How to select a MIM supplier?

With the development of increasingly smaller metal parts comes the challenge of identifying the best supplier and manufacturing method to meet extremely tight tolerances.

Complex components with millimeter-sized features are pushing the limits of traditional casting and machining methods. As tolerances become tighter, investment casting is less consistent and supplier costs increase. Suppliers understand that metal injection molding (MIM) is becoming a go-to process for small complex metal parts.

MIM can be a viable manufacturing alternative for parts currently being machined such as metal connectors in implantable pulse generators and gear pump components. It’s also an alternative for components for cardiac rhythm disease management, dental, ophthalmic, orthopedic, drug delivery and the surgical ablation markets.

As components become smaller, weighing less than a few milligrams, the challenge with conventional machining is maintaining the extremely tight tolerances necessary to produce high-quality metal components efficiently at high volume.

Machining processes are unable to consistently produce micro features. Different types of cutting tools are needed to machine different features to produce a single part, and there may be a need to use more than one machine tool — making the manufacturing process expensive and inconsistent.

When considering MIM suppliers, be aware of the critical capabilities needed to produce quality parts.

Based on our work, we identified four areas where MIM suppliers can fail – causing delays, added costs and often the need for a new supplier.

1. Using scientific principles to develop manufacturing processes

Perhaps the most important consideration in choosing a MIM supplier is finding one who understands manufacturing process variability and the controls needed to minimize the variation through the manufacturing process. The process needs to be developed using data to understand the relationships between process inputs (e.g., material, melt temperature, mold temperature, hold pressure) and process outputs (e.g., dimensions, surface finish), to create predictable manufacturing processes. This level of understanding the MIM process helps minimize the risk of releasing non-conforming product into the field.

2. Materials expertise

Materials play a critical role in the success of MIM. Understanding the feedstock composition determines the success of any MIM project. Metal particle size distribution and binder type are important variables in determining the manufacturing cost and feasibility of consistent feature production.

Material sourcing is often a challenge because of the limited number of material manufacturers for micro particle size in the United States. Selecting the right material for each part is critical.

In some cases, a unique material may need to be developed to meet the performance and visual requirements of the component. This requires a supplier with the expertise to identify needs and to work with material compounders to create the right material. If the correct material is not sourced, and if it doesn’t meet the requirements or standards, the resulting product will be inconsistent.

FineMIM has developed proprietary materials to produce parts with specific corrosion resistance and electrical properties, mimicing a commonly used material in the medical device industry.

3. Equipment and technology expertise

In addition to material control, equipment selection plays an important role in producing parts with minimal variation. With MIM, building molds for part sizes less than a millimeter is a challenge. It requires specialized machinery, innovative techniques, knowledge and experience in machining — all at the micro size.

The supplier should not only be able to identify the right size equipment to mold the small components, but have expertise in designing the manufacturing process as a whole system. They need to consider downstream operations with the customer’s end requirements in mind.

4. Understanding the product requirements

Identifying the proper requirements for the product in terms of strength, surface finish, feature sizes and dimensional tolerances will help in selecting the correct feedstock, in addition to process parameters to mold, debind and sinter. Micro features demand specialized handling procedures through molding, debinding and sintering operations.

As medical devices continue to become smaller, conventional metal cutting processes are limited in producing micro features and meeting tight tolerances. If you have a high-volume product with tight tolerances or micro features, MIM may be a solution. Even though the initial investment cost may be high, MIM offers better accuracy, consistency and cost advantages for high-volume manufacturing.