Special Focus seal diameter, and both the shaft and front cap were reworked to accept the new seals. The outcome: The MTBF (Mean Time Between Failure) for the customer’s spindles dramatically increased from a matter of only weeks (before the rebuild) to 18 months – more than six times longer than before. Another customer encountered a three-fold problem: A spindle’s existing tool interface was not fulfilling required accuracy and repeatability demands for the application, the design was inefficient for tool changes, and coolant contamination was leading to frequent spindle failure, because the spindle was positioned in a nose-up configuration allowing coolant to flood over the top of the spindle. “Our solution,” Zitney says, “was to convert to an HSK toolholder, which provided a highly accurate, quick, and easy tool change to deliver the desired repeatability. We also redesigned the spindle’s front cap and replaced it with a rotating slinger to dispense the coolant away from the spindle and keep it at bay.” The customer ultimately realized much higher quality, greater efficiency, and a five-fold increase in MTBF for maximized uptime. A spindle assembly is prepared to run and “break in” as part of SKF’s spindle repair and rebuild services.
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OPPORTUNITY TO UPGRADE
When a spindle is turned over for repairs, an opportunity can open up to consider upgrading or otherwise customizing a unit to realize improved performance, gain greater versatility, and/or accommodate new or changing application requirements. Making an upgrade while a spindle is already down and due for repair inherently makes economical sense. “Some upgrades for spindles can be relatively simple to implement, while others may become more involved,” Zitney observes, “but all can help improve upon spindle performance and operation.” An SKF customer found this out firsthand. The operation logged ongoing incidents of motor coolant clogging and environmentally related problems with an oil mist lubrication system. As a result, spindles were failing repeatedly due to plugged coolant lines, and overheated motors. “Our solution was to totally replace the spindle with an air-cooled grease-packed version,” Zitney says. “This particular air-cooled spindle resolved all the problems plaguing the motor coolant system and eliminated the costs for coolant tank, pump, and air oil supply. Contamination and clogging disappeared, motors no longer overheated due to clogged coolant lines, and spindle uptime increased. “Even more dramatic from a ‘green’ perspective,” he adds, “the new 5½ HP spindles running at 18,000 RPM compared with the old 15 HP spindles were able to achieve documented power savings by matching the spindle to the required job and not overpowering the
| IMD | FEBRUARY 2015 | www.IndMacDig.com
spindle.” The overall power savings translated to an annual reduction of 7000 kilowatts per spindle per 8-hour shift, which multiplies significantly with four spindles running five days per week at three per shifts every day.
FREQUENTLY ASKED QUESTIONS
SKF customers typically will pose basic questions to assist them in the decision-making on how best to return a failed spindle to service or otherwise improve performance. Among them: • Are you sure that you can successfully repair my “XYZ” spindle? The thinking behind this inquiry is that a customer effectively wants to know for certain that a particular spindle is a prime candidate for repair over replacement – especially since there are thousands of makes and models of spindles. This question can best be answered with as complete a spindle profile as possible. Helpful information includes the spindle’s manufacturer (not always the same as the machine), the model number, maximum RPM, HP (horse power), tool nose configuration, and drive type (belt, gear, coupled, or integral motor). In addition, does the spindle have manual or automatic tool change? Can the spindle’s bearings be identified from the OEM manual? • How long will it take for a repair? Based on initial information from a customer, a best/worst case delivery timeline can generally be developed. When a customer offers accurate information about the spindle and the equipment appears in reasonably good shape, then a delivery date will likely be more on target. If a customer’s spindle is in bad shape or has unseen damage internally, an evaluation by a repair technician will be necessary in determining a true timeline for return to service. • Can an exchange spindle be provided? With thousands of spindles in the field, it is usually only by chance that an exact replacement spindle will be in stock to match a particular unit. Sometimes, though, an alternative model can make an exchange possible. One of the questions most often asked – and with universal appeal – refers both to failed spindles and those in service: How can I get more life from my spindle? Understanding the way that each spindle is used in daily operation is essential to realizing extended spindle lifetime. More often than not, spindles must perform in harsh environments, often leading to potential internal contamination and subsequent failure. When contaminants are present, modifications to a spindle – especially to the sealing system – can be implemented to mitigate problems and extend service life. In some applications, too, a spindle may be run too hard or forced to operate where it was never intended according to its original design. In these cases, design changes can be made to reconfigure and tailor spindle setup consistent with the specific application. For more information, visit www.skf.com/us/services/ spindle-repair-and-rebuild-services/index.html, email Edward. Zitney@skf.com, or call 440-720-1545.