Customers come to Dordan at different stages of package development. Some have a concept that needs to be designed, while others have an existing package to replicate or specific features that need to be maintained.
Regardless of where the project starts, the package has to be designed for the thermoforming process. Even replication projects require consideration of how the part will form, how the tooling will be developed, and what is required to manufacture the package consistently.
Designing for Thermoforming
A design that works in CAD does not necessarily translate directly to thermoforming.
Controlling material distribution is a priority when designing a thermoformed package. As the heated plastic forms into the cavities and features of the tool, the design affects how the material moves and stretches. Deep cavities, sharp transitions, and complex features can create greater thinning in certain areas of the part.
The challenge is controlling malleable plastic as it forms and cools. Package design can help or hinder that process, which is why manufacturability has to be considered while the design is being developed.
Above: Some of Dordan's plastics thermoforming lines
Thermoforming Design Requirements
Certain design parameters are inherent to the thermoforming process. Draw ratio, draft, radii, and flange all influence how a part can be formed, tooled, released, and trimmed. While these features can be adjusted based on the requirements of the package, they have to be considered during design.
Draw ratio: Draw ratio has a direct impact on material distribution. At Dordan, we prefer a 1:1 ratio - for every inch of depth, approximately one inch of width. This gives the material room to distribute more consistently as it forms into the cavity. Tighter draw ratios are certainly achievable, but as a cavity becomes deeper and narrower, maintaining consistent material distribution becomes more challenging. There is a balance between the package design and the performance required from the finished part.
Draft: Draft angles allow the material to move down cavity sidewalls during forming and help the finished part release from the tool. Draft also affects how parts stack and separate. Draft can be modified to meet package requirements, but reducing it can make forming and part release more challenging.
Radii: Radii are inherent to how thermoforming tooling is machined. The cutting tools used to machine aluminum tooling are round, so they cannot cut a perfectly square 90-degree internal corner. The radius in the tooling ultimately becomes part of the formed package.
Flange: Customers generally want as little flange as possible, but flange is necessary because the package has to be trimmed from the plastic sheet after forming. Dordan's standard total flange is approximately 0.375" inches total, or 0.1875" per side. Smaller flanges are certainly possible, but they leave less room for trimming and can make manufacturing more complicated.
Draw ratio, draft, radii, and flange are standard considerations in thermoformed package design. They can be modified depending on the requirements of the project, but moving away from preferred parameters can affect how consistently the part can be manufactured.
Above: Engineering drawing of a medical device tray
Balancing Design & Manufacturing
The most challenging projects are often complex designs or redesigns where specific customer requirements cannot change. A non-standard tolerance, reduced flange, tighter draw ratio, limited draft, or other part feature may push against what would normally be preferred for thermoforming.
That does not necessarily mean the part cannot be made. It means engineering has to understand which requirements are fixed, where there is flexibility, and how those decisions will affect tooling and production.
There is a difference between successfully forming a part and manufacturing that part consistently at the required quality. When a design pushes the limits of thermoforming, adjustments may need to be made elsewhere in the package or tooling to maintain the function and performance the customer requires.
Engineering & Tooling Integration
Package design and tooling are both developed in Siemens NX at Dordan. Our Engineering Manager oversees tooling development, providing continuity between the package design and the tool used to manufacture it.
The package is not designed and then simply handed off to tooling. Decisions made during design directly affect how the tool is developed and how the part will perform in production. Keeping design and tooling within the same engineering process allows manufacturing considerations to be addressed as the project develops.
Above: Thermoform tooling developed, machined, and assembled in-house
Designing for Production
Designing for thermoforming does not mean every package has to follow the same set of design parameters. It means understanding what happens when it does not.
Tighter draw ratios, reduced flange, limited draft, and complex features can all be accommodated depending on the application. The role of engineering is to understand how those decisions affect tooling and production, and where adjustments can be made to achieve the customer's requirements while reliably manufacturing a quality part.
Interested in learning more about thermoform packaging design? Download our Materials Selection Report to learn which material is best for your application.