(V) Case study- Controlling the Distortion of Crown wheel (Hypoid Gear)
The Primary Function of Crown Wheel Pinion is to Transfer the Power from Transmission to Wheel Ends. Dimensional Accuracy is extremely important to meet the part Life requirement. A Study is carried out to reduce the Heat Treatment Distortion of Hypoid Gear sets. The mechanism of Distortion is understood & Dry Gear cut process metallurgy is studied. Batch A Gear set are Processed with Regular Process Route but batch B Gear sets are processed with introducing the New Annealing process in Between Hypoid Gear Cutting & Case Carburizing Treatment. Annealing process is carried out as per Regular HT cycle with respect to Material Grade. Carburizing Cycles, Loading Fixtures, Quench Press Parameters, Quench oil Characteristics & other all Material Parameters are Kept same for Batch A & B. Residual Stress Analysis is carried out for both Batch A & B Gear sets before & After Annealing Treatment. The signification drop in Tensile Residual stress observed in Batch B gears up to 19% after Annealing. Also the stress value variation with in part are dropped to 71% & Part to Part variation dropped to 66%. This is evidenced by the Klingelnberg P 65 Measurement result of Tooth Profile for Both Batch A &B gear sets. The Tooth Topography of Batch A shows more dimensional imperfections than Batch B gears. Majority of Batch B gears falls in AGMA classs8 & above, where as Batch A gears Falls below the AGMA Class 8 specification. The Study shows that Non- Annealed Gears found asymmetric distortion & Annealed gears have symmetric distortion. The New Heat treatment process Annealing introduced after Hypoid Gear cutting removes all the induced machining stresses, there by homogenizing the structure, resulting in controlling the distortion.