Vibrating Feeders: How They Work and Effectiveness
Newton's First Law is the backbone of vibratory feeders. Contingent on the laws of physics, an object must first be in motion to stay in motion.
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A vibratory feeder is an instrument that uses vibration to feed material through a process or a machine while controlling the rate of flow. Vibratory feeders utilize both vibration and gravity to move material forward. The force of gravity influences these parts to shift direction, causing them to move down or laterally. Simultaneously, vibration is employed to trigger the material's movement. In response, the material on the feeder moves in imperceivable tiny hops or jumps. Think of the material skipping along the feeder. Voila! Newton's Law in the works.
What Industries Rely on Vibratory Feeders?
Vibratory feeders can become the ringleaders at factories across many industries. This equipment can consistently move thousands of items that may require people countless hours, exhaustion, and even physical detriment. They are also designed to be much safer for operators. Vibrating feeders are used to handle bulk materials across all industries, including the pharmaceutical, automotive, electronic, cosmetic, food, and packaging industries. So, whether you are dealing with bulky, chunky material, or more delicate particles, vibratory feeders can get the job done. Additionally, these machines are used to advance materials such as glass, foundry, steel, and plastics through construction and manufacturing facilities, not to mention recycling materials, pulp and paper, metal-working industries, dry bulk solid materials, and others. This flexibility in design, process, and utility can make vibratory feeders a great option for most production systems.
What Does A Vibratory Feeder Do?
Vibratory feeders have had no small part in creating the modern world of manufacturing. In turn, our economy has evolved with tools such as vibratory feeders, which have reduced the need for workers to stand on assembly lines and automated production processes. A feeder can move raw materials into its processing station or finished products to their final destination. As a result, manufacturers save money that they would spend on manual labor. With the utilization of conveyors, products can move more quickly through production, thus meeting greater demand. Demand has also risen over time as populations have increased. In general, when incorporating a vibratory feeder into a system, everyone's time is saved.
Features To Consider When Buying A Vibratory Feeder
Buying a vibratory feeder can be a worthwhile investment, but it's important to look at the factors to make sure it's the right decision for you. As with any piece of machinery, you should consider how much energy is required for operation. Secondly, evaluate how quickly the material will be sorted and how quickly it will need to convey on the vibratory feeder to maintain your company's required materials flow. Remember that the costs of repair on a vibratory feeder can also be much lower than the repairs of a mechanical feeder. Once you've considered these factors, ask yourself, 'Will both meet my budget and daily quota?'
The good news: General Kinematics creates one machine that provides the happy medium to all of these objectives. The PARAMOUNT II® Vibrating Feeder does more work but requires less energy.
Why?
PARA-MOUNT II® Vibrating Feeders offer a revolutionary design called a Two-Mass vibratory system. Through the use of precision-engineered coil springs, the vibration sends energy through the equipment, which allows the flow to drive forward consistently and evenly. The feeders do not dampen under a load, thus reducing the risk of a jam-up of materials. As a result, systems can more easily incorporate multiple process lines or secondary unload points. Furthermore, both straight or curved configurations are available for installation.
No matter what vibratory feeder you are on the hunt for'or if you are not sure exactly what you are looking for'General Kinematics can help you from the discovery phase to custom installation.
Vibratory Feeder: What Is It? How Does It Work? Types Of
Vibratory Feeders
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Introduction
This article covers everything you need to know about vibratory feeders.
Read further to learn more about:
What is a Vibratory Feeder?
Overview of Bulk Material Handling
Working principles of Vibratory Feeders
Feeder Trough Design
And much more'
Chapter 1: What is a Vibratory Feeder?
A vibratory feeder is a conveying system designed to feed components or materials into an assembly process using controlled vibratory forces, gravity, and guiding mechanisms that position and orient materials. They have accumulation tracks of various widths, lengths, and depths, which are carefully chosen to fit the needs of the application, material, component, or part.
The goal of vibratory feeders is to move, feed, and convey bulk materials while using various forms of vibrations so that the materials are properly oriented for addition to a production line. They are a highly efficient method for increasing the speed of assembly operations and gently separating bulk materials. The guided movement produced by a vibratory feeder is dependent on horizontal and vertical accelerations that produce the exact amount of force needed to put materials in position.
The accumulation track of a vibratory feeder, which can be linear or gravity, slows feeder vibrations and assists in directional movement. Drive units can be piezoelectric, electromagnetic, or pneumatic motors that supply the vibrations, rotation, and necessary force.
