Plastic lenses are light and can be mass-produced. Large-diameter aspheric plastic lenses play a substantial role in the optical industry. Injection molding is a popular technology for plastic optical manufacturing because it can achieve a high production rate. Highly efficient cooling channels are required for obtaining a uniform temperature distribution in mold cavities. With the recent advent of laser additive manufacturing, highly efficient three-dimensional spiral channels can be realized for conformal cooling technique. However, the design of conformal cooling channels is very complex and requires optimization analyses. In this study, finite element analysis is combined with a gradient-based algorithm and robust genetic algorithm to determine the optimum layout of cooling channels. According to the simulation results, the use of conformal cooling channels can reduce the surface temperature difference of the melt, ejection time, and warpage. Moreover, the optimal process parameters (such as melt temperature, mold temperature, filling time, and packing time) obtained from the design of experiments improved the fringe pattern and eliminated the local variation of birefringence. Thus, this study indicates how the optical properties of plastic lenses can be improved. The major contribution of present proposed methods can be applied to a mold core containing the conformal cooling channels by metal additive manufacturing.

In the present study, semi-crystalline polypropylene (PP) and amorphous polystyrene (PS) were adopted as matrix materials. After the exothermic foaming agent azodicarbonamide was added, injection molding was implemented to create samples. The mold flow analysis program Moldex3D was then applied to verify the short-shot results. Three process parameters were adopted, namely injection speed, melt temperature, and mold temperature; three levels were set for each factor in the one-factor-at-a-time experimental design. The macroscopic effects of the factors on the weight, specific weight, and expansion ratios of the samples were investigated to determine foaming efficiency, and their microscopic effects on cell density and diameter were examined using a scanning electron microscope. The process parameters for the exothermic foaming agent were optimized accordingly. Finally, the expansion ratios of the two matrix materials in the optimal process parameter settings were compared. After the experimental database was created, the foaming module of the chemical blowing agents was established by Moldex3D Company. The results indicated that semi-crystalline materials foamed less due to their crystallinity. PP exhibits the highest expansion ratio at low injection speed, a high melt temperature, and a low mold temperature, whereas PS exhibits the highest expansion ratio at high injection speed, a moderate melt temperature, and a low mold temperature.

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.

FEA of orthodontic miniscrews has predominantly assumed isotropic, homogeneous bone, neglecting directional variations in mechanical properties. This study investigated the biomechanical behavior of miniscrews under different insertion angles and loading directions using both isotropic and orthotropic mandibular bone models. The results indicated that isotropic modeling may underestimate miniscrew displacement and associated instability, whereas orthotropic material properties better reflect the true mechanical response of bone. Oblique insertion at 60° (U60°) led to higher strain and greater variability, which may compromise osseointegration; aligning the loading direction parallel to the insertion plane is therefore recommended when oblique placement is unavoidable. Screw thread design had minimal influence on displacement, von Mises stress, or bone strain during vertical insertion. Stress and strain distributions exhibited symmetry, suggesting that analyzing partial loading directions can predict the overall biomechanical response. All predicted values remained below bone and material strength limits, confirming the mechanical safety of the current miniscrew design under a 2 N load. Implant failure is likely attributable to poor osseointegration or inflammation rather than structural limitations.