The Effects of Ultrasonic Vibration on the Weldline Strength of Injection Molded

• Main Authors: TSAI-SHIH KUO, 蔡世國
• Other Authors: Shih-Jung Liu
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/89633352057911718780

碩士 === 長庚大學 === 機械工程研究所 === 95 === Injection molding has been one of the most important methods for the manufacture of plastic products. However, there are several unsolved problems that confound the overall success of this technique. The forming of weldlines wherever polymer flow fronts meet is one of them. In this report, an ultrasonic vibration assisted injection molding was proposed to improve the weldline strength of molded parts. A dumbbell cavity equipped with an ultrasonic vibration was used to mold the parts. Experiments were carried out on an 80-ton reciprocating screw injection molding machine. After molding, the strengths of the weldline were measured. The experimental results suggested that ultrasonic vibration could improve the weldline strength of injection molded parts for melt temperatures up to 210oC, after that, the effect of assisting vibration is relatively limited. The increase of the weldline strength was mainly due to the molecular entanglement across the weldline interface. In addition, the optimization of the weld strength can be obtained by appropriate combination of the melt temperature, the vibration time and the vibration delay time. Keywords: injection molding, ultrasonic vibration, weldline strength, processing parameters