START YOUR ENGINES FROM THE START

Sales of Honda cars in China increased by over 50 percent year on year during 2009. And with another joint venture factory being built in 2010, the manufacturer is very optimistic about delivering more of their fashionable and high quality cars to the Chinese market.

Contributing to this success are the modern and reliable engines manufactured by Dongfeng Honda, a joint venture factory located right next to the Honda car assembly plant, in Guangzhou. Equipped with advanced manufacturing machinery the engine factory produces engines in the range 1.3 to 2.4 liters for Honda cars in China. And a central machine in each production line, critical for high productivity and quality, is the multifunction machining center.

These machining centers must operate for very long times in a range of speeds and loads, which often change very quickly, as they drill, cut and turn away the metal to form the finished products of engine block and engine head. So it is absolutely essential that the machining center spindle operates within very tight tolerances to deliver the accuracy required of Honda engines.

Key to spindle performance are the bearings that support and rotate the spindle across its tough work cycles. And bearing performance and reliability are therefore critical to keeping the very high cost spindles delivering high quality machining output at cost effective levels demanded of all modern manufacturing plants. This in turn means it is very important, to detect early indications of any bearing wear that could take the spindle outside its required tolerances or lead to bearing failure that would damage the spindle assembly and require very heavy costs to repair, as well as a long period of loss of production.

Depending on a number of factors a typical machining center spindle would have an operational life of one-two years before replacement of bearings was needed. The actual life is difficult to determine and a lot of off-line measuring, requiring stopping production, is needed before taking the decision for a full spindle bearing replacement action.

Dongfeng Honda maintenance manager Chen Shi was using off-line monitoring in this way for some years and was concerned about the amount of lost time needed to carry out this necessary maintenance. So, in the Honda tradition of challenging and trying new technology, he had the desire to upgrade to on-line monitoring. With on-line monitoring, sensors would track the spindle bearing?s condition 24 hours a day, and give a signal at any signs of bearing wear or drop in performance outside specified limits. But on-line monitoring of this sort had not been applied before by Honda in China, so he had no in-house experience to draw on.

So, looking for a partner in this challenge, Chen attended a maintenance conference and, as a result, got to know about combined condition monitoring and crash detection systems that automatically collect dynamic machinery data 24 hours a day, from permanently installed sensors, and evaluate the data against user-defined alarm conditions. Data is captured and available for notification, analysis and storage at work stations anywhere in the plant.

After hearing positive feedback about one provider of these systems, SKF (Nieuwegein, Netherlands), from others at the conference, he invited us to propose a solution for his machining centers. An inspection report led to a five-month test and evaluation program of the TMU together with Honda engineers. During this period a number of factors needed to be determined:
? best location of vibration sensors on the spindle
? arranging cabling for good data transmission yet allowing spindle full uninhibited movement for all functional machining operations
? getting accurate control points from Honda?s PLC for all machining operations
? determining the spindle?s vibration spectrum and trend pattern for its machining operations for both the spindle head and the bearing, across a range of typical application speeds and forces.

At the end of the test period the Honda engineers, now fully trained on the TMU, were enthusiastic about the potential, so Chen had three TMUs installed on three different machining centers. Success was almost instant, with one TMU detecting a condition later diagnosed as poor lubrication and immediately rectified, and a second TMU detecting a bearing defect that could be allowed to continue until an optimum time for replacing at a scheduled machine maintenance stop.

A further 19 TMUs have since been installed at the Guangzhou engine plant and three more have been ordered for the Honda plant in Wuhan. Commenting on this, Chen says, ?I have been very satisfied with the performance of the TMU and its ease of use by our maintenance personnel. I am also very impressed with the professionalism of the engineers, who gave fast and knowledgeable support whenever we needed it. Dongfeng Honda is safe in the knowledge that the spindles will not fail unexpectedly, with the corresponding catastrophic effect on production and costs. Furthermore, we can optimize our production, as far as machining center availability is concerned, by replacing any necessary bearings during planned maintenance stops.?

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Colin Roberts is the vice president of group technical press at SKF Group Communication, Postbus 2350, 3430 DT, The Netherlands, +31 30 607 56 08, Fax: +31 30 604 38 12, colin.roberts@skf.com, www.skf.com.