Thermoforming
Thermoforming is a manufacturing technique that involves taking a sheet of plastic, heating it to soften it, and then shaping it under vacuum using a mould to give it the desired shape. The material hardens as it cools and retains the shape of the mould.
Thermoforming is most commonly used for the production of small or medium-sized batches or for the creation of prototypes. At Soudoplast, we have chosen a modern machine capable of producing parts up to 1 metre by 1 metre.
Step-by-step guide
- Step 1: Heating the plastic to make it malleable
- Step 2: The mould rises to shape the material against it
- Step 3: A vacuum mechanism presses the plastic against the mould and removes all air bubbles
- Step 4: Cooling
- Step 5: Removing the part from the mould
The benefits of thermoforming
One of the advantages of thermoforming is the low cost of tooling compared to other plastic processing techniques such as rotational moulding or injection moulding.
Thermoforming allows parts with relatively complex or repetitive shapes to be produced in a short time. Only the manufacture of the mould requires particular attention to achieve the desired design.
A very wide range of materials is available for thermoforming, which allows for great creativity in terms of product strength or colour (including transparent).
Examples of bespoke projects by Soudoplast
Thermoforming is used in a wide range of applications across many sectors, including the automotive industry, general manufacturing, aerospace, cosmetics, healthcare, transport, packaging and even interior design.
FAQ
What are the suitable starting thicknesses for plastic sheets used in thermoforming?
Thermoforming allows for a very wide range of thicknesses, from thin films (0.5 mm) to thick sheets (often up to 8 or 10 mm depending on the material). Please note: When the material is vacuum-formed onto the mould, it stretches. The final thickness of the part will therefore not be entirely uniform, particularly in deep corners. Our technicians will advise you from the design stage onwards to anticipate these variations.
What types of plastics (polymers) can be thermoformed?
Virtually all thermoplastics are suitable. The most common are HDPE (highly impact-resistant), PP (excellent chemical resistance), ABS (attractive appearance, ideal for casings), PS, as well as PC (polycarbonate) and PMMA for transparent parts. The choice will depend on the requirements of your specifications: UV resistance, fire/smoke standards (aerospace/railway) or food contact suitability.
Do you carry out finishing and welding operations after demoulding?
Exactly. A raw thermoformed part almost always requires trimming to remove excess material and cut out the necessary openings. As specialists in plastic processing and welding, we can then assemble these parts using welding techniques (hot air, extrusion, mirror welding) or integrate inserts into them to deliver a ready-to-use sub-assembly.
What is the difference between ‘positive mould’ and ‘negative mould’ thermoforming?
The choice of mould depends on which side of the part requires the greatest precision:
- Positive mould (raised): The plastic is drawn over the mould. The inner surface of your part will perfectly match the dimensions of the mould.
- Negative mould (recessed): The plastic is drawn into the mould. It is the outer surface of the part that will have the most precise geometry and surface finish.
What is the average lead time for producing the mould and the first parts?
This is one of the key strengths of thermoforming: responsiveness. The moulds (often made of MDF or PMMA for prototypes, or aluminium for production runs) are much simpler and quicker to machine than steel injection moulds. Depending on the complexity of the part, it generally takes between 3 and 6 weeks at Soudoplast to design the tooling and validate the first prototype parts.