The design of a vibratory feeder begins with a transporting trough or platform through which materials are moved by controlled linear vibrations that create the materials' jumping, hopping, and tossing motions. Depending on design features, travel speeds vary from a few feet per minute to over 100 feet (30 m) per minute, regulated by frequency, amplitude, and the slope angle.
The various vibratory feeders control material flow similarly to how orifices or valves control fluid flow. They can be set to feed bulk materials at a fixed rate with a structure that has soft springs to control vibrations and capacities, from a few pounds of bulk materials per hour to over several tons per hour.
One advantage of vibratory feeders is their ability to avoid bridging, which slows up processes and assemblies and prevents efficient material flow. The free flow in the throat of a vibratory feeder eliminates the possibility of bridging created by friction. The forces that provide smooth and even flow are classified as direct force and indirect force, with direct force sending force directly to the deck while indirect force is a resonant or natural frequency.
Recent vibratory feeder designs have enclosed feeders in a box shape and flanged inlets and outlets, making units dust or watertight to eliminate spillage and simplify installation. Some enclosed designs have a vibrating bin bottom activator combined with a vibratory feeder to control flow.
Chapter 2: Overview of Bulk Material Handling
Bulk materials are dry solids in powder, granular, or particle form, with different sizes and densities randomly grouped to form a bulk. These materials have varied behaviors depending on temperature, humidity, time, and so on. They do not flow as easily and as predictable as liquids and gases. They can also easily degrade any equipment for conveying and handling by erosion and impingement.
In handling bulk materials, it is important to know their properties, as summarized below. These properties must be determined to properly design bulk handling equipment.
Adhesion: This is the property of a material to stick or cling to another material. When being gravimetrically discharged, materials tend to arc, bridge, cake, etc. while clinging onto the surface of the container. This behavior can interrupt the material flow. A debridging mechanism is needed to break this formation.
Cohesion: This is the ability of the material to attract or stick onto materials with the same chemical composition. Highly cohesive material does not flow readily as they tend to clump together.
Angle of Repose: This is the maximum angle made by the lateral side of a cone-shaped pile of falling material with the horizontal. This indicates how free-flowing a material will be. The angle of repose is particularly useful in designing feeders and conveyors relying on gravity.
Angle of Fall: This is the angle made by the slope of the cone with the horizontal after getting the angle of repose and applying an external force to collapse the cone.
Angle of Difference: This is the difference between the angle of repose and the angle of fall. The greater is the angle of difference, the greater is the free flow characteristic of the material.
Angle of Slide: This is the angle made by a flat surface containing a certain amount of material with the horizontal. This indicates the material's flow characteristics inside hoppers, pipes, chutes, etc.
Angle of Spatula: This is measured by taking a spatula into a heap of sample material and lifting it with maximum material coverage. The angle of spatula is the average of the angles made by the lateral sides of the material with the horizontal.
Compressibility: This is the percentage difference between packed density and aerated density. Compressibility describes the material's size, uniformity, deformability, surface area, cohesion, and moisture content of the material.
Bulk Density: This is defined as the mass of the material per unit volume. Bulk density is important for finding the equipment capacity and the compressive strength of the material that can occur within the container.
Particle Size: This is the average dimension across a single particle. This is commonly determined by getting the equivalent diameter of the particle. Typical particle sizes of common bulk materials are shown in the table below. Bulk Material Typical Size Range Coarse Solid 5 ' 500 mm Granular Solid 0.3 ' 5 mm Coarse Powder 100 ' 300 µm Fine Powder 10 ' 100 µm Superfine Powder 1 ' 10 µm Ultrafine Powder < 1 µm
Moisture Content: Moisture content is the amount of water dispersed throughout the bulk. Materials with high moisture content are more difficult to handle due to the more pronounced effects of adhesion and cohesion. Moisture also contributes to the variation of the weight of the material.
Hygroscopicity: This is the tendency of the material to absorb moisture. The design of the equipment that handles materials with high hygroscopicity must prevent air containing high moisture from entering.
Static Charge: Because of the continuous contact of particles with each other and the walls of the container, the particle tends to build up a static charge. This phenomenon is problematic because the cohesive and adhesive forces become stronger, making the flow more difficult.
Abrasion: Abrasion is the ability of the material to scrape or wear the surface of the handling equipment. This is a problem when handling materials such as coke and sand. To counter abrasion, steels with high hardness or plastics with high abrasion resistance are used.
