In crusher and stone-crushing plants there is a motor group as critical as the main crusher yet often overlooked: the vibration motors used in vibrating feeders, under-bunker feeding units and vibrating screens. These motors produce controlled vibration to feed material steadily from the bunker to the crusher and to separate it by grain size on screens. They work entirely differently from a standard drive motor; thanks to the unbalanced (eccentric) weights inside them, they create centrifugal force, and this force vibrates the feeder or screen. A wrongly selected vibration motor disrupts material flow, feeds the crusher unevenly and lowers screening efficiency. As both a manufacturer and supplier, HEM Motor supplies stone crushing-screening plant motors built to withstand heavy dust, impact and continuous vibration. In this article we cover vibration motor selection, centrifugal force adjustment, IP66 dust protection and correct supply from a commercial buyer's perspective.

Vibration motor selection for crusher feeders and under-bunker units

How Does a Vibration Motor Work?

Although a vibration motor resembles a standard asynchronous motor, it differs through adjustable unbalanced weights (eccentric flanges) mounted on the shaft ends. When the motor turns, these weights produce centrifugal force; this force vibrates the feeder tray or screen body to which the motor is attached, with a back-and-forth or circular motion. This vibration is used to feed material smoothly from the bunker to the crusher, or to pass it across the screen separated by grain size.

The important difference is this: while a normal motor rotates a load connected to its shaft, a vibration motor vibrates a mass together with its own body. Therefore the bearings of a vibration motor must be reinforced to carry continuous radial vibration load. We also emphasized the importance of these motors beyond the main crusher in our screen, feeder and belt drive in crushing-screening plants article; vibrating feeders and screens are the most critical application area of these motors.

Centrifugal Force Adjustment and Weight Setting

The most practical feature of a vibration motor is that its produced vibration force is adjustable. By changing the angle of the unbalanced weights at the shaft ends, the centrifugal force (usually expressed in kN) is increased or decreased. More force means stronger vibration and faster material flow; however, excessive force fatigues the feeder body and connections. The correct setting balances the feed rate to the material type and crusher capacity. At the ordering stage, the required centrifugal force (kN) and speed should be determined according to the values given by the feeder/screen manufacturer.

Vibrating Feeder, Bunker and Screen Applications

Vibration motors serve at several different points in a stone-crushing plant; each demands a different force and speed:

  • Under-bunker vibrating feeder: Feeds the material under the bin steadily and prevents bridging (clogging). High centrifugal force is needed.
  • Grizzly feeder: Directs coarse material to the crusher while screening out fine soil. Runs under continuous heavy load.
  • Vibrating screen: Separates crushed material by grain size. Usually dual-motor units synchronized for balanced vibration are used.
  • Bunker anti-clogging: Small vibration motors mounted on silo and bin walls keep the material flowing.

Because each of these motors works under heavy dust and impact, the dust, moisture and impact measures in our stone quarry and mine motor protection article apply here too.

IP66 protected vibration motor on a vibrating screen and grizzly feeder

IP66 Dust Sealing: Why Is It Essential?

A stone-crushing plant is the dustiest environment in the sector. The fine stone dust produced during crushing and screening penetrates everywhere. Because the vibration motor constantly vibrates, dust sealing is more critical than for an ordinary motor; vibration accelerates the loosening of gaskets and seals. Therefore, at least IP66 protection should be requested for feeder and screen vibration motors; this class is fully dust-tight and also withstands powerful water jets. Our crusher motor dust sealing and IP65/IP66 protection article, which addresses dust protection together with field measures, also guides vibration motor selection. In addition, strong cataphoresis coating protects the frame in a constantly dusty and humid environment.

Single-Motor and Dual-Motor Vibration Systems

In vibrating feeders and screens, single or dual vibration motors are used depending on the type of motion to be produced. In single-motor systems, the motor is usually positioned at a certain angle on the body and produces a circular or elliptical vibration motion; it is sufficient for small feeders and simple screens. In dual-motor systems, two vibration motors rotate opposite to each other; these motors synchronize electromechanically and produce a linear vibration. Linear vibration carries the material smoothly forward across the screen surface and is standard in large vibrating screens. In a dual-motor system, the two motors must have the same centrifugal force and speed; otherwise synchronization breaks down and the screen runs unbalanced.

Therefore, when replacing a motor on a dual-motor screen, it is important to supply not only the failed motor but also its pair with the same specification. Specifying whether the system is single or dual motor and the required centrifugal force at the ordering stage ensures the correct motor arrives. HEM Motor can supply matched-specification vibration motors together for dual-motor systems.

Speed Selection and Its Relation to Centrifugal Force

In vibration motors, speed and centrifugal force are evaluated together. Low-speed (1000 or 750 rpm) vibration motors produce a larger-amplitude, softer vibration; they are preferred for conveying coarse, heavy material and preventing bridging. High-speed (3000 or 1500 rpm) motors give a smaller-amplitude, higher-frequency vibration; they suit fine screening and precise separation applications. The right speed is chosen by the material grain size, moisture content and desired feed rate. A wrong speed choice leads either to the material not flowing enough or passing over the screen too fast and not being screened well.

