Welding of Acryalics Using Laser Beam:An Experimental Investigation

Abstract

Laser beam welding (LBW) uses high energy density beam making it suitable for welding of wide category of materials. As energy density around the focal point of laser beams is quite high, this technique is being increasingly used in the fabrication industry. Since laser beams follow the principle of optics, it can be easily regulated by selecting appropriate lenses. In this paper, a report on the experimental work involving laser beam welding (LBW) is presented where lap joints of two acryalic (polycarbonate) flats-one opaque and the other transparent, are tried to make. Laser beam passes through the transparent piece of plastic flat, and is focused on to the opaque flat around the interface region. Laser beam gets absorbed in the opaque flat in the interface region and generates heat energy causing local melting, and subsequent welding of both the flats. This method is named as through transmission laser welding. The bonding between the two components is likely to occur by interpenetration of molecular chains in the area that is promoted by fluidity of acrylic during welding. Process parameters such as clamping pressure and current are varied at some selected scanning speeds to explore the appropriate condition to obtain sound, strong weld joint within the experimental domain. The laser has a repetitive operating current less than 60 A with pulse frequency of 0.25-10 kHz. The used 30 W laser system is having spectral width of 1.69 nm, beam divergence of less than 0.20 N.A. and beam diameter of 800 urn with a wavelength of 809.40 μn. Scanning speed of 240,280,320 and 360 mm/min, current flow of 25,28,31 and 34 A, and clamping pressure of 20, 30,40 and 50 Kg/cm² are chosen in this work. Sound welded joint between transparent and opaque acryalic components with high weld strength above 8 MPa is obtained under scanning speeds of 280 and 360 mm/min and 20 Kg/cm² clamping pressure with weld current setting of 28, 31 and 34 A. Suitable heat input to the weld interface may have resulted in this observation. Therefore, these conditions may be recommended to apply to obtain large weld strength.