Vibratory feeders have been used in the manufacturing industry for several decades to efficiently move fine and coarse materials which tend to pack, cake, smear, break apart, or fluidize. Because they can control material flow, vibratory feeders handle bulk materials across all industries, including pharmaceuticals, automotive, electronic, food, and packaging. These feeders also advance materials like glass, foundry steel, and plastics at construction and manufacturing facilities.
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Feeders can range from small base-mounted, pneumatic-powered models moving small quantities of dry bulk material to much larger electro-mechanical feeders that convey tons of material an hour. Users turn to vibratory feeders when they want to move delicate or sticky materials without damaging or liquefying them.
Vibratory feeders handle a wide assortment of materials including but not limited to: almonds, crushed limestone, shelled corn, powdered metal, metal billets, various pipe fittings, scrap brass and bronze, crushed and shredded automobiles, hot dross, and much more. Because they emit precise vibrations, vibratory feeders are also used to process small parts, like coins, washers, or O-rings, as they move along a belt conveyor.
Other common applications of vibratory feeding include:
* Controlled flow of ingredients to mixing tanks
* Sprinkling toppings or coatings on food and dairy products
* Adding binders and carbons to foundry sand reprocessing systems
* Chemical additive feeding in the pulp and paper bleaching or chip handling processes
* Feeding metal parts to heat treating furnaces
* Feeding scrap or glass cullet to furnaces
Manufacturers have upgraded and modified vibratory feeders and conveyors over the years to enhance their role in multiple processing applications. The latest equipment offers increased energy savings, more precise control over material flow, easier maintenance, and a broader variety of options. Leading suppliers also now provide better technical support, and, in some cases, faster delivery of product to your plant.
Virtually all vibratory equipment—regardless of type or size—is built with materials that can withstand the harsh environment of the manufacturing industry. Vibratory feeder trays can be made from stainless steel which is far less susceptible to corrosive materials. The internal motor’s fully enclosed construction offers protection from environmental elements to ensure maximum uptime.
Vibratory feeders save users time and money on maintenance as well, because they have no moving parts, aside from the vibrating drive unit. This means they break down less frequently and vibratory feeder parts are easy to replace. Other advantages of vibratory feeders include: ergonomic design, adaptability and versatility, effectiveness and accuracy.
How to Select the Proper Vibrating Feeder Design
There are two basic designs available when selecting a vibrating feeder: electromagnetic and electromechanical. A third option—air-powered vibrating feeders—are basically an alternate to electromechanical feeders since they have the same simple brute force design concept—the vibratory drive is directly attached to the tray.
Here are the basic advantages and disadvantages to these three feeders:
Electromagnetic feeders provide variable intensity with typically fixed frequency of vibrations per minute (VPM). They only require single phase power, offer quick stopping, and are ideal for cold weather. However, they are sensitive to line voltage fluctuations and temperature swings are not suitable for hazardous areas. They also need constant tuning if there are rate or load changes.
These units work well with dry, free-flowing, pelletized or granulated material. They can control material flow from a few pounds to several tons per hours and can be custom designed to accommodate material flow from a few feet (with a single drive) to up to 20 feet (with multiple drives).
Electromechanical feeders are powered by twin rotary electric vibrators which provide a broader range of stroke/frequency combinations. Their flexibility is further enhanced with a variable frequency drive (VFD), which provides quick and easy adjustment without having to manually adjust the eccentric weights.
A VFD with dynamic braking or a starter with a dynamic brake will end the vibration faster to limit the erratic motion a shut down. This design provides the quietest operation and is less susceptible to head loads. These feeders work well in hazardous conditions when explosion proof vibrators are installed.
Air-powered feeders work best under hazardous conditions because they are driven by an air-cushioned piston vibrator, which produces smoother linear force and can work safely in high temperatures. It’s the simplest of the three feeders to maintain and the controls are the most economical.
While an air-powered feeder doesn’t require tuning, there are limitations to the physical size of the tray and feed rates. These units are also less suitable for outdoor operation because the air lines can freeze up. These feeders are also susceptible to head load.
