The difference between volumetric and gravimetric of powder processing machine②

Gravimetric screw feeders are devices used to feed a specific amount of powder or granular material at a constant rate during the manufacturing process. This type of screw feeder provides high accuracy and stability because the material feed rate is controlled by weight.

The main components of this device are a screw conveyor, a scale (load cell), and a control system. The screw conveyor is the part to which the screw is attached to transport the material, moving it at a constant speed. The scale is installed under the screw conveyor and measures the weight of the material. The control system then receives the information from the scale and adjusts the speed of the screw to maintain the target feed rate.

The principle of operation is as follows. First, material is fed onto the feeder and evenly distributed by the screw conveyor. Then, as the material moves on the screw conveyor, a scale detects its weight. The control system adjusts the speed of the screw to reach the target weight of material based on the set feed rate. The screw speed is automatically adjusted according to the weight of the material and controlled to feed a constant amount of material. Finally, a scale measures the weight of the material and the control system feeds it back to adjust the continuous feed.

The differences between gravimetric screw feeders and volumetric screw feeders and the advantages and disadvantages of each are summarized below.

Gravimetric Screw Feeders:
Definition
Gravimetric screw feeders measure the weight of material and adjust the feed rate based on that weight.
Control Method: Material feed rate is controlled by weight.

Advantages:
High accuracy: Direct measurement of material weight ensures high feeding accuracy.
Stable feeding: Less susceptible to material fluctuations and density differences.

Disadvantages:
Space limitations: Requires additional space for additional scales and control systems.
Cost: Initial investment may be high due to additional measuring equipment and control system.

Volumetric Screw Feeder:
Definition
A volumetric screw feeder delivers a fixed volume of material by adjusting the number of rotations and speed of the screw.
Control Method: Material feed rate is controlled by the number of rotations and speed of the screw.

Advantages:
Simplified control: Control system is simplified because material volume is controlled by screw speed and revolution.
Low cost: No measuring device or control system is required, resulting in a low initial investment.

Disadvantages
Reduced feeding accuracy: Changes in material density and particle size can reduce feeding accuracy.
Unstable Feeding: Material fluctuations may result in unstable feeding rates.
Factors such as product specifications, material properties, manufacturing process requirements, and budget should be considered when making a selection. Gravimetric screw feeders are suitable when accuracy and stability are important, while volumetric screw feeders are suitable when relatively stable feeding is possible while keeping costs down.

Thus, gravimetric screw feeders play an important role in controlling material feeding with a high degree of precision and improving the stability and efficiency of the manufacturing process. They are widely used in industrial fields such as food processing, chemical industry, mining, and construction materials.

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