The Formation Principle Of Ring Laser Beam And Research On Laser Welding Of Polymer Materials

Polymer material has the characteristics of low density, high strength and corrosion resistance, it has become more and more widespread use in the industry. For a lot of large and complex parts, it is hard to form the parts as a whole. Therefore different joining methods are demanded to connect the different parts to be a unit. Compared with the traditional welding methods of polymer material(vibration friction welding and hot plate welding), laser welding has drawn a lot of attention for its advantages, such as excellent welding quality and high efficiency, which has been widely used in the high-end equipment manufacturing industry. Compared to the international study, the gap become more and more greater. Therefore, starting research on laser welding has significant meaning.The welding for ring seam parts were performed that is made to rotate a laser head or rotate a worktable in the conventional methods. Therefore, a ring beam optics is developed for a circular seam welding of the automotive using the optical system, and the polymer material with a circular seam are firmly welded in a super-short times. It rises the welding quality and processing productivity. As the results, with increase of focal length of collimating lens, the outside diameter as the ring laser beam is hardly changed, the inside diameter of the ring laser beam decreases, the width of the ring laser beam is increased in the experiment. A distance(L12) between first axi-cone lens and second axi-cone lens increases, the outside diameter and inside diameter as the ring laser beam increases simultaneously, and the width of the ring laser beam is almost fixed. Moreover, it is confirmed that the intensity distribution of the ring beam becomes uniform by adjusting the coaxial performance of collimating lens, first axi-cone lens, and second axi-cone lens. Justing the distance between the first axi-cone lens and the second axi-cone lens L12=61.5mm, the ring laser beam has been outside diameter of 55 mm, inside diameter of 44.2mm, and width of 5.4mm, performing the high speed welding of lap joints in the 1+2mm thickness of polymer material, pressure is 200 N, laser power is 300 W, irradiation time is 2.0s, the tensile-shear strength of the polymer material joint with laser welding was approaching to the base mental, the fracture of the stretching pieces is appeared in the base mental(TPV).Traditional laser welding head has high energy density, beam Gaussion distribution, Heating zone temperature was Gaussion distribution, the heating temperature of weld intermediate was too high, but the both side of the heating temperature was low, the defects were appeared in the joint surface, such as ablation or pores. Therefore, it add a focus lens of f=60mm under the ring beam optics head, the ring laser beam has been outside diameter of 2.0mm, inside diameter of 1.7mm, and width of 0.15 mm. Select laser power, welding speed, beam diameter, dwell time after welding parameters for the main study, welding the thickness of 3.5mm PA6 material in orthogonal tests. As the results, the order of processing parameters affecting welding quality is laser power, welding speed, focus spot size, and dwell time after welding. The optical parameter is laser power of 80 W, welding speed of 2mm/s, focus spot size of 3.0mm, dwell time of 40 s after welding. The tensile-shear strength of the polymer material joint with laser welding was approaching to percentage of 86% compared with the base mental(19.05MPa), the fracture of the stretching pieces is appeared in the weld base mental.