Tray Designs Are Limitless
The shape, length, and width of modern feeder trays are almost limitless. Customers can order custom feeder trays to suit their unique process applications. Every configuration of flat, curved, vee, and tubular designs are available.
Units can be furnished with special coatings, such as neoprene, UHMW, urethane, non-stick polymer, non-stick textured surfaces, or removable abrasive-resistant steel plate. Liners made from either neoprene, UHMW, or urethane protect the feed tray while processing harsh materials. The trough can be furnished in steel or polished stainless steel to meet the most demanding requirements.
Trays can be designed for fast removal and cleanout to avoid cross contamination of materials and decreased production line downtime. Custom trays can have quick release clamps to enable removal of the tray and cover without tools. The tray is simply lifted and disconnected from the frame for easier cleaning.
Spring Systems from Steel to Fiberglass
Springs are an integral part of the feeding system process because they convert the vibration from the drive to the tray, thus causing the material to move. Like trays, springs today come in a variety of materials, sizes, and configurations depending upon the application.
Fiberglass springs are the most popular configuration for light- and medium-duty applications. Small electromagnetic feeders, light- to medium-duty conveyors, and most high-precision vibratory equipment use fiberglass or multiple pieces of fiberglass as their primary spring action material.
Steel coil springs are commonly used on heavy-duty and high-temperature applications. These coils are effective in ambient temperatures up to 300°F.
Dense rubber springs are typically used on heavy-duty feeders and conveyors to provide stability and motion control between the drive and tray. However, rubber springs are limited to use in environments below 120°F.
Air mount springs are designed to handle tough industries such as construction and mining, which present dirty, dusty, and wet environments. They withstand common issues such as rust and corrosion that typically lead to broken parts. They also reduce structural noise and are versatile.
Factors to Determine a Vibratory Feeder
Typically, a feeder application will require the movement of some given material with a known bulk density over a desired distance. Parameters that influence the sizing and design of a vibratory feeder include:
* The inlet and discharge conditions for that piece of equipment
* How the material is being placed on the feeding surface
* The dimensions of the incoming material stream
* Batch dumping vs. continuous flow
* Feeding another piece of equipment, such as a belt conveyor, bucket elevator or furnace
* Feed rate
* Material properties, including bulk density and particle or part size.
The distance the material must travel drives the length of the unit and may include some additional length to properly interface with the receiving equipment. The volume of material moved per hour plus the material’s bulk density helps determine the width and depth of the vibratory tray. The size of equipment that passes material onto the vibratory feeder also factors into the feeder’s width.
Proper Location of Vibrators on Feeders
There are several options when deciding where to install the vibrators on a particular feeder model. With vibratory feeders, there is a concern about the product discharge height, as the equipment is often feeding material downstream to other devices.
Typically, on vibratory feeders the default location is “below deck” where the vibrators are attached on the underside of the unit. With below deck vibrators, the feeder will need a higher discharge height compared to a similarly-sized unit where the vibrators are “side mounted” or even in some applications where the vibrators are attached “above the deck.”
Functionally, there is no benefit to locating the vibrators above, on the side or below the unit. Provided the structure is appropriately designed for the force output of the vibrators and they “sense” each other, either vibrator location can provide satisfactory results.
Controlling Material Flow from a Feeder
Precise metering of material flow (whether moist or dry) onto trays or other receptacles is critical to the operation of any vibratory feeder, particularly those equipped with a hopper. Several factors below influence the material flow, but when all three are combined, it is possible to vary the flow rate and provide very repeatable results as the material cascades off the feeder end.
Bed depth of material on the tray. The material must be free flowing and always available in the hopper to charge the feeder. Not enough material will “starve” the feeder, reduce the bed depth and cause inconsistent discharge rates.
A hopper slide gate helps adjust material depth. Opening the gate allows for a higher volume of material to be removed from the hopper, resulting in a deeper material flow and higher volume off the feeder end. Likewise, reducing the opening restricts the volume of flow out of the hopper, resulting in more shallow material flow as well as lower volume.
