How to Thermoform Heavy-Gauge Complex Parts, from Material Selection to Custom Tooling

In many instances thermoforming of heavy-gauge plastics (thicknesses of 1.5 mm (.060 in.) or greater) is the technology-of-choice for manufacturers and new product designers. Using this process of vacuum forming heated plastic sheets is ideal for many products and components required by aerospace, automotive, medical, manufacturing and countless other industries.  A wide variety of heavy-gauge plastic materials are available for this process, many of which can be used for complex parts that demand tight tolerances, intricate geometries and special properties such as fire resistance. Heavy-gauge thermoformed plastics are also a practical solution for many larger parts, such as automotive dashboard sections, refrigerator door shelving and snowmobile body panels.

At the same time, thermoforming prototypes and tooling are often developed more quickly than many conventional molding methods and can be performed through a number of economical processes.

If customers are too self-reliant when they design parts for the heavy-gauge thermoforming process, these same attributes may also be the source of confusion, wheel spinning, and the expenditure of unnecessary costs. What is often needed is a collaborative process that includes thermoforming specialists early in the design of the products that will be formed.

Get design support early

“In my experience, it is highly beneficial for the customer’s design engineers to collaborate with their thermoforming vendor early in the process,” says Jesse Hahne, design engineer at the Center for Advanced Design (CAD), Elk River, Minn. “The vendor, Alpha Plastics, can help validate the geometry and features of the product design, confirm or assist with material selection, determine how tooling should be developed, provide prototypes quickly and economically, and of course confirm the best process for meeting production volume requirements.” CAD is a design firm that focuses on the plastics industry, including design for vacuum forming, rotational molding, injection molding and blow molding. 

Hahne, a highly experienced design engineer, consults with many in-house engineers of clients as well as with thermoforming specialists and the molders of different plastic forming technologies. He has a close relationship with Alpha Plastics (www.alphaplastics.net), a design and fabrication specialist located nearby in Minneapolis, Minn. In addition to heavy-gauge thermoforming, the company offers pressure forming and traditional vacuum forming services.

“In our eyes, Alpha Plastics has carved out a niche for complex, hard-to-form, heavy gauge thermoformed products,” Hahne explains. 

Confirm the process

Jeff Walczak, Alpha Plastic’s executive vice president, says that in some cases he receives requests to evaluate the use of thermoforming a product that might best be produced by another process. “I tell them, ‘Yes, it’s a well-designed part, but pressure forming may be a more appropriate process for producing it,” Walczak says. “So, it’s easy to see why it is vital to get support from a supplier’s technical staff early in a project, especially if they are familiar with various forming and molding technologies. This can be very valuable in helping the customer validate that they are considering the right process.”

For example, because Walczak’s firm also offers pressure forming of heavy-gauge plastics, he can also handle projects most suitable for that process as well. He describes pressure forming as similar to the vacuum forming process, but with specific tooling that can produce parts with much greater definition. In instances where volumes are relatively low, pressure forming may be a viable alternative to much more expensive injection molding.

With both thermoforming and pressure forming projects, Walczak assists customers from design to materials selection, tool development, prototyping or 3D modeling and production. 

Check tooling specifications

It is often vital that design engineers validate tooling with thermoforming specialists, particularly when the project includes design complexities. These could include such requirements as undercuts, the use of breakaway molds, two-piece products involving manifolds or ductwork, or products that require special trimming or surface finishes. Forming complexities can be problematic for some thermoforming shops. Walczak says they are often achievable, but may require modifications in tooling that could result in cost savings.

“With thermoforming you have much greater flexibility with tooling than you have with technologies such as blow molding or rotational molding,” says CAD’s Hahne. “For example, for smaller projects you can 3D print and test the tool. If a large tool is required, then you build a wood pattern and produce test parts from it, then make changes to the pattern before you finalize the tool design. This technology is so forgiving and flexible it really works well for larger products like snowmobile body panels.”

Hahne adds that for many projects, a 3D test sample or product run from a wood pattern may suffice as a prototype for the project.