By Sean Fenske, Editor-in-Chief

Plastic molding is virtually synonymous with medical device manufacturing. It is the most relied upon component fabrication process across most healthcare segments. That said, it still creates challenges for companies that don’t maintain a core competency in its practice. Multiple challenges can often emerge for developers of medtech when specifying molded parts without being familiar with all the considerations.

A variety of factors can influence the success or failure of a molded part. Using the wrong material, setting too tight of tolerances, getting the tooling wrong, or any other of a number of aspects can rapidly derail the success of a molding project. As such, it can be critical to bring in a trusted, experienced partner to help ensure the task is successful and all facets are kept in mind.

To help further explain just how important such a molding firm can be in the development of a medical device component, representatives from Röchling Medical responded to a series of questions. In the following Q&A, Lukas Rath, Head of R&D MedTech EU, and Kimberly Sheehan, Molding Group Leader, address scale-up, DFM, micro molding, and other relevant topics.

Sean Fenske: To avoid costly design mistakes when molding parts, when is the best time to involve your molding partner?

Lukas Rath: As early as possible! The earlier you incorporate plastic-compatible design into the layout of the components, the better. With some geometries, it may not be a problem to make minor changes later. However, when interfacing with other components, bringing in the partner too late can lead to major problems if these are considered at a very advanced stage of the project. Furthermore, it has been shown that early interdisciplinary collaboration often leads to new approaches and topics such as sustainability, combining functions, adding features, and simplifying subsequent steps can lead to a better product.

Fenske: As the scale-up phase can result in many pitfalls, what should companies be doing to avoid risk at this stage, and how can a molding partner help in this effort?

Rath: A concrete planning phase and a mutual understanding of the requirements for the component or assembly are of fundamental importance. Testing feasibility as far as possible (e.g., using simulations and digital twins) makes it possible to identify and resolve potential challenges at an early stage, before the first chip has even been cut in tool construction.

Depending on the complexity, it is advisable to plan a meaningful test of prototypes or abstracted functional areas before the actual construction of the series production tools, equipment, etc. The clear task is to complete development before the actual start of series production and not to resolve any outstanding issues during the sampling phases. A professional and targeted sampling phase for the series tools and subsequent validation phase then guarantees a smooth series production process.

If there are clear ramp-up scenarios, planning should also be carried out in advance with the manufacturer. For example, the development of additional high-cavity tools, the transition from manual assembly to semi-automated or fully automated processes, and issues such as the assembly of subsystems within the injection molding process must be considered. Every component and project is different; there is no one right approach or solution, and each must always be tailored to the requirements of the component, the possibilities on site, and the customer’s demands.

Fenske: While many know DFM as design for manufacturing, what best practices can you share for another DFM—design for (injection) molding?

Rath: As mentioned previously, there is no blanket answer or one correct way to do it. The first step is to understand the requirements, but also the customer, end customer, and application, to evaluate and assess all the options.

When considering design for injection molding, several topics and interfaces should be considered. These include the material, a plastic-compatible design of the component itself, tool technology, machine technology, process options, etc. These individual areas interact with each other; the “miracle coating” from the last project for one material does not necessarily work in combination with another material or the geometry of the component in a different project.

Further, in addition to experienced employees, a good network of the necessary professionals and suppliers for their respective technologies also helps to guarantee success.

Fenske: In terms of micro molding, how should tolerances be handled? Are there guidelines that can be followed? How does this approach differ from more typical molding applications?

Kimberly Sheehan: When it comes to micro molding, small variations can quickly translate into bigger issues. Mold design and processing cannot be approached the same way as with standard injection molding. With significantly thinner wall sections, extremely small gate sizes, and high shear rates, a deep understanding of the material’s properties is critical to achieving consistent results.

From a tolerancing perspective, it’s important to avoid unnecessary tight tolerances and prioritize critical-to-function dimensions. Tight tolerances demand extreme precision in tool steel design and fabrication, which can significantly increase costs. Additionally, measurement capabilities for micro-molded components must align with the specified tolerances, often requiring specialized inspection equipment and fixturing.

Fenske: Can you offer some insights on common challenges you see regarding tooling? What are best practices here, and what innovations are you seeing in the space?

Sheehan: When it comes to medical product mold tooling, the biggest challenges are typically price, delivery, and quality. In medical manufacturing, quality is critical, but that usually comes at a higher cost and longer lead times. The challenge is to balance those three factors while ensuring the final product meets the standards required for patient safety and performance.

With innovations, we’re seeing the use of metal 3D printing in tooling, particularly with conformal cooling. This technique allows for the creation of cooling channels that follow the contours of the mold cavity, allowing for more uniform cooling that benefits by reducing cycle times, minimizing warpage, and improving surface finishes.

Fenske: Do you have any additional comments you’d like to share based on any of the topics we discussed or something you’d like to tell medical device manufacturers?

Sheehan: Keep in mind that partnering with a strong molding organization is valuable not only for manufacturing your medical device, but also because they can truly become an extension of your team. The right partnership adds value in many ways, from design input and material selection to process optimization and long-term support.

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