My final year thesis during my bachelor's degree was a study on the "Product Performance Improvement of Hydrostatic Steering Units (HSU)" at Rane's manufacturing plant in Mysore, India. The HSUs being made here were primarily used in tractors and were one of the company's leading products. However, quality issues plagued the production line, and the First Time Yield (FTR) of the HSU was as low as 78%.

All HSUs undergo a validation at the hydraulic testing station, and components that don't pass this quality check are either re-machined or discarded. Several characteristics such as relief valve pressure, port pressure, rotation pressure, leakage, slippage, and steering torque are tested. After several months of root cause analyses, and creating detailed reports of defected parts, and Regression Analysis the problems were isolated to two variance in the spool diameter and stator perpendicularity. Upon further investigation, it was found that the the slit width on the spool was causing inconsistent diameters and the surface grinding procedure on the stator was the cause of the poor perpendicularity.

Permanent counter measures were put into effect to mitigate these quality issues. The worn roller bearings in the surface grinding machine were replaced with angular bearings to better protect against axial fatigue loads during the stator machine process. In addition, the traditional 1.4mm HSS slit cutting tool was replaced with a narrower 1.05mm carbide tool to maintain a consistent spool diameter. These updates saw a notable increase in HSU quality, with FTR numbers at 87%.