Rail grinding has become a widely accepted practice in the railroad industry to not only remove surface defects but to also shape the head of the rail to achieve a specific wheel/rail contact interface. Optimal wheel/rail contact is paramount for a variety of reasons including (but not limited to): reduced rail wear and fatigue defects with associated increased rail life, improved steering, and reduced wheel/rail noise. Historically, the process of profile grinding has been performed through the selection of a grinding pattern from a predefined library of preset motor angles and power settings, as well as grinder traveling speed. By applying calibrated metal removal equations created to estimate the metal removal of a single grinding stone on a specific grinding vehicle and a measured shape of the rail, it is possible to iteratively create a grinding pattern and estimate the post-grind rail shape in both real-time and offline. These dynamically created grinding patterns position and power grinding motors to remove metal only where it needs to be removed to achieve the desired rail shape (template). Over grinding and extraneous grinding is minimized using this grind optimization technique.
The concept of dynamic rail grinding pattern generation was applied to optimize grinding for the VLI railroad in Brazil. Based on a survey of both wheel profiles and rail profiles throughout the VLI network (in which digital coordinates of the transverse cross-sections were recorded using handheld profile measurement devices), new rail grinding templates (desired rail shape dependent upon rail curvature and elevation) were developed to control the wheel/rail interface. These new rail grinding templates were aligned to measured rail profiles categorized by curvature and high/low rail types to create representative average metal removal curves. The resulting metal removal curves were then used as inputs to the dynamic grinding pattern generation functions to create custom grinding patterns specifically calibrated to the grinder in operation on VLI.
Results showed that applying dynamic grinding pattern generation resulted in increased productivity of the grinder (faster speeds and less passes) with corresponding improvement of the post-grind rail shape, i.e., increased quality of the final rail shape.
This paper will discuss the background theory behind dynamic pattern generation and how it can be applied to normal grinding operations. Additionally, an application of this process will be presented which utilized dynamic pattern generation to create targeted corrective grinding patterns for the VLI railroad.