PET/PP plastic steel strapping melt pump
The melt metering pump, as the core precision fluid conveying equipment in the PET/PP plastic steel strapping production line, is precisely installed between the extruder and the die, constructing an integrated and stable conveying system of "extruder metering pump die". It is a key hub to ensure the quality of strapping products and improve production efficiency. With its three core functions of precise measurement, voltage stabilization and pressurization, and homogeneous conveying, it solves industry pain points such as uneven weight distribution, molding defects, high energy consumption, and insufficient performance in the production of packaging belts from the source, comprehensively improving product consistency and production economy. It is an indispensable core component of modern plastic steel packaging belt production lines.
1、 Core functional positioning: four-dimensional empowerment of quality improvement, stability control, production increase, and energy conservation
The core value of Bart melt metering pump lies in optimizing and upgrading the entire process of packaging belt production through precise fluid control, balancing product quality and production efficiency. This is reflected in its four core functions, which comprehensively solve the bottleneck of industry production.
（1） Accurate measurement, laying a solid foundation for product consistency
The melt metering pump belongs to high-precision volumetric gear pumps, and its core advantage lies in the strict linear correspondence between the output flow rate and the spindle speed, which is not affected by external factors such as pressure fluctuations in the extruder system and changes in melt viscosity. The metering accuracy far exceeds traditional conveying methods. During the production process, the frequency conversion speed control system accurately controls the pump body speed, which can strictly control the fluctuation of the melt output flow rate within ± 1%, ensuring that the PET/PP melt is continuously transported to the mold head at a fixed flow rate. This feature directly ensures the high consistency of key indicators such as weight, thickness, and width of the packaging tape, effectively reducing waste caused by size deviations and reducing the production line waste rate by 10% -15%, significantly improving raw material utilization and production stability.
（2） Stabilize voltage and buffer, eliminate various defects in the molding process
During the PET/PP melt extrusion process, the periodic rotation of the extruder screw can easily generate pressure pulsation, which can be directly transmitted to the die head, resulting in forming defects such as uneven thickness, surface wrinkling, edge burrs, and uneven cutting of the packaging tape, seriously affecting the appearance and performance of the product. The melt metering pump can effectively buffer this pressure pulsation, and through precise transmission through gear meshing, the pressure fluctuation of the melt at the entrance of the die is controlled within ± 1%, achieving smooth transportation of the melt. A stable pressure environment ensures that the melt flows uniformly and is fully formed in the mold head, fundamentally eliminating various forming defects, improving the surface smoothness and dimensional accuracy of the packaging belt, and meeting the quality requirements of high-end packaging belts.
（3） Energy conservation and increased production, achieving maximum production efficiency
In traditional production lines, extruders need to simultaneously undertake the dual tasks of melt conveying and pressurization, with a large load, which can easily lead to high energy consumption and limited production capacity. The melt metering pump is specifically responsible for system pressurization, which can significantly reduce the workload of the extruder, allowing it to operate under lower back pressure and more stable conditions, effectively reducing the energy consumption of the extruder's motor. Practical data shows that when combined with a melt metering pump in the PET/PP plastic steel strapping production line, the overall energy consumption of the production line can be reduced by 15% -30%. At the same time, due to the improvement of melt conveying efficiency and molding stability, the production line output can be increased by 15% -20%, truly achieving the dual benefits of energy conservation and production increase, reducing enterprise production costs, and enhancing market competitiveness.
（4） Homogeneous conveying enhances the core mechanical properties of the product
Although PET/PP melt has undergone initial plasticization in the extruder, there may still be problems such as uneven temperature distribution, insufficient mixing of molecular chains, and uneven dispersion of additives, which directly affect the tensile strength, toughness, and impact resistance of the packaging tape, and cannot meet the high-strength use requirements such as heavy object binding and long-distance transportation. During the operation of the melt metering pump, the melt is subjected to secondary homogenization treatment through the shearing and squeezing action of high-precision gears, resulting in a more uniform temperature distribution inside the melt, more complete molecular chain winding, and more uniform dispersion of additives, thereby significantly improving the mechanical properties of the packing belt. Through actual testing, it has been found that packaging belts produced with melt metering pumps can increase tensile strength by 8% -12%, toughness by more than 10%, and significantly improve impact resistance, making them suitable for various heavy-duty packaging scenarios.
