MIM Application Characteristics
Metal Injection Molding or MIM (also referred to as Powder Injection Molding or PIM) is a net-shape process for producing solid metal parts that combines the design freedom of plastic injection molding with material properties near that of wrought metals. With its inherent design flexibility, MIM is capable of producing an almost limitless array of geometries in many different alloys. Today, MIM is serving critical performance applications in a wide range of products including, automotive fuel and ignition systems, aerospace and defense systems, cellular telephones, dental instruments and braces, electronic heat sinks and hermetic packages, electrical connector hardware, industrial tools, fiber optic connectors, fluid spray systems, hard disk drives, pharmaceutical devices, power hand-tools, pumps, surgical instruments, and sporting equipment.
An emphasis on plastic part design flexibility should be applied to metal part geometries developed with the MIM process in mind. Traditional metalworking technology limitations should be ignored. The MIM process can allow significant shape sophistication, the combination of multiple parts, multiple feature/functions within a single component, product assembly enhancement features, miniaturization of mechanical assemblies, mass reduction, and custom tailored physical properties for the intended end use are all possibilities with MIM.
MIM represents the most cost effective manufacturing approach for small intricate metal components that are required in medium to very high volumes. One approach to defining a candidate application is to imagine how many machining operations would be required to produce the shape if it were to be machined. In general, MIM is the preferred process for component designs that would require 4 or more machining set-ups or operations. Keep in mind that machining adds incremental cost for each machined feature, while the molding process used in MIM adds very little or no incremental cost for each molded feature. Fig. 1 provides a cost versus part complexity comparison of MIM against other manufacturing technologies.
The following is a list of general characteristics that describe good MIM applications:
Some parts
Lengths to 7 inches
Wall thickness to 0.5 inches
Weights above 100 grams
Volumes as low as 5,000 annually
Most parts
Lengths less than 3 inches
Wall thickness from 0.04 to 0.12 inches
Weights under 60 grams
Volumes of 100,000 to >100,000,000 annually
A very effective way of utilizing MIM's inherent design freedom is to combine multiple components in an assembly into a single MIM component. Fig. 2 illustrates the conversion of a 4-component assembly into one MIM component. This eliminates 3 assembly steps and related costs, plus reduces the number of parts that have to be purchased, tracked, and managed through inventory. The resulting MIM component is stronger, more cost effective, and is produced closer to the original design intent than the assembly. Fig. 3 displays an actual application of this design approach. Three parts were combined into one, which provided improved product performance at a much lower cost.
While the best cost benefit of MIM generally comes from applications designed with the technology in mind, successful technology conversions routinely take place. Kinetics' design engineering team can assist your efforts to evaluate potential technology conversions from a preliminary cost analysis to a comprehensive review of dimensional tolerance specifications.
