菜单
  

     
    process. Mold temperature can be kept at high temperatures for a longer time than in water heating. Therefore, the filling and packing can be improved, making the contact between mold surface and melt improved.
    Hardness is one of the most important properties of a material. It can be used as an indicator of the polymer product. When the other parameters are fixed, based on the standard of ISO 868, type D and resolution of 1%, Fig. 12 shows the Shore D hardness of the TV housing (measured at point P, Fig. 4) when the steam heating process with different mold target temperatures was used. It can be seen that the higher the target temperature, the higher the hardness of the TV housing. This can be explained by the effect of crystallinity in the product after molding. As mentioned above, by using steam heating, the mold temperature at the cavity surface can rise to a higher value, hence, after a filling period, the melt can be kept at high temperatures for a longer time. In this period, the crystals will continuously increase until
     Fig. 11. Gloss of the TV housing with different target temperatures.    Fig. 12. Hardness of the TV housing with different target temperatures.
     melt temperature is lower than tg. This process shows that the heating time and target temperature are the important factors for hardness.
    6.    Conclusions
    In this study, a steam heating system combined with water cooling to achieve rapid mold temperature control for injection molding was established. The effect of steam heating and the uniformity of mold temperature for simple plate mold were first evaluated. Then the effect of steam heating was applied for a TV housing mold and compared with water heating. By experiment and simulation, the temperature at the surface was observed and compared. In addition, the product quality was also compared between two types of heating. Based on the result, the following conclusions can be made:

    •    For the simple mold plate, steam can increase the mold surface from 50 °C to over 135 °C in 9 s (9 °C/s), and cool down to 50 °C in 44 s (2 °C/s). In this case, 5 periods of temperature history in each cycle can be observed clearly by experiment and simulation.
    •    For the real TV housing mold, steam system had shown a higher
    efficiency in both heating and cooling. Compared with water heating, steam heating can reduce from 18 s to 8 s for the heating step and 16 s to 12 s for the cooling step. By changing the target temperature from 70 °C to 110 °C, the heating time varies from 7 s to 19 s, with the highest heating rate at about 3 °C/s.
    •    Part quality is also improved when the steam was used for heating.
    Both hardness and groove were increased due to the high temperature maintained at the cavity surface in the filling and packing processes.
    Acknowledgment
    The authors would like to thank the financial support from The Center- of-Excellence Program on Membrane Technology from the Ministry of Education and the project of the specific research fields in the Chung Yuan Christian University, Taiwan, under grant CYCU-98-CR-ME.
     References
    [1] K.M.B. Jansen, Heat transfer in injection molding system with insulation layer and heating element, International Journal of Heat and Mass Transfer 38 (2) (1995) 309–316.
    [2] D.G. Yao, B. Kim, Development of rapid heating and cooling system for injection molding   applications,   Polymer   Engineering   and   Science   42   (12)   (2002)
    2471–2481.
    [3] S.C. Chen, Y. Chang, Y.P. Chang, Y.C. Chen, C.Y. Tseng, Effect of cavity surface coating on mold temperature variation and the quality of injection molded parts, International Journal of Heat and Mass Transfer 36 (10) (2009) 1030–1035.
    [4] S.C. Chen, H.M. Li, S.S. Hwang, H.H. Wang, Passive mold temperature control by a hybrid filming-microcellular injection molding processing, International Journal of Heat and Mass Transfer 35 (7) (2008) 822–827.
  1. 上一篇:暖通空调英文文献和中文翻译
  2. 下一篇:模具注塑成型英文文献和中文翻译
  1. 立体光照成型的注塑模具...

  2. 注射成型机配置设计英文文献和中文翻译

  3. 塑料制品的注塑模具设计...

  4. 异型件缠绕成型的研究英文文献和中文翻译

  5. 塑料注射模具设计U型铣槽...

  6. 塑料制品模具设计英文文献和中文翻译

  7. 塑料成型生产过程中形成...

  8. 乳业同业并购式全产业链...

  9. 十二层带中心支撑钢结构...

  10. 大众媒体对公共政策制定的影响

  11. 中考体育项目与体育教学合理结合的研究

  12. 电站锅炉暖风器设计任务书

  13. 杂拟谷盗体内共生菌沃尔...

  14. 河岸冲刷和泥沙淤积的监测国内外研究现状

  15. java+mysql车辆管理系统的设计+源代码

  16. 酸性水汽提装置总汽提塔设计+CAD图纸

  17. 当代大学生慈善意识研究+文献综述

  

About

751论文网手机版...

主页:http://www.751com.cn

关闭返回