Several Forming Methods of Vacuum Thermoforming

Last Updated on October 31, 2023 by assistant


As a professional vacuum thermoforming company, in addition to providing you with necessary thermoforming manufacturing services, it is necessary to popularize some knowledge about the vacuum forming process. In this article, we would like to take you to know several forming methods for vacuum thermoforming.

As a vacuum thermoforming process that is comparable to injection molding, it has many molding methods. In many cases, what we can see with the naked eye is that between blowing and sucking, the shell of a trolley case is ready. This is the magic of the vacuum blister process.


Vacuum blister is a kind of plastic thermoforming. Maybe you have never seen this process, but you have used the products made with it, such as trolley case shells, refrigerator linings, or the surfaces of various toys, etc. They are all processed using this process. The working principle is straightforward. First, fix the thermoplastic sheet on the mold, then rely on the heater to bake the sheet until it softens, and then use a vacuum pump to extract the air between the sheet and the mold quickly. In this way, the softened sheet is directly adsorbed on the surface of the mold, and the desired plastic product can be obtained after cooling and demolding.

On the other hand, the vacuum blister process is divided into two processes due to different product requirements, namely concave mold vacuum forming and male mold vacuum forming. Let’s take a closer look at the common processes of vacuum thermoforming.

Concave vacuum forming

Concave mold vacuum forming, also called single female mold vacuum forming, or concave vacuum forming, is one of the most common vacuum forming methods. Its processing principle is to fix the plate above the mold cavity, heat and soften it, and then suck it directly into the mold cavity. During this process, if the depth of the product is too large, the plastic sheet will be stretched too much, causing the bottom to be too thin. Therefore, concave mold vacuum thermoforming is mainly suitable for products with high appearance precision and low molding depth.

Concave vacuum forming image

Convex vacuum forming

Convex vacuum forming, also known as single positive mold vacuum forming, convex vacuum forming is to fix the plate above the mold, then controls the mold to lift and finally extracts the air between the plate and the mold to form. This is also the manufacturing process of trolley cases. It is suitable for thin-walled plastic parts with high inner surface precision and convex shapes. Products processed using this process have the advantages of low cost, easy processing, and high efficiency.

Convex vacuum forming-image

Concave and convex vacuum forming

The molding process of deep-cavity plastic parts is completed by sequentially evacuating the female mold and the male mold. This process is to heat the plate fixed above the mold to soften it, then remove the heater and blow compressed air through the mold to bulge the plastic sheet. The mold is then inserted down into the raised plastic sheet and a vacuum is used to suck the mold into it. During this process, compressed air is passed into the fixed mold in time, so that the plastic plate is pushed to the outer surface of the mold to form. With this molding method, the softened plastic sheet can be easily blown and stretched before molding, which is useful for molding plastic parts with deep cavities.


Blowing vacuum forming

Blow vacuum forming is also called air buffer vacuum forming. For some plastic parts that require more uniform wall thickness, the blow vacuum forming method is the best solution because it reduces the plastic sheet during the final forming process. Thickness remains even and level. The processing principle of blow-suction vacuum forming is to heat the fixed plate, and then blow compressed air into the sealed box to blow the plate out.


You can imagine this process like blowing up a balloon in a sealed space box. When the external atmospheric pressure comes into contact with the mold on the thin plate, the air is quickly extracted from the sealed box. At this time, the atmospheric pressure will act around the mold to form the plate part. In this process, the thickness of the plastic sheet changes. Reduce in advance to maintain uniform integrity of the molding process.

In conclusion

This article introduces several common processing techniques of vacuum thermoforming. In the previous article, we initially explained vacuum thermoforming. Vacuum molding combined with thermoforming molds is a popular molding method that is very suitable for large-size, small-volume manufacturing projects. Typically, vacuum thermoforming is cheaper and faster than the injection molding process, taking only about ten days to produce a high-quality sample.

At Ruitai, we have mature blister equipment that can help you produce vacuum-formed products. Whether it is thermoformed ABS or thermoformed manufacturing of other materials, we can provide you with processing services. If you need to manufacture plastic parts casings or process other metal parts, please feel free to contact us and upload your CAD files, and we will provide you with a free quotation service.