8 lies about thermoforming

Thermoforming is one of the many ways to make a part. As with most technologies, there are misconceptions about the capabilities and uses of this technology, even though it has evolved over the years. Recently, Design World magazine hosted a webinar where Brian Ray, President of Ray Products and Jason Middleton, Vice President for Sales and Development at Ray Products, clarified several of these misconceptions, or “lies,” about this technology.

Thermoforming is different from injection molding and other forms of processing plastics. The thermoforming process consists of heating a plastic sheet to a pliable forming temperature. The sheet is then moved over or into a mold, and as it cools, it is trimmed to the proper size for the end product.

Despite the differences, it can be used to make cups, containers, lids, clamshells, door panels, utility vehicle beds, and so on.

Lie 1. All thermoforming service providers are the same.

Of course this is not true. There are several capabilities you can look for in a thermoformer, such as the ability to control temperature of the tooling. A good thermoforming machine will operate at the right temperature, part to part, run to run, day after day for a repeatable part every time.

Some automate many steps of the process, such as using robots for trimming, which delivers parts faster at high accuracy.

Check to see if the provider also pressure forms. This is an added capability that can be useful. Can the service provider bring detail into a female cavity tool using 80 to 100 PSI? Do they know how to machine in undercuts? Do they know how to retract their tools? How do they process part to part with pressure forming? These are some of the questions you should ask when you get involved with thermoforming.

Lie 2. Thermoforming is the perfect process for everything that’s not injection molded.

Thermoforming is an alternative to injection molding and can offer advantages in molding in color, cosmetics, and multi-texturing. It is possible to achieve the same cosmetic outside features of any injection-molded part.Thermoforming is also great for large parts, especially in the area of tooling costs.

Thermoforming suits production runs that range from the low to mid hundreds up to high thousands.

Multi-part assemblies suit thermoforming. End parts with ten or more sub-parts coming together, matched and molded in color work well with thermoforming capabilities.

Lie 3. Thermoforming is only good for projects that don’t need detail or part-to-part consistency.

For those thermoforming manufacturers that use robots for trimming, the robots will hold tolerances to +/- 0.005. Formed features can have tolerances of +/- 0.020.

Lie 4. All tooling materials are equal.

Ray Products finds that temperature controlled aluminum tooling delivers quality, repeatability, and longevity.

Aluminum temperature controlled molds allow customers to mix and match materials or run complex shapes. Molds made from this material are guaranteed for the life of production, and they allow the tooling to be cooled from the first part to the thousandth part.

Molds must be cooled to the correct temperature between uses to ensure part-to-part repeatability, flatness, and eliminate warpage issues.

Lie 5. Thermoforming cannot replace urethane.

Urethane, depending on the production choice, will use either a rubber mold or an aluminum tool. One aspect to consider is that urethane production will typically require two halves. With aluminum, the process will require a core cavity. Thus, the cost of working with thermoforming is less expensive because of the need for fewer tooling parts.

Thermoforming often results in lighter weight parts. Urethane typically has to start with ¼-in. wall section. With thermoforming, the density of a part tends to be lighter.

Thermoforming offers the benefit of easy design changes. Moving a hole location 0.5 in. can be done with a program change. If a boss location must move more than 0.005 in., it’s a secondary process for thermoforming, therefore it’s not a tool change.

Lie 6. Thermoforming cannot compete with injection molding.

Thermoforming does offer several benefits in a comparison with injection molding. First, tooling is less expensive because you are using a one sided tool–one side of a core and cavity.

Many materials are available. Any thermoplastic will work, including ABS, styrene, polycarbonate, polypropylene, polyethylene, weatherable ABS, and PVC acrylic.

Mold turnaround time is typically within 4 to 8 weeks depending on the tool requirement.

Large parts are possible; molds up to 10 ft x 18 ft, and in pressure form, sizes go to 6 ft x 10 ft.

Lie 7. Thermoformed enclosures have to be painted.

The truth is that thermoformed enclosures look great right out of the mold. You can buy pre-colored sheet any color you want, and thermoform in texture. You can also paint or silkscreen thermoformed parts

Lie 8. Part complexity is not a good fit for thermoforming.

Thermoforming can be a great option for complex parts. Examples include zero or negative draft. Sidewalls can have a vent detail. You can have texture, including on the zero draft or a negative draft, which is achievable using pressure forming.

Large undercuts, even perimeter undercuts, are possible too.

Deep draws are also possible. Ray Products offers draws with a five to one draw ratio.

So next time you are considering how to produce your part, thermoforming could be an option.


  1. Great job on this article!

  2. René Neele says:

    Well written.they know their business.

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