Multiple parameters and stages in the extrusion molding process in Dalian can affect the performance of plastic products. The following provides a detailed introduction from the aspects of temperature, pressure, screw speed, etc.:

temperature

Melt temperature: If the melt temperature is too high, the thermal motion of plastic molecular chains will intensify, the intermolecular forces will weaken, and the mechanical properties of the product will decrease, such as tensile strength and hardness. But if the melt temperature is too low and the plastic is not fully plasticized, there will be unmelted particles inside the product, resulting in a rough surface and poor mechanical properties due to uneven internal structure.

Cooling temperature: Uneven cooling temperature can cause uneven shrinkage in various parts of the product, resulting in internal stress and affecting the dimensional stability of the product. This can easily lead to deformation, cracking, and other issues during subsequent use. If the cooling rate is too fast, it may cause a hard shell to form on the surface of the product, while the interior remains at a high temperature, resulting in high internal stress and reducing the toughness of the product.

pressure

Extrusion pressure: Appropriate extrusion pressure can better shape the plastic melt in the head and die, ensuring the dimensional accuracy and surface quality of the product. The pressure is too low, and the melt cannot fully fill the mold cavity, resulting in problems such as material shortage and insufficient size of the product; Excessive pressure may cause burrs in the product, increase the load on the equipment, and even lead to equipment damage.

Holding pressure: The pressure during the holding stage has a significant impact on the density and mechanical properties of the product. Insufficient holding pressure can cause pores and a decrease in density inside the product, resulting in a decrease in mechanical properties such as strength and stiffness; Excessive holding pressure may cause internal stress in the product due to excessive compression, affecting dimensional stability and appearance quality.

Screw speed

The impact on plasticization effect: Increasing the screw speed can enhance the shear effect on the plastic, making the plasticization of the plastic more uniform and complete. But if the speed is too high, it will cause excessive shear heat to the plastic, which may lead to plastic degradation and affect the performance of the product; Low rotational speed, low plasticization efficiency, insufficient plasticization of plastics, and difficulty in ensuring product quality.

The impact on the mechanical properties of products: Appropriate screw speed can help improve the mechanical properties of products. When the rotational speed is moderate, the orientation and crystal structure of plastic molecular chains are reasonable, and the tensile strength, impact strength, and other properties of the product are good. When the rotational speed is unreasonable, the orientation and crystallization of molecular chains are poor, which can reduce the mechanical properties of the product.

Extrusion speed

The relationship with the appearance of the product: If the extrusion speed is too fast, the flow rate of the melt at the die is uneven, which can easily cause the melt to rupture, resulting in defects such as roughness and cracks on the surface of the product. The extrusion speed is too slow, the production efficiency is low, and it may cause cold scars on the surface of the product, affecting the appearance quality.

The impact on the uniformity of product performance: A stable extrusion speed is beneficial for ensuring the uniformity of performance in various parts of the product. When the extrusion speed fluctuates, uneven thickness and density of the product may occur, resulting in differences in mechanical and thermal properties in different parts.

Mold structure

Mouth mold shape: The mouth mold shape determines the shape of the product, and different mouth mold shapes will cause different velocity and pressure distributions of the plastic melt during the flow process, thereby affecting the dimensional accuracy and surface quality of the product. If the flow channel design of the mouth mold is unreasonable, it may cause the melt flow rate to be too fast or too slow in some parts, resulting in deformation, warping and other problems of the product.

Mold roughness: The surface roughness of the mold is low, that is, the surface is smooth, the surface quality of the product is high, the demolding is easy, and defects such as scratches and strains are not easy to occur. If the surface roughness of the mold is too high, it will increase the friction between the melt and the mold, affect the flow of the melt, lead to a decrease in the surface quality of the product, and may also cause the product to adhere to the mold, making it difficult to demold.