High Pressure in Vacuum Forming: Precision, Strength and New Possibilities

By combining vacuum with compressed air, we can press the thermoplastic more tightly against the tool – and deliver sharp details, uniform material thickness and cost-effective production in medium and large series.

Portrait of Espen Johansen, project engineer at Plexx AS.

Espen Johansen
Project Engineer Plexx

A red, molded plastic cover with intricate lines and geometric details, made using the High Pressure method.

What is High Pressure Vacuum Forming?

Traditional vacuum forming works by stretching a heated plastic sheet over a mold, and vacuum sucks the plastic down into the details. In high-pressure vacuum forming, compressed air is also used from above to reinforce the forming. This provides a much more even pressure distribution and makes it possible to reproduce small details, steep angles and thin walls with far greater accuracy than with vacuum alone.

Typical working pressure is 2–6 bar – significantly lower than with injection molding, but more than enough to complement the suction power of the vacuum.

A yellow plastic cover showing sharp corners and precise edges after high-pressure molding.

SHARP DETAILS SHAPED WITH HIGH PRESSURE

Diagram showing the principle of vacuum forming with a plate.

SELECTED THERMOPLASTIC IS PLACED IN THE VACUUM TOOL

Illustration of heating in a vacuum forming machine.

HEAT IS ADDED FROM ABOVE AND BELOW TO MAKE THE PRODUCT FORMABLE

Diagram of high pressure vacuum forming against a mold.

VACUUM IS CREATED BY SUCTION FROM BELOW WHILE COMPRESSED AIR IS SUPPLIED FROM THE TOP

Diagram showing the high pressure process in vacuum forming.

THE RESULT IS A SHAPE WITH CLEAR AND SHARP DETAILS

Advantages of high pressure in vacuum forming

High Pressure has a number of advantages compared to other production methods. Here are some of the most important:

Higher detail reproduction

The combination of vacuum and compressed air provides better pressing into the mold cavity.

Less deformation

Even pressure produces more uniform wall thickness, especially in deep shapes.

Better edge definition

Steep corners and lines are formed more clearly with overprinting.

Faster forming

The process is faster because the compressed air helps the plastic to set faster.

Reduced tension in the material

More controlled forming gives better mechanical properties in the final product.

Close-up of a gray industrial plastic cover with defined grooves and sharp radii.

SHARP DETAILS SHAPED WITH HIGH PRESSURE

Areas of application

Medical technology: Enclosures and covers for equipment with precision requirements.

Electronics: Shells and components for displays, panels and instruments.

Transportation: Interior panels, covers and seat components.

Agriculture and industry: Protective screens, boxes, tubs and containers.

Packaging: Molded packaging with high fit and stability.

A light blue cover for cars or electronics, formed with High Pressure Vacuum Forming.

Blue vacuum formed cover for medical equipment.

A large, yellow plastic panel with a complex, functional geometry prepared for post-processing.

Questions and answers

The precision is significantly higher than with standard vacuum forming, but somewhat lower than with injection molding. Typical shape tolerance is ±0.5 mm, depending on material type, geometry and post-processing.
Yes. It is common to combine the process with CNC milling for high precision in holes and edges, and it can be integrated into a value chain with bonding, assembly and surface treatment such as painting, printing or foiling.
The design has a big impact. Undercuts, very deep shapes or sharp corners can be challenging. The design should be adapted to the method — with even radii and uniform material thickness — for best results.
Complex geometries with undercuts, as well as the production of extremely small parts or thin walls with high loads, are better suited to injection molding or other techniques.
After the design and material selection are finalized, it often takes 3–6 weeks to manufacture tools and initiate first production — significantly faster than many other forming techniques.
Yes, as long as the plastic has good thermoplastic behavior and consistency. Many PP and PET varieties work well.
ABS provides good impact resistance and processability, while polycarbonate provides high heat resistance and strength. The choice of material affects strength, flexibility, UV resistance and chemical resistance — and must be adapted to the application.

Sustainable benefits

High-pressure vacuum forming not only stands out through precision and flexibility – it is also a production method with several sustainable advantages. Thermoplastic materials can be recycled, which reduces both waste and the need for new raw materials. The process requires less energy than, for example, injection molding, and thus has a lower carbon footprint.

High material utilization and the ability to produce on demand results in less waste and overproduction, making the method a good choice for companies looking to combine technical performance with environmental responsibility.

Would you like to know more about high pressure vacuum forming?

We help you from concept to series production — with vacuum forming, ORS reinforcement and integrated fastening solutions.