Vibrating Conveyor

What is a Vibrating Conveyor

A vibrating conveyor, also called a vibratory conveyor, is a bulk material handling machine that transports product along a trough using controlled oscillating motion rather than a moving carrying surface. CEMA, the Conveyor Equipment Manufacturers Association, defines this family simply as conveying machines that transport material using an oscillating or vibrating motion. The defining feature is that the trough itself is the only moving part the material touches: there is no belt to run off, no chain to stretch, and no screw flight to abrade. The drive imparts a directed throw to the trough, and the material responds by moving forward in a series of small, fast jumps.

Structurally, every vibrating conveyor has four functional parts. First, the trough or pan, which is the open channel, covered duct or tube that carries the product and is the principal wear surface. Second, the drive, which is the mechanism that generates the oscillating force, whether an unbalanced motor, an eccentric shaft and connecting rod, or an electromagnetic coil. Third, the spring and reactor system, which transmits, tunes or amplifies the motion and on two-mass machines stores and returns energy each cycle. Fourth, the isolation system, which is the soft mounts, base springs or air bags that keep the shaking force from being transmitted into the supporting steel or building floor.

Vibrating conveyors sit alongside belt, roller, chain, screw, pneumatic and bucket conveyors as one of the core bulk-handling categories, but they occupy a specific niche. They excel where the material is hot enough to scorch a rubber belt (foundry castings, hot clinker), abrasive enough to grind out a screw (sand, slag, crushed ore), fragile enough to be damaged by tumbling (snack foods, pharmaceuticals, friable granules), or sticky and prone to bridging (wet chemicals, fertiliser). The same gentle hopping action that conveys these materials also lets the trough double as a screen, dewatering deck, cooling bed or spreader, so a single vibrating unit often does more than one job.

Historically, vibratory conveying grew out of the foundry and mining industries in the mid twentieth century, where the need to move hot, gritty material reliably made the absence of a wearing belt or chain decisive. The electromagnetic feeder, driven directly from the alternating-current line, became common in the 1950s and 1960s for fine and medium materials, while heavier mechanical and two-mass drives took over the high-tonnage end. Today the technology spans laboratory feeders dosing a few grams per minute up to industrial trough conveyors quoted around 1,000 t/h, and the same physics governs the parts-orienting bowl feeders that feed automated assembly lines.

Two engineering metrics dominate vibrating conveyor selection: the conveying rate that the trough and drive can sustain, and the energy and maintenance cost to sustain it. A poorly matched machine either fails to move the rated tonnage, transmits damaging vibration into the structure, or burns excess power because it is fighting its own mass instead of working with a tuned spring system. The chapters that follow build the framework to avoid each of these failure modes.

Drive Types and Classification

The single most important classification is by drive type, because it sets the energy cost, the tuning complexity, the achievable stroke and frequency, and ultimately the price. Three drive families dominate industry: brute-force (direct drive), two-mass natural-frequency (tuned), and electromagnetic. A secondary classification by duty separates light and standard-duty machines for food, plastics and light minerals from heavy-duty machines for rock, scrap and foundry sand. The table below compares the three drive families on the metrics that matter for selection.

Brute-force (direct drive) conveyors are the simplest design. One or two unbalanced motors, or an eccentric shaft, bolt directly to a single trough mass mounted on soft isolation springs. When energised, the rotating eccentric weight shakes the entire unit. The appeal is mechanical simplicity and minimal tuning, but the drawback is that the exciting force must overcome the full inertia of the trough plus the material load, so as the machine grows larger it demands disproportionately more horsepower. Counter-rotating twin motors are arranged so their horizontal forces cancel and their forces add along the throw line, producing a clean directed stroke. Brute-force machines suit short conveyors and feeders where low first cost outweighs running cost.

Two-mass natural-frequency conveyors are the high-efficiency answer for long or heavy duty. The machine is divided into two masses, a drive mass and the product-carrying trough mass, connected by precisely engineered reactor springs (steel coil, fibreglass leaf or rubber). The drive runs just below the assembly resonant frequency, so a small exciting force is magnified at resonance into a large trough stroke. General Kinematics describes its PARA-MOUNT II two-mass feeders as using sub-resonant magnification of a small exciting force on a two-mass coil-spring system, and states the design uses up to 60 percent less energy than an equivalent brute-force machine. The penalty is that the spring system must be tuned to the load, and large changes in headload shift the tuning, so two-mass machines need correct dynamic design.

