MoldMaking Technology

AUG 2018

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Hot Runners 24 MoldMaking Technology —— AUGUST 2018 By William Sames, Ph.D. Guidelines for Advanced Hot Runner Manifold Channel Design H ot runner manifold channel design is essential for the operation of an injection mold, impacting change-out time, part quality and even the number of possible drop locations in the mold. The key to advancing manifold design is having the ability to manufacture and implement curved channels in blocks of steel. Cross-drilling and plugging a block of steel produces the simplest manifolds. Advanced manifolds may use brazed plug inserts to round internal corners or two-piece brazed manifolds to achieve curved internal channels without plugs. However, plugs are a complicated solution that can still leave drag spots. Brazed plates can be successful, but Recent simulation research highlights the difference between a drilled, straight manifold channel design and a curved channel design produced via additive manufacturing. they have limited size and potential quality issues because of the weakness of braze joints (which are basically a metal "glue"). Manifolds are typically subject to the hottest tem- peratures and the highest pressure of either the mold or the hot half, making steel strength critical for maintaining the mechanical integrity of the hot half. Curved manifold channel design produced by metal additive manufacturing (AM) is a new method capable of achieving a better balance of fill across drop locations (or equalized residence time of the polymer), according to a recent research project by Oak Ridge National Laboratory (ORNL) and HTS International Corp., with the simulation These manifold CAD models show straight versus curved designs analyzed for an eight-drop system. FIGURE 1 Figures courtesy of HTS International Corp.

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