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One way to improve the quality of injection molded parts is through a variotherm, or dynamic, approach to controlling mold surface temperature. This strategy requires that the mold surface temperature react as quickly and homogeneously as possible to changes in coolant temperature, helping to avoid shrinkage and other defects in the part. Additively manufactured mold components are especially well-suited to this strategy, because they can incorporate conformal cooling channels that closely follow the mold’s surface geometry for better responsiveness.

A recent case study from GF Machining Solutions details the redesign of a mold for a valve component that was prone to shrinkage. After other approaches—such as changing the material of the mold and dividing the core into three different components—failed to ensure the necessary reaction speed in the mold components, the company turned to a solution incorporating metal additive manufacturing.

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The final mold design features a core that combines a close-contour channel system produced additively with a simpler lower portion machined conventionally on a mill-turn center. The resulting mold inserts were milled on a high-speed Mikron Mill S 400 U and processed with an AgieCharmilles Form 200 die-sinking EDM. 

In testing, the additively manufactured core insert maintained a more homogeneous surface temperature, stabilizing in less than 20 percent of the time taken by the conventionally machined original. As a result, the shrinkage in the part was virtually eliminated, reject parts were reduced, and cycle time decreased by 10 to 15 percent.

on the Additive Manufacturing website.