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Interpretation of blow molding process knowledge

May 5, 2023

1. Injection stretch blow molding

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Injection stretch blow molding technology is currently more widely used than injection blow molding. This blow molding method is actually injection blow molding, but the axial stretch is increased, which makes blow molding easier and reduces energy consumption. Injection stretch blowing can process a larger volume of products than injection blowing, and the volume of the blown container is 0.2~20L. The working process is as follows:

① Inject the parison first, the principle is the same as ordinary injection molding.

② Transfer the parison to the heating and temperature adjustment process to make the parison soft.

③ Go to the pull-blow station and close the mold. The push rod in the core stretches the parison axially, and at the same time blows air to make the parison stick to the mold wall and cool down.

④ Go to the de-molding station to pick up the parts.

In addition, extrusion stretch blow molding is also very commonly used, even more widely used than injection stretch blow molding. Unlike injection stretch blow molding, the molded parison is formed by extrusion, with residual material and flash, and no injection stretch blow molding. Blowing precision is high.

Whether it is injection blow molding, injection stretch blow molding, or extrusion blow molding, it is divided into one-time molding and two-time molding processes. The one-time molding method has a high degree of automation. The clamping and indexing system of the parison requires high precision and low equipment cost. high. Generally, most manufacturers use the double molding method, that is, the parison is first formed by injection molding or extrusion, and then the parison is put into another machine (injection blow machine or injection stretch blow machine) to blow out the finished product, and the production efficiency is high.


2. Extrusion blow molding

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Extrusion blow molding is the most widely used plastic blowing method in blow molding. It can process a wide range of products, from small products to large containers and auto parts, aerospace chemical products, etc. The processing process is as follows:

① First melt and knead the rubber material, and the melt enters the machine head to become a pipe condition parison.

② After the parison reaches the predetermined length, the blow mold is closed and the parison is sandwiched between the two halves of the mold.

③Blowing air, blowing air into the parison, inflating the parison, and then forming it close to the mold cavity.

④ cooling products.

⑤ Open the mold and take away the chilled product.


3. Injection blow molding:

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Injection blow molding is a molding method that combines the characteristics of injection molding and blow molding. At present, it is mainly used in beverage bottles and medicine bottles that require high-blowing precision, as well as some small structural parts.

① At the injection molding station, the parison is injected first, and the processing method is the same as that of ordinary injection molding.

② After the injection mold is opened, the mandrel together with the parison moves to the blow molding station.

③ The mandrel places the parison between the blow molds and closes the molds. Then, compressed air is blown into the parison through the middle of the mandrel, inflated to make it close to the mold wall, and allowed to cool.

④ The mold is opened, and the mandrel is transferred to the de-molding station. After the blow molding is taken out, the mandrel is transferred to the injection station for circulation.


Injection blow molding has the following advantages and disadvantages:

Advantages: The strength of the product is relatively high and the precision is high. There is no seam formed on the container, and no trimming is required. The transparency and surface finish of the blow-molded parts is better. It is mainly used in hard plastic containers and wide-mouth containers.

Disadvantages: The equipment cost of the machine is very high, and the energy consumption is large. Generally, only containers with relatively small volumes (below 500ml) can be formed, and containers with complex shapes cannot be formed, and it is difficult to form oval products.