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Chapter 3: Working Principles of Vibratory Feeders
The general design of a vibratory feeder consists of a drive unit that generates the vibratory action and a deep channel, or trough, that contains the bulk material. The drive unit causes vibrations with both horizontal and vertical force components. The vibration causes a straight-line motion, provided the vibration is sinusoidal, and the force components are in-phase. Besides the drive unit and trough, a vibratory feeder is made up of the following parts:
Feed End: This is the part of the trough located at the most upstream end where the material is fed.
Discharge End: Opposite the feed end is the discharge end, located at the most downstream part of the trough. This is where the material is ejected off of the unit.
Eccentric Weight This is the weight attached to the shaft or flywheel with a slight offset from the axis of rotation. Rotating the shaft produces an unbalanced moment creating oscillations.
Reactor Springs: These are the primary springs in the vibrating system that continuously store and release energy during operation.
Isolation Springs: These springs support the feeder while protecting the supporting structure from the generated vibrations.
Tuning Springs: These springs are used to tune the frequency of a natural frequency feeder. This is done by adding or subtracting springs or by modifying the spring rate. Other feeder designs tune the frequency by adding or subtracting weights.
Dynamic Balancer: Balanced vibratory feeders use a dynamic balancer that reduces the transmitted dynamic forces to the supporting structure. This is achieved by reacting to the reversing forces of the drive unit.
Liner: Material added to cover the surface of the trough design to resist wear, heat or cool, reduce noise and friction, or prevent material buildup.
Screen: An additional part that is used to separate fine particles from coarser materials.
Grizzly: This is a heavy-duty screen consisting of bars, rails, or tubes running in the direction of material flow. This is used for screening coarser materials.
Vibratory feeders and conveyors have operating frequencies that range from 200 to vibrations per minute with an amplitude of 1 to 40 mm. The vertical acceleration component is usually near gravitational acceleration (9.81 m/s2). This is enough to transport materials with a gentle shuffling motion producing minimal impact and noise. Because of this, the material moves across the trough by sliding action. The material does not actually leave the trough's surface when the pressure between the surface and the material is at a minimum. In applications where the material has to lift from the trough and then impact again as it falls, special considerations must be made to counter the impact force and the increased noise levels.
Vibratory feeders are distinct from other bulk material handling equipment because the material moves independently from the conveying medium. This contrasts with equipment such as conveyor belts and aprons, where the material is static relative to the conveying medium. This enables additional processes to be integrated while the material is in transit. Below are some processes that can be performed while transporting with vibratory feeders.
Scalping
Screening
Sorting
Spreading or Distributing
Cooling
Drying
Dewatering
Water Quenching
Besides the integration of additional processes, vibratory feeders are desired due to these reasons,
Low Headroom Requirement: Vibratory feeders are a solution to gravimetric feeding in installations with limited vertical clearance. Conveying using vibratory feeders is suited for the horizontal movement of bulk products.
Handling of Hot Materials Without Excessive Heating: Vibratory feeders can be tuned so a little lift is produced from the upward phases of the oscillation cycle. This allows some air to pass and cool the material while at the same time minimizing contact.
Handling Abrasive Materials: Tuning the vibratory feeder to minimize contact with the material reduces vibration. Also, vibratory feeders can be lined with abrasion-resistant materials.
Inherent Self-Cleaning Properties: Since the material is not static on the surface of the machine, the material does not easily adhere. There is no chance for the material to accumulate on the surface of the trough.
Adherence Strict Sanitation Requirements: Aside from its self-cleaning properties, the trough or pan of a vibratory feeder is a continuous surface. There are no cavities or holes where contaminants can accumulate. The pan can be made of stainless steel suited for food applications.
Water and Dust-Tight: Vibratory feeders can be designed with IP or NEMA-rated covers and sealing.
No Moving Parts Where Material Can Impinge and Interrupt Operation: The trough is a continuous channel with no hinges, joints, or deformable members, unlike belt and apron conveyors. Because of these benefits, vibratory feeders are widely used in mining, smelting, metal casting, recycling, glass batch processing, furnace charging, wood processing, food processing, pharmaceuticals, and packaging.