2、 Structure composition and working principle: Precise collaboration to achieve precise conveying
The precise operation of the melt metering pump relies on the precise coordination of various core components. Its structural design fully adapts to the high temperature and viscosity characteristics of PET/PP melt, ensuring stability and service life under harsh working conditions. The working process is scientific, efficient, and highly controllable.
（1） Core structure composition
The melt metering pump is mainly composed of five core components: pump casing, main/driven gears, sliding bearings, front and rear end plates, and sealing components. Each component has clear division of labor and works together to ensure the precision and reliability of the equipment:
Pump casing: Made of high temperature resistant and wear-resistant alloy steel precision casting, the overall structure is tightly sealed, providing a closed chamber for melt transportation. At the same time, it has good thermal conductivity and compression resistance, and can adapt to PET/PP melt working temperatures of 200-300 ℃, resist melt erosion and corrosion, and extend equipment service life.
Main/driven gears: High precision involute helical gears are used, which are precision ground and processed to achieve high tooth surface smoothness and small meshing clearance, ensuring the accuracy of quantitative conveying; The design of helical gears can effectively reduce operating noise, minimize gear wear, improve equipment stability, and meet the transportation needs of high viscosity melts.
Sliding bearings: made of high-temperature resistant and wear-resistant hard alloy materials, specially adapted to high-temperature melt environments, mainly used to support the main and driven gear shafts, ensure the coaxiality and smoothness of gear rotation, and avoid measurement errors and equipment failures caused by gear offset.
Front and rear end plates and sealing components: The front and rear end plates are tightly attached to the pump casing, forming a closed conveying space; The sealing components are made of flexible sealing materials that are resistant to high temperatures and wear, effectively preventing high-temperature melt leakage, ensuring system sealing, while reducing component wear and maintenance costs.
（2） Working principle
The working process of the melt metering pump is based on the principle of volumetric conveying, which is mainly divided into three continuous and coherent stages: suction, conveying, and pressure stabilization. The entire process is automated and precisely controlled:
Suction stage: When the motor drives the driving gear to rotate, the driving gear drives the driven gear to rotate synchronously in the opposite direction, and the volume at the gear meshing gradually increases, forming a negative pressure area. At this point, the PET/PP melt output by the extruder is smoothly sucked into the pump chamber through the pump inlet under negative pressure, completing the suction process.
Transport stage: With the continuous rotation of the gear, the molten material sucked into the pump chamber is wrapped by the meshing teeth of the gear. Under the pushing effect of the gear, it moves smoothly along the inner wall of the pump casing towards the outlet direction of the pump body. Throughout the entire transport process, the molten material will not have problems such as backflow or leakage, ensuring the continuity of the transport.
Pressure boosting and stabilizing stage: When the melt is transported to the outlet of the pump body, the gears gradually mesh tightly, and the volume at the meshing point continuously decreases, exerting a squeezing effect on the melt, causing the melt pressure to continue to rise. Finally, it is output to the die in a high-pressure and stable state, providing stable pressure and flow guarantee for the uniform forming of the packing belt, and completing the entire conveying process.
The melt metering pump has become the core supporting equipment of PET/PP plastic steel strapping production line due to its precise metering ability, stable pressure stabilizing effect, significant energy-saving and production increasing advantages, and good homogenization effect. It can not only effectively improve product quality and reduce production costs, but also enhance the automation level and stability of the production line, help enterprises achieve large-scale and high-quality production, adapt to the development needs of the high-end strapping market, and is an indispensable precision equipment in modern plastic steel strapping production.
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