How do Electromagnetic Vibratory Feeders Work? – Components & Principles
There are 3 different kinds of vibrating feeders, and each one works in a different way. Here’s what they are:
- Electromagnetic Vibratory Feeder
- Natural Frequency Vibratory Feeders
- Out-of-Balance Vibratory Feeders
This piece is all about how electromagnetic vibrating feeders work.
What is an Electromagnetic Vibrating Feeder?
Electromagnetic rotating feeders are a common piece of machinery in factories that make things.
They are used in a lot of different ways, like to move things, screen things, and package things.
Electromagnetic vibrating feeders come in a huge range of sizes, from small models that sit on a lab’s desk to long systems that move materials over several meters.
All of these networks work the same way, no matter how big they are.
Vibrating Feeder Working Principles
Like other vibrating feeders, an electromagnetic vibrating feeder moves food by making the feeder tray shake.
The item is put on the tray. When the tray vibrates, the object moves in a series of small jumps. The steady motion of the product comes from the way these hops work together.
The slope of the springs determines the direction of movement. The product will move up from the box in the opposite direction of how the springs are angled.
System Arrangement
The device has a base, a coil, some flat springs, a magnet, and a tray.
The flat springs connect the tray to the base unit. The flat springs let the two parts move in relation to each other. The product will be fed by this relative change.
In simple words, the coil, which is an electromagnet made from a magnet wrapped in copper wire, is attached to the base unit, and the magnet is attached to the feeder tray. The coil pulls the magnet toward it and lets it go, which makes the base unit and food tray move around each other.
There are drive systems that combine the coil, magnet, and springs, which are all parts of an electromagnetic drive, into a single unit. At the top of the springs, there is a mounting plate that lets you add a food tray that is right for the job.
Generating Product Movement
When an alternating electric current goes back and forth through the wires of the coil, the electromagnetically driven feeder starts to shake.
The flat springs keep the magnet a few millimeters away from the coil. The magnet is stuck to the feeder tray. As the current flows in one direction, the coil pulls the magnet toward it and gives the springs more force.
When the direction of the current changes, the magnet is freed, and the tension in the springs is used to move the tray. The hop is made when this action throws any item in the tray forward.
When this process is done often enough, it creates a steady run of products.
Vibratory Feeder Components
Springs
Getting the right link between the springs and the vibratory feeder tray isn’t as easy as it might seem.
A set frequency will be used by an electric drive.
(Important note: With an inverter control system, you can change the frequency of the drives. This is talked about more in the “Feeder Control Systems” part below.)
It is important to try to set up the system so that the frequency of the electromagnetic drive fits the natural frequency of the tray’s oscillation on the springs. This will make the feeder tray less stressed and help the product move as quickly and smoothly as possible.
The natural frequency of the movement is based on how the stiffness of all the springs in the system relates to the mass of the feeder tray and any products in it.
Since the application determines a lot about the feeder tray and the amount of product, and since the electromagnetic drive (without variable controls) will run at the frequency of the alternating input (for example, mains supply at 50Hz), the springs are the only design variable.
The spring will be stiffer if there are more of them, if they are wider, and if they are thicker. Also important is the length of the spring; longer springs are less stiff.
Feeder Tray
The feeder tray’s main job is to guide the product being fed to where it needs to go.
To do this, the tray needs to be shaped so that it holds the product and doesn’t let it spill out. It also needs to be able to move as much of the energy from the drive into the product as possible.
This is made possible by having a stiff feeder tray, which is set by how the tray is made.
If a tray is not solid, different parts of it will move at different speeds. These are called secondary movements. In these places, the flow of products isn’t normal, so they can slow down, stop, or even go backwards.
Base
The base is important for more than just holding the flat springs in place at the bottom.
The weight of the base keeps the food tray from moving, and it keeps the system’s vibrations from spreading to the structures that hold it up, which could cause serious damage over time.
The base moves at the same speed and in the opposite direction as the tray.
Flexible rubber blocks connect the base to a supporting frame so that it stays in place. Even though these blocks are stable enough to ensure safety and stability while in use, the base can move a little bit in relation to the supports.
During regular operation, the feeder tray will move up and down by about 1.5 mm.
The rubber blocks wouldn’t be able to handle this much moving in the base.
To stop the base from moving and still make up for all the movement of the tray, the base needs to get heavier.
Movement and mass have an inversely proportional link, so to make the base move half as much as the tray, the mass must be doubled.
Usually, the feeder is made so that the base can’t move more than 0.5mm in any direction. However, different blocks can be made to allow more movement, so for a high-frequency feeder with a tray amplitude of 1.5mm, the base would be 3 times as heavy as the tray plus any product. This is how it works out:
Base Mass x Base Amplitude = Tray Mass x Tray Amplitude
X x 0.5 = 1 x 1.5
X = 1 x 1.5 / 0.5
X = 3
So the ratio of the mass of the tray to the mass of the base in 3 : 1.
For feeding systems with higher amplitudes, ratios of up to 8 : 1 can be required.
Feeder Control Systems
As a vibrating feeder is a comparatively straightforward piece of equipment, its control needs are minimal.
Once a feeder has been configured to execute its intended function, control requirements are typically restricted to “stop” and “start.”
This form of control is typical when the feeder is controlling the flow of product into a subsequent production process.
Vibrating Feeder Control Application
When the feeder is discharging onto a multihead weighing system is one example of this.
As the multihead weigher can only process a limited quantity of product, the input onto the weigher must be stopped.
Sensors on the multihead weigher will detect when the product level becomes excessively high. On the basis of this input, a halt signal is sent to the feeder.
As the product is processed and the level decreases, the feeder will reactivate.
Variable Speed Control
Using an inverter can give you a little more power over the system.
To change how fast the product moves, the converter changes the frequency of the feeder. When the frequency goes up, the number of times the product moves per second goes up, which makes the product move faster. But this way of control doesn’t work very well.
Since the springs in the feeders are tuned to work at certain frequencies, using an inverter to raise the frequency above this useful range can make the feeder less effective overall.
During the production process, a variable speed control tool is rarely used. Product throughputs generally rely more on the actual processing equipment in a process than on the feeder, which usually just moves products from one process to the next.
The changeable speed feature could be used, for instance, when putting ingredients into a mixer and needing to measure them out exactly.
In this case, a hopper can be set to send most of an ingredient into the mixer at full speed, while the last few percent are added at a slower rate to keep the system from getting too full.
This piece has talked about how electromagnetic vibrating feeders work in some of their most basic ways. If you have any questions about the devices or want to know what a vibrating feeder could do for you, you can use the form or information at the bottom of the page to get in touch with us.
