Thin micro sheath heaters are embedded just under the surface of a mold during the process of laser metal sintering. This is to reduce the weld line on the molded surface by heating it just before the injection. Laser metal sintering process was interrupted at a level just below the final height to make grooves into which to insert micro sheath heaters. After the heaters were installed, laser metal sintering continued over the heaters until the final mold height was reached. Through this process, micro heaters 1 mm in diameter were embedded 2 mm under the mold surface. The mold surface was heated to 20°C over the cooling temperature by the embedded heaters just before the injection, and heating was stopped after the injection. By so doing, the weld line on the molded surface was reduced, while the cooling time was the same as in molding without such heating.

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