Frequency of vibration applied to the feeder tray. Different materials respond better to different frequencies of vibration which influences the type of vibrator installed on the feeder.
For example, rotary electric vibrators are designed with various frequencies to accommodate different materials:
* Two-pole vibrators that operate at vibrations per minute (VPM) have the highest frequency and smallest amplitude
* Four-pole vibrators that operate at VPM
* Six-pole vibrators that operate at VPM
* Eight-pole vibrators that operate at 900 VPM
Heavier materials tend to require higher frequency drives while lighter materials feed more effectively with lower frequency drives.
Vibrators are installed based on the selected feed rate. This selection is based on the frequency of vibration and the maximum force output of the vibrator.
Necessary adjustments to the eccentric weights of the vibrators can be made to reduce the force output from the unit’s rated maximum. For a given frequency, more force output will result in a larger amplitude or stroke of the finished equipment.
Technical Support is Key
Purchasing and installing a vibratory feeder poses fewer risks today because of increased technical assistance before and after the sale. Material samples of various densities and configurations can be tested beforehand to determine the optimum piece of vibratory and conveying equipment. This pre-testing virtually eliminates the potential problem of installing an under or oversized piece of equipment for the job at hand.
Jack Steinbuch is equipment sales engineer, Cleveland Vibrator Co. (Cleveland, OH). Cleveland Vibrator’s in-house testing lab allows engineers to determine optimal vibration conditions for any material and prediction of feed rates and process outcomes. Customers can visit the facility or view the testing online in real-time or request a video of their product test. For more information, call 800-221- or visit www.clevelandvibrator.com.
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Feeders: A Brief Discussion
A vibratory feeder is a transportation mechanism engineered to supply components or materials into an assembly process using controlled vibratory forces, gravity, and guiding systems to ensure accurate positioning and alignment. The system incorporates accumulation tracks of varying widths, lengths, and depths, carefully chosen to suit the specific requirements of the application, material, or component.
The principal function of vibratory feeders is the movement, transfer, and conveyance of bulk materials utilizing various forms of vibrations that secure proper alignment for seamless integration into a production sequence. They are exceptionally effective for enhancing assembly operations and gently segregating bulk materials. The guided movement created by a vibratory feeder depends on horizontal and vertical accelerations, delivering the precise force needed for accurate material positioning.
The accumulation track of a vibratory feeder, whether it employs a linear or gravity-based approach, contributes to reducing vibrations and assists in guiding the material flow. Vibrations, rotation, and the necessary force for optimal operation are supplied by drive units, which may include piezoelectric, electromagnetic, or pneumatic motors.
The construction of a vibratory feeder begins with a transportation trough or platform, where materials are moved through controlled linear vibrations. These vibrations induce motions like jumping, hopping, and tossing of the materials. Depending on design features such as frequency, amplitude, and trough or platform slope angle, material travel speeds can vary from a few feet per minute to over 100 feet (approximately 30 meters) per minute.
Vibratory feeders regulate material flow akin to the control exerted by orifices or valves over fluid flow. They can be modified to deliver bulk materials at a consistent rate. Typically, a vibratory feeder comprises soft springs that manage vibrations and capacities, allowing it to handle bulk materials ranging from a few pounds per hour to several tons per hour.
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A notable benefit of vibratory feeders is their capability to prevent bridging, an issue that can decelerate processes and obstruct effective material flow. The free-flow design within the throat of the vibratory feeder minimizes friction-induced bridging. The forces that facilitate smooth and even material flow are categorized into direct and indirect forces. Direct force applies energy straight to the feeder's deck, while indirect force utilizes resonant or natural frequencies to accomplish the desired material motion.
Contemporary designs of vibratory feeders often incorporate enclosed, box-shaped structures with flanged inlets and outlets, enhancing their ability to contain dust and stave off water intrusion. This design evolution assists in reducing spillage and simplifying installation procedures. Additionally, some enclosed designs combine a vibrating bin bottom activator with the vibratory feeder for enhanced material flow control and effectiveness.
