Assembly Planbook - April 2008 - (Page 41) Finally, fixtures should be designed to accommodate expected future design changes or production demands. Anticipating future needs can substantially extend the life of the robot dispensing system. Communication Options There are many choices when it comes to robotic dispensing communications. In fact, the typical robot will have many more inputs and outputs (I/O) than the application actually requires. In a basic system, the robot starts its cycle, moves to the point of dispense, signals the dispenser to “start dispense,” moves to the final dispense position, removes the dispense signal to stop dispense, and then moves to a home position. Additional signals are transmitted through the I/O to ensure correct part, dispensing, faults, quality control and safety. The human-machine interface located on each control panel or pendant can be a simple keypad display, a small color touch-screen or a larger graphical user interface. Advanced robot and dispensing system controls improve user interface capabilities, machine uptime and supervisor convenience. Controls can be PLC- or PC-based. Basic controls may use digital or discrete I/O communication, while advanced controls may use DeviceNet, Profibus or Ethernet IP. One advantage to high-end communication is that it enables remote access to the machine control system, allowing engineers to extract everything from job data to information on where and how to fix system issues. Precision is Critical Always remember that equipment selection choices made at the beginning of a project can directly affect its final quality. Again, the correct robot, metering-dispensing system, controllers and communication interface all play a critical role. In addition, manufacturers may want to consider implementing various accessories to improve dispensing and positional accuracy. For example, many manufacturers employ a temperature control system to ensure consistent material dispensing profiles irrespective of ambient temperatures. This can be done through the use of heating and cooling water; with a heat-only electric system; or through the use of a heating and cooling Peltier electric system. Another means of ensuring consistency and precision is through the use of vision bead control. With this technology, cameras view the fluid as it exits the dispense nozzle to ensure it matches a preset profile for bead placement and size. This allows the system to automatically correct the dispensing application or mark it for physical inspection. Another use for vision is to ensure correct part position, whereby the cameras first locate the part and then fine tune the robot path program to the correct coordinates. A www.assemblymag.com April 2008 / ASSE M B LY 41 ASB09074Baltec.indd 1 8/22/07 2:54:45 PM http://www.baltecorporation.com http://www.baltecorporation.com http://www.assemblymag.com
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