Several modern conveniences that we enjoy every day are made possible thanks to vacuum forming. Without this versatile manufacturing process, life-saving medical devices, food packaging, and automobiles might look very different.
Read on to learn how the low cost and efficiency of vacuum forming make it a great option for commercial manufacturers, independent craftsmen, and DIYers alike.
What Is Vacuum Forming?
Vacuum forming is a manufacturing method used to shape plastic materials. During the process, a sheet of plastic is heated and then pulled around a single mold using suction.
Vacuum forming is used for a wide range of manufacturing applications, ranging from small custom parts produced on desktop devices to large parts manufactured on automated industrial machinery.
What are the Differences Between Vacuum Forming, Thermoforming, and Pressure Forming?
Thermoforming is a manufacturing process where a sheet of plastic is heated to become pliable, then shaped or contoured using a mold, and trimmed to create a final part or product. Vacuum forming and pressure forming are both different types of thermoforming processes. The main difference between pressure forming and vacuum forming is the number of molds that are used.
simplest type of plastic thermoforming, that uses one mold and vacuum pressure to obtain the desired part geometry. It is ideal for parts that only need to be precisely formed on one side, such as contoured packaging for food or electronics.
There are two basic types of molds—male or positive (which are convex) and female or negative, which are concave. With male molds, the sheet of plastic is placed over the mold to contour the inside dimensions of the plastic part. With female molds, the thermoplastic sheet is placed inside the mold to form the outer dimensions of the part precisely.
In pressure forming, a heated sheet of plastic is pressed (hence the name) between two molds instead of being pulled into place around a single mold using suction. Pressure forming is ideal for manufacturing plastic parts or pieces that need to be more precisely shaped on both sides and/or require a deeper draw (they need to extend farther/deeper into a mold), such as appliance casings that need to look aesthetically pleasing on the exterior and snap into place or fit a precise size on the interior side.
How Does Vacuum Forming Work?
The step-by-step process works as follows:
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Clamp: A sheet of plastic is placed in an open frame and clamped into place.
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Heat: The plastic sheet is softened using a heat source until it reaches the appropriate forming temperature and becomes pliable.
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Vacuum: The framework containing the heated, pliable sheet of plastic is lowered over a mold and pulled into place via a vacuum on the other side of the mold. Female (or convex) molds need to have tiny holes drilled into crevices so that the vacuum can effectively pull the thermoplastic sheet into the appropriate form.
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Cool: Once the plastic has been formed around/into the mold, it needs to cool. For larger pieces, fans and/or cool mist are sometimes used to speed up this step in the production cycle.
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Release: After the plastic has cooled, it can be removed from the mold and released from the framework.
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Trim: The completed part will need to be cut out of the excess material, and edges may need to be trimmed, sanded, or smoothed.
Vacuum forming is a relatively quick process with the heating and vacuuming steps typically taking only a few minutes. However, depending on the size and intricacy of the parts being manufactured, cooling, trimming, and creating molds can take considerably longer.
The Pros and Cons of Vacuum Forming
Many manufacturers, designers, and other professionals choose vacuum forming because it offers a blend of design flexibility at a relatively low cost compared to other manufacturing methods. The benefits of vacuum forming include:
Affordability
Particularly for smaller production runs (250-300 units per year), Thermoforming Products are typically more affordable than other manufacturing methods, such as plastic injection molding. The affordability of vacuum forming is largely due to the lower cost for tooling and prototyping. Depending on the surface area of the parts being manufactured and the dimensions of the clamp frame, tooling for injection molding can cost two to three times more than the amount for tooling for plastic thermoforming or vacuum forming.
