MIM combines the benefits of net-shape metal parts and molded-in part functionality not possible with machining. MIM is a growing technology, with automotive being one of the promising application markets.
High costs of machined metal parts are triggering greater interest in a semi-obscure metal molding process rapidly moving into the manufacturing mainstream.
According to a new report from BCC Research in Wellesley, Mass., the global metal injection molding (MIM) components market is projected to nearly double from $1.5 billion in 2012 to nearly $2.9 billion by 2018.
“MIM still is growing fast, as it brings real value to customers by bringing down their product cost, which adds to the bottom line even if the top line stays flat, which is very important in a slow-growing economy,” said, Vijay Subramanian, the BCC analyst who wrote the report.
One big benefit: The molding process provides the opportunity to integrate functionality that is not possible in a one-off process like machining. At the same time, suppliers say that MIM achieves the strength and integrity of metals formed through more traditional processes.
Some players think the BCC forecast of 11.4 percent compound annual growth rate (CAGR) may be too conservative.
According to the ARC Group Worldwide, the global MIM market exceeds $1.2 billion annually, with recent annual growth rates above 20 percent. The domestic and European MIM markets are both estimated at about $350 million, while the Asian market is $550 million and growing rapidly. ARC is significantly expanding metal molding capacity at its AFT plant in Firestone, Colo., and is reporting 50 percent year-on-year sales gains.
One of the promising markets for MIM is automotive.
A value analysis project at global components producer Bosch achieved savings of 80 percent by converting a fuel-control gear segment to the metal injection molding process. The low-alloy steel component goes into a device that regulates the entry of fuel into an engine.
It demonstrates one of the big advantages of MIM: net-shape molding that requires no secondary operations. The part has a density of 7.5 g/cu-cm, 46,000 psi ultimate tensile strength, 19,000 psi yield strength, 25 percent elongation, and 100 HRB maximum hardness (Rockwell scale). Production volume is three million parts per year. The fabricator is Indo-US MIM Tec Pvt. Ltd., which is based in Bangalore, India.
MIM usually competes against parts made via machining or casting.
One of the fast-growing markets for MIM is firearms, which requires small precision components.
A fabricator named Parmatech Corp., in Petaluma, Calif., saved a customer a reported 25 to 35 percent through the metal molding of a complex actuator used in a tool‐less locking system that enables quick changing of a shotgun stock. Molding the part required the use of stepped ejector pins on the sloped surface to allow for smooth ejection with no part damage. The component has a 0.05 mm (0.002 in) straightness requirement of the longer‐than‐25.4 mm (1 in) shaft, as well as a tight profile requirement of the curved and sloped cosmetic surface.
MIM is not a new process but has had a slow takeoff because of its complexity and the investment required for molds. There are four processing steps: compounding, molding, debinding, and sintering. Some finishing may be required.
In the compounding phase, fine metal powders are blended with thermoplastic and wax binders in a roughly 60:40 ratio by volume. The mixture is formed into pellets that can be processed by an injection molding machine.
Molded parts (called “green”) shrink about 20 percent in a predictable manner. Binder materials are usually removed in the third step through a solvent extraction process. The parts are then loaded on ceramic setters and placed in a high-temperature, atmosphere-controlled furnace where voids are eliminated as the particles fuse together.
Applications for metal molded parts span a spectrum of industries including automotive, aerospace, defense, consumer electronics, dental, electronics, fiber optics, hermetic packages, surgical instruments and implants, power and hand tools, hardware, and sporting gear.
To determine if MIM may be a good candidate for a value analysis project, see if the part in question meets these criteria:
Size: Because of the expense of the materials, the process best fits small components. The most economical applications are parts that weigh less than 50 g (1.75 oz).
Volumes: Significant production is required to amortize tooling costs.
Complexity: The case for MIM rises exponentially every time an additional feature or function can be molded in, eliminating what would have been expensive secondary operations for machining.
Tolerances: According to major suppliers, the general guideline for MIM precision of net shape features is ±0.5 percent of the dimension. Machining is best when extremely tight tolerances are required.
Materials that can be used in the metal injection molding process include steel alloys, superalloys, titanium alloys, copper alloys, refractory metals, cemented carbides, and metal matrix composites. Processes like die casting are generally more economical for aluminum and brass.
Doug Smock is a former chief editor of several industry magazines and currently writes a plastics blog called TheMoldingBlog.com. He is co-author of two leading books in supply management: Straight to the Bottom Line (2005, J. Ross Publishing) and On-Demand Supply Management (2007, J. Ross Publishing). Straight to the Bottom Line is now in its second printing. Doug has a bachelor’s degree from Case Western Reserve University, in Cleveland, Ohio.
This article was originally published at My Purchasing Center and has been republished with permission. For more stories, visit MyPurchasingCenter.com.