Electromagnetic drives use an alternating current through a coil to pull an armature against a tuned leaf spring, releasing it on the off half-cycle. With no rectification the armature is pulsed twice per line cycle, so the deck vibrates at twice line frequency: 3,600 vibrations per minute on a 60 Hz supply and 3,000 per minute on a 50 Hz supply. Half-wave rectified controllers halve this to the line frequency for higher-stroke operation. Electromagnetic feeders are tuned sub-resonant, meaning the mechanical natural frequency is set above the operating frequency for stable behaviour under headload. The high frequency and small stroke (around 1.6 to 3.7 mm) give very fine, instantly controllable flow, ideal for dosing fine powders and small parts, but the achievable trough size and tonnage are limited compared with mechanical drives. Eriez, Syntron and similar makers dominate this segment.

A further distinction is the trough geometry: open-pan conveyors for general bulk, covered or tubular conveyors for dust containment and food hygiene, and spiral or helical vibratory elevators that gain height in a small footprint. Trough geometry is chosen independently of drive type, so for example a sanitary tubular conveyor can use either an electromagnetic or a two-mass drive depending on capacity and rate-control needs.

Working Principle and Mechanics

The conveying action depends on three coupled quantities: frequency (how many cycles per minute), amplitude or stroke (how far the trough moves each cycle), and the vibration angle (the direction of the throw relative to the trough floor). Together these set the throw, the instantaneous acceleration, and whether the product slides, hops or is thrown clear of the surface. Understanding their interplay is what separates a working installation from one that either stalls the material or shatters it.

Each cycle, the drive throws the trough forward and slightly upward along the vibration line, then returns it. If the upward acceleration exceeds gravity, the product briefly leaves the surface and travels forward as a projectile before landing further down the trough, then is thrown again. This micro-tossing is what advances bulk material. The key dimensionless number is the vibration intensity, the ratio of peak trough acceleration to gravity (often written as a multiple of g). Below about 1 g the product only slides; above 1 g it begins to hop, and most conveyors run in a band that produces controlled hopping without violent throw. Acceleration rises with the square of frequency and linearly with stroke, so a high-frequency low-stroke machine and a low-frequency high-stroke machine can reach the same intensity by very different routes.

The vibration angle decides how the throw splits between advancing and lifting the product. A steeper angle lifts more aggressively, conveys faster and handles wetter material, but bounces fragile product harder; a shallower angle is gentler and slower. On a horizontal trough the throw angle that maximises conveying speed is generally in the region of 30 to 45 degrees from horizontal, and many fixed-stroke designs are built near this band. On two-mass natural-frequency machines the reactor springs are often mounted steeply, around 70 to 80 degrees to the horizontal, which is the design choice that sets the vibration line geometry, not the same thing as the throw angle of the product.

The drive family changes how frequency and stroke are produced. The table below shows how the common drive sources map to operating frequency, which directly constrains the available stroke and the materials each can convey well.

The general design rule is inverse: fine, fragile or light product wants high frequency with low stroke, which gives gentle, dense conveying with minimal product damage, while heavy, lumpy or sticky material wants low frequency with high stroke, which delivers the forceful hops needed to keep coarse lumps moving and to break loose sticky buildup. This is why an electromagnetic feeder running at 3,600 vibrations per minute and a couple of millimetres of stroke is ideal for snack food or pharmaceutical granules, while an 8-pole unbalanced-motor trough at 750 rpm and several millimetres of stroke is the right choice for foundry sand or crushed rock.

Brute-force drives use counter-rotating eccentric weights so that the unwanted side forces cancel and only the directed throw remains. Two-mass drives instead let a tuned spring system store the kinetic energy of the trough at the end of each stroke and return it on the next, so the motor only has to top up the small losses to friction and material work, which is the physical reason for their large energy advantage. Electromagnetic drives have no rotating parts at all: the coil and armature are the only moving elements, giving instant start, instant stop and stepless amplitude control from a simple controller.

Trough Materials and Media

Because a vibrating conveyor has no belt, chain or screw, the trough surface is the principal wear and contamination item, so the material of the pan and any liner is a first-order selection decision, not an afterthought. The choice is driven by the conveyed media: is it hot, abrasive, corrosive, fragile, or must it meet food and pharmaceutical hygiene? Each answer points to a different trough construction.

