Surface Texture Design for Sheet Metal Forming Applications

Sheet metal surfaces are generally textured to improve tribological performance in deep drawing applications. Variations in coefficient of friction in forming processes is one of the major causes of defective products. The major reasons for an unstable friction condition are the tool wear and inhomogeneity in lubricant amount. Textured surfaces can offer enhanced and stable friction condition. However, there is no clear design guidelines available for texturing sheet metal surfaces for a robust friction condition. Various types of texturing methods are available. In this study, the friction sensitivity of surface texture made by laser-texturing method to variations in tool wear and inhomogeneity in lubricant distribution is investigated. The laser-textured surface parameters such as crater diameter and texture density are chosen within the physically attainable range such that a robust friction behavior during forming process is achieved. A multi-scale friction model is used to determine coefficient of friction for textured surfaces in boundary and mixed lubrication conditions. The friction model in combination with surface generating algorithm is used to optimize individual crater geometry and their spacing. The objective is to determine the surface texture which is least sensitive to the potential variations in the tool roughness and lubricant amount in sheet metal forming applications.