Door hinge reliability: A case study
Purpose: The purpose of this paper is to verify if the model method based on estimation of observations of customer complaint levels, when applied to the hinges of a range door, is an acceptable method of estimating future warranty costs. Design/methodology/Approach: Data based reliability was calculated by converting service failures reported in time to service failures in cycles. The data based reliability was then compared against the model method and MTBF calculations at different confidence estimates to verify the accuracy of the calculations against this application. Findings: The use of the model method based on estimation of observation is acceptable as a method of estimating future warranty cost. Calculated reliability matched the actual test data. Data from the MTBF method did not support a robust method to predict failure rates in field data. The reliability at the 95% confidence estimate from the MTBF costing is approximately 38% below actual failure costs. Based on the high margin of error the MTBF method is not accurate enough to estimate warranty cost. Research Limitations/implications: The study relied on estimates of the ratio of cycles to time, manufacturing instability, and limited consistency of a field definition of failures. Methods to achieve a more robust estimate would be to create multiple models at multiple estimate levels. Originality/Value: Applications of this study include product reliability estimation before new product introduction. While a product is in the design stages the consumer average usage charts available through outlets like Association of Home Appliance Manufactures (AHAM) or Consumer Union may be consulted to predict warranty costing. An increase in design robustness could be achieved by using a Design Failure Mode and Effects Analysis (DFMEA) approach and eliminating causes of design errors. DFMEA has been presented.