Undercuts - External/Internal
External undercuts can be produced readily with the MIM process. The component on the left in Fig. 16 shows an external undercut that provides relief for burrs on a mating stamped component. The ability of MIM to provide the feature by placing it in the mold design eliminates the need and related cost associated with removing the burr on the stamping. Essentially, an increased level of complexity can be provided in the MIM part without effecting the part's cost, while at the same time the MIM part design eliminates the need for a secondary deburring or chamfering process on the stamping. Consideration of product assembly requirements should always be considered when designing components to be produced by the MIM process.
Internal undercuts are possible with MIM under the right conditions. Internal undercuts that can be produced with a mechanical or hydraulic actuated slide can be readily produced. Fig. 16 (top, right) shows a "T-slot" internal undercut that can produce with a slide. Fig. 16 (bottom, right) also shows a similar component but the internal undercut requires a collapsible core. This undercut requires the internal feature to be large enough to accommodate a robust collapsible core. Generally though, MIM components are small and collapsible cores are often impractical and some times impossible to produce that is robust enough to take the injection pressures used by the MIM molding process. Collapsible cores also provide challenges in maintenance to minimize flash. Seek advice from Kinetics' Applications Engineer's when considering such features.
