A vibrating screen is a mechanical screening machine that uses mechanical vibration to separate and classify granular or powdered materials. It is widely used in mining, coal processing, chemical processing, and building materials industries. The machine uses a vibration motor or exciter to generate excitation force, causing the screen box and screen surface to vibrate along a specified trajectory. Materials are spread across the screen surface and separated according to particle size.
Different types of vibrating screens use different excitation mechanisms and vibration trajectories. Some vibrating screens use upper and lower rotating eccentric weights to generate compound spatial vibration. By adjusting the excitation force and phase angle of the weights, the motion of the screen surface can be changed to suit different screening requirements.
Working principle of vibrating screens
A vibrating screen relies on periodic mechanical vibration to move materials across the screen surface. Particles are thrown, rolled, or slid across the deck to achieve continuous screening.
In vibrating screens equipped with upper and lower rotating eccentric weights, the operation depends on the combined action of these two weights.
Upper rotating eccentric weight: Generates horizontal circular vibration, causing the screen surface to follow a circular motion in the horizontal plane.
Lower rotating eccentric weight: Generates conical rotary vibration, introducing the corresponding motion component in the vertical direction.
Combined action of the upper and lower weights: The excitation forces produced by the two weights combine to form a compound spatial motion trajectory. This movement drives materials across the screen surface and facilitates screening.
This vibration arrangement produces motion in both horizontal and vertical directions, helping distribute materials across the screen surface and supporting the screening process.
It is important to note that the upper and lower eccentric weight arrangement is used in certain vibrating screen designs. Linear vibrating screens, circular vibrating screens, and other configurations may use different excitation mechanisms and produce different motion trajectories.
Vibration trajectory of a vibrating screen
In vibrating screens with upper and lower rotating eccentric weights, the screen surface follows a compound spatial curve.
When viewed from different directions, the motion trajectory has the following characteristics:
Horizontal projection: The motion trajectory appears circular.
Vertical projection: The motion trajectory appears elliptical.
Spatial motion: The combined horizontal circular motion and vertical rotary motion produce a compound vibration trajectory.
This movement subjects materials on the screen surface to periodic forces in different directions. As a result, particles can spread, roll, and move across the deck, allowing material classification to take place.
How to adjust excitation force and vibration trajectory
For vibrating screens equipped with upper and lower eccentric weights, the vibration characteristics can be adjusted by changing the weight configuration. The main adjustment methods involve regulating excitation force and changing the spatial phase angle.
Adjusting the excitation force of the upper and lower weights
The excitation forces generated by the rotating eccentric weights affect the vibration amplitude of the screen surface. By adjusting the positions or effective eccentricity of the weights, the excitation force and resulting screen amplitude can be changed.
Changes in amplitude affect particle throwing height, material movement speed, and distribution across the screen surface. The excitation force should therefore be adjusted according to material particle size and screening requirements.
Adjusting the spatial phase angle between the upper and lower weights
The spatial phase angle between the upper and lower weights affects how their excitation force components combine. Changing this angle modifies the shape of the screen's motion trajectory and influences the direction and movement pattern of materials across the screen surface.
Proper phase angle adjustment helps match material movement to the screening requirements and can improve material distribution and screening performance.
The eccentric weight settings and phase angle must remain within the adjustment limits specified by the equipment manufacturer. Adjustments should also account for motor loading, bearing load capacity, and screen box structural strength. Incorrect settings may cause excessive vibration or fatigue damage to mechanical components.
Main applications of vibrating screens
Vibrating screens are used to classify materials according to particle size. Depending on their design, they can also perform dewatering, desliming, and other material processing operations.
Common applications include:
Mining: Used for particle size classification after ore crushing and material screening during mineral processing.
Coal processing: Used for raw coal classification, coal screening, and related material handling operations.
Chemical processing: Used to screen powdered and granular chemical materials and separate particles of different sizes.
Building materials: Used for classifying sand and gravel aggregates, crushed stone, and other construction materials.
Different production applications have different requirements for screening accuracy, processing capacity, and operating parameters. The appropriate vibrating screen structure and excitation method should therefore be selected according to material properties and actual operating conditions.
Custom machining of vibrating screen components
The manufacture and maintenance of vibrating screens involve various mechanical components, including screen boxes, exciter shafts, eccentric weights, motor mounting bases, connecting parts, and supporting structures. The dimensions, machining accuracy, and assembly quality of these components affect the vibration characteristics and operating stability of the equipment.
We provide single-piece and small-batch precision machining based on customer-supplied drawings and dimensional specifications. Hansheng Automation supports drawing-based custom manufacturing of shafts, eccentric components, connecting parts, and other non-standard mechanical components according to their structural features and machining requirements.
Our precision machining services also cover components for various industries, including precision structural parts for yacht equipment, mechanical components for RC racing cars, functional parts for tobacco packaging machinery, and components for filling machinery. Non-standard components for these applications can be manufactured according to customer drawings and specific machining requirements.
