OPTIMIZING WIRE CRIMPS USING TAGUCHI DESIGNED EXPERIMENTS

A large number of Apache Helicopter wire harness failures were attributed to faulty electrical connections. Further investigation showed that 43% of all unscheduled electrical repairs involved broken wires and connectors. Through interviews with army field maintenance personnel, bad wire-to-pin crimps were identified as the major problem. To help solve this problem, a Taguchi styled design of experiment was selected to optimize the wire-to-pin crimping process. To define factors necessary for testing, a natural work group was assembled. Group members came from various departments such as Electrical System Design, Manufacturing Research and Development, Quality Assurance, Total Quality Management and Systems Engineering. Team members became involved in all aspects of defining factors, designing experiments, conducting tests, analyzing results, preparing recommendations, and implementing corrective action. Six experimental control factors were chosen as follows: 1) Crimp type; 2) Crimp depth; 3) Strip length; 4) Window centering; 5) Operators and; 6) Wire vendors. Three of the factors were varied between the acceptable extremes of applicable military standards. The measure of a good crimp was determined to be crimp strength and conductivity. Therefore, the experiment was set up to optimize these properties. A visual inspection of the crimp was also required to ensure crimp indentations were 90 degrees to each other and that all wire strands were inserted into the pin. Through the use of Taguchi methods, crimp depth was identified as the major contributor to the strength of a crimped connection. Furthermore, crimping the connection using a setting one under the nominal value, or under crimping, yielded the highest pull strength response. Also, under crimped connections are more tolerant to different vendor’s wire as well as to different quality of wire.