National Bearings Company — a U.S. bearing manufacturer specializing in custom thrust bearings, radial bearings, angular contact bearings, subassemblies, and bearing components — was able to apply its decades of bearing-specific engineering experience to help a leading power tool manufacturer identify ways in which modifications to legacy assembly processes combined with the use of a custom bearing could significantly reduce product costs while maintaining quality and requirements of the application.
The problem: Bearing over-inspection
The leading power tool manufacturer’s issue arose when it had inadvertently over-specified a needle thrust bearing for the load requirements of a drill application. Needle thrust bearings are typically specified for high axial loads, high rotation speeds, and minimal envelope space. The bearing in this application was a standard bearing that contained more needles than required for the drill. This bearing over-specification resulted in unnecessarily high component costs.
Over-specification of a bearing occurs when a product designer or engineer selects a standard bearing that is too complex or oversized for the application needs. Thousands of bearing sizes and types exist, and in some cases, specifying a standard bearing can provide a successful result. However, many standard bearings can support much higher load and speed requirements than are necessary for an application, thus are over-specified. Although many engineers may see this as a safe and practical design decision, the use of standard bearings can become expensive.
The National Bearings team of engineers was called on to review the design specifications and compare them to the actual operational requirements. The team realized that the standard bearing was over-specified and contained more needles than was necessary to meet load requirements. The standard needle thrust bearing specified for the drill application had a load capacity of 16,000 N, which far exceeded the 11,000 N required to operate the drill under the most extreme condition. This resulted in thousands of dollars in unnecessary costs.
The next step in the customization process would be to identify how many needles were actually needed for the application.
National Bearings worked collaboratively with the drill designer to identify the actual axial load requirements. As a result, the team was able to also identify the required number of needles that would successfully meet the load requirements without compromising the product’s life span.
National Bearings recommended that the over-specified bearing, which contained 36 needles, be replaced with a custom-designed needle thrust bearing with 18 needles. Modifying the design with the use of a custom solution reduced the cost of the bearing by 50 percent. The size of the bearing remained the same, leaving the other components in the drill unchanged and avoiding an expensive and time-intensive product redesign.
Although it was not the primary focus of the bearing replacement, material selection was another area that National Bearings chose to address. The standard bearing’s thrust retainer, which holds and separates the balls or needles, was originally made of metal in the standard bearing. National Bearings’ engineering team realized that this metal retainer could be replaced with a similarly performing plastic retainer, which achieved additional cost savings.
This custom bearing solution allowed the power tool manufacturer to achieve a 50-percent reduction in the cost of the needle thrust bearing by reducing the number of needles from 36 to 18, while conforming to the actual application needs in terms of load and size. Also, an additional 30 percent reduction in tooling costs was achieved by changing the bearing material from metal to plastic. The product design analysis skills of the National Bearings team helped the power tool manufacturer rethink its reliance on less-expensive standard bearings without having to sacrifice quality and requirements of the application.