Experiment Research And Temperature Distribution Simulation Of Thermoplastics In Laser Transmission Welding

Laser transmission welding (LTW) of plastics has advantages of low residual stress, excellent welding quality, easy controlling and automatization. Thus, it's widely used in many industries such as automotive and micro welding. LTW is the focus of research abroad, and has a large-scale of industrialization. However, in our country the related research is scarce and only done by the universities and institutes. Therefore, it's very important and necessary to research on LTW of plastics.In this paper, LTW of polycarbonate(PC) and polypropylene(PP) were carried out separately. Influences of laser power(P), weld speed(v) and concentration of carbon black(CB%) as absorbent on welding quality have been discussed in details.First of all, welding specimens are obtained through injection molding. There are 8 kinds of injection molded parts in which pure PC and PP parts are used as transparent part in LTW, the corresponding parts with carbon black concentration of 0.05%, 0.1% or 0.15% are used as absorbent part. Transmittances of the 8 parts at 980nm(wavelength of laser device) are obtained in transmittance test which are all available in LTW.Then, LTW of PC and PP are carried out according to Orthogonal Experimental Design. Destructive tensile test and microscope snapshot are done after LTW, from which tensile strength and weld line photos are obtained. Through analysis we found out that for both PC and PP laser power(P) influences LTW most, followed by weld speed(v) and carbon black concentration(CB%). The best welding parameters for PC are listed as follows: Laser power(P) is 40W, weld speed(v) is 40mm/s and carbon black concentration is 0.15%.The best welding parameters for PP are 50W(P), 15mm/s(v) and 0.15%(CB%).At last, ANSYS software is used to simulate the temperature distribution in LTW process of PC. Simulations with parameters of 40W(P) and 40mm/s(v) as well as 20W(P) and 50mm/s(v) are calculated respectively which are corresponding to No.23 and No.4 of PC LTW. The results of simulations match well with the real experiments.