Assembly Planbook - April 2008 - (Page 46) Fastening produce little torque reaction. They also have a good combination of speed and torque. This makes them ideal for manual assembly, enabling operators to work the tool with one hand while positioning components with the other hand. All pulse tools have some form of direct or indirect torque control. The simplest is a stall torque adjustment in the pulse mechanism that limits torque output. Another option is a shut-off mechanism that stops the tool when the set torque is reached. A third type is equipped with a transducer and electronic controller. When the set torque is reached, the tool is shut off by a valve. This type of pulse tool can be used for precision fastening. The widespread use of pulse tools in assembly suggests that engineers are have found a workable balance between ergonomics and torque accuracy. However, the same cannot be said of impact tools. Few torque-controlled models are available. Cordless impact tools have recently been introduced, but most lack adjustment or shut-off mechanisms. The author’s test joint consists of a high-strength aircraft bolt, hardened washers and a nut. Clamp load was measured by a load cell inserted in the joint. Torque was measured with an electronic torque wrench. Photo courtesy Impact Fastening LLC Because there is no equivalent to ISO 5393 for discontinuous tools, little data exists on the tightening accuracy or consistency of impact and pulse tools. Impact and Pulse Tools Despite the absence of performance standards, the popularity of pulse tools is growing. Their main attraction is that they Where does the world turn for the world’s most advanced laser systems technology? The world turns to Precitec. you weld, cut or bond materials to make your products; Some of th world’s most innovative companies turned to the we can come alongside, roll up our shirt sleeves s Precitec when they needed help solving complex manufacturing problems with laser systems. PRECITEC and offer solutions. Call on us the next time you need a partner that you It’s been our privilege to call them partners. can turn to. You can turn to us, too. Whether you Contact a Precitec Sales Engineer at are large or small, located in Europe, Cutting System YRC for all Fiber PreciTrac : For advanced 248.446.8100 to find out more. North America or in the Far East; whether Laser/Nd:YAG robot applications. seam welding applications. 3 ? CENTER PRECITEC NORTH AMERICA • 28043 OAKS C T. • WIXOM • MI 48393 46ASB03084Prec.indd / 1April 2008 www.assemblymag.com ASSEMBLY 2/19/08 10:51:21 AM http://www.assemblymag.com
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