We specialize in molding thermoplastic closed-cell polyolefin foams, including cross-linked polyethylene (XLPE) and ethylene vinyl acetate (EVA). These lightweight, durable, and versatile materials provide an excellent balance of cushioning, protection, and structural integrity.
This is an ideal process for producing foam components with complex geometries and excellent surface quality. To achieve optimal performance, lower cost, and consistent results, it’s essential to design parts specifically for the process. The following guidelines outline best practices to help engineers and designers create parts that are compression mold-friendly.
Tip – Avoid designing solid foam parts much thicker than 0.625 inches (15.8mm) unless cored-out areas are included on the backside.
Why – Foam becomes increasingly difficult to mold consistently beyond 0.625 inches (15.8mm) due to limited heat penetration. Thicker parts are also more likely to have air pockets/voids.
Best Practice – Core out thicker parts from the back to reduce mass and improve moldability. Maximum practical molding thickness is typically 0.75 inches (19mm), with an upper limit near 1 inch (25.4mm) in special cases.
Tip – Keep wall thickness as consistent as possible throughout the part.
Why – Variations can cause voids, inconsistent curing, or poor surface quality, especially in thicker areas.
Best Practice – Use gradual transitions rather than abrupt changes in thickness to facilitate smooth foam flow and even pressure distribution.
Tip – Eliminate features that could complicate release of parts from the mold, like undercuts or sharp internal angles.
Why – These can increase tooling complexity and make parts difficult to remove from the mold.
Best Practice – Use internal radii of ≥ 0.06 inches (1.52 mm) to promote smooth part removal.
Tip – Apply a draft angle of at least 3–5° on vertical walls.
Why – Helps prevent foam from sticking to the mold and tearing during part removal.
Best Practice – Use positive draft for male molds and negative draft for female molds.
Tip – Strive for design simplicity without sacrificing functionality.
Why – Simpler parts are easier to mold and less likely to require post-processing.
Best Practice – Combine features where possible to reduce assembly steps, adhesives, or multiple parts.
Tip – Maintain a 1:1 ratio between width and depth of molded details (e.g., ribs, grooves, or cavities).
Why – Prevents issues like voids, tearing, or incomplete filling due to poor foam flow.
Example – or a groove .197 inches (5 mm) wide, keep its depth no more than .197 inches (5 mm). For deeper features, increase the width accordingly.
Tip – Design no features smaller than .04 inches (1 mm) in width or diameter, and no spacing between features less than 0.04 inches (1 mm).
Why – Tooling limitations make it difficult to machine such fine details accurately and reliably.
Best Practice – Avoid fine details that are difficult to machine and may compromise tool longevity or part quality.
Tip – All logos and text should be debossed (recessed) into the foam surface at a minimum depth of 0.040 inches (1mm) to 0.060 inches( 1.52mm).
Why – Shallower depths may lose definition due to foam rebound, resulting in poor readability and reduced long-term visibility.
Best Practice
Tip – Collaborate with Flextech technical sales team to understand how the selected foam material behaves under compression.
Why – Materials like cross-linked polyethylene may expand, shrink, or rebound after molding.
Best Practice – Account for these behaviors in your CAD model and mold design to ensure dimensional accuracy.
Tip – Design the part to encourage smooth foam flow and adequate venting.
Why – Poor flow paths or venting can cause surface defects, voids, or incomplete fill.
Best Practice – Strategically place vents, channels, and ribs to manage airflow and compression paths.
Tip – Validate your design with prototype tooling first.
Why – Early testing identifies potential manufacturing issues and gives you time to make refinements before committing to production tooling.
Bonus – Ensures material selection, geometry, and function all meet expectations.
Tip – Design your foam parts with their end-use application and assembly process in mind.
Why – Foam components are often bonded or fit into housings—your design should accommodate these needs.
Best Practice – Include bonding surfaces, registration features, and alignment aids directly in your molded design.
Need Help with a Custom Compression Molded Foam Part?
At Flextech, we work directly with OEMs and product development teams to ensure their designs are fully optimized for compression molding. From early concepting to final production, we help minimize revisions, shorten timelines, and improve part performance.
Compression molded foam is widely used to produce components for medical devices and medical device packaging, industrial applications such as thermal insulation parts, and personal protection parts used in law enforcement, military, and tactical gear. It is also used in automotive and consumer product applications, but Flextech does not supply parts for these markets.
Yes. Our Research and Development team is skilled in using SolidWorks and can assist with CAD reviews, design modifications, and manufacturability assessments to ensure your part is optimized before tooling. However, we are not a full-service CAD design firm. If possible, a prospective customer can provide 2D or 3D CAD files, which we can then revise for manufacturability in our foam compression molding process.
Prototype tooling and parts can normally be built in 5–6 weeks. Production tooling and first article parts can usually be completed in 6–8 weeks. In some cases, we can produce 3D-printed prototype tool components to expedite the prototyping process.
Yes. A key advantage of partnering with Flextech is our comprehensive in-house tool shop. We not only design but also build our molds, cutting dies, and fixtures, ensuring cost-effective tools that maintain tight tolerances throughout your project’s lifecycle. We use SolidWorks to design tool components. While we design machined metal components in-house, we source the actual machining from several trusted local partners. Our tool shop includes state-of-the-art digital CNC-controlled laser cutting and precision steel rule bending machines. We also have 3D printing capabilities that allow us to quickly build prototype tool components and fixtures. Together, these capabilities allow us to make swift adjustments during prototyping and minimize downtime for tool repairs during production.
We invite you to connect and collaborate with our technical sales team. Ideally, you can provide CAD models or part drawings to begin the conversation. Our experts will guide you through the project review, recommend modifications for manufacturability, and explain the product development process.
