Metal Injection Molding

Application of Metal Injection Molding MIM in Aerospace

There are about 700,000 parts in a Boeing 737NG, and the production of Boeing 737NG has reached more than 7,000 so far. Many of these parts are produced by traditional manufacturing methods including die casting, machining, metal finishing, electroplating, and more.

Since the 1980s, aerospace designers have used new metal injection molding techniques in the production of major aircraft components. Metal Injection Molding (MIM) provides an alternative machining method for a wide range of fasteners, screws, seat belt components, wing flap screw seals, bushings and many plasma components. By using MIM, the durability and aesthetics of these important aerospace components can be enhanced.

MIM Titanium Injection Molded Parts for Commercial Aircraft

Suitable Manufacturing Process

To ensure quality while saving costs, more and more aerospace designers are turning to MIM technology. With more than 49,000 aircraft expected to be produced globally by 2026, MIM can support the huge demand for components.

Just as composite fibers have replaced aluminum in fuselage and wing structures, and ceramics have replaced key engine components, MIM is replacing smaller traditional metal machined parts. MIM is a mesh forming process for the production of solid metal parts that combines the design freedom of plastic injection molding with the superior material properties near forged metal.

MIM mixes metal powder with a thermoplastic binder and molds the cavity. The molded part is heat treated (sintered) to remove the binder while producing a network of high density components. Because it is a forming process, it can produce an almost infinite number of highly complex three-dimensional geometries in many different metal alloys.

Electronic components can be excellent MIM candidates with excellent mechanical properties, such as microswitches, connectors, solenoids, heat sinks, optical connectors and patch panels.

Manufacturing Cycle

Completion of a metal injection molding (MIM) project can take up to 16 weeks from mold design and build. Once tooling is set, batch production of 2,500 or more can typically be completed in 4 weeks or less. Aircraft manufacturers need at least 10,000 starters per year, and in order to guarantee the number and timing of parts delivered each quarter, aircraft manufacturers should release no less than 2,500 to 3,000 copies per quarter, 3 or 4 times per year. Compared to in-house or outsourced precision machining that requires parts, MIM is more consistent and reliable in terms of quality, price, and on-time delivery.

Aircraft designers should consider the initial tooling cost and the price for the number of parts per year, and then amortize it over the projected design life of that part.

Advantages of MIM

Historically, aerospace manufacturers have used powder metallurgy (PM), injection molding and precision machining to complete smaller part designs, but MIM has several advantages.

MIM parts have greater metal density and 3 times the fatigue strength of PM parts. MIM parts also retain the tensile strength of the original material. Furthermore, PM parts are limited to 2D features, whereas MIM is capable of satisfying complex aerospace geometries including undercuts, holes perpendicular to the main axis, and 3D features.

MIMs are generally lighter than precision machined aerospace components. Often, excess material is left in the part to save machining time and reduce costs. Whereas MIM scoops out excess material, saving part weight, manufacturing time, materials and money in final part cost.

At the same time, MIM parts also show better properties than injection molded parts in certain parts such as cockpits, seat assemblies, and seat belts. Because MIM parts are electrically conductive, magnetic, strong, rigid, chemically resistant, and perform well at temperatures well above the melting temperatures of most polymers.

The metal injection molding (MIM) process has become a popular and trusted technology for manufacturing high-quality, high-precision metal parts. That's why the aerospace industry is closely related to this process! MIM has distinct advantages justifying its requirements for accuracy and quality, which can be explained in the following points.

1. Complex 3D geometric designs become possible

The metal injection molding process has been found to be very effective in the high-precision manufacturing of complex 3D designed parts. As a result, complex geometrically designed assemblies for aero-engines and other parts can be easily manufactured through MIM.

2. The components produced are suitable for use in applications with tight dimensional tolerances

Aerospace components require high dimensional accuracy, and metal injection molding technology can achieve the same. Manufacturers are making various such machine parts through the MIM process.

3. Micro parts manufacturing

The metal injection molding process is suitable for the manufacture of complex miniature parts, which are used in large quantities in the aerospace industry. These parts can be easily developed to the required dimensions without re-machining to achieve the desired result.

4. Precise marking on components

The metal injection molding process allows dates, codes and part numbers to be stamped among other specifications of the part. According to the standard, these marks identify the true purpose of the part.

5. The part manufacturing process is controlled by accurate weight input, thus eliminating wastage

The process of MIM itself is highly controlled, and the input material is delivered in a specific weight, which corresponds to the weight of the components. Compared to technologies such as CNC, the loss of material is greatly reduced, which also guarantees economy, especially when the substrate is an expensive superalloy!

6. Relatively low cost to produce complex parts compared to other technologies

The aforementioned properties of MIM ensure that complex assemblies can be manufactured while reducing time, increasing efficiency and cost-effectiveness.

Application

MIM is an excellent choice when part batches exceed 10,000 pieces, parts are 3" or smaller in size, weigh no more than 25g but have complex shapes, and need to reduce cost. MIM is often specified for applications ranging from surface finish flexibility allowing everything from dumb Surface treatment and color from light stainless steel to highly polished. Zhongwei Precision can now produce oversized metal injection molded parts with a maximum weight of up to 450 grams, overcoming the technical problem of difficult molding of large parts.

Lightweight is a goal of aircraft design, and MIM technology is a powerful boost to this goal.