Metal injection molding is best suited for relatively small parts. On a volume basis, parts should typically be smaller than a tennis ball, with the process being most cost effective when parts are smaller than a golf ball. Irregularly shaped parts can be produced with a major axis of up to about 4 inches (102mm) in length. The lower limit of the size range is determined only by the limitations of the injection molding process itself. Parts as small as 0.25 X 0.10 X 0.05 inch (6.4 X 2.5 X 1.3mm) are feasible.

Table I
Typical Properties of Injection Molded Alloys

The upper limit of part size is established by processing economics, not technical limitations. Larger parts can be made, but may not be cost-effective due to the current price of the preferred fine powders.

WALL THICKNESS

The cross-section or wall-thickness is what ultimately determines whether it is feasible to produce a particular InjectAlloy® part. The part thickness must be kept relatively low to facilitate efficient binder removal. The practical range of section thickness is from 0.03 inch (0.75 mm) to 0.25 inch (6.4 mm). Parts can be molded with thinner cross-sections, but are limited with regard to flow length. MIM parts are sensitive to the relationship of cross-section to length, and it is difficult to form long, tubular parts with thin walls.

WEIGHT

Parts can be made which weigh from 0.1 to 150 grams or more. However, InjectAlloy® parts are most cost-effective in the range of 1 to 50 grams per part, which reflect size and wall thickness considerations.

1 The above properties were obtained from molded tensile specimens. They are considered typical, and are for information only. Properties may vary somewhat on actual parts, depending on size and processing variables.

2 Nickel steels (Fe-2% Ni) may be case hardened. Mechanical properties of the heat treated parts will depend upon the depth of the case and the cross section.