Extrusion molding, as an efficient and flexible molding process, has broad application prospects in industrial production. With the continuous advancement of materials science and manufacturing technology, extrusion molding process is also constantly developing, such as its application in composite materials, nanomaterials and other fields is gradually increasing. In the future, extrusion molding technology will continue to develop towards high precision, high efficiency, and green environmental protection, providing more possibilities for the progress of the manufacturing industry.
The pressure during the extrusion process mainly comes from the push of the screw and the resistance of the die head. Appropriate pressure helps plastic to plasticize and flow evenly, ensuring the compactness and quality of the product. Excessive pressure can increase the load on the equipment and may even lead to increased wear and tear on the screws and barrels; If the pressure is too low, it will cause defects such as voids and looseness inside the product.
How to adjust the process parameters of Dalian extrusion molding according to different product requirements?
Shape requirements
Complex shaped products
Temperature control: Properly increase the temperature of the material barrel and machine head to improve the flowability of the plastic melt, making it easier to fill complex shaped molds. For example, for the production of plastic products with fine patterns or complex structures, the temperature of the barrel can be increased by 10-20 ℃ compared to conventional methods to ensure that the plastic can fully flow into every corner of the mold.
Screw speed: Reducing the screw speed reduces the shear force of the plastic melt during extrusion, avoiding the deterioration of plastic properties due to shear overheating, and also helps to maintain the integrity of the product shape.
Extrusion speed: Using a lower extrusion speed allows the plastic melt to enter the mold evenly and slowly, which helps to shape complex shapes and reduce defects.
Simple shaped products
Temperature control: The temperature can be slightly lower for complex shaped products to improve production efficiency, but it is necessary to ensure that the plastic is fully plasticized. Taking the production of ordinary plastic pipes as an example, the temperature of the barrel can be controlled within the range of 5-10 ℃ lower than that of producing complex shaped products.
Screw speed and extrusion speed: It is possible to increase the screw speed and extrusion speed appropriately to improve production efficiency while ensuring product quality.
Dimensional accuracy requirements
High precision manufacturing
Temperature control: More precise temperature control is required to ensure stable viscosity of the plastic melt and consistent extrusion volume. Usually, high-precision temperature control systems are used, with temperature fluctuations controlled within ± 1 ℃.
Screw speed: The screw speed should be stable, and even small fluctuations in speed can cause changes in extrusion volume, affecting the dimensional accuracy of the product. A high-precision screw drive system can be used to control speed fluctuations within a very small range.
Traction speed: The traction speed and extrusion speed should be accurately matched. According to the size requirements of the product, the stability of the traction speed is ensured through precise transmission devices and control systems to achieve high-precision size control.
Low precision products
Process parameter adjustment: The control accuracy requirements for temperature, screw speed, and traction speed are relatively low. The temperature fluctuation range can be relaxed to ± 5 ℃, and the control of screw speed and traction speed does not need to be too strict. It can be adjusted appropriately according to factors such as production efficiency and cost.
Performance Requirement
High strength products
Temperature control: Optimize temperature parameters to fully plasticize and mix the plastic melt, in order to improve the mechanical properties of the product. For example, in the production of high-strength engineering plastic components, the temperature of the material barrel needs to be precisely adjusted according to the material characteristics to ensure that the plastic reaches a better plasticizing state.
Screw speed and back pressure: Reduce the screw speed appropriately and increase the back pressure to ensure that the plastic melt is more fully sheared and compacted in the barrel, improve the orientation and crystallinity of the molecular chains, and thus enhance the strength of the product.
High transparency products
Temperature control: Accurately control the temperature to avoid plastic degradation caused by excessive temperature, which affects transparency. Taking the production of transparent polystyrene products as an example, the temperature of the material barrel needs to be controlled within a narrow range, with fluctuations generally not exceeding ± 2 ℃.
Cooling conditions: Optimize the cooling conditions by using a slow and uniform cooling method, such as using warm water or special cooling media, which can help improve the transparency of the product.
Appearance requirements
High gloss products
Temperature control: Increasing the temperature of the material barrel and machine head to ensure good fluidity of the plastic melt, which helps to form a smooth and high gloss appearance on the surface of the product. For example, when producing high gloss polycarbonate products, the head temperature can be increased by 5-10 ℃.
Mold surface treatment: In addition to adjusting process parameters, the smoothness and treatment method of the mold surface also have a significant impact on the appearance glossiness of the product. The surface of the mold needs to be polished with high precision to obtain a high gloss product surface.
Matte products
Process parameter adjustment: Reduce the temperature appropriately, increase the viscosity of the plastic melt, and form small concave convex structures on the surface of the product, thus presenting a matte effect. At the same time, an appropriate amount of matting agent can be added to the raw materials, and the process parameters can be adjusted to achieve the desired matte appearance.
Temperature control: The temperature setting of each section of the material barrel is crucial for the plasticization and extrusion process of the material. Excessive temperature may cause material decomposition, while excessively low temperature can affect the fluidity of the material. Screw speed: The screw speed determines the extrusion speed and shear force of the material. Excessive rotation speed may cause material overheating or unstable extrusion, while low rotation speed can affect production efficiency.
During the extrusion process, plastic raw materials undergo chemical reactions such as polymerization, grafting, cross-linking, etc., thereby endowing the plastic with new properties or improving its original properties. This technology can prepare polymer materials with special functions, such as high-performance engineering plastics, thermoplastic elastomers, etc. Adding foaming agent during the extrusion process to create a microporous structure in the plastic melt after extrusion. Micro foam plastic products have the characteristics of light weight, good thermal insulation performance, and excellent mechanical properties, and have broad application prospects in fields such as automobiles, construction, and packaging.
