Ra (average roughness)

Ra, or average roughness, is a measurement that describes how smooth or rough a surface is. It calculates the average height difference between the highest peaks and lowest valleys across a section of the surface. A lower Ra value indicates a smoother surface, while a higher value means more roughness. This measurement is important in industries like manufacturing and engineering because surