Five greases with different composition were synthesized and characterized for preliminary examination. The typical grease physical properties and grease life were investigated. And the OIT (oxidation induction time) values of the greases before and after life test were measured using PDSC (pressure differential scanning calorimeter). Large differences in the grease performance depending on the composition were observed. On the basis of the preliminary test, the synthetic factors for orthogonal array were selected. And various conditions for greases synthesis were established by using powerful Robust Engineering Orthogonal Array. Using these conditions various greases were synthesized and measured the dropping points and OIT values. Then optimized five greases were selected by SSRED (Six Sigma Robust Engineering Design) program using dropping point and OIT value respectively. These optimum greases were evaluated by comparing with the estimated dropping points and OIT values. The optimized five greases showed the same level with estimated value and showed high endurance life time.
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