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Extrusion blow molding process principle, advantages and influencing factors

February 26,2022

With the gradual maturity of modern blow molding technology, plastic products have appeared in various industries and are widely used by everyone. Today, I will take you to understand how the plastic molding process is made. Here we focus on extrusion blow molding. Molding process, not much nonsense, look down!

The principle of extrusion blow molding process

To put it simply, a semi-molten tubular preform is obtained by extrusion, compressed air is injected into the pipe preform to expand it, close to the inner wall of the mold cavity, and then cooled and demolded. Obtain various hollow products. The whole process is divided into two parts: the manufacture of plastic preforms and blow molding. Daily containers such as bottles, pots and barrels of different calibers and capacities are obtained by extrusion blow molding.

Second, the advantages of extrusion blow molding process

1. In the blow molding process, the parison is formed by the die and inflated under a relatively low pressure, which determines that the blow molding product has less residues and has high strain resistance such as stretching, bending, and impact. Better service life.
2. The raw material (PE) used in the extrusion blow molding machine has excellent low temperature resistance, good chemical stability, and good crack resistance.
3. The molding equipment is simple and easy to operate, and the choice of raw materials is more extensive.
4. After the parison flows out through the extruder head, it directly enters the blow mold for molding without secondary heating, and the production efficiency is high.
3. Factors affecting extrusion blow molding process
1. Screw speed. It is another important factor that affects the extrusion blow molding parison. The extrusion speed determines the quality of the product and reduces the surface sagging of the parison.
2. Temperature control. The extrusion temperature depends on the nature of the resin. Too low a temperature will cause the surface of the parison to be rough, and too high a temperature will result in uneven wall thickness of the parison.
3. Die size and quality. The size of the die determines the size of the preform, so the inner surface of the die is required to be smooth, which is conducive to obtaining a smooth preform on the surface of the product.
4. Selection of raw materials. It is very important in the blow molding process. Generally, HDPE is selected according to its fluidity characteristics.
It can prevent the parison from sagging and the wall thickness is uniform, which is particularly important for the production of large hollow blow molded products.