Reducing Weld Line by Heating Mold Surface with Heater Embedded by Laser Metal Sintering
Takeshi Yoneyama*, Satoshi Abe**, and Michiru Miyamaru***
*School of Mechanical Engineering, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
**Panasonic Corporation Eco Solutions company, 1048 Kadoma, Osaka 571-8686, Japan
***Miyamaru Precision Mold Co., 1-31 Higashi-kayatsume, Kanazawa 920-0209, Japan
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.
-  S. Abe, Y. Higashi, I. Fuwa, N. Yoshida, and T. Yoneyama, “Milling-Combined Laser Metal Sintering System and Production of Injection Molds with Sophisticated Functions,” Proc. of the 11th Int. Conf. on Precision Engineering, pp. 285-290, 2006.
-  T. Yoneyama, H. Kagawa et al., “Effective Cooling and Accuracy Improvement in Injection Molding Using a Metal Mold with Cooling Channels Composed by Laser Sintering (3rd report),” J. of Precision Engineering, Vol.71, Issue 3, pp. 347-351, 2005. (in Japanese)
-  T. Yoneyama, H. Kagawa et al., “Accuracy Improvement in Injection Molding Using Milling-combined Laser Metal Sintered Mold,” J. of Precision Engineering, Vol.73, Issue 9, 2007. (in Japanese)
-  T. Yoneyama, H. Kagawa et al., “Reduction in Injection Cycle time Using a Milling Combined Laser Metal Sintered mold,” Seikeikakou, Vol.19, No.10, pp. 662-668, 2007. (in Japanese)
-  T. Yoneyama and H. Kagawa, “Fabrication of Cooling Channels in the Injection Molding by Laser Metal Sintering,” International J. of Automation Technology, Vol.2, No.3, pp. 162-167, 2008.
-  T. Yoneyama, K. Naito, S. Abe, and M. Miyamaru, “Reduction of Injection Pressure for Thin Walled Molding using the Laser Metal Sintered Mold,” J. of Precision Engineering, Vol.76, Issue 2, pp. 188-192, 2010. (in Japanese)
-  T. Yoneyama, S. Abe, and M. Miyamaru, “Reduction of Weld-line by the Laser Metal Sintered Mold and the Effect of Hot Air Preheating,” Journal of Precision Engineering, Vol.77, Issue 10, pp. 955-959, 2011. (in Japanese)
-  R. Yoshino and U. Takeno, Japanese patent No.4052600.
-  Y. Sato et al., Japanese patent No.3977565.
-  S. C. Chen, Y. Lin, R. Chien, and H. Li, “Variable mold temperature to improve surface quality of microcellular injection molded parts using induction heating technology,” Advances in Polymer Technology, Vol.27, Issue 4, pp. 224-232, 2008.
-  N. Renou and J. Feigenblum, “How Inductive Heating Can Improve Plastic Injection,” Seikei-kakou, Vol.23, No.12, pp. 705-710, 2011.