Melt pump and screen changer

The melt pump for the PVC 20-110mm dual-tube plastic extruder plays a crucial role in plastic extrusion processing. Below is a detailed analysis of this melt pump:

I. Definition and Function

A melt pump is a conveying power equipment used for high-temperature, high-viscosity polymer melts. It is mainly used for conveying, pressurizing, and metering high-temperature, high-viscosity polymer melts. In the PVC 20-110mm dual-tube plastic extruder, the main functions of the melt pump include:

Pressure Stabilization: The melt pump provides stable melt pressure and prevents pressure fluctuations, which is crucial for maintaining the stability of the extrusion process and product quality.

Flow Control: By adjusting the rotational speed of the melt pump, the flow rate of the melt can be precisely controlled, ensuring consistency during the extrusion process.

Homogenization of Melt: During the process of conveying the melt, the melt pump achieves shear and mixing of the melt through the rotation of gears or screws, thereby improving the uniformity and stability of the melt.

Reduction of Pulsation: The melt pump reduces pulsation in the melt flow rate, further enhancing the quality of the extruded product.

II. Structure and Working Principle

The melt pump is mainly composed of a pump casing, driving gear, driven gear, sliding bearings, front and rear end plates, gland seals, etc. Its working principle relies on the change in working volume caused by the intermeshing of the driving and driven gears to convey the melt. When the gears rotate in the specified direction, the melt enters the tooth spaces of the two gears in the feed area. As the gears rotate, the melt is brought into the conveying area from both sides. The re-engagement of the gears extrudes the melt in the tooth spaces into the discharge area and presses it into the outlet pipeline.

III. Characteristics and Advantages

Optimized Melt Channel Design: Eliminates dead corners in the flow channel, reduces polymer residue, and improves product quality.

Improved Gear Parameter Design: More precise displacement design results in more stable output pressure and suitability for precision extrusion conditions.

Extremely Wide Viscosity Range: Different sealing methods can be applied to conditions ranging from low to extremely high viscosity.

Multiple Installation Methods: Satisfies users' personalized needs, such as A-type horizontal installation, B-type downward installation, C-type upward installation, D-type side installation, etc.

High-Precision Manufacturing and Excellent Heat Treatment: Ensures that the melt pump is more precise and durable.

IV. Application and Benefits

In the PVC 20-110mm dual-tube plastic extruder, the application of the melt pump brings significant economic benefits and improvements in product quality. It minimizes the dimensional tolerance of extruded products, reduces scrap and reject rates; at the same time, it also reduces the load on the extruder, conserving energy and costs. Additionally, the melt pump helps improve production efficiency, extends equipment life, and reduces reverse flow and temperature fluctuations, thereby increasing extrusion output.

V. Parameter Range

For the PVC 20-110mm dual-tube plastic extruder, the parameter range of the melt pump typically includes:

Viscosity of Conveyed Medium: Generally up to 140,000 Pa·s (or 1,000,000,000 cP).

Suction Pressure: Ranges from vacuum state (-0.00 to -0.03 MPa) to 30 MPa.

Output Pressure: Up to 40 MPa.

Operating Temperature: Typically not exceeding 350°C (or 400°C, depending on the pump material and design).

In summary, the extrusion melt pumps for the PVC 20-110mm dual-tube plastic extruder plays an important role in plastic extrusion processing. Through functions such as pressure stabilization, flow control, melt homogenization, and pulsation reduction, it significantly enhances the quality and production efficiency of extruded products, bringing remarkable economic benefits.

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