Development of Multi-grit cBN Grinding Wheel for Crankshaft Grinding

Licentiate thesis, 2019

Crankshaft is a geometrically challenging component to grind. Over the years a number of grinding strategies have been developed to overcome thermal damage issues and excessive wheel wear. Radial and angular plunge processes have been adopted on some of the production machines. Recently a new, temperature-based strategy, has been proposed. A continuation project was launched, focusing on grinding wheel development and the initial work is presented in this thesis.

A series of grinding trails have been used to correlate the grit properties with the grinding performance. The two evaluated grit characteristics are newly proposed aspect ratio (𝐴𝑅) and the concentration in the grinding wheel. The results show that blockier particles (lower𝐴𝑅) generate high forces and lower grinding wheel wear. On the other hand, the elongated particles require less power for grinding and act more free-cutting, improving the grindability. Further trials using higher concentration grinding wheels, exhibit similar behavior as grit(s) with lower 𝐴𝑅. The two properties that are driving this performance are the contact area between the grinding wheel and the workpiece and the undeformed maximum chip thickness ℎ𝑚 which changes with process and wheel design parameters.