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January 2016 • SMT Magazine 21 WHy MEDTECH ManuFaCTurErS SHOuLD auTOMaTE FLuID DISPEnSInG OPEraTIOnS automated Dispensing: Hardware and Software The accuracy associated with dispensing flu- ids manually is highly dependent on the skill of the operator. In contrast, automated dispensing systems can be programmed to dispense dots, lines, circles, arcs, and compound arcs with ac- curate and repeatable tolerances. Such systems are usually designed to store multiple dispens- ing programs that can be retrieved as desired. The more advanced the system, the more accu- rately it dispenses fluids and performs complex dispensing patterns. One such tool allows the user to move the dispensing head into the required position and program the coordinates. Another, more intri- cate option uses a vision-guided automated dis- pensing system that enables the robot to mag- nify the part to better position the dispensing head while providing an on-screen preview of the dispensing path. As shown in Figure 3, this functionality can enable the operator to view a magnified image of the part. The use of a vision system removes much of the guesswork from the process, minimizing programming times in complex dispensing applications. Automated dispensing systems incorporat- ing vision capability can often align programs to changes in part-to-part placement or fixture tolerance. They can also often integrate the vi- sion system with embedded software to align the program to set fiducial points on a part, allowing the system to move the dispensing points and the path to accommodate placement changes from one part to another. In many in- stances, these systems can also provide optical confirmation that the workpiece is present to avoid dispensing fluid when a part is missing. More sophisticated vision-guided automated dispensing systems often utilize higher-level vi- sion systems, more complex programming, and encoders in a closed-loop configuration, provid- ing precise, accurate, and repeatable results in complex applications. Because part positioning, irregular surfaces, thickness differences, and distortion can exceed dispensing tolerances, contact between the tip and the part is almost certain if the dispensing system cannot compensate for such variances. And depending on the complexity of the medi- cal device, contact dispensing can damage frag- ile substrates. To manage these variances, some figure 3: a vision-guided automated dispensing system enables a robot to magnify a part to better position the dispensing head while providing an on-screen preview of the dispensing path. FEATurE

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