Chapter 4: Types of Vibratory Feeders
Vibratory feeders can be classified according to their drive unit, method of applying vibration to the trough, and generated reaction to the supporting structures. In selecting a vibratory feeder, it is important to know the distinction between these categories. For example, it is not enough to specify only brute force vibratory feeders. Brute force feeders are available with electromagnetic or electromechanical drive units. This chapter tackles the working principle of each type and their recommended applications.
Below are vibratory feeders classified according to their drive unit:
Vibratory Feeders by Drive Unit
Electromechanical Vibratory Feeders
These feeders create vibration by rotating eccentric weights using electric motors. They are also referred to as eccentric-mass mechanical feeders. A simple design consists of a single rotating eccentric mass. However, the more common is the use of two counter-rotating masses. The axes of rotation of these two masses lie within the same plane, and their rotation is synchronized to produce the right oscillation.
Electromagnetic Vibratory Feeders
Electromagnetic feeders operate using the cyclic energization of one or more electromagnets. In comparison with electromechanical drives, electromagnetic drive units contain lesser moving parts. The trough is caused to vibrate using the magnetic force impulses supplied by the electromagnet. In terms of cost, electromagnetic feeders are cheaper for low-volume applications. This is true at rates less than 5 tons per hour.
Hydraulic and Pneumatic Vibratory Feeders
These types of feeders operate using pneumatic or hydraulic oscillating pistons. The main advantage of using these types is their suitability for hazardous areas. The motors for driving the pumping units can be located in remote areas. This eliminates the need for expensive explosion-proof specifications.
Direct Vibratory Feeders:
Direct or positive mechanical vibratory feeders use a crank and connecting rod that generate oscillation with a low frequency and high amplitude. Positive conveyors are rarely used due to the high vibration transmitted to the supporting structures. A way to counter the high vibration transmitted is to use a counterweight or counter-vibrating double troughs.
Next are the types of vibratory feeders according to the method of applying vibration to the trough. They differ in the configurations of their springs and the frequency and amplitude of their drive unit.
Brute Force Feeders:
This type of feeder is called single-mass systems because the vibratory drive is directly connected to the trough assembly. They are generally used for heavy-duty applications. The drive system can also be electromagnetic, but the electromechanical drive is mostly used. Brute force feeders create oscillating forces by rotating a heavy centrifugal counterweight.
Brute force feeders have the simplest design among the vibratory feeders. However, they have limited feed rate regulation and range since they are designed as constant rate feeders. The feed rate can be adjusted by changing the slope of the trough, opening, amount of counterweight, and length of stroke. Variable speed drives are rarely installed since the trough stroke is slightly independent of the operating speed of the motor. Tuning the motor speed is not necessary for brute force feeders.
Centrifugal Feeders:
Centrifugal feeders, also known as rotary feeders, consist of a spinning bowl that moves parts towards the outside of the bowl. They have a conical centrally driven rotor surrounded by the bowl walls. As the feeder spins, the rotary force separates parts and components. The revolving parts, moving at high speed, are pulled and pushed to the outside circumference of the bowl.
The uses for centrifugal feeder systems include food processing, the pharmaceutical industry, and medical suppliers, which are industries that have small, unusually shaped components that require rapid handling. Centrifugal bowl feeders sort and properly orient components at a rate of per minute regardless of the size and shape of the components. They are a cost-effective processing method with a simple design, are exceptionally reliable, and have low maintenance.
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Natural Frequency Feeder:
Natural frequency feeders, also known as tuned or resonant feeders, use two or more spring-connected masses. The most common is the two-mass, spring-connected vibratory system. One mass is for the trough, while the other is for the reaction or excitation mass. The natural frequency feeder takes advantage of the natural magnification of the oscillations, which occurs when the system operates at a speed near its natural frequency or resonance condition. Because of this, a relatively small force is required to generate the necessary vibratory forces. The vibratory force can be generated by rotating eccentric weights or electromagnets.
The main design factor that needs to be considered is not the weight of the material or load but the damping capacity of the bulk. The damping effect is the result of the energy absorption of the material. Granular and powdered materials tend to dissipate energy through intergranular friction and deformation when vibrated.
Vibratory feeders are also classified according to their reactions to their foundations and supporting structures. Selecting which type depends on the rigidity and allowable stresses of the structure.
