Plant Services - September 2007 - (Page 55) FISH Designers spend much time and money calculating the reliability (failure rate) of individual modules as well as the reliability and failure rate of the entire system. Many times, they are greatly disappointed when the final system is built and fielded because real-world reliability just doesn’t stack up to their predictions. That’s the price one pays for ignoring this fact of nature. Designers plug all their nice modules together, into a system, and discover that, in the real world, equipment often fails because of physical or environmental interface stress. In the plant, focusing on functional interfaces for opportunities to stress harden will bring returns in reduced replace and re-tune a bad board. As soon as you open the axis drive panel, you realize what had caused the problem – it’s too hot in the cabinet. So, you replace the board. The machine is fixed and the operator begins using it again, but with the cabinet door opened and a shop personnel fan blowing in it to keep the drives cooler, as operators often do in summer months. Now, you’ve got both a safety hazard and shorter machine life because of the dirt blowing into the electronics. But, hey, it works. Rather than carrying on with this way of reviving machines, go FISHing. You pull an ”electronic cabinet cooler” catalog from your shelf and find the Vibration Analysis & Balancing The goal is to discover the root-cause stresses and find ways to harden against them. amounts of malfunctions, scrap, equipment failures, unscheduled downtime and related production losses. Stress hardening equipment and components to protect them from root-cause stress can result in increased equipment uptime, accuracy, repeatability, yield, availability and productive profits, as well as reduced maintenance frustration and overhead. right model to add to that CNC lathe axis drive cabinet. But, wait. Heat is only one stressor that causes equipment malfunction, scrap, and sometimes failure. Other circuit card root-cause stressors include: Heat, vibration, dirt, oxidation or corrosion, voltage transients and current surges. For hydraulic systems, the list includes: Heat, dirt, water, acids and varnish. Harden or protect against all these and what would happen to failure rate? What would happen to uptime? Do you see or fee a paradigm shift? This should convert a maintenance engineer from a fire fighter to being a “Smokey the Bear,” a fire prevention bear, a reliability engineer. This scenario actually happened. John Deere’s Dubuque plant had three of those CNC lathes. Air-conditioning them stopped the summertime scrap, malfunctions and failures. The next summer, a sister plant called. Their operation was entirely dependent on 25 such lathes. The summer heat had them www.PLANTSERVICES.com VIBXPERT® How to FISH Discover the root-cause stresses and find ways to harden against them. By way of example, consider a hot July afternoon spent trying to revive a CNC lathe that has been shut down after high scrap rate characterized by extremely rough rather than smooth ID cuts. It might take a couple of hours of unscheduled downtime before you identify, h Watc O IDE e Vn Onli VIBSCANNER® The right tool for every user, job and budget 305-591-8935 • www.ludeca.com 55 http://www.ludeca.com http://www.ludeca.com http://www.PLANTSERVICES.com
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