What are the reasons affecting the effect of Shanghai blow molding processing technology

The blow molding process is divided into injection pull blow molding process and extrusion blow molding process. Here, we mainly analyze the process of extrusion blow molding and the factors that affect the Shanghai blow molding process.

1. Selection of blow molding materials

The selection of raw materials is crucial in blow molding processing in Shanghai. Firstly, it is required that the performance of the raw materials meet the requirements for the use of the product, and secondly, the performance of the raw materials must comply with the requirements of the blow molding process. High density polyethylene has a melt index range of 0.94-0.96 grams per centimeter. Low melt index resin blow molding is beneficial in preventing the sagging of the billet and easily obtaining a uniform wall thickness of the billet. However, when the screw speed increases, the appearance of low melt index resin becomes rough. Therefore, for the selection of the above melt index range, large and medium-sized blow molded products should focus on preventing the sagging of the billet and should be slightly lower; The selection of small blow molded products is slightly higher.

2. Temperature control

The accuracy of temperature control during the extrusion process has a significant impact on the quality of the billet. For example, when the temperature is too low, the surface of the billet becomes rough, while when the temperature is high, the surface has good gloss but severe sagging. When extruding easily thermally degradable resins such as polyvinyl chloride, it is also important to control the temperature so that it does not exceed the degradation temperature.

3. The influence of screw speed on extruded pipe blanks

The screw speed is an important factor affecting the quality of the pipe blank. High extrusion speed can increase production and reduce billet sagging, but the surface quality of the billet decreases. Especially with an increase in shear rate, certain plastics, such as high-density polyethylene, may experience melt fracture. Moreover, when the rotational speed increases, a large amount of frictional heat is generated, which poses a risk of instantaneous degradation of plastics such as polyvinyl chloride. So a Shanghai blow molding machine uses larger extrusion equipment to keep the screw speed below 70 revolutions per minute.

4. The influence of die on extruded pipe blanks

The mouth mold is an important device that determines the size and shape of the billet, so it is required that the inner surface smoothness should reach 10 and the size should be processed according to the design requirements. The size of the mouth mold shaping section can generally be selected as 8 times the gap value between the mouth mold core rods.

It can be seen that in order to make good blow molding products, good material selection, temperature control of Shanghai blow molding processing machines, and selection of screws and mouth molds are very important.