Bulk materials are dry solids that come in powder, granular, or particle forms and are often grouped randomly to form a bulk. These materials exhibit diverse behaviors depending on factors such as temperature, humidity, and time, which can affect their flow properties. Unlike liquids and gases, bulk materials do not flow as easily or predictably. Additionally, their handling can pose challenges, as they can cause erosion and impingement that may degrade conveying and handling equipment.
In handling bulk materials, it is essential to understand their properties, as outlined below. These properties are critical for the proper design of bulk handling equipment.
Cohesion: This refers to the material's ability to attract or adhere to other materials with the same chemical composition. Materials with high cohesion do not flow easily because they tend to clump together.
Angle of Difference: This represents the difference between the angle of repose and the angle of fall. A larger angle of difference indicates better free flow characteristics of the material.
Angle of Spatula: This is measured by inserting a spatula into a heap of sample material and lifting it to achieve maximum material coverage. The angle of spatula is the average of the angles formed by the lateral sides of the material with the horizontal.
Moisture Content: Moisture content refers to the amount of water distributed throughout the bulk material. Materials with high moisture content are more challenging to handle due to increased adhesion and cohesion effects. Additionally, moisture contributes to variations in the material's weight.
Static Charge: Continuous contact between particles and the walls of the container can cause the particles to build up a static charge. This buildup of static electricity strengthens cohesive and adhesive forces, making material flow more challenging.
The general design of a vibratory feeder includes a drive unit that generates the vibratory action and a deep channel, or trough, that holds the bulk material. The drive unit produces vibrations with both horizontal and vertical force components. When the vibration is sinusoidal and the force components are in-phase, the resulting motion is straight-line. In addition to the drive unit and trough, a vibratory feeder comprises the following parts:
Eccentric Weight: This is a weight attached to the shaft or flywheel, slightly offset from the axis of rotation. As the shaft rotates, the unbalanced moment produced creates oscillations.
Liner: This is material added to the surface of the trough to resist wear, manage heat or cooling, reduce noise and friction, or prevent material buildup.
Vibratory feeders and conveyors typically operate at frequencies ranging from 200 to vibrations per minute and have amplitudes of 1 to 40 mm. The vertical acceleration component is usually close to gravitational acceleration (9.81 m/s²). This setup provides a gentle shuffling motion that minimizes impact and noise, allowing materials to move across the trough through sliding action. The material generally remains in contact with the trough's surface, with minimal pressure between the surface and the material. In cases where the material must lift from the trough and fall back down, additional measures may be needed to manage impact forces and reduce noise levels.
Vibratory feeders differ from other bulk material handling equipment because the material moves independently of the conveying medium. This is unlike equipment such as conveyor belts and aprons, where the material remains static relative to the conveying medium. This unique feature allows for additional processes to be integrated while the material is in transit. Below are some processes that can be performed during transport with vibratory feeders.
Besides the integration of additional processes, vibratory feeders are preferred for the following reasons:
Low Headroom Requirement: Vibratory feeders are ideal for installations with limited vertical clearance, providing an effective solution for gravimetric feeding. They are well-suited for the horizontal movement of bulk products.
Handling of Hot Materials Without Excessive Heating: Vibratory feeders can be adjusted to produce minimal lift during the upward phases of the oscillation cycle. This configuration allows air to circulate and cool the material while reducing contact and heat buildup.
Handling Abrasive Materials: By tuning the vibratory feeder to minimize contact with the material, vibration is reduced. Additionally, vibratory feeders can be lined with abrasion-resistant materials to enhance durability.
Inherent Self-Cleaning Properties: Because the material is not static on the surface of the machine, it does not easily adhere. This prevents material from accumulating on the trough's surface.