Mild carbon steel is the default for general dry bulk that is neither abrasive nor corrosive: aggregates within reason, wood chips, many chemicals and waste streams. It is the lowest-cost option and easy to fabricate and repair, but it offers no corrosion or abrasion margin, so it is usually combined with a replaceable liner when the media has any bite. For aggressive abrasive duty such as crushed rock, slag, glass cullet or foundry sand, the trough floor is upgraded to abrasion-resistant plate (AR400 or AR500 wear steel) or lined with bolt-in wear plates, ceramic tiles or ultra-high-molecular-weight (UHMW) polyethylene that can be swapped out without scrapping the trough.

Stainless steel 304 and 316L is mandatory for food, beverage, pharmaceutical and corrosive duty. 304 covers most dry food and mild chemical service; 316L, with 2 to 3 percent molybdenum, adds resistance to chlorides and acids for wet food, salt and chemical streams. Sanitary troughs are built with continuous ground-and-polished welds, no internal crevices, drainable geometry and surface finishes commonly specified to Ra 0.8 micrometre or finer so that residue cannot lodge and clean-in-place fluids reach every surface, consistent with 3-A and EHEDG hygienic-design guidance. Tubular covered troughs are preferred in food and pharma to contain dust and protect the product from the environment.

Special linings handle the cases plain metal cannot. Hot foundry castings and clinker need uncoated heavy steel because no polymer survives the temperature, and the absence of a belt is precisely why a vibrating conveyor is used. Very sticky or hygroscopic materials benefit from a low-friction UHMW or PTFE-faced liner that resists buildup. Highly abrasive fine slurries on dewatering decks use perforated stainless or wedge-wire screen panels so liquid drains while solids convey, turning the conveyor into a dewatering screen. The table below maps common media to a recommended trough construction; treat it as a first-pass guide and confirm against the maker corrosion and wear chart before purchase.

Two often-overlooked material factors are the reactor springs and the isolation mounts. Reactor springs on two-mass machines are fatigue-critical and are made from spring steel, fibreglass-reinforced laminate or rubber depending on the stroke and frequency; fibreglass leaf springs resist corrosive and fatigue environments well and are common in food and chemical duty. Isolation mounts, the soft springs or air bags between the machine and its support steel, are sized to a low transmissibility so that under 10 to 15 percent of the dynamic force reaches the building structure, which is what keeps a heavy vibrating conveyor from shaking a mezzanine or cracking a floor.

Key Specification Parameters

A vibrating conveyor datasheet lists many numbers, but only a handful drive the selection: capacity, conveying velocity, frequency, stroke, vibration angle, trough width and length, drive power, and noise. Reading these correctly, and knowing how they trade against each other, is the core skill. Each is decoded below.

Capacity is the throughput the machine can sustain, quoted in tonnes per hour (t/h) or cubic metres per hour, always tied to a stated bulk density. Standard-duty machines handle roughly 1 to 40 t/h, while heavy-duty units for rock, scrap and foundry sand exceed 500 t/h, and large unbalanced-motor trough conveyors are quoted by makers such as Cyrus and AViTEQ up to about 1,000 t/h. Capacity is a function of trough cross-section times conveying velocity times bulk density times a fill factor, so a quoted t/h figure is only meaningful with its assumed density and trough loading; always restate capacity at your actual material density.

Conveying velocity is how fast the material travels along the trough, commonly a few metres per minute up to about 30 m/min (100 ft/min) on a horizontal pan. Standard-duty machines run up to roughly 18 m/min (60 ft/min); heavy-duty machines up to about 27 m/min (90 ft/min). Velocity drops sharply once the trough is inclined uphill, because each hop now has to fight gravity, which is why most installations are horizontal or only slightly sloped, and why steep lift is left to spiral vibratory elevators or other conveyor types.

Frequency and stroke are the paired dynamic parameters set in Chapter 3. Frequency runs from around 750 rpm on an 8-pole mechanical drive up to 3,600 vibrations per minute on a 60 Hz electromagnetic drive; stroke runs from about 1.6 mm on small electromagnetic decks up to 8 mm or more on heavy two-mass and unbalanced-motor machines. The product of these, expressed as peak acceleration in multiples of g, is the figure that actually predicts conveying behaviour, so a good datasheet states stroke, frequency and the resulting g together rather than any one alone.

