Metal Injection is Lower-Cost Alternative to CNC Machining
While plastic injection molding receives the lion's share of attention, its lesser-known cousin, metal injection molding (MIM), is an effective, highly valued process in its own right. According to Paul Hauck, director of sales and marketing at Kinetics, a Dynacast Company, metal injection molding is inherently capable of producing highly complex, net-shape components that routinely provide significant cost savings over traditionally CNC-machined components.
"For high-strength, very complex metal parts, generally those of the size that can fit within a coffee mug, metal injection molding is a much lower cost than CNC machining," says Hauck. "MIM is also lower cost for moderate- to high-volume investment casting applications and those investment cast parts that may require secondary machining to obtain tolerances, surface finishes, and fine feature details that are readily available from standard MIM processing."
The process uses many of the technologies practiced by thermoplastic injection molders, including hot runner systems, unscrewing cores in molds, and extraction and placement of parts using servo robotics. MIM is effective for a variety of applications, such as automotive, business machines, computers, electronics, and medical and dental equipment. The process can also be employed for power hand tools, sporting equipment, and telecommunications applications, including fiber optics and cellular telephones. However, a lack of awareness of the process, as well as the lack of a thorough understanding of dimensional capabilities and of part and mold design requirements, have inhibited the selection of MIM over traditional metalworking technologies.
According to Hauck, MIM does have a size limitation that generally reflects the high cost of the fine metal powders required by the process. For large components (over 1/4 lb. or approximately 100 grams), costs of material generally offset the value of complexity that the process offers. But as material costs come down, MIM is expected to serve larger parts, Hauck said.
In the meantime, Dynacast takes on a variety of metal injection-molding challenges, generally involving mechanical components. Its jobs range from high-strength requirements to highly complex geometries that would otherwise be cost-prohibitive to produce by conventional means. The company provides a complete package that includes heat-treating, plating, assembly, and other secondary requirements. A significant capability, Hauck says, is the firm's ability to accurately predict process dimensional capabilities prior to fabricating expensive injection molds.
"In MIM, this is a significant accomplishment as many factors influence the outcome of the process," Hauck asserted. "Selected material chemistry, tooling, injection molding, debinding, and sintering all influence the resulting dimensional tolerances of the parts that are produced. Dynacast works closely with its customers on MIM part designs and to answer the important dimensional stability questions prior to producing the final part."
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