What Is the Difference Between Injection Molds and Blow Molds?

Injection molding and blow molding are two processing techniques for mold products, but their processing techniques have differences and unique characteristics. Simply put, injection molds use the "injection + pressure" mode, while blow molds use the "injection + blow" mode, and injection molds are solid-core, while blow molds are hollow-core.

In addition, molds made with injection molding have a gate section, while molds made with blow molding have uneven surfaces and air vents. Below, we will take you to a detailed understanding of what injection molds are and what blow molds are, and where the differences lie between the two.

What are injection molds and blow molds?

Injection molding is the method of injecting thermoplastic plastics for molding. This method melts the plastic material and injects it into the mold cavity. Once the melted plastic enters the mold, it will be cold-formed and processed into the desired shape, and its shape is often the final product shape, without further processing.

Injection molding offers a highly efficient process for molding thermoplastic plastics, wherein the molten plastic is injected into a mold cavity. This method allows for the cold forming of protomold plastics into the desired shape, typically resulting in the final product shape without the need for additional processing.

Moreover, injection molding can control details well, such as protrusions, ribs, threads, and other parts that can be formed in the injection molding step.

Blow molding, also called hollow blow molding, is a rapidly developing plastic processing method. Its processing principle is to place a heated and softened thermoplastic resin or an injection-molded tubular plastic blank in the mold, and then inject compressed air after the mold is closed, so that the plastic blank is blown and adhered to the inner wall of the mold, then cooled and ejected to obtain the desired hollow product.

It is worth mentioning that the manufacturing process of blow film is similar in principle to that of hollow products, but its production does not use molds, which is completely different from injection molding molds. From the perspective of plastic processing technology classification, the molding process of blow film is usually classified into the extrusion process. According to the method of making blanks, blow molding can be divided into extrusion blow molding and injection blow molding, and newly developed ones include multi-layer blow molding and stretch blow molding.

The difference between blow molding and injection molds

Through the above introduction, I believe everyone has a certain understanding of these two processing techniques. In fact, the main difference between injection molds and blow molds lies in the form of the product. Products made by injection molding processes are usually thicker, relatively easy to manufacture, and have low raw material requirements.

The blow molding process is different. The products produced are thinner and transparent. Any slight flaws are easily noticed. It is precisely because of this that the processing requirements for blow molds are higher and certain requirements are placed on the toughness and elongation of the raw materials.

Injection molds and blow molds are widely used in daily life and each has its own characteristics and advantages. Their processing techniques are also improving year by year, and they have a good development prospect in the future.

With their distinct characteristics and advantages, injection molds and blow molds have become indispensable in various aspects of daily life. As their processing techniques continue to evolve and improve, these molding methods hold promising development prospects for the future, providing practical prototype solutions for a wide range of industries and applications.