Assembly - November 2008 - (Page 56) Fastening performance of the motor and tracks how many hours the tool has run. If problems occur, the controller will shut down the tool and alert maintenance personnel. A pneumatic tool can be paired with a controller that monitors and regulates air pressure. The device will alert the operator if there’s not enough air pressure to run the tool. Electronic error-proofing technology doesn’t necessarily prevent errors. In most cases, it merely alerts the operator to the fact that a fault has occurred. The operator must still correct the error or alert a supervisor that something is amiss. Ironically, technology can play a role here, too. For example, a computer-controlled tool can signal a PLC to keep a conveyor from passing an assembly to the next station unless the required number of fasteners have been installed. Similarly, a major tractor manufacturer uses Atlas Copco’s computer-controlled DC electric tools to tighten many critical fasteners. If two consecutive faults occur at an individual station, the tool locks up and a supervisor must investigate the cause of the problem, explains Melis. After taking corrective action, the supervisor unlocks the tool by scanning his badge with the controller’s bar code reader. Error-proofing doesn’t have to be high-tech, adds Tayler. Drawings, photographs and even videos can be displayed at assembly stations to show operators where to install fasteners or the order in which to install them. Fasteners for different assemblies or fastening locations can be stored in color-coded bins. In the aerospace industry, bolts for jet engine assemblies are supplied in plastic trays—each bolt has its own pocket in the tray. Thus, an operator can tell at a glance if every fastener for the assembly has been installed. As powerful as error-proofing technology and methods can be, they don’t obviate the need for thorough training. “Training makes all the difference,” insists Staiger. “Operators are often working at a As powerful as error-proofing technology and methods can be, they don’t obviate the need for thorough training. Photo courtesy Daimler Technology can also alert operators when the tools themselves aren’t functioning correctly, says Steve Tayler, vice president of business development at Makita USA Inc. (Mount Prospect, IL). For example, cordless tools from Makita are equipped with voltage sensors that shut off the tools when battery capacity drops below 5 percent. The tool won’t operate if the battery does not have enough power to apply the required torque, even if there’s enough juice to turn the motor. A flashing LED warns the operator when battery capacity is close to the 5 percent limit. Similarly, the controller for a DC electric tool monitors the electrical A right-angle tool should be operated with two hands. One hand should be near the head of the tool; the other should be at the base of the handle. Photo courtesy Atlas Copco Tools & Assembly Systems 56 ASSEMBLY / November 2008 www.assemblymag.com http://www.assemblymag.com
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