How is thermoforming done?

Thermoforming is a manufacturing process used in various industries to create plastic products.

We are Walterpack, a company specializing in decorative and industrial plastic manufacturing, and today we want to explain this technique in detail. Keep reading!

Definition and Basic Principles of Thermoforming

Thermoforming is a manufacturing process in which a plastic sheet is heated until it becomes malleable and conforms to the shape of a specific mold. This method allows the production of a wide variety of products, ranging from disposable packaging to industrial components.
During the process, the heated plastic is shaped by applying pressure or vacuum, and once it cools down, it retains the mold’s shape.

The basic principles of this procedure are heat control to heat the plastic sheet to the appropriate temperature, use of pressure or vacuum to mold the material, and uniform cooling to ensure the thermoformed plastic maintains its shape.

Materials Used in Thermoforming

The choice of material determines the final properties of the product. Here, we detail the most common types of plastics for this process.

Common Types of Plastics in Thermoforming

• Polypropylene (PP): a lightweight material with good chemical resistance. Used for products requiring durability and impact resistance, such as packaging, trays, and automotive components.
• Polystyrene (PS): features rigidity and malleability. Employed in the manufacture of disposable packaging, food trays, and electronic products due to its ability to mold into detailed shapes and its low cost.
• Polyethylene Terephthalate (PET): a clear, strong, and recyclable material, perfect for transparent applications. Found in bottles, food packaging, and medical products.
• Low-Density Polyethylene (LDPE): flexible and moisture-resistant, making it suitable for applications like bags, plastic sheets, and coatings. Easily moldable and relatively low-cost.
• High-Density Polyethylene (HDPE): more rigid and durable than LDPE, suitable for products requiring greater durability, such as containers, caps, and toys. Widely used in industrial applications for its chemical resistance.
• Polyvinyl Chloride (PVC): a versatile material used in numerous applications, such as medical products and construction components. Can be formulated in various degrees of rigidity and flexibility.
• Acrylonitrile Butadiene Styrene (ABS): impact-resistant and with good dimensional stability. Used in the manufacture of electronic housings, automotive parts, and toys due to its durability.
• Polycarbonate (PC): a strong and transparent plastic with optical clarity. Common in the manufacture of lenses, optical discs, and safety components.

Thermoforming Process

The thermoforming process is divided into a series of sequential stages that transform a plastic sheet into a finished product.

1. Material Preparation: the plastic sheet is cut to the appropriate size and prepared for heating. This preparation includes cleaning to ensure there are no contaminants.
2. Heating: the sheet is heated using ovens or infrared heaters until it reaches the thermoforming temperature. The heating time and temperature vary depending on the type of material and the thickness of the sheet.
3. Forming: the heated sheet is placed over the mold inside the thermoformer. Depending on the type of mold and equipment, pressure or vacuum can be applied to shape the plastic to the mold. In the vacuum method, air is sucked out between the sheet and the mold. In the pressure method, compressed air is used to push the sheet against the mold.
4. Cooling: the formed piece is allowed to cool to maintain its shape. The cooling must be uniform to avoid deformations and internal stresses in the piece.
5. Demolding: once cooled, the piece is removed from the mold and inspected for quality. This step includes trimming edges and removing burrs if necessary.
6. Finishing: some pieces require additional operations such as trimming, drilling, or assembly to complete the final product.

Types of Thermoformed Products

Thermoforming allows the manufacturing of a wide range of products, such as:

• Food and Beverage Packaging: containers for prepared meals, trays for meat and fruit, packaging for dairy products and beverages.
• Blister and Pharmaceutical Packaging: protective packaging for medications to ensure their integrity.
• Automotive Components: door panels, instrument panels, roof linings.
• Appliance Parts: parts for refrigerators, washing machines, and other appliances.
• Consumer Goods: toys, molded parts, presentation packaging.
• Construction Applications: wall coverings, ceilings, floors, control panels.

Benefits of Thermoforming

This manufacturing method offers numerous benefits that make it a great option:

• Cost Efficiency: a more economical technique compared to other molding methods due to better tooling and mold costs.
• Production Speed: allows rapid production of large volumes of parts.
• Design Flexibility: designs with detailed features can be easily created.
• Versatility: suitable for a wide variety of materials.
• Waste Reduction: leftover material can be recycled and reused.

Take advantage of the potential of thermoforming in your projects. Contact Walterpack and discover how we can help you create exceptional products.

Frequently Asked Questions about Thermoforming

You have now learned about the thermoforming process, its applications, and the materials used. Now, let’s answer some of the most common questions about this technique.

What is the difference between thermoforming and thermoconforming?

Both terms are used to refer to the same process, but technically there is a difference. Thermoforming refers to the process of heating a plastic sheet and forming a piece using a mold, while thermoconforming involves a similar technique but may include additional processes such as the use of positive or negative pressure to shape the material.
However, in practice, both words are used to describe the same plastic forming process.

What are the most recommended materials for thermoforming?

The most recommended materials for thermoforming are polystyrene (PS) and polyethylene terephthalate (PET).
PS is ideal for its rigidity and ease of forming, making it perfect for disposable packaging and electronic products. PET, on the other hand, is commonly used for transparent and recyclable packaging, such as bottles and food containers, due to its clear properties.

Which industries use thermoforming the most?

The industries that use this technique the most are:

• Food Industry: for the production of packaging and trays.
• Medical Industry: for manufacturing blisters and medical device packaging.
• Automotive Industry: for the production of interior and exterior vehicle components.
• Electronics Industry: for producing housings and components.
• Toy Industry: for creating toys and related parts.

What are the limitations of thermoforming?

Although thermoforming offers numerous benefits, it also has certain limitations. Very complex parts are difficult to manufacture due to process restrictions. Additionally, the thickness of plastic sheets is limited, affecting the strength and durability of some final products.
In terms of precision, it is less accurate than other molding methods, such as injection molding. Finally, some high-quality materials used in this method are very expensive, which increases the total production cost.