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Thermoforming Plastic Manufacturing, Explained


What is thermoforming, and why is it one of the most versatile and cost-effective methods for manufacturing plastic products?

In this article, we break down the fundamentals of thermoforming, explore some common thermoformed products, and explain a prototypical thermoforming manufacturing process.

What Is Thermoforming Plastic?

Thermoforming plastic refers to a specific manufacturing process that employs heat to increase pliability, allowing a plastic sheet to be molded into a desired shape. The sheet is forced onto a mold (typically aluminum) using force applied directly (using a mechanical “plug”) or using a vacuum or pressure. The plastic will harden and retain its molded shape after it cools, allowing this molded plastic part to be trimmed into a finished product.

As the variety of materials, products, and manufacturing approaches explained below illustrate, thermoforming is a highly versatile process that has proven to be a cost-effective solution across an incredibly broad (and still growing) range of applications.

Common Thermoforming Plastics

A variety of common thermoplastics are compatible with thermoforming, allowing this process to be flexibly employed for a number of different products by using different materials to achieve the desired characteristics.

Leading examples include:

  • ABS (acrylonitrile butadiene styrene): known for high heat resistance.
  • PET (polyethylene terephthalate): durable with strong resistance to chemicals and excellent recyclability.
  • PETG (polyethylene terephthalate – glycol): the addition of glycol provides added flexibility compared to PET.
  • Polystyrene: insulating and impact-resistant, polystyrene is relatively difficult to recycle.
  • Polycarbonate: offering transparency with UV resistance, polycarbonate is sensitive to certain chemicals.
  • PP (Polypropylene): a versatile choice that offers chemical resistance, fatigue resistance, and desirable thermal properties.

Common Thermoforming Products

Thermoforming is commonly used to manufacture products for industries ranging from aerospace, to medical equipment, to consumer goods. It can be used to make both durable parts for long-term use (like automotive, aircraft, and equipment components) and disposable and/or recyclable products (like pharmaceutical and food packaging).

Common thermoformed plastic products include:

  • Enclosures for medical devices, kiosks, point of sale solutions, ATMs, and other equipment solutions.
  • Food packaging, trays, and other food handling products.
  • Automotive, aerospace, and rail interior parts.
  • Components for common household items and appliances, including refrigerator trays/liners, bathtub/shower enclosures, and casings for exercise/fitness equipment.
  • Casings and enclosures for agricultural equipment.
  • Shipping trays, packaging inserts, and other material handling applications.

How the Thermoforming Process Works

The thermoforming process begins with a sheet of extruded plastic, which can be produced from resin pellets in-house using an extrusion facility or purchased from a supplier. 

  1. Thermoforming relies on a specialized plastic manufacturing machine called a thermoforming machine. This machine is used to achieve the requisite temperature and apply the force needed to stretch the heated, pliable sheet over a mold.
  2. A variety of mold designs are used to create the desired shape and features. Depending on the application and intended production volume, molds may be machined, hand-crafted, or even 3D printed. Metal molds are the most common choice for high-volume production. Other key design considerations include part complexity, thermal resistance, and tolerance to molding forces.
  3. Thermoforming can employ virgin plastic material or a combination of virgin and recycled plastic material. These sheets are fed via conveyor chains into a thermoforming machine to begin the process.
  4. The thermoforming machine heats the plastic material and applies force to the sheet and/or mold using a variety of different mechanisms outlined below.
  5. The mold is cooled prior to trimming and cutting.
  6. Some thermoforming machines have integrated trimming and cutting capabilities, while other manufacturing processes accomplish this work by hand. Leftover plastic from trimming can be collected for recycling.
  7. The product proceeds to any final steps such as labeling and assembly.

Please see our article here for a deeper exploration of the thermoformed plastic packaging manufacturing process, including a behind-the-scenes look at new packaging ideation, prototyping, tooling, and production.

Types of Thermoforming Processes

While this high-level process remains the same, thermoforming machines rely on a number of different mechanisms to form the heated plastic. For example:

    • Mechanical forming uses direct force applied by a plug to the sheet.
    • Vacuum forming employs a vacuum to force the heated plastic sheet against the mold.
  • Pressure forming is similar to vacuum forming, but employs added pressure during the cooling stage to help improve retention of the molded shape.
    • Drape forming is a simplified, low-cost approach that drapes the heated sheet over a mandrel to create a simple shape.
  • Matched mold forming employs matching male and female molds which are forced together for added precision.
    • Twin sheet forming involves pressing two sheets together during the molding process to create a double wall or hollow structure.
  • Billow forming is a unique approach that employs air jets in lieu of a physical mold. 

Pros and Cons of Thermoformed Plastic

Thermoformed plastic components are lighter weight than metal alternatives while providing a much lower cost than injection molded parts of the same size and geometry. The ability to use different grades of plastic makes it easy to match components to the optimal mix of cost, strength, durability, and other desired characteristics. 

The thermoforming process is highly scalable and can be a cost-effective option for both small production runs and high-volume production. Thermoforming equipment is available at an industrial scale, in small desktop models for prototyping and other small projects, and even in affordable formats for home DIY projects.

The most important limitation of thermoforming is its restriction to a relatively thin wall thickness, due to the need for a thin enough sheet of plastic to be stretched. 

Thermoformed Food Packaging Advantages

Thermoforming is a leading manufacturing process for food packaging because it can deliver on some of the most important priorities for food products.

  • A proven food-safe material. 
  • Reduced weight to minimize transportation and handling costs.
  • Cost-effective customizability to fulfill unique branding and design needs.
  • Outstanding transparency to highlight the appearance and quality of the food product inside and maximize shelf appeal.
  • The ability to use thermoformed structures to create features like tamper- and leak-resistant seals that allow containers to be used for a wide variety of foods: hot and cold, dry and wet, microwaveable and ready-to-eat.
  • Properties that allow for enhanced shelf life. You can learn more about plastic packaging for food and the science of shelf life here.

Thermoformed Plastic Sustainability

Mixing post-consumer regrind (PCR) plastic with virgin plastics offers a flexible solution for mitigating the environmental impact of thermoformed plastic products and helping organizations drive ESG progress. Because PCR plastics can be mixed in at a wide range of blend percentages, manufacturers have the freedom to hit their sustainability targets without sacrificing the appearance and performance of their product or packaging

We take a deeper look at recyclable plastics in the context of food containers in our article here.

Learn More About Thermoformed Plastic Food Packaging

With their durability, light weight, and recyclability, thermoformed plastics are a strong choice for food packaging.

The key to selecting the right packaging for your food products? Ensuring that packaging design is carefully aligned with your sustainability, functional, and branding requirements. 

Lacerta is here to help.

Ready to begin designing your custom plastic packaging solution? Get started here.

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