Tribology and Lubrication Technology December 2011 : Page 18ful in the application in support of qualifying a new source of supply. However, industrial bearing users were taking a reac-tive approach to the problems occurring from using a new source. So I developed the Source Qualifi cation Inspection (SQI) program, which is essentially the industrial version of the FAA-approved PMA reverse engineering program. I found that most OEM design engineers did not know why the original supplier or baseline bearing worked in their application—they only knew that it did. Perhaps at some point they had performed lab or fi eld testing and the bearing passed. Unfortunately they did not know why it passed. They lacked any real knowledge of the internal design char-acteristics and the manufacturing plant’s ability to carry out the design intentions to assign cause to its success. The deep-er you go in bearing inspection, from dimensional character-istics, noise quality, visual inspection to chemical and metal-Figure 1 Figure Figure 1. 1. Convex Profile Profile with with Logarithmic Logarithmic Characteristics Characteristics Convex lurgical characteristics, the more you uncover the power of bearing inspection as a real qualifi cation tool. This is no mys-tery for most reputable bearing manufacturers, but for OEMs it’s really a new tool for them. tLt: with the global supply chain of bearing products today, can bearings be considered a commodity? napoleon: I have over a decades worth of inspection and test-ing data showing that not all bearings are created equal, even from the same source of supply. There are two reasons: (1.) the quality standards governing the design of a bearing are minimal, leaving plenty of opportunity for creativity. That is not necessarily bad until you compare a world-class bearing manufacturer with substantial research and development be-hind their product to a manufacturer who lacks those re-sources and (2.) the large quantity of acquisitions and joint ventures taking place in the industry, primarily by the large bearing manufacturers looking to establish a global manu-facturing presence. I regularly fi nd different design and man-ufacturing characteristics from a manufacturer who has mul-tiple plants around the world. However, this does not mean that a successful global supply base for bearings cannot be achieved. It just requires the use of a qualifi cation program that provides the correct amount of risk reduction. If you consider the internal design of a tapered roller bearing, for example, it possesses several very important roll-Asymmetrical Convex Convex Contour Contour Asymmetrical Unsatisfactory Concave Contour Unsatisfactory Concave Contour Symmetrical Convex Contours Symmetrical Convex Contours Undesirable Area of Concavity Undesirable Area of Concavity Contours with with Undesirable Undesirable Irregular Characteristics Contours Irregular Characteristics Unsatisfactory Concave Contour 18 • DE CEMBER 2 011 TRIB OL OG Y & L UBRIC A TION TE CHNOL OG Y WWW .S TLE. OR G Publication List Using a screen reader? Click Here |
