, the lower the current and the higher the stroke.

What is tuning?

Tuning is the process of adjusting the quantity of leaf springs in the unit to match the trough weight being carried.  This is done by removing the spring clamping bolts and adding or subtracting leaf springs.  Make certain to only work on one stack at a time and always have spacers between each spring.  A proper tuning will allow the unit to be stable when voltage and material head load fluctuates.  Once the proper tuning is achieved, the air gap is adjusted to achieve the proper stroke and current.

What is sieve analysis?

A sieve analysis, or gradation test, distributes a sample of bulk material by size.  In order to obtain the size distribution, mesh screens called sieves are stacked on top of a mechanical shaker.  Each sieve has a different sized mesh screen, meaning they have different sized openings.  When stacked, the sieves should decrease in size from top to bottom.  A material sample of known weight is thoroughly mixed and placed on the top screen.  The machine agitates and each particle of material passes through the sieves until it reaches a layer it can’t fit through.  The result is a layer of sieves, each with a percent of the total weight of the sample retained, which ultimately decides how much of the sample passes.

How does a rectified vibratory feeder work?

Vibratory feeders, or electromagnetic feeders, use magnetic coils and springs to create motion.  The magnet is energized and pulls the spring mounted trough down and back.  The particles in the trough are carried down and back also.  The magnet is then de-energized allowing the spring mounted trough to move forward and upward.  Providing the vertical acceleration of the particles in the trough is greater than 1 g, the particles will launch forward.  As the coil is reenergized, the trough moves down and back allowing the particle to fall downstream from its original position.  This catch, carry, drop motion is how a vibratory feeder works.

What is trough stroke?

Trough stroke, or feeder stroke, is the distance traveled by the trough during one complete vibration cycle.  During operation, the trough moves back and forth, as well as up and down.  A single stroke is measured by the uppermost forward position to the downward most backward position.  The trough stroke can be measure with a V-shaped gauge with horizontal lines that are parallel to the line of drive.

What is material classification factor?

Material classification factor is a number between 0.0 and 1.0, 1.0 being the best, given to a material based on its ease of flow through a feeder.  An example of an easy flowing material is sand, which would be given a 0.9.