1. Introduction

This is a study of the effects of temperature of injection mold on the injection molded article. By supplying water of the proper temperature in the cooling line of mold in the cooling process, the mold was the appropriate temperature, and the deformation of the injection molded article was examined according to the mold temperature. In this study, we conducted simulation analysis and experiments, and the results were analyzed. The minimum deformation of the injection molded article model obtained by supplying 50°C water in the cooling line is 0.003 mm, and the maximum deformation was 0.813 mm. Injection molded article models obtained by supplying 20°C water were found to be a minimum of 0.002 mm, with deformation of up to 0.761 mm. When comparing both conditions, the error rate of injection molded article obtained by supplying 20°C water in the mold cooling line was lower by about 0.18%.

In modern industry, in addition to mass production, consumer preferences are persified, and products have an important design element. Many products are made using injection molded articles. Injection molding is a process where by a thermoplastic resin is heated and melted in a cylinder and then injected into a mold where it solidifies to become the final product. Injection molding die is made of die steel, and mold temperature has an effect on the thermoplastic resin . The temperature of the mold plays an important role in determining the quality of the molded products . We are working on improving the quality of our products by changing the mold temperature . In this study, by supplying water of the proper temperature in the cooling line of mold in the cooling process, the temperature of the mold is adjusted to a temperature suitable for injection, and the effects of the temperature of the mold on the quality of the injection molded article were analyzed. Modeling of the mold and mold injected articles was performed by creating 3D models using CATIA V5. The results of the experiment, which was conducted by injecting the obtained results and mold injected articles, were analyzed using a finite-element analysis program.

2. Simulation and Experiment

The injection mold industry endeavors to shorten the injection process time and eliminate deformation of the injection molded article. In order to eliminate deformation of the injection molded article, the cooling time and mold temperature are important factors. The models were composed of a lower die and an upper die. The injection product is shown in Fig. 1. The number of nodes of the model was 682,176 and the number of elements was 421,524. Width, height, and length of the models were 230 mm, 360 mm, and 960 mm respectively. The die of the models is composed of die steel, and the injection molded articles of the models are composed of ABS. The properties of ABS is shown in Table 1.

Fig. 1. 3D model for the analysis

TABLE1  Properties of ABS

Property Value

Young’s modulus (MPa) 2100

Poisson’s ratio 0.392

Density (g/cm3) 0.93673

Yield strength (MPa) 41

Ultimate strength (MPa) 40

Thermal conductivity (W/m·K) 0.189

Specific heat (J/kg·K) 2342

To perform heat conduction analysis, as shown in Fig. 2, the outer mold was given a convective heat transfer coefficient through contact with ambient temperature air. It was set up under two conditions in order to change the temperature of  the injection mold and the cooling time: (a) 50°C, 67sec and (b) 20°C, 46sec. The reason for changing the cooling time is that it’s a condition set for reducing the cycle time by reducing the cooling time. Finite element analysis was performed under the above conditions. In addition, the initial temperature of the injection molded article was set to 200°C. The reason for this is that the temperature when ABS in melted and injected into the mold frame during the injection process is approximately 200°C.

Fig. 2. Transient thermal analysis condition of model :

(a) 50°C, 67sec and (b) 20°C, 46sec