The Economies of Scale in Thermoforming: How Volume Impacts Cost

Thermoforming is a manufacturing process where plastic sheets are heated, formed into shapes using molds, and trimmed, commonly used for packaging, automotive parts, and more. As production volume increases, the cost per part typically decreases due to economies of scale¹, making it a cost-effective choice for many industries.

Understanding how production volume² affects costs in thermoforming is crucial for manufacturers, designers, and industry professionals. This article explores the intricacies of thermoforming, its applications, and the technical factors that influence cost, providing a comprehensive guide to making informed decisions.

What is Thermoforming and How Does It Work?

Thermoforming is a versatile manufacturing process used to create plastic products by heating a plastic sheet to a pliable temperature, forming it over a mold, and trimming it to produce the final part. It is widely used across industries like packaging, automotive, and consumer goods due to its cost-effectiveness, especially for large parts and moderate production volumes.

Thermoforming, also known as vacuum forming, involves heating a plastic sheet, shaping it with a mold, and cooling it to create products like packaging trays, automotive panels, and medical device housings.

The process is highly adaptable, making it suitable for both prototyping and high-volume production. However, one of the most significant factors influencing its cost-effectiveness³ is production volume. As volume increases, the cost per part decreases due to economies of scale, where fixed costs like tooling and setup are spread over more units.

Key Steps in the Thermoforming Process

The thermoforming process⁴ consists of several critical steps, each influencing the final product's quality and cost:

1. Heating: The plastic sheet is heated to its forming temperature.

2. Forming: The heated sheet is stretched over a mold using vacuum, pressure, or mechanical means.

3. Cooling: The formed part is cooled to retain its shape.

4. Trimming: Excess material is removed to create the final product.

For high-volume production, these steps are often automated and continuous, allowing for efficient, large-scale manufacturing.

How Does Production Volume Affect Costs in Thermoforming?

In thermoforming, production volume has a direct impact on the cost per part due to economies of scale. Fixed costs, such as tooling and setup, are spread over a larger number of parts as volume increases, reducing the per-unit cost.

Higher production volumes in thermoforming generally lower the cost per part by distributing fixed costs like tooling and setup over more units, making it ideal for large-scale manufacturing.

Tooling Costs and Amortization

Tooling is one of the most significant fixed costs in thermoforming. Molds can range from $2,000 to $30,000, depending on complexity and material. For low-volume production, these costs are spread over fewer parts, making the per-part cost higher. However, as production volume increases, the tooling cost per part decreases significantly.

For example:

• Low Volume (50 parts): Tooling cost of $400 per part ($20,000 tooling / 50 parts).

• High Volume (500 parts): Tooling cost of $40 per part ($20,000 tooling / 500 parts).

This demonstrates how economies of scale reduce the impact of fixed costs as volume increases.

Material and Waste Management

Material costs also play a role in the overall economics of thermoforming. The process requires plastic sheets, which are more expensive than raw pellets used in other processes like injection molding. Additionally, trimming generates waste that must be reprocessed, adding to the cost.

However, at higher volumes, manufacturers can optimize material usage and reprocess trim waste more efficiently, reducing the per-part material cost.

What Are the Typical Applications of Thermoforming?

Thermoforming is used across a variety of industries due to its flexibility and cost advantages for specific production volumes.

Thermoforming is commonly used in packaging, automotive, healthcare, aerospace, and consumer goods for products like trays, panels, and housings, offering a balance of cost, speed, and design flexibility.

Packaging Industry

In packaging, thermoforming is ideal for high-volume, thin-gauge products like disposable cups, food containers, and blister packs. Its ability to produce large quantities quickly makes it a go-to process for consumer packaging.

Automotive Industry

For automotive applications, thermoforming is used to create large, structural components like dashboards and interior panels. The process is well-suited for medium-volume production, where tooling costs are manageable, and part size is a factor.

Healthcare and Medical Devices

Thermoforming is also prevalent in the medical field for producing sterile trays, equipment housings, and other components that require clarity and cleanliness.

