Application Note Issued: 2016-06-01 Aluminum / Copper oscillation welding with a 500 W direct diode laser SUMMARY The performance of the 500 W DirectProcess direct diode laser for oscillating welding by utilizing a novel trepanning optic is discussed for its application to aluminum/aluminum and aluminum/copper joints. Welding results were analyzed for but welds of aluminum samples with thicknesses up to 1.5 mm and copper with sample thicknesses up to 0.2 mm. The trepanning optics for an oscillating beam enabled the DirectProcess 900 at the 500 W level to effectively weld aluminum. The DirectProcess 900 C achieved very good welding quality for aluminum as well as thin copper aluminum joints with comparable welding speeds as with fiber lasers in similar configurations. Still, the oscillation of the laser beam with a trepanning optic is more accurate and easier as similar welding pattern achieved by 2D-Scanners. The DirectProcess 900 laser may also be employed for welding of other materials such as steel or plastics. For thicker materials especially in case of copper and brass a higher laser power is required to compensate thermal losses and low absorption in those materials. The topic of steel welding and conventional welding will be addressed in a separate application note. PRODUCT LINE / APPLICATION Product DirectProcess 900-500-C by DirectPhotonics Industries Application Direct diode laser material processing at 500 W Process Oscillation Welding Material Aluminum, Copper The ultra-high brightness of the DirectProcess 900 laser system is perfectly suited for direct diode laser material processing in demanding industrial environments. Table 1 1) Using the technology of wavelength division multiplexing, the DirectProcess 900 can be operated at a higher output power without losses in beam quality [1]. 1 of 7
Application Note, issued 2016-06-01: Oscillation welding with a 500 W direct diode laser SETUP All welding tests were performed utilizing a trepanning optic. The DirectProcess 900 direct diode laser was operated with the following settings: Cutting parameters Aluminum Copper Output power Beam quality Focussing lens oscillating speed 580 W 6 mm mrad f = 100 mm 1000 rpm Osciliation size 300 µm - 1500 µm 1500 µm Gap distance 1.5 mm 1.5 mm Sample thickness (range in mm) 0.5-1.5 0.2 Assist gas Argon Table 2: Welding conditions for DirectProcess 900 The trepanning optic is a relatively simple setup for a fast beam displacement the work piece from few µm up to some mm. The beam is rotated around a fixed spot for generating a circle. This circle can be moved by a 2D gentry along any desired path. Oscillating optic TREPPANING OPTIC The Trepanning optic consists in it s basic setup of 2 motors, one for changing the tilt of the quartz glass plate which results in the size of the the beam displacement and another motor for rotating that plate for generating the beam oscillation with up to 16.000 rpm. This trepanning optic is here directly mounted to the collimated DirectProcess 900. This way the beam profile is rectangular, nearly flat top and has a Beam parameter product of 6 mm mrad without the power loss of fiber coupling. The laser was operated in cw mode. Fig. 1: Power distribution in the focal plane of the collimated DirectProcess 900 2 of 7
Application Note, issued 2016-06-01: Oscillation welding with a 500 W direct diode laserr Fig. 2: principle of the trepanning optic to generate a circular beam displacement. Fig. 3: Mounted Direct- Process 900-500-C on top of the trepanning demo optic, both together on a 2 D gentry. 3 of 7
Application Note, issued 2016-06-01: Oscillation welding with a 500 W direct diode laserr Butt weld ALUMINUM BUTT WELD The DirectProcess 900 achieved welding speed was in a range of 50 mm / min 300 mm/min with an oscillation speed of 1000 rpms. A higher oscillating speed will not result in better welding quality. The gap size could be increased to 1.5 mm Aluminum ALUMINUM 0.5 MM - ALUMINUM 0.5 MM JOINT With an oscillating zone of 500 µm welding was achievable, the heat affected zone around the oscillation spot is homogenous and not very strong. For further experiments the oscillation zone was increased to 1.5 mm, the process speed was set to 100 mm/min. The ratio of gap size and material thickness is about 3:1 Fig. 4: shows the melting - and heat affected zone at 0.5 mm aluminum when utilizing a 500 µm oscillation zone. On the back side the melting zone is prominant where as the heat affected zone is nearly not visible Melting zone Heat affected Zone ALUMINUM 0.5 MM - ALUMINUM 0.5 MM JOINT With an oscillating zone of 500 µm welding was achievable, the heat affected zone around the oscillation spot is homogenous and not very strong. For further experiments the oscillation zone was increased to 1.5 mm, the process speed was set to 100 mm/min. The ratio of gap size and material thickness is about 3:1 Fig. 5: Surface back side oscillation welded 0.5 mm aluminum sample. The weld is very homogeneous. Especially in the cross section the weld is not visible. 4 of 7
