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Optimize Spindle Performance by Analyzing Failure Edited by Russ Willcutt TECH BRIEFS 28 PRODUCTION MACHINING :: NOVEMBER 2016 W hen high performance equipment such as a CNC spindle underperforms or fails, the owner of that machine can have a million dollars' worth of equipment that is not being used. It is therefore critical to get the spindle repaired or replaced as quickly as possible. At the same time, repairs provide the opportunity to identify exactly what led to the spindle's failure so the scenario can be avoided in the future. ere are several components and systems related to spindles that can contribute to or cause spindle failures. Many of these causes can go undetected and instigate recurring failures, resulting in weeks of downtime and costly damage to related equipment, unless the root cause of failure is precisely determined and reported by the spindle repair shop. "What is really needed after a spindle is damaged, and especially after a catastrophic failure, is a detailed failure analysis report, including the data accumulated through comprehensive inspection and testing," says David Kirkpatrick, president of Superior Spindle Service in Taylor, Michigan, a company that specializes in repairing and remanufacturing machine tool spindles. "Unfortunately, not every repair shop can provide that." He says a comprehensive failure analysis report should clearly show when the real cause of failure is not the spindle itself, but something related to the motor, bearings, gages or even improper spindle mounting. Generally, failure analysis amounts to the process of collecting and analyzing data to help determine the true cause and/or causes of a failure. "It is often assumed that failure analysis is an inten- sive, complete process, as it should be," he says. "Yet, when applied to a CNC spindle, to be truly comprehensive, the failure analysis process has to extend to all equipment that interacts with a spindle. Our technicians have discovered things such as faulty lubrication lines and control issues that would actuate the drawbar and encoder issues." Mr. Kirkpatrick says these problems were all solvable, but it was necessary to work with the machine shop customers to identify each issue and correct each one of them. e critical phase of an in-depth failure analysis process is the report that documents findings and includes recom- mendations for corrective actions. Mr. Kirkpatrick recom- mends an intensive program that encompasses not only attention to the spindle, but also motors, bearings, air purge and other associated components. His company treats failure analysis as a primary service function. "During the tear down procedure, every part is inspected to identify why and how the spindle failed," he says. "Once the equipment has been thoroughly cleaned, every part of the spindle's geometry is examined, referencing OEM standards for dimensions and concentricity. Every step of this process is photographed, documented and included with all findings in a comprehensive failure analysis report, along with specific recommendations on how similar failures can be avoided and spindle life can be extended." In some cases, particularly when it appears that customers might be perplexed by failure analysis reports that indicate complex root causes of failures, the spindle repair shop should provide another level of validation via the component manufacturer or supplier. :: Failure analysis refers to the process of collecting and analyzing data to help determine the true causes of a fail- ure. Avoiding downtime and expensive repairs in the future is the goal.