How Does Thermoforming Compare to Other Manufacturing Processes?

When deciding on a manufacturing process, it’s essential to compare thermoforming with alternatives like injection molding, blow molding, and metal stamping.

Thermoforming offers lower tooling costs and faster development times compared to injection molding, making it ideal for low to medium volumes, but it may not be as cost-effective for very high volumes or complex parts.

Thermoforming vs. Injection Molding

• Tooling Costs⁵: Thermoforming molds are cheaper ($2,000–$30,000) compared to injection molding dies ($10,000–$100,000+).

• Production Speed⁶: Injection molding is faster for high volumes, while thermoforming is quicker to set up for smaller runs.

• Part Complexity: Injection molding can produce more complex parts with undercuts, whereas thermoforming is limited to simpler geometries.

Thermoforming vs. Metal Stamping

• Material: Thermoforming uses plastics, while metal stamping uses metals, making them suitable for different applications.

• Tooling: Metal stamping requires expensive dies, but for very high volumes, it can be more cost-effective than thermoforming.

What Are the Key Factors Influencing Cost in Thermoforming?

Several factors influence the cost of thermoforming, beyond just production volume.

Key cost factors in thermoforming include tooling⁷, material selection⁸, part size, and waste management⁹, all of which are affected by production volume.

Tooling Costs

As mentioned, tooling is a significant upfront cost. However, for high-volume production, this cost is amortized over many parts, reducing its impact.

Material Selection

Different materials have varying costs and forming requirements. For example:

• Polystyrene (PS): Low cost, used for packaging.

• Polyethylene Terephthalate (PET): Higher cost, used for food packaging due to its barrier properties.

Material choice also affects energy consumption, as some plastics require higher forming temperatures.

Part Size and Complexity

Larger parts require more material and longer cycle times, increasing costs. Complex shapes may necessitate more expensive molds or additional forming steps.

Waste Management

Trim waste must be reprocessed, which adds to the cost. However, at higher volumes, the efficiency of reprocessing improves, reducing the per-part cost.

How Can Designers Optimize for Thermoforming?

Designing for thermoforming requires consideration of process limitations to ensure cost-effectiveness and part quality.

Designers should account for draft angles¹⁰, avoid undercuts, and aim for uniform wall thickness¹¹ to optimize thermoforming production and minimize costs.

Design Checklist for Thermoforming

• Ensure draft angles of 1–2° for easy demolding.

• Avoid sharp corners and undercuts to prevent material trapping.

• Maintain uniform wall thickness to reduce waste and ensure strength.

• Account for material shrinkage during cooling.

• Consider part size: Large parts may require multiple sheets, increasing costs.

These guidelines help designers create parts that are easier and cheaper to manufacture.

When Should You Choose Thermoforming Over Other Processes?

Selecting the right manufacturing process depends on several factors, including production volume, part complexity, and material requirements.

Choose thermoforming for low to medium production volumes, large parts, or when lower tooling costs and faster development times are priorities.

Decision-Making Guide

• Production Volume: For low to medium volumes (e.g., 250–3,000 parts annually for thick-gauge), thermoforming is often more cost-effective.

• Part Size: Ideal for large parts where other processes like injection molding would be prohibitively expensive.

• Complexity: Best for parts without undercuts or intricate details.

• Lead Time: Faster setup makes it suitable for prototyping and quick-turn projects.

For very high volumes or complex parts, consider alternatives like injection molding or metal stamping.

Conclusion

Thermoforming is a highly adaptable manufacturing process that offers significant economies of scale, making it cost-effective for a wide range of production volumes. By understanding how volume impacts cost, businesses can optimize their manufacturing strategies, balancing fixed costs like tooling with variable costs like materials and waste management. While thermoforming excels in producing large, complex parts at moderate volumes, it may not be the best choice for very high-volume production or parts requiring extreme precision. By considering factors like production volume, part size, and material selection, manufacturers can leverage thermoforming to achieve cost savings and efficiency.