Injection VS Blowing Mold

How much do you know about it?

The difference between injection mold and blow mold.

Do you know their respective production processes, differences in demand for raw materials, and uses? This is the best popular science article for those who have just entered the mold industry and who want to understand the mold industry.


The two processing technologies of mold products are injection molding and blow molding. They have their own characteristics. Simply put, the blow molding mold adopts the “injection + blowing” method, and the injection mold adopts the “injection + pressing” method. The plastic molding is hollow, the injection mold has a gate section, and the blow molding mold surface and air blowing port are uneven.


1. Injection mold

Injection molding, or thermoplastic injection molding, is a method of melting plastic material and injecting it into a film cavity. Once the molten plastic enters the mold, it is cooled and shaped into a cavity-like shape. The resulting shape is the final appearance of the finished product, and no further processing is required. Many details, such as bosses, ribs, threads, can be formed in a single injection molding operation. An injection molding machine has two basic components: the injection unit, which melts and feeds the plastic into the mold, and the clamping unit.


2. Blowing mold

Blow molding is a relatively fast-developing plastic processing method, also known as hollow blow molding. The tubular plastic parison obtained by extrusion or injection molding of thermoplastic resin is placed in a split mold while it is hot (or heated to a softened state), and compressed air is introduced into the parison immediately after closing the mold to blow the plastic parison. It expands and sticks closely to the inner wall of the mold, and after cooling and demoulding, various hollow products are obtained. The manufacturing process of blown film is very similar in principle to blow molding of hollow products, but it does not use a mold. From the perspective of plastic processing technology classification, the molding process of blown film is usually included in extrusion.

According to the method of making the parison, blow molding can be divided into extrusion blow molding and injection blow molding. The newly developed ones include multi-layer blow molding and stretch blow molding. With the birth of high-density polyethylene and the development of blow molding machines, blow molding technology has been widely used. The volume of hollow containers can reach thousands of liters, and some production has adopted computer control. Plastics suitable for blow molding include polyethylene, polyvinyl chloride, polypropylene, polyester, etc., and the obtained hollow containers are widely used as industrial packaging containers.

Plastic Blowing Mould

hollow blow molding


So what's the difference between them

Plastic Injection Mould

Thermoplastic Injection Molding

difference 1


Blow molding: Blow molding is to use gas pressure to inflate the hot parison closed in the mold into a hollow product, or the tube parison is blown into a tube film without a mold.

Injection molding: Injection molding is to melt the plastic material and then inject it into the film cavity for molding.

difference 2

raw materials

Blow molding: The raw materials for blow molding are usually polyethylene, polyvinyl chloride, polypropylene, polystyrene, thermoplastic polyester, polycarbonate, polyamide, cellulose acetate and polyacetal resin, etc. most.                                                                                                                                                                                           Injection molding: The raw materials for injection molding are usually thermoplastics or thermosets.

difference 3


Blow molding: Blow molding is widely used in bottles, cans, baby products, sporting goods and other industries.

Injection molding: Injection molding is widely used in mobile phones, laptops, various plastic casings, communications, micro-motors, computers, electrical appliances, electronics, toys, watches, lighting, locomotives and other industries.

In fact, the product representation of injection molds and blow molds is the main difference. Products made by the injection molding process are usually thicker, relatively simple to manufacture, and require relatively low raw materials. The blow molding process is different, and the products are thin and transparent. Because of this, there are certain requirements for the toughness and tensile properties of raw materials, and the processing requirements of blow molding molds are relatively high.

Injection molds and blow molds are widely used in daily life, and both have their own advantages and characteristics, and the development prospects are good.

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