MICRO’s Executive Vice President Steve Santoro was a keynote speaker at this week’s MIM2021: International Conference on Injection Molding of Metals, Ceramics and Carbides, held virtually February 22-25. During his presentation, Santoro highlighted the use and benefits of metal injection molding (MIM) in medical device manufacturing, specifically minimally invasive surgical instruments, parts, and products.

Medical device manufacturers have a number of processes to choose from when producing parts and instruments designed for surgical applications. The key, Santoro explained, is to pick the best process for each component. Cost is one important consideration, and manufacturers must factor in what raw materials will be used. For minimally invasive surgical instruments, metal components will account for a large portion of the cost. Adding processing steps also increases costs. He explained that MICRO preforms detailed cost models and generates process capability data to make the best decisions on process before any project begins.

As in most other industries, including computer and consumer products, MIM is well suited for medium to high volume medical device applications. Today MIM is used to make surgical instruments in powered device drive chains, end effectors, and connectors. It’s a low risk, proven technology, and Santoro noted that MICRO has used MIM successfully over the last 20 years, producing millions of pieces annually.

An array of materials is suitable for medical device manufacturing using a MIM process. Santoro noted that the vast majority — 95% — of MICRO’s output uses a 17-4 grade stainless steel, which has the ability to be tempered to various hardness and close to 300 series stainless in corrosion resistance. He said 316 and 400-series stainless steel are used in specialty applications, but 316 stainless steel is the gold standard for MIM for corrosion resistance. Mechanical properties are important considerations, as some stainless steel grades, such as 316 and 440, can’t achieve as much strength as other grades. Manufacturers can consider ceramic injection molding for certain projects as well, and in general, readily available, widely used materials will reduce costs and process time.

Beyond materials, design and commercial considerations are also important factors for medical devices. Santoro described MICRO’s Design for Manufacturability approach to help optimize MIM with secondary processes, such as machining, to achieve effective and cost-efficient results for customers.

MICRO uses both batch and continuous processes for medical device manufacturing. All feedstocks and processes are not equivalent, however, and the key to the process is the consistent shrinkage and diffusion of organics out of the metal matrix. Another important consideration is furnace furniture, which is often overlooked. The part datum structures must be married to the furnace furniture to get the most consistent results, especially if secondary machining is involved.

MICRO’s proprietary feedstock formulation utilizes high quality alloy powders needed for surgical instruments, with high green strength for medical parts. Santoro noted that these higher quality feedstocks have virtually eliminated failures due to molding and handling defects. Proper diffusion also is critical for achieving optimal mechanical properties of medical devices.

With modern techniques combined with innovative engineering, MICRO is able to deliver high quality devices for its customers, and their patients. Santoro added that original equipment manufacturers need to consult with contract manufacturers early in the process to review and agree on design and commercial considerations of each project. This will ensure that the output has the required functionality without commercial, technical and compliance risks introduced.