The centrifugal force must be chosen in proportion to the vibrated mass (feeder tray or screen body + the material on it). Too low a force leaves the vibration weak; too high a force fatigues the body and connections. The feeder or screen manufacturer usually specifies the required force value (kN) and speed; the motor should be selected according to these values. In a crusher plant, the correct selection of these auxiliary drive motors alongside the main crusher directly determines the line capacity; our electric motor selection for crusher and stone crushing plants article takes a holistic look at plant-wide motor selection.

Bearings, Durability and Continuous Vibration Life

The most strained part of a vibration motor is the bearings. Working under continuous radial vibration load, these bearings are selected in a far heavier duty class than a standard motor's. A quality vibration motor has a reinforced bearing structure and vibration-resistant winding connections. To reduce the risk of early failure, the motor must be designed by the manufacturer specifically for this application; using a general-purpose motor as a vibration motor leads to fast failure. The cost of a failure in a crusher plant is very high; we covered these losses and the spare strategy in our motor failure and downtime cost in crusher plants article.

Mounting and Connection Safety of the Vibration Motor

Because a vibration motor constantly produces vibration, its mounting requires different attention from a standard motor. The bolts connecting the motor to the feeder or screen body can loosen over time due to vibration; this loosening can result first in imbalance, then in a connection breaking and serious damage. Therefore, the use of high-strength bolts, lock nuts and anti-vibration washers is essential on vibration motors; in addition, the connection torques should be checked periodically. The unbalanced weight covers on the motor shaft must also stay tight under vibration and be protected with dust seals; if dust enters the weight adjustment mechanism, the force balance is disturbed. During assembly, the cable connection must also be made vibration-resistant. The cable entering the terminal box should be fixed at a suitable distance so vibration does not fatigue it, and connected with a high-IP cable gland. A loose or wrongly fixed cable can break quickly under vibration. A plant-wide maintenance discipline is needed for all motors in a crusher plant to run safely under dust and vibration.

Stock and Emergency Replacement Strategy

A stopped bunker feeder or screen halts the entire crushing line. Therefore spares of critical vibration motors should be kept in stock. This is even more critical in mobile and portable plants; the fast-supply approach in our motor supply in mobile crushers and portable crushing plants article also applies to vibration motors. Because HEM Motor produces with standard connection dimensions, it can quickly supply a one-to-one replacement of your failed motor; you can also source the plant-wide high-efficiency electric motors and main crusher drive motors from a single supplier.

Conveyor and Belt Drive: The Line's Other Motors

Besides vibrating feeders and screens, the conveyor belts carrying material in a stone-crushing plant also require their own drive motors. These motors are not vibration motors but geared standard asynchronous motors; they work with a gearbox to reduce belt speed and produce the required torque. A conveyor belt motor needs high starting torque to set a loaded belt into motion from standstill and runs in a continuous, dusty environment. Therefore cast iron framed motors with high IP protection and a sufficient torque class are preferred. Because a conveyor motor failure can stop the entire line, nameplate data should be kept on record for one-to-one replacement. Sourcing vibration motors, conveyor drive motors and the main crusher motor plant-wide from a single supplier simplifies stock management and enables a fast solution in an emergency. HEM Motor also offers motors suited to geared applications, supplying belt and screw drives with IEC-frame motors compatible with worm gear reducers and helical-worm gear reducers.

Frequently Asked Questions

What is the difference between a vibration motor and a standard motor?

While a standard asynchronous motor rotates a load connected to its shaft, a vibration motor produces centrifugal force with adjustable unbalanced weights at the shaft ends and vibrates the feeder or screen body to which it is attached. A vibration motor's bearings are reinforced to carry continuous radial vibration load. Therefore it is not correct to use a general-purpose motor in a vibration application; a vibration motor specifically designed for this job is required.

How is the vibration force of a vibration motor adjusted?

By changing the angle of the unbalanced weights at the shaft ends of the vibration motor, the produced centrifugal force (kN) is increased or decreased. Higher force provides stronger vibration and faster material flow; however, excessive force fatigues the feeder body and connections. The correct setting balances the feed rate to the material type and crusher capacity. The required force and speed should be selected according to the feeder/screen manufacturer's values.

Which IP protection class is needed for a feeder and screen motor?

Because a stone-crushing plant is the dustiest environment in the sector and the vibration motor constantly vibrates, at least IP66 protection is recommended. IP66 is fully dust-tight and also withstands powerful water jets. Since vibration accelerates the loosening of gaskets and seals, dust sealing is more critical here than for an ordinary motor. In addition, strong cataphoresis coating protects the frame in a constantly dusty, humid site and extends motor life.

Get a Quote

Supply a vibration motor with the right centrifugal force, IP66 protection and heavy-duty rating for your crusher feeder, under-bunker feeding unit or vibrating screen from HEM Motor. Share your required force (kN), speed and application; we will quickly offer a suitable stock delivery or project solution. Call now: +90 (532) 345 49 86 or request a quote from our contact page.