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Abstract：Rapid heating cycle molding (RHCM) is a novel plastic injection molding process. It can be used effectively to prevent many defects of products produced in conventional injection molding process. In this paper, the panel of large-size liquid crystal display TV was taken as an example. Thermal, deformation, and fatigue analysis models for RHCM injection mold were established. Firstly,by analyzing the heat transfer process of the RHCM mold,the temperature distributions on the mold cavity surface were studied. Secondly, through numerical simulation, the tendency of the stress and deformation of the RHCM mold was obtained. It showed that the fixing mode between the stationary mold insert and the stationary mold plate had a great influence on the thermal stress and deformation of the mold. As a result, a new fixing mode for the stationary
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mold insert was proposed which could effectively decrease the deformation caused by the temperature changing.Lastly, the lifetime of the mold under different fixing modes was evaluated, and reasonable suggestions which 19600
could improve the lifetime of RHCM mold were also proposed. Application in engineering proved that it was a very effective way to improve the lifetime of RHCM mold by using the suggested fixing mode.
1 Introduction
Injection molding technology has been widely used in almost all fields of the national economy. However, there are always many problems on the parts produced by conventional injection method, such as weld mark, flow mark, and other poor surface appearance. As a result, the mechanical
properties and appearance of the plastic parts usually cannot meet the requirements of customers. The subsequent reprocessing operations such as spraying and coating have to be employed after injection molding process in order to improve the part’s properties. These operations increase the manufacturing processes of parts and waste raw material and energy.What is worse, they also increase the production cost and cause environment pollution inevitably. Rapid heating cycle molding (RHCM) technology is a novel polymer injection molding method developed by Ono Sangyo Co. Ltd. In cooperation with Mitsu Chemical Co. Ltd. in recent years. It can produce high-quality plastic parts with excellent appearance and no weld marks. The surface hardness and strength of the parts can also be improved. Especially, the subsequent processes—spraying and coating which seriously pollute the
environment—can be eliminated. Thus, the flowchart of the whole production process is shortened. The energy, material,and production cost are decreased as well. RHCM is a kind of potential green manufacturing technology in plastic injection molding industry.
For the past 2 years, RHCM technology has been used more and more popularly. More and more companies in Japan, Korea, America, and other European countries have dedicated themselves to developing RHCM technology. In China, our research group in cooperation with engineers
from Hisense Corporation has developed this technology independently and succeeded in producing the panel of large-size liquid crystal display (LCD) TV with very good performance. Several production lines have been established and worked very well. However, as a new technology, there
are still many problems that need to be researched. Until now, there are a few papers published concerning RHCM technology used in practical processes. Chen et al. [1] have proposed a RHCM model for the true 3D and transient thermal response heating and cooling analysis, but it was not aimed at producing real products. Chen et al. [2] have studied the
mold surface temperature and its effects on the surface appearance of weld mark, but the mold deformation and fatigue was not mentioned. Au and Yu [3] proposed a novel and more conformal cooling design for plastic injection mold, but it could be used only in conventional injection
mold. Other scholars such as Nakao and Dimla [4–12] have done a lot of researches on injection molding process but they all did not aim at RHCM injection technology, too.Because of the complexity of the RHCM technology, it has special requirements for structure and machining of the mold.The mold material is also different from the conventional injection mold. The lifetime of the RHCM mold is lower than the convention mold due to its high working temperature. Thus, the RHCM mold costs about two to five times than the convention mold of the same production type. It is very necessary to analyze the thermal, deformation, and fatigue