Metal additive manufacturing of conformal cooling channels for improving the quality of metal injection–molded products
Chen-Yuan Chung, Chuan-Jen Liu
Abstract
The primary advantage of metal injection molding (MIM) is that it can be used to mass-produce complex metal products; however, it requires a few secondary processes. Metal additive manufacturing (MAM) technology is maturing, and conformal cooling channels have been widely used in injection molding. However, plastic injection molding remains the topic most often discussed in the literature. The present study combined MIM with MAM to explore the effect of conformal cooling channels on green parts and molds, which is the novelty of this study. In the design stage, the benefits of the conformal cooling channels were evaluated using the injection molding simulation software Moldex3D. The results revealed that the mold preheating time required when conformal cooling channels were used was 92.8% shorter than that required when conventional cooling channels were used. This study used three-dimensional printing of metal to fabricate the die cores and cavities for conformal cooling channels, and trial runs were conducted to compare the conformal cooling channels with conventional cooling channels. Infrared thermographic imaging revealed that the conformal cooling channels improved cavity temperature uniformity by 15.46% and core temperature uniformity by 3.49%; these improvements are crucial because the quality of green parts is strongly affected by the control of temperature in the mold. When a suitable coolant temperature was applied, the conformal cooling channels removed heat more effectively, resulting in a lower mold temperature and shorter cooling time. During an actual trial run, the cooling efficiency of the adopted conformal cooling channel mold was higher than that of the adopted conventional mold. In addition, the production of green parts remained smooth operation. The dimensions of the green parts obtained using the conformal cooling channels were comparable to those obtained using the conventional cooling channels, which proved that the conformal cooling channel mold yielded green parts with similar dimensional accuracy while reducing the cycle time.