Metal Injection Molding Of Titanium And Stainless Steel Provides Cost And Quality Advantages For Today’s Aircraft Manufacturers

Jim Beyer, Account Manager

Advanced aerospace materials using the metal injection molding (MIM) method are providing an alternative, and often better processing method than casting and machining. Important, smaller aerospace components that never make headlines in aerospace manufacturing are candidates for cost savings, weight savings, durability improvements and even enhanced cosmetic appearance using the MIM process.

Today’s commercial and military aircraft require huge quantities of fasteners, screws, seatbelt components, wing flap screw seals, bushings and dozens of similar related components. As an example, there are an estimated 700,000 components in a Boeing 737NG with over 7000 of those planes built to date. Traditional manufacturing methods of current aircraft components more often than not require die casting and value added processes such as machining, metal finishing and plating. With today’s MIM technology, these older methods come up short by comparison.

Use Of MIM Is Historically Proven As An Appropriate Aerospace Manufacturing Process And Is Even More Appropriate In The Current High Volume Aircraft Era

In-the-know aerospace designers have specified MIM for key aircraft components since as far back as the 1980’s. These parts range from latches and fittings to seat belt assemblies and a wide range of adjustment levers. Similarly, Smith Metal Products has been producing many aircraft components dating to the company’s MIM startup in the mid-1990’s. From an industry standpoint, MIM hasn’t attracted the number of customers and users of its technology that it rightly deserves. Until now when designers are searching for better ways to ensure quality while saving money with their designs.

The pace of new aircraft designs and sheer volume of new planes manufactured have ramped up considerably compared to the 1980’s. Just in the ten-year period from 2007-2016, over 45,000 commercial and military aircraft were built, according to Aerospace and Defense Manufacturing 2017 Yearbook. And for the future, over 49,000 aircraft are projected to be manufactured between 2017 and 2026. There’s tremendous component volume in these new aircraft quantities and MIM has a preferred role. Here’s why:

Metal Injection Molding (MIM) Technology Meets The Challenges Of The Aerospace Age

Just as composite fiber has replaced aluminum in fuselage and wing structures and ceramics have replaced key engine components, MIM is replacing the smaller, traditional metal components. Here’s why:

Metal injection molding (MIM) is a net-shape molding process for producing solid metal parts that combines the design freedom of plastic injection molding with superior material properties near that of wrought metals.

Metal injection molding mixes metal powder with a thermoplastic binder and is molded into a cavity. The molded part is thermally processed (sintered) removing the binder while producing a net shaped, high density component. Because it is a molding process, it is capable of producing an almost limitless array of highly complex three dimensional geometries in many different metal alloys. Among these are stainless steel, Titanium and other custom ferrous alloys preferred by the aerospace industry.

What Are MIM’s Advantages Over Other Processes?

For many years, aerospace manufacturers have used powdered metallurgy, plastic molding and precision machining processes in smaller part designs. A comparison reveals several advantages for MIM:

MIM is a superior process to powder metallurgy (PM) because MIM parts have greater metal density and three times the fatigue strength. For safety reasons, aerospace components must provide maximum durability often well past the service life of the aircraft. Also, MIM parts tensile strength is consistent with the metal selected for the process. In other words, a MIM processed part has the tensile strength of the original material. Also, powdered metallurgy parts are limited to 2D features while MIM allows complex aerospace geometry including undercuts, holes perpendicular to the main axis and precision 3D features.

MIM is often a superior process to precision machining, a common aerospace component manufacturing method. However, each machined feature adds time and cost to the part price. When excess material is left in the part to save time and removal cost, excess weight is retained. And today’s aircraft designs strive for lighter weight. In contrast, MIM parts can have many features incorporated into the tooling with excess material cored out, saving part weight, manufacturing time, material and money in the final component cost. Smith Metal Products offers free Design for Manufacturability assistance, and will help designers identify areas where component wall thickness are excessive, and then make recommendations for alternate, cost-saving designs and lower tooling costs.

MIM is superior to plastic components because MIM parts are conductive, magnetic, strong, stiff, tough, chemically resistant and can operate at temperatures far over the melting range of most polymers.