Experiment and Mechanism Analysis of Gas-assisted Extrusion Forming for Plastic Micro-tube
REN Zhong1,2, HUANG Xingyuan3, LIU Hesheng4
1 Key Laboratory of Optic-electronic and Communication, Jiangxi Science and Technology Normal University, Nanchang 330038, China 2 Key Laboratory of Optic-electronic Detection and Information Processing of Nanchang City, Jiangxi Science and Technology Normal University, Nanchang 330038, China 3 College of Mechanical and Electric Engineering, Nanchang University, Nanchang 330031, China 4 School of Chemical Biology and Materials Science, East China University of Technology, Nanchang 330013, China
Abstract: In order to solve the extrudate swell, extrusion fracture and extrusion distortion problems generated by the traditional extrusion of plastic micro-tubes, the inner and outer layers of gas-assisted technique was applied into the extrusion forming of plastic micro-tubes in this work. The gas-assisted extrusion experiments of plastic micro-tubes were carried out. The experimental results were compared with that of the traditional extrusion. To further ascertain the reason that the gas-assisted method can overcome the problems produced by traditional method, the numerical simulations of traditional method and gas-assisted extrusion method were performed and compared with each other. Experimental results show that the gas-assisted technique not only overcomes the extrudate swell of traditional extrusion of plastic micro-tubes, but also improves the glossiness and transparency on the surface of extruded plastic micro-tubes. Numerical results show that by using the gas-assisted method, the pressure, shear and normal stress difference distributions of melts in the channel of die are greatly eliminated, especially at the outlet of die, which results in the melt’s sticky and no-slip shear flow of traditional extrusion is changed into the full slip and no sticky flow. Moreover, at the outlet of die, the flow velocity distributions of melt are uniformed even without sudden change and radial flow velocity. Therefore, the extrusion problems of plastic micro-tubes are well solved by means of the gas-assisted technique.
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