7 Thermoforming Design Choices That Can Make Your Part More Expensive

September 17, 2026

Thermoforming can be a cost-effective manufacturing process for plastic parts, particularly for low to mid-volume runs. But the way that the part is designed can have a major impact on the production costs.

Designs that increase material waste, add machining time, or make forming less predictable can all drive up your costs. In some cases, those features are necessary to meet the part’s performance requirements. In others, they may just be adding manufacturing complexity without performance improvement.

Look out for these seven common design mistakes that can make your thermoformed part more expensive than it needs to be.

7 Design Mistakes That Drive Up Thermoforming Costs

1. Specifying Tighter Tolerances Than the Part Needs

Tight tolerances aren't inherently a problem. Some parts need them to fit, function, or align correctly with other components. The problem is specifying tighter tolerances than the application actually requires.

Tighter tolerances can require more advanced tooling, additional setup, slower feed rates, more frequent tool changes, or additional secondary operations. All of that can add time and cost to production.

Before locking in a tolerance, consider what the part actually needs to do. If a dimension is critical to fit or function, tighter control may be justified. If it isn't, allowing more flexibility can make the part easier and less expensive to manufacture.

2. Designing Without Enough Draft

Because the draft allows easier tool release, it’s important that the design accommodates for this. Anything that increases the risk of sticking, distortion, or damage during the demolding process can damage the part during this step and affect aesthetics.

Accounting for the appropriate draft during CAD development can make the forming process more predictable and help avoid costly changes after tooling has already been developed.

3. Creating Deep Draws or Aggressive Geometry

ICP can form parts up to 40 inches deep when an application requires it. The challenge isn't necessarily the depth itself. It's designing deep draws or aggressive geometry without considering how the plastic sheet will stretch during forming. As material stretches into a deep or complex feature, some areas can become thinner than others. Excessive thinning can affect strength and performance and may require changes to the geometry, material, or tooling to produce the part consistently.

An early evaluation to determine draw ratios and how the geometry works with the material is crucial to determine the practicality of the design. By determining this early on rather than later in the thermoforming process, it can reduce costs and keep the project on track.

Related Content: Thermoforming Design Basics

4. Cutting Corners (Literally)

Creating too sharp of corners and insufficient radii can often result in weak points, inconsistent wall thickness, and other cosmetic issues that make thermoforming more difficult and the end result not as strong.

That doesn't mean every sharp feature needs to disappear. If a sharp corner or feature serves a functional purpose, identifying it early gives your thermoforming partner a chance to determine how the design or tooling can accommodate it without creating unnecessary manufacturing problems.

5. Choosing Material Without Considering Manufacturability

Material selection affects more than the performance of the finished part: It also affects how consistently the part can be formed.

Different thermoplastics behave differently when heated and stretched, and the right material depends partly on the geometry you're trying to produce. A material that meets the application's performance requirements may still create challenges with a particular design.

Choosing the least expensive sheet doesn't necessarily produce the least expensive part if it increases scrap or makes consistent forming more difficult. At the same time, a higher-cost material may add properties the application doesn't actually need.

6. Designing the Formed Part Without Considering Trimming and Assembly

The cost of a thermoformed part doesn't stop once it comes off the tool. Many parts require secondary operations such as trimming, CNC routing, drilling, hardware installation, fabrication, or assembly. If those steps aren't considered during design, a part that is relatively straightforward to form can become expensive to finish.

7. Skipping a DFM Review

Many of the cost drivers above are much easier to address before tooling and production begin. Once a design is finalized and tooling has been developed, even a relatively small change can mean additional engineering time, tooling modifications, or delays.

A design for manufacturability (DFM) review gives your thermoforming partner a chance to identify potential manufacturing challenges while there is still flexibility to make changes. That doesn't mean simplifying every feature or changing the intent of the design. The goal is to identify where complexity is necessary for the part to perform and where it may be adding cost without adding value.

How a DFM Can Reduce Thermoforming Costs

An early DFM review can evaluate:

Design tolerances
Part geometry
Draft, draw depth, and radii
Material selection
Tooling complexity
Secondary operations

Making these decisions before tooling begins gives engineers and manufacturers more flexibility to address potential problems without costly redesigns or tooling changes later.

If you're developing a thermoformed part or evaluating an existing design, ICP can review your design and help identify opportunities to improve manufacturability while maintaining the performance requirements that matter to your application.

Request a DFM review

Industrial Custom Products is a one-stop-shop for custom manufacturing and plastic fabrication, including: prototyping and product development, die cutting and dieless knife cutting, thermoforming and vacuum forming, large part thermoforming, CNC plastic routing, fabrication and assembly and drape forming.

Tags:

Thermoforming, Design