Vibratory Feeders by Supporting Structures
Unbalanced Vibratory Feeders:
These feeders have oscillating forces that subject the supporting structures to reversing load conditions. A reversing load condition means continuous and alternating tensile and compressive forces while the mean stress is zero. Though the supporting structure can easily carry the static load of the feeder, it becomes easily fatigued during operation. Unbalanced vibratory feeders can only be installed on structures that have very large allowable deflections compared to the amplitude of the vibrations. Moreover, the structure must have a natural frequency that greatly exceeds the operating frequency of the feeder.
Balanced Vibratory Feeders:
A balanced vibratory feeder is equipped with a dynamic balancing system composed of counterbalancing weights installed on the conveyor base. Other designs employ secondary weights attached to the reactor springs. These types of feeders are designed to reduce the unbalanced reaction force transmitted to the supporting structure. This is achieved by vibrating the secondary weights 180° out of phase with the oscillation of the trough. Balanced vibratory feeders are recommended for installation on structures with questionable rigidity.
Horizontal Motion Conveyors
Horizontal motion conveyors, also known as horizontal differential conveyors, differential motion conveyors, or differential conveyors, use a two-cycle slow advance, quick return motion to slowly move free-flowing bulk materials horizontally. The conveying surface is an open pan or closed conduit with seamless one-piece construction that moves slowly forward and backward. During forward movement, components remain at quiet rest. On the return cycle, the open pan or closed conduit moves swiftly and rapidly backward, depositing the components.
A horizontal motion conveyor's forward and backward motion is continually repeated to smoothly convey materials at 40 feet (12 m) per minute over distances as long as 200 feet (61 m). They have no moving parts other than the drive unit, which reduces safety risks, simplifies cleaning, and decreases maintenance. The smooth, even motion of horizontal motion conveyors is ideal for fragile materials that need to be handled carefully.
Horizontal motion conveyors can move components backward or forward one direction at a time. They can be configured to work on slight inclines or declines for flat rectangular or square parts. If necessary, horizontal motion conveyors can be set up to deliver parts in their midsection. Components move along the open pan or conduit without being subjected to vertical acceleration bouncing action.
Chapter 5: Feeder Trough Design
The capacity of the vibrating feeder depends on the width of the trough, depth of material flow, bulk density of the material, and the linear feed rate. This is expressed by the formula,
C = WdR /
Where C is the capacity in tons per hour (metric tons per hour), W is the trough width in inches (millimeter), d is the depth of material in inches (millimeter), γ is the bulk density in pounds per cubic feet (grams per cubic centimeter), and R is the linear feed rate in feet per minute (meter per minute). For metric units, change the 4,800 constant to 16,700.
Usually, the required capacity is already given by the rate requirement of upstream or downstream processes. From the required capacity, combinations of trough width and linear feed rate can be obtained along with the bulk density of the material and expected feed depth. Manufacturers typically provide charts, tables, and graphs describing the feeder's characteristics.
Feeder troughs are usually made from mild steel, grade 304 stainless steel, and abrasion-resistant alloys. Other constructions feature ordinary steels lined with replaceable materials such as rubber, plastic, or ceramics. Troughs are formed into different shapes depending on the type and properties of the materials and the integrated processes. Common trough shapes and features are:
Flat Bottom
Half Round Bottom
Radius Bottom
V Shape
Tubular
Grizzly Section
Dust and water-tight sealing and cover
Belt-centering Discharge
Diagonal Discharge
Screen Decks
Water-jacketed
Chapter 6: Vibratory Bowl Feeders
Vibratory bowl feeders have troughs wound helically and use vibrations to toss and shuffle materials along the slightly slanted surface of the helical trough. The tossing and shuffling actions position parts with asymmetrical shapes to be oriented as they move through the bowl feeder.
The benefits of a vibratory bowl feeder include conveying parts and positioning them properly. Troughs have specific profiles for accepting materials in the correct orientation. Screening devices attached to the bowl remove parts that are not positioned or oriented properly. Vibratory bowl feeders are used in assembly and packaging lines in the electronics, automotive, and pharmaceutical industries.
Conclusion:
Vibratory feeders are short conveyors that transport bulk materials utilizing a controlled vibratory force system and gravity. The vibrations impart a combination of horizontal and vertical acceleration through tossing, hopping, or sliding-type of action to the materials being handled.
Bulk materials are dry solids that can be in powder, granular, or particle form with different sizes and densities randomly grouped to form a bulk. They do not flow as easily and predictably as liquids and gasses.
The general design of a vibratory feeder consists of a drive unit that generates the vibratory action and a deep channel, or trough, that contains the bulk material.
