Sales of Honda cars in China increased by more than 50 percent year on year during 2009. And with another joint-venture factory being built in 2010, the company is very optimistic about delivering more of its 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. A central machine in each production line, critical for high productivity and quality, is the multi-function 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 is the bearings that support and rotate the spindle across its tough work cycles. And bearing performance and reliability are, therefore, critical to keeping the 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 to two years before replacement of bearings was needed. The actual life is difficult to determine, and plenty 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 sign 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 of SKF’s combined condition monitoring and crash detection system, the SKF Multilog On-line System TMU. The TMU automatically collects dynamic machinery data 24 hours a day from permanently installed sensors and evaluates 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 on SKF from others at the conference, he invited SKF to propose a solution for his machining centers.

An SKF inspection report led to a five-month test and evaluation program of the TMU together with Honda engineers. In this period, a number of factors needed to be determined:

  1. the best location of vibration sensors on the spindle;
  2. arranging cabling for good data transmission yet allowing spindle full uninhibited movement for all functional machining operations;
  3. getting accurate control points from Honda’s PLC for all machining operations; and,
  4. 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, and 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. …  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”

Features of the SKF Multilog On-line System TMU
The TMU is a three-channel, 24-hour-per-day surveillance device designed to protect critical rotating assets in rugged manufacturing environments. It can warn of developing machine problems such as bearing damage, spindle or shaft imbalance, poor lubrication, etc., and provide diagnostic information for improving reliability and quality. Monitoring is done according to user-defined conditions, making it applicable in a wide number of industries. In addition, it has a special feature that rapidly detects shocks, such as would occur with a spindle crash, and instantly shuts down the machine helping to prevent severe damage to machine components.

It has a distributed architecture allowing easy and flexible expansion to cover small, medium or large machine or manufacturing systems.

For more information, visit the SKF Web site at www.skf.com.