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story by Kapyoung Choi / photos courtesy FANUC Robotics America, Inc. As the U.S. economy makes a slow recovery, and foreign competition, particularly in China, continues to gain momentum, small shops are realizing that industrial robots are more than just pieces of manufacturing equipment. They are key business tools that provide a means for companies to fight back, win orders and remain profitable. In fact, since the first industrial machine-tending robot was introduced in the U.S. in the 1960s, the industry has grown to more than 126,000 machine-tending robots in operation, according to the Robotic Industries Association (RIA). Many companies now realize that, in order to stay competitive, they must have the manufacturing flexibility to respond quickly to market demands. As companies strive to enhance their time to market, the role of robots becomes particularly critical for smaller shops, where ergonomic issues and absenteeism impact the bottom line. By implementing robotic solutions, small shops are able to increase their revenue per production employee by 50 percent, and reassign workers to less hazardous and repetitive tasks. Also, robotic automation helps companies streamline operations and realize a quick payback. The following provides pointers on how small shops can get started on the road to automation. Understanding Your Needs An effective automation supplier is one that understands its customers’ process needs. By performing a needs analysis to evaluate current manufacturing processes and business priorities, the automation supplier can make recommendations that will provide efficient and cost-effective results. Because the day-to-day activity of running a job shop often prevents production managers from evaluating manufacturing alternatives, it’s best to find a local integrator or robot OEM to kick-start the needs analysis process with an automation audit. The RIA is a good resource to locate suppliers/integrators (http://www.robotics.org). The RIA website offers a list of robot suppliers, integrators, tooling suppliers and other robotic peripheral equipment suppliers. Advantages of Robotic Automation
For all types of applications, including machine tending, today’s industrial robots are much more sophisticated than earlier models. Several choices are available, with capabilities to meet a wide range of payload, reach, speed and flexibility requirements. Typically, robots can handle payloads that range from 3 kg to as much as 600 kg, and offer reach capabilities of 700 mm to more than 3000 mm. Servo-controlled industrial robots are used to tend CNC lathes, mills, machining centers, drills, grinders, EDM machines and more. They are accurate enough to load three-jaw chucks, live tooling, collets, fixtured tombstones or pallets. Robots with at least four axes of motion can help manufacturers optimize cell layout, floor space usage, chip management and workpiece flow. Robots can be mounted on the floor, upside down, on a machine tool or on a floor track. More recently, a six-axis, overhead, rail-mounted robot (toploader) has gained popularity for tending multiple machines from the top. These robots operate as articulated gantries, and allow for more efficient use of floor space and capital. Another advantage of robotic solutions is speed: The load and unload cycle time for robots is just five seconds or slightly more. The time is based on how long it takes for a robot to move into the machine, exchange a part with the machine’s workholding device, and for the machine door to open and close. If the robot supplier designs the system correctly, the robot should wait for the machine, not the other way. Picking a Robot that Fits the Application There are several items to consider when sizing a robot to a machine-tending application. The robot OEM or integrator will assign a team that will help evaluate the application during the needs analysis.
The use of gravity conveyors with part escapement is an effective means of presenting parts to an automation cell, and typically is less expensive than powered conveyors. Another choice might be part pallets that move manually or automatically into and out of the robot work area. The use of vision with a simple indexing belt conveyor or table is another possibility. Vision provides higher flexibility and reduces the cost of part location. More than one part type can run on the same cell without the need to invest in dedicated fixtures. Vision is more forgiving of slight part-to-part variations, compared to a fixtured part-delivery system designed to handle nominal part tolerances. When a six-axis robot is used with vision, the robot will position itself at the optimum pickup location based on how the part is positioned for pick-up, versus dedicated automation, which is designed to pick up parts at the same location each time. Vision provides part location and orientation information to guide the robot. Part-delivery flexibility will increase if vision is integrated into the robot’s end-of-arm tooling. This allows parts to be delivered to the cell in a structured bin or on a simple multi-layered tray system. In addition to eliminating the high cost of part fixturing, vision provides the capability to automate small part runs. End-of-arm tooling (EOAT) design is defined by part size, weight, gripping location, gripping surface quality, throughput and workholding device interference zones. Many grippers used for machine-tending applications are off-the-shelf, pneumatic, parallel motion types with two or three jaws, depending on the part’s shape at the gripping location. Others have customized fingers and pneumatic valve systems, which control the EOAT. Based on the requirements of the application, some gripper modules are assembled with part-present sensors, vision and/or part-orientation mechanisms. Application software has also been simplified to the point that users with little or no experience can program a robot. Today’s programs are provided in plain English, and use drop-down menus to select commands or functions. The Teach pendant can be used for programming, to jog the robot, and to monitor and control the robot cell. A single robot can tend one or two machines, with the robot set as the master and the CNC machine as the slave. This allows the robot Teach pendant and the controller to be used as the operator station, offering simplified panel functions such as graphic status displays, online help and diagnostics, production reporting and the ability to surf the Web. Local and remote monitoring networks can be created with Ethernet connections on robot controllers. Other controller features include the ability to multi-task different activities; perform PLC ladder tasks; detect collision without the use of external sensors; define interference zones between the robot and peripheral devices; and control auxiliary axes. Guarding and safety are important aspects that should be reviewed and understood by everyone involved in the design, implementation, and production of a robotic system. The American National Standard for Industrial Robots and Robot Systems – Safety Requirements (revision of ANSI/RIA R15.06-1986) was approved August 19, 1992, and is available from the Robotic Industries Association.
Today’s robots provide maximum flexibility and are often capable of duplicating human dexterity. With six axes of coordinated motion and a programmable machine controller, robots can be used to automate an existing or new machine. In either situation, the machine tool must be updated to accept robot automation, with features such as an automatic door, automatic workholding device, physical I/O points to control the external device, and logic in the PMC to interface with a robot. Industrial robots provide a number of direct and indirect economic benefits. Usually, one robot can perform the work of three to five people, reducing the cost of labor in the machine-tending area. As the price of robots continues to drop, manufacturers can realize other direct and indirect economic benefits, including:
With the ability to perform a variety of tasks and achieve a mean time between failure of more than 60,000 hours, robots are also more advanced than traditional automation process systems, such as linear gantries. Faced with global competition, manufacturers are reinventing their factories and building manufacturing systems using robotic technology that helps produce high-quality products at a reasonable cost. If a company’s objective is to achieve one or more of the following competitive advantages, then robotic automation is the right business tool for success.
FANUC Robotics
America, Inc.
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