Application Note, issued 2016-06-01: Oscillation welding with a 500 W direct diode laser Fig. 6: shows the microscopic immage of Fig. 5 after etching the cross section etched (DiX-Keller) transition zone melting zone raw material At 400 W the weld could be performed, as seen in the cross-section polish, the welding zone is very homogenous. After etching the cross section a microscopic picture shows that only minor material separation took place, the granularity is very small and not much bigger as in the raw material. Over the whole cross section, no cavities were observed which indicates a very strong connection. ALUMINUM 1.0 MM - ALUMINUM 1.0 MM JOINT For 1 mm Al-Al but weld the power was increased to full power as well as the process speed could be increases to 300 mm/min, while maintaining similar weld qualities. The ratio of gap size and material thickness is about 1.5:1 Fig. 6: Surface back side oscillation welded 1 mm aluminum sample. The weld is very homogeneous. Especially in the cross section the weld quality is better as with the 0.5 mm joint 5 of 7
Application Note, issued 2016-06-01: Oscillation welding with a 500 W direct diode laserr ALUMINUM 1.5 MM - ALUMINUM 1.5 MM JOINT For 1.5 mm Al-Al welding the process speed was slightly reduced to maintain similar welding qualities. The Gap size and material thickness is hereby 1:1 Fig. 7: Surface back side oscillation welded 1.5 mm aluminum sample. As seen in the cross section the weld quality remains even at a gap - thickness ration of 1:1 Copper - Aluminum COPPER - ALUMINUM JOINT With the configuration as described above it was possible to join copper (0.2 mm) and aluminum (0.5 mm). The melted cross section was determined to be 100 µm, which is about 50% of the copper thickness. As seen no cavities occurred which indicates a strong connection. Fig. 8: Surface back side oscillation weld of 0.2 mm copper with 0.5 mm aluminum. As seen in the cross section, the material interconnection zone is about 50% of the copper thickness and without any cavities. front side back side cross section cross section polished etched (10 sec DiX-Keller) material interconnection 6 of 7
Application Note, issued 2016-06-01: Oscillation welding with a 500 W direct diode laser For all samples the DirectProcess 900 direct diode laser exhibits excellent weld qualities. Due to the utilization of a trepanning optic for the generating of an oscillating beam the gap size could be increased to 1.5 mm. Strong Aluminum-aluminum joints with material thicknesses of up to 1.5 mm have been achieved. Also copper aluminum joints have been successfully demonstrated. All eperiments have been performed at the 500 W level of the DirectProcess 900 in cw operation. Thicker materials can be processed with higher output power as well as faster process speeds, which can be found in another application note. DirectPhotonics focuses on developing and producing ultra-high brightness direct diode laser solutions for use in micro- and macro-material processing applications/markets. Founded in 2011, the company has its headquarters in Berlin, Germany. Leveraging patented technologies from Fraunhofer Institutes, DirectPhotonics has significantly increased the brightness of fiber-coupled and direct diode laser systems to become the new workhorse in cutting and welding applications. DirectPhotonics Industries GmbH Max-Planck-Straße 3 12489 Berlin, Germany T +49 30 6392 87240 F +49 30 6392 8742 info@directphotonics.com www.directphotonics.com DirectPhotonics Industries GmbH product specifications are subject to change without notice. For complete details, please contact your local DirectPhotonics Industries GmbH sales representative or visit our website at www.directphotonics.com Warning: Class 4 Laser, Invisible Laser Radiation Avoid Eye or Skin Exposure to Direct or Scattered Radiation 7 of 7