Application of Manufacturing Science to UH 60 Rotors

Design for Manufacture (DFM) and Process Certification are powerful tools that can be used to improve quality, reduce fabrication cost and increase throughput. Statistical methods such as process capability studies, probability analysis, and tolerance stacking are some of the tools that can be used to validate DFM proposals. Process Certification can be used to quantify the capability and predictability of process changes. The Spindle/Horn manufacturing process was a perfect candidate to demonstrate, confirm, and verify these tools. The Spindle and Horn assembly (figure #1) is part of a fully articulated rotor head system. A fully articulated system has multi-blades that act independently of each other, capable of feathering, flapping, leading and lagging. To alleviate potential bottlenecks at the grinding process stage, an analysis was performed on the Spindle/ Horn assembly. The liners, washers and bushings on these parts have to be precisely ground to tight tolerances; this takes a long time to machine. Through process investigation and analysis it was found that: • The manufacturing tolerance of the bushing can be reduced. • Stock removal via milling allows process to be automated.1 • Bonding of the washers induces variation into the process. These resulting changes will eliminate the grinding process; in essence reducing the setup and process time by 70% and 50% respectively. A cost analysis was generated to quantify the savings associated with making changes to all similar processes. It is projected that a recurring savings of more than $700K may be realized across the operation center. Several other part families use similar processes. For example, the Seahawk helicopter uses the same type of bushings and liners with different part numbers with the same issue. In addition, there will be savings in overhead, grinding wheel consumption, and machine maintenance. The concept of evaluating additional products to determine the optimal manufacturing processes will help launch us into the new age of manufacturing science versus the historical “gut feeling” approach.