Thermoforming vs Injection Molding for Your Project

When you’re planning a new plastic product, choosing the right manufacturing method is critical. Two popular options are injection molding and thermoforming. Each process comes with its own strengths, costs, and design capabilities — so picking the right one can make all the difference in your project’s success.

In this guide, we’ll dive into what is thermoforming, how it compares to injection molding, and help you figure out which one fits your project best.

What is thermoforming?

Thermoforming is a plastic manufacturing process where a sheet of plastic is heated until it’s flexible, then shaped over a mold using pressure or vacuum force. After forming, the sheet is then cooled and trimmed into the final part.

Vacuum forming is a specific type of thermoforming that uses suction to pull the heated plastic tightly against the mold, allowing for detailed shapes without trapped air bubbles.

Plastic thermoforming is widely used across industries for products like food containers, appliance housings, agricultural components, and even windshields for boats. It’s a popular option for creating larger parts at lower tooling costs compared to injection molding.

Thermoforming Process

A typical thermoforming machine works like this:

• A sheet of plastic (like polyethylene or polycarbonate) is loaded into the machine.
  
• The sheet is heated to a temperature where it becomes pliable.
  
• It is then pressed or vacuum-formed onto a mold.
  
• After cooling, the part is trimmed and finished.
  

Since thermoforming uses only one side of a mold, it’s typically faster and more cost-effective to change designs compared to processes like injection molding.

Injection Molding vs Thermoforming

Both methods are highly effective — but depending on your project goals, one might suit you better than the other. Here’s how they compare:

Applications

Injection Molding: Ideal for high-detail, high-volume items like gears, packaging, toys, electronic housings, and medical devices. You can read more about the details of injection molding in our blog here.

Thermoforming: Great for larger parts like bathtubs, trays, food containers, agricultural tanks, and boat parts.

Materials

Both methods use similar types of plastics — polyethylene, polycarbonate, PVC — but in different formats.

Injection Molding: Plastic pellets.

Thermoforming: Plastic sheets.

Volume

Injection Molding: Best for high-volume production. Once the mold is built, each cycle can create many parts at once.

Thermoforming: Better for lower to medium volumes, especially when part designs may change.

Repeatability

IM: Extremely repeatable — perfect for identical parts across large production runs.

TF: Also repeatable, but with slightly more variation due to sheet material inconsistencies.

Tooling Costs

IM: Higher upfront tooling costs due to the complexity of multi-cavity molds.

TF: Lower tooling costs, making it a faster, more economical choice for prototyping or lower production volumes.

Have more questions? Contact Rex Plastics!

Choosing between injection molding and plastic thermoforming isn’t always straightforward — it depends on your product, your production goals, and your budget. If you’re still weighing your options, the experts at Rex Plastics can help.

Contact us today to get personalized advice and a free quote for your project!