Dimensional Tolerances
As a starting basis, MIM is capable of as-sintered tolerances of: 0.3% of nominal (i.e. 1.000" .003")
This compares to the investment casting process with tolerances of: 0.5% of nominal (i.e. 1.000" .005")
The exact tolerance capability on any feature is influenced by a variety of variables that are inherent in the MIM process. The resulting tolerance capability may be less than the ±0.3% noted above or greater in some cases. Variables such as part design, size, shape, material, gate location, number of cavities, mold construction techniques, annual part volume, and inspection techniques need to be taken into consideration. The material chemistry selected for your application can have a greater effect on tolerances that you might imagine. Not all materials produce the same tolerance results. Gauging or inspection requirements are an integral element of a component design and could have a heavy influence on tolerance capabilities. It has been our experience that theoretical intersections, centers of radii, and very small features require larger percentage tolerances due to gauge resolution, repeatability, and capability limitations. Kinetics' design engineers are available to discuss gauging designs while assisting your component design efforts.
Fig. 31 shows examples of the typical tolerance requirements for a MIM component without the need for any secondary operations.
Depending on component geometry, flatness and straightness specifications of down to .001 inch-per-inch are achievable. This is especially true if the entire critical surface can be supported during debinding and sintering, or the critical feature is perpendicular to the supported surface. Gate location, cross-sectional thickness, and cross-sectional geometry have an effect on the resulting straightness or flatness. Fig. 32 & Fig. 33 show examples of various MIM geometries and the resulting flatness or straightness.
0.3% of nominal (i.e. 1.000"