Vibratory feeders can be classified according to their drive unit, method of applying vibration to the trough, and generated reaction to the supporting structures.
Vibratory bowl feeders are special types of vibratory feeders that have troughs wound helically with special profiles and attachments. They are used in part or item feeding applications where the items are required to be in a specific orientation.
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Linear Vibratory Feeders and their Working Principles
How do Electromagnetic Vibratory Feeders Work? ' Components & Principles
There are 3 varieties of vibratory feeder, which work on different principles. They are as follows:
Electromagnetic Vibratory Feeder
Natural Frequency Vibratory Feeders
Out-of-Balance Vibratory Feeders
This article focuses on the working principles of electromagnetic vibrating feeders.
What is an Electromagnetic Vibrating Feeder?
Electromagnetic vibrating feeders are a common piece of equipment in many manufacturing facilities.
They are used as part of many processes, including conveying, screening, and packaging.
Electromagnetic vibrating feeders come in a huge range of sizes, from small desktop versions in laboratory settings, to conveying systems several metres long.
No matter the size, all these systems work on the same principle.
Working 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.
System Arrangement
The system is composed of a base unit, coil, flat springs, magnet, and a tray.
The tray is connected to the base unit by the flat springs. The flat springs allow relative movement between the two. It is this relative movement that will feed the product.
In simple terms, the coil (a magnet wound in copper wire to create an electromagnet) is attached to the base unit, and the magnet is attached to the feeder tray. The coil attracts and releases the magnet, generating the relative movement between the base unit and the feeder tray.
Drive systems are available that incorporate all the components of the electromagnetic drive (i.e. the coil, magnet, and springs) into a complete drive unit. A mounting plate is provided at the top end of the springs to add a feeder tray suitable for the application.
Generating Product Movement
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.
When this process is repeated at high frequency, a continuous flow of product is created.
Components
Springs
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.
Feeder Tray
The main purpose of the feeder tray is to channel the product being fed to where is 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.
Base
As well as being the lower mounting point for the flat springs, the base serves another essential purpose.
The mass of the base counteracts the movement of the feeder tray, and prevents vibration from the system transferring into supporting structures, which over time could lead to serious structural damage.
The base moves equal and opposite to the tray.
To keep the base secured to a supporting structure, it is connected to the structure using flexible rubber blocks. These blocks, while being stable enough to guarantee safety and stability during operation, do allow some movement of the base relative to the supports.
During normal operation, the feeder tray will vibrate at an amplitude of approximately 1.5mm.
This movement in the base would be too much for the rubber blocks to absorb.
To reduce the movement of the base, while still compensating for all the movement of the tray, the mass of the base needs to increase.
The relationship between the movement and the mass is inversely proportional, so to reduce the movement of the base by half relative to the tray, the mass must be doubled.
Typically the feeder will be designed to keep the movement of the base to below 0.5mm in any direction (although different blocks will be designed to allow greater ranges of 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. The calculation is:
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 relatively simple piece of equipment, the control requirements are small.
Once a feeder is set up to perform it's 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.
Feeder Control Application
An example of this would be when the feeder is discharging onto a multihead weighing system.
As the multihead weigher can only process a finite amount of product, the feed onto the weigher will need to be paused.
Sensors on the multihead weigher will detect when the level of product on the weigher is getting too high. Based on this input, a signal is sent to the feeder to stop.
As the level drops off as product is processed, the feeder will re-activate.
Variable Speed Control
An additional measure of control can be provided by using and inverter.
The inverter changes the frequency of the feeder to adjust the speed of the product. A higher frequency increases the number of product hops per second and speeds up the product.
However, this method of control is limited.
As the springs of the feeders are tuned to work at specific frequencies, increasing the frequency above this effective range using an inverter can reduce the overall effectiveness of the feeder.
It is rare that a variable speed control function will be used during a production process. Product throughputs are usually much more dependent on actual processing equipment within the overall process, with feeder usually only moving product from one process to another.
One example of where the variable speed function might be put to use is where ingredients are being fed into a mixer and accurate measures of ingredients are required.
Under these circumstances, a feeder may be set to deliver the majority of an ingredient into the mixer at maximum speed, with the final few percent of product added at a reduced rate to prevent overfilling the system.
This article has covered some of the core principles of how electromagnetic vibrating feeders work.
If you have any questions about the systems, or are interested in what a vibrating feeder might be able to do for you, you can contact us using the form or details at the bottom of the page.
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