Adherence to Strict Sanitation Requirements: In addition to its self-cleaning properties, the trough or pan of a vibratory feeder is a continuous surface without cavities or holes where contaminants could accumulate. The pan can be made of stainless steel, making it suitable for food applications.
Water and Dust-Tight: Vibratory feeders can be designed with IP or NEMA-rated covers and sealing to prevent the ingress of water and dust.
No Moving Parts Where Material Can Impinge and Interrupt Operation: The trough of a vibratory feeder is a continuous channel without hinges, joints, or deformable members, unlike belt and apron conveyors. This design minimizes interruptions and enhances reliability. As a result, vibratory feeders are extensively used in various industries, including mining, smelting, metal casting, recycling, glass batch processing, furnace charging, wood processing, food processing, pharmaceuticals, and packaging.
Vibratory feeders can be classified based on their drive unit, vibration application method, and the reactions generated by the supporting structures. When selecting a vibratory feeder, understanding these distinctions is crucial. For instance, specifying only brute force vibratory feeders is insufficient, as they come with various drive units, such as electromagnetic or electromechanical. This chapter explores the working principles of each type and their recommended applications.
Below are vibratory feeders classified according to their drive unit:
These feeders generate vibrations by rotating eccentric weights with electric motors and are also known as eccentric-mass mechanical feeders. A basic design features a single rotating eccentric mass, but the more common approach uses two counter-rotating masses. These masses rotate in the same plane with synchronized axes, creating the desired oscillation.
Electromagnetic feeders use the cyclic energization of one or more electromagnets to operate. Compared to electromechanical drives, electromagnetic drive units have fewer moving parts. The electromagnets provide magnetic force impulses that cause the trough to vibrate. Electromagnetic feeders are more cost-effective for low-volume applications, particularly at rates below 5 tons per hour.
These feeders use pneumatic or hydraulic oscillating pistons for operation. They are particularly advantageous in hazardous areas because the motors driving the pumping units can be situated in remote locations, reducing the need for costly explosion-proof specifications.
Direct or positive mechanical vibratory feeders employ a crank and connecting rod to create oscillations with low frequency and high amplitude. These feeders are infrequently used because they transmit significant vibration to the supporting structures. To mitigate this, counterweights or counter-vibrating double troughs can be used to balance the vibrations.
Next are the types of vibratory feeders classified by the method of applying vibration to the trough. They vary based on their spring configurations and the frequency and amplitude of their drive units.
This type of feeder is known as single-mass systems because the vibratory drive is directly connected to the trough assembly. They are typically used for heavy-duty applications. While the drive system can be electromagnetic, electromechanical drives are more commonly used. Brute force feeders generate oscillating forces by rotating a heavy centrifugal counterweight.
Brute force feeders have the simplest design among vibratory feeders. However, they offer limited feed rate regulation and range, as they are designed as constant rate feeders. Feed rate adjustments can be made by changing the slope of the trough, the opening size, the amount of counterweight, or the length of the stroke. Variable speed drives are rarely used because the trough stroke is only slightly dependent on the motor's operating speed. Tuning the motor speed is generally unnecessary for brute force feeders.
Centrifugal feeders, also known as rotary feeders, use a spinning bowl to move parts towards its outer edge. The feeder features a centrally driven conical rotor surrounded by the bowl walls. As the feeder spins, rotary force separates the parts and components, pushing them towards the outer circumference of the bowl.
Centrifugal feeder systems are commonly used in industries such as food processing, pharmaceuticals, and medical supplies, where rapid handling of small or unusually shaped components is necessary. These systems can sort and properly orient components at rates of up to 3,000 per minute, regardless of their size or shape. With a simple design, centrifugal feeders are cost-effective, highly reliable, and require low maintenance.
Natural frequency feeders, also known as tuned or resonant feeders, utilize two or more spring-connected masses. The most common configuration involves a two-mass system: one mass for the trough and the other for the reaction or excitation mass. These feeders take advantage of the natural magnification of oscillations when the system operates near its natural frequency or resonance condition. This design allows a relatively small force to generate the necessary vibratory forces. Vibratory force can be produced by rotating eccentric weights or electromagnets.