Vibration angle is the throw direction relative to the trough floor, typically around 30 to 45 degrees on horizontal conveyors. Some machines fix it; others let it be adjusted by repositioning the drive or the springs. An adjustable angle is valuable when one machine must handle several materials, because the optimum is gentle and shallow for fragile product but steep and aggressive for sticky or wet product.

Drive power and control is the installed motor or coil rating, where the two-mass advantage shows: a tuned machine needs only a fraction of the power of a brute-force unit of the same duty because resonance returns most of the energy each cycle. Most modern installations add a variable-frequency drive (VFD) on mechanical machines or a thyristor controller on electromagnetic machines to give stepless rate control, soft start and the ability to pass through resonance safely on shutdown.

Noise and dimensions close the list. Sound levels are typically 60 to 75 dBA, rising with hard lumpy impact and sometimes needing enclosures or liners to meet a workplace limit. Trough width and length set the footprint and, with cross-section, the capacity; unbalanced-motor trough conveyors are offered up to roughly 8 m long and 3 m wide, while feeders are usually under 3.7 m (12 ft) long. The summary table below collects the headline ranges across drive types for a first-pass shortlist.

Selection Decision Factors

To turn the preceding chapters into a real model, follow the decision sequence below. Most selection mistakes come not from one wrong number but from deciding a downstream detail before an upstream one, for example fixing the drive type before characterising the material. These eight steps work as a fixed RFQ template.

1. Characterise the material first: bulk density, particle size and lump size, temperature, moisture and stickiness, abrasiveness, fragility, and corrosiveness. Every later choice flows from this. Hot, abrasive or fragile material is exactly where a vibrating conveyor beats a belt or screw.
2. Set capacity and distance: required tonnes per hour at the real density, the conveying length, and any change in elevation. Remember that capacity falls fast on an incline, so plan steep lift with a spiral elevator or a different conveyor type rather than forcing a flat trough uphill.
3. Choose the drive family: brute-force for short, simple, low first-cost duty; two-mass natural-frequency for long, heavy, energy-sensitive duty where the up to 60 percent energy saving repays the higher purchase price; electromagnetic for fine product needing fast, precise, stepless rate control.
4. Match frequency and stroke to the product: high frequency and low stroke for fine or fragile material to convey gently; low frequency and high stroke for heavy, lumpy or sticky material to deliver forceful hops. Confirm the resulting peak acceleration in g, not stroke alone.
5. Specify trough material and surface: mild or AR steel for abrasive bulk, 304 or 316L with hygienic finish for food and pharma, replaceable liners (UHMW, ceramic, wear plate) where the media has bite. Decide open, covered or tubular geometry per dust and hygiene needs.
6. Design the isolation: select soft mounts or air springs so the transmitted dynamic force is a small fraction of the generated force, protecting the support steel, mezzanine or floor. This is non-negotiable for heavy machines and is a common cause of structural complaints when skipped.
7. Add controls and instrumentation: a VFD or thyristor controller for stepless rate and soft start, plus optional load cells, level probes or interlocks if the conveyor must dose or coordinate with upstream and downstream equipment.
8. Total cost of ownership (TCO): purchase price plus installed power cost plus spare-liner and spring replacement plus downtime. A two-mass machine with a higher sticker price but far lower energy and near-zero wearing contact parts often wins over a cheap brute-force unit within a few years of continuous running.

One last dimension is serviceability. Because the trough surface and the reactor and isolation springs are the wear items, ask how liners are replaced, whether spring kits are stocked, and how the machine is re-tuned after a duty change. Established makers cover this differently by segment: General Kinematics, Carrier Vibrating Equipment, Kinergy, Action Vibratory and JVI Vibratory Equipment serve heavy two-mass and brute-force bulk duty in mining, foundry and aggregate; Eriez and Syntron Material Handling (the former FMC Syntron line) cover electromagnetic and mechanical feeders and conveyors; AViTEQ and Cyrus supply large unbalanced-motor trough conveyors up to around 1,000 t/h in Europe. All work within CEMA conventions for North American projects, but confirm 3-A or EHEDG sanitary certification separately for food and pharmaceutical service.