The Thermoforming Plastic Packaging Process, 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.  From there, we take a step-by-step look at thermoformed packaging design using Lacerta’s packaging development process.

What Is Thermoforming?

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.

Pros and Cons of Plastic Thermoforming

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.

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 and consumer goods. It can be used to make both durable parts for long-term use (such as automotive, aircraft, and equipment components) and disposable or recyclable products (such as 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.

Thermoforming Process Fundamentals

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.

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. 

Billow Forming

Instead of a mold, air jets inflate the plastic into a bubble before it’s shaped. This technique is used for large, symmetrical parts with minimal detail

Drape Forming

A cost-effective option that drapes the softened plastic over a mandrel, it is best suited for simple, curved shapes without high detail.

Matched Mold Forming

This process uses male and female molds pressed together to form the plastic. It allows for higher precision and tighter tolerances.

Mechanical Forming

This method uses a plug or mechanical force to push the heated plastic sheet into the mold. It is often combined with other forming methods for added precision.

Pressure Forming

Similar to vacuum forming but with added air pressure, this method improves detail and definition, especially for complex or textured surfaces.

Twin Sheet Forming

Two heated sheets are pressed together in a mold to form a hollow or double-walled structure. This process is ideal for strong, lightweight components.

Vacuum Forming

A vacuum pulls the heated plastic tightly against the mold to create the desired shape. This simple, widely used process is ideal for shallow or lightweight parts.

Thermoformed Plastic Food Packaging

In the food industry, thermoformed packaging stands out for its ability to balance safety, cost, and presentation. This section explores why it’s so widely used and how thoughtful design can bring different packaging concepts to life.

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.

1. A proven food-safe material. 
2. Reduced weight to minimize transportation and handling costs.
3. Cost-effective design and easy customizability to fulfill unique branding needs.
4. Outstanding transparency to highlight the appearance and quality of the food product inside and maximize shelf appeal.
5. 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.
6. 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.

How Is Thermoformed Food Packaging Designed?

The thermoforming design process must align material selection, product function, visual appeal, and production efficiency, all while meeting the unique demands of food products.

The example below, drawn from Lacerta’s custom packaging workflow, offers a detailed look at how these considerations take shape from concept to final product.

1. Ideation

We begin with assessing needs and identifying problems. Do you need a leak-resistant package for a delivery service? Are you seeking a salad container that extends food shelf life? Are you looking for packaging for an innovative new food product line? Our expert design team leverage the latest trends and insights to design a package aligned with product goals.

Next, we dive into how this product compares to similar products on the market. We conduct competitive research on packaging solutions to identify ways to help you stand out on the shelf. From there, we discuss our stock and custom options to determine the optimal choice. Working alongside our packaging experts, we brainstorm concepts and create designs backed by extensive research and experience.

By the end of this step, our customers receive concept drawings from our in-house design team for review like the one below.

Sample concept art for our single-serve cupcake container.

2. Concept Review

In addition to the concept drawings, Lacerta includes realistic renderings to showcase the packaging’s appearance. At this stage, customers also provide feedback and refine their thermoformed packaging options, including color, material, thickness, barrier, and coating.

Before moving forward, we give our clients ample time to review our proposed designs and provide feedback to ensure the end product meets expectations. We use SolidWorks — a 3D CAD design software — to streamline review communications, provide an easy-to-understand visualization of the stock or custom packaging solution, and approve new versions.

3. Prototyping

This is where designs are put to the test. 

Our prototyping team provides samples in chosen material options, including recyclable PET, PP, or PCR content. We evaluate features such as snap, lid integrity, film seal, and tamper resistance to ensure they are up to standard. Next, we test the material stressors along with product-package interaction to make necessary changes based on your feedback for production approval.

During this step, we also conduct a life cycle assessment to determine the sustainability attributes of the package. This is especially helpful to our customers who are considering ways to lower their carbon footprint. A life cycle assessment can quantify the impact of the selected packaging, as well as opportunities to further reduce its carbon impact, such as switching to sustainable packaging that uses recycled PET.

4. Tool Design

Next, we move from prototype to production. Each mold is evaluated and measured against the product before its release. If any issues arise, our engineering and manufacturing teams will address them before testing and measuring the molds again.

We then meet to collaborate on the optimal run times. Based on the package, our tools can incorporate gun drilling, cooling, robotics, and stacking into the production process.

Once the manufacturing team determines the details of the production runs, we’re ready to start making your packaging!

Our CNC high water pressure aluminum mold cutting machines.

5. Production and Release

We produce thermoformed plastic products at one of three locations nationwide on our fleet of thermoforming machines. Once the molds are inserted into place, the heating process begins.

As we noted above, the plastic is heated until it becomes pliable, and then it’s formed into shape using vacuum, pressure, and mechanical forces.

Once the plastic cools and hardens, the excess plastic around the edges is trimmed. The packaging then undergoes rigorous inspection checks during both trial and product runs, which ensures quality and adherence to customer specifications.

From here, your packaging may be labeled or assembled. As an end-to-end manufacturer, our expert design team can create and print custom graphics on lidding solutions — including colors and patterns — that are sure to catch consumers’ eyes.

Frequently Asked Questions on the Thermoformed Packaging Process

What Materials Are Used in Thermoforming? 

Common materials include PET, PETG, PP, polystyrene, polycarbonate, and ABS, each offering different strength, clarity, and recyclability characteristics.

Is Thermoformed Packaging Recyclable?  

Yes, many thermoformed products (especially those made from PET or PP) can be recycled, and post-consumer content can also be used in production.

How Fast Can Thermoformed Packaging Be Produced? 

Production is fast and scalable, with lead times ranging from days to weeks depending on design complexity and order size.

What Are the Pros and Cons of Thermoforming? 

Thermoforming offers cost efficiency, design flexibility, and speed, but is limited to relatively thin-walled parts and requires upfront investment in a mold.

How Long Does Thermoforming Take? 

Once tooling is complete, forming and trimming take just seconds per unit on high-speed machines.

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.