The main design factor to consider is not the weight of the material or load but the damping capacity of the bulk. Damping effect refers to 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 based on their reactions to their foundations and supporting structures. The choice of type depends on the rigidity and allowable stresses of the supporting structure.
These feeders generate oscillating forces that subject the supporting structures to reversing load conditions. This means the structures experience continuous and alternating tensile and compressive forces with a mean stress of zero. While the structure can handle the static load of the feeder, it can become easily fatigued during operation. Unbalanced vibratory feeders should only be installed on structures with very large allowable deflections relative to the amplitude of the vibrations. Additionally, the structure must have a natural frequency that significantly exceeds the operating frequency of the feeder.
A balanced vibratory feeder features a dynamic balancing system with counterbalancing weights mounted on the conveyor base. Some designs use secondary weights attached to the reactor springs. These feeders are designed to minimize the unbalanced reaction force transmitted to the supporting structure by vibrating the secondary weights 180° out of phase with the trough's oscillation. Balanced vibratory feeders are recommended for installation on structures with questionable rigidity.
Horizontal motion conveyors, also known as horizontal differential conveyors, differential motion conveyors, or differential conveyors, use a two-cycle motion to transport free-flowing bulk materials horizontally. This motion involves a slow forward advance followed by a quick return. The conveying surface can be an open pan or a closed conduit with a seamless one-piece construction. During the forward movement, components remain stationary, while in the return cycle, the pan or conduit moves rapidly backward, depositing the components.
A horizontal motion conveyor operates with a continuous forward and backward motion, allowing materials to be conveyed smoothly at speeds of up to 40 feet (12 m) per minute over distances of up to 200 feet (61 m). With no moving parts other than the drive unit, these conveyors minimize safety risks, simplify cleaning, and reduce maintenance. Their smooth, even motion makes them particularly suited for handling fragile materials that require careful handling.
Horizontal motion conveyors are capable of moving components either backward or forward one direction at a time. They can be configured for slight inclines or declines to handle flat rectangular or square parts. Additionally, these conveyors can be set up to deliver parts at their midsection. The design ensures that components move along the open pan or conduit without experiencing vertical acceleration or bouncing action.
The capacity of a vibrating feeder is determined by several factors including the width of the trough, the depth of material flow, the bulk density of the material, and the linear feed rate. This can be expressed using the formula:
C = WdR /
In this formula, C represents the capacity in tons per hour (metric tons per hour), W denotes the trough width in inches (millimeters), d is the depth of material in inches (millimeters), γ stands for the bulk density in pounds per cubic foot (grams per cubic centimeter), and R indicates the linear feed rate in feet per minute (meters per minute). When using metric units, replace the constant 4,800 with 16,700.
Typically, the required capacity is determined by the needs of upstream or downstream processes. Given this required capacity, you can derive possible combinations of trough width and linear feed rate, factoring in the material's bulk density and the anticipated feed depth. Manufacturers usually offer charts, tables, and graphs that outline the feeder's specifications and performance characteristics.
Feeder troughs are typically constructed from mild steel, grade 304 stainless steel, or abrasion-resistant alloys. In some designs, ordinary steels are lined with replaceable materials like rubber, plastic, or ceramics. The shape of the troughs varies based on the type and properties of the materials being handled and the specific processes they are integrated into. Common trough shapes and features include:
Vibratory bowl feeders feature troughs that are wound in a helical pattern and utilize vibrations to move and shuffle materials along the gently inclined surface of the trough. This tossing and shuffling action helps to orient parts with irregular shapes as they progress through the feeder.
Vibratory bowl feeders offer several advantages, including efficient conveying and proper positioning of parts. The troughs are designed with specific profiles to ensure materials are oriented correctly. Screening devices attached to the bowl help remove parts that are not properly positioned or oriented. These feeders are commonly used in assembly and packaging lines across industries such as electronics, automotive, and pharmaceuticals.