Metal Injection Molding (MIM) Process

What does MIM mean in metal?

Metal Injection Molding (MIM) Overview:

1. Cost-Effective Precision Manufacturing:

Over the past 15 years, MIM has gained prominence as a cost-effective solution for crafting small-to-medium-sized precision components. This technique has proven instrumental in achieving intricate shapes with precision, making it a preferred method in various industries.

2. Versatile Production Capability:

MIM stands out for its ability to manufacture both complex-shaped components and parts in varying volumes. This versatility is a key factor driving its adoption across industries, providing manufacturers with a flexible solution for diverse production requirements.As a professional mim manufacturer, FTMIM is your loyal partner.

3. Integration of Technologies:

MIM represents a fusion of plastic injection molding and traditional powder metallurgy, seamlessly incorporating aspects from both disciplines. This integration enables the production of intricate metal components with enhanced efficiency and cost-effectiveness.

4. Process Details:

Feedstock Preparation: The MIM cycle initiates with the meticulous preparation of a feedstock. This mixture typically comprises metal powders and a binder, forming a granulated feedstock suitable for injection molding.

Injection Molding: Similar to plastic injection molding, the prepared feedstock undergoes heating and injection into a mold cavity. This stage yields a “green part,” essentially the initial shaped form of the desired component.

Binder Removal and Sintering: Subsequent steps involve the removal of the binder from the green part. The part then undergoes sintering, a critical process where the brown part is subjected to controlled heating. This enables the metal particles to bond, resulting in a durable final product.

Pore-Free Density (PFD): Post-sintering, the brown part achieves an impressive over 95% pore-free density (PFD). This high density is crucial for ensuring the mechanical and physical properties meet stringent standards.

5. Fig. 6.1 – MIM Process Flow:

The visual representation in Fig. 6.1 serves as a comprehensive guide to the MIM process flow, offering a clear overview of the sequential steps involved from feedstock preparation to the attainment of the final product.

What are the steps in the MIM process?

Metal Injection Molding (MIM) integrates plastic injection molding and powdered metallurgy, combining two well-established technologies. This liberates designers from the conventional limitations when shaping metals like stainless steel, nickel-iron, copper, titanium, and others. The outcome? Increased design flexibility and a broader scope for innovative possibilities.

The process

Step 1: Formulating Feedstock

In this initial stage, finely powdered metals are meticulously blended with thermoplastic and wax binders according to a precise formula. Through an exclusive compounding process, a homogenized pelletized feedstock is created, allowing for injection molding comparable to plastic. This method ensures the achievement of ultra-high density and tight tolerances across extended high-production runs.

Unlike conventional powder metallurgy, which typically reaches only 80-90% of theoretical density, Metal Injection Molding (MIM) attains an impressive 95-100% density. This exceptional capability enables the production of small, intricate parts with close tolerances, leading to cost savings during extensive production cycles.

Step 2: Molding

The formulated feedstock undergoes heating and is injected into a mold cavity with high pressure. This allows for the production of intricate shapes and reduces cycle times significantly. Once molded, the component is known as a “green” part, mirroring the final piece’s geometry but approximately 20% larger to accommodate shrinkage during the ensuing sintering phase.

Step 3: Debinding

The controlled debinding process is employed to systematically remove the majority of binders, preparing the component for the final stage, which is sintering. Following the completion of debinding, the component is now referred to as “brown.”

Step 4: Sintering

The delicate brown part, held together by a small amount of binder, undergoes the crucial sintering stage. This step eliminates the remaining binder, shaping the part into its final geometry and enhancing its strength. Throughout sintering, the part is exposed to temperatures near the material’s melting point.

What is MIM powder?

Metal Injection Molding (MIM) powder acts as the fundamental building block for MIM feedstock, wielding a decisive impact on both the sintering process and the ultimate properties of the final product. Simultaneously, the choice of additional binder materials not only shapes the injection molding process but also dictates the methods employed for debinding. Consequently, it is clear that MIM powder stands as the critical element, exerting significant influence over the ultimate properties of the manufactured components.

Within the domain of metal injection molding, diverse characteristics of MIM powder produce varying effects on the final properties of identical alloys. These crucial characteristics encompass the types of alloys utilized, the application of distinct atomization techniques during powder production, the distribution of particle sizes, and the methods employed for amalgamation in the manufacturing process. Each of these factors plays a fundamental role in determining the distinct qualities and features of the end product.

Recommended Reading:

1.What is Aluminum Metal Injection Molding

2.Metal Injection Molding vs. Die Casting

3.Exploring What are MIM parts?

Reference:

Todd, A.T. Sidambe, in Advances in Powder Metallurgy, 2013