Laser Engraving

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Supervisor:
Dr. Berényi Richárd
Department of Electronics Technology

This semester I have been dealing with the laser marking device of the Continental Temic Hungary Ltd.. I started my task learning the applied barcodes and laser marking technologies in the electronical manufacturing industry. Electronic manufacturers mostly use solid-state lasers (Nd:YAG) in pulse mode and gas lasers (CO2) in continuous or pulse mode, so I studied these laser types in detail during literary research. Continental Ltd. uses a 60 W powered CO2 laser to mark 2D barcodes into the PCB’s solder mask layer. Engineers of the firm built the laser into a workstation. The control of the workstation is solved with an IO card and a PLC. Previous checks showed a lot of problems. After studying processes of the workstation I inspected the connections between different units using circuit diagrams. I didn’t find any deviation, so I started analyzing control program loaded in the PLC. After elimination the problems the workstation have been able to work with the repaired program code. However the marked barcodes were unreadable, therefore it was necessary to set the laser parameters to the proper level. I made experiments to analyze the effects of the different parameters. At first I determined the size of smallest point that could be drawn. Then knowing that size I found the optimal resolution of an ECC 200 datamatrix’s one cell with changing resolution in the x and y axis direction. To find the optimal laser power and resolution together I changed the former parameter between 12 and 24 W, while the latter one between 10 and 40 points/mm. I looked for the repetition frequency’s optimal value of laser beam changing from the 5 % of maximum 100 kHz to 15 %. In all experiments I marked the same 5 mm ∙ 5 mm sized barcodes on the surface of sample. I drew a 3 cm ∙ 3 cm sized matrix code to test the effect of laserhead’s speed. The matrix’s one cella was 12 ∙ 12 points sized. In this test I inspected whether interruption is among two points or laserbeam draws continuous strips, if the points are closely next to each other. In the latter case the sample’s surface gets more power. Results of the experiments gave the optimal parameter values, that are needed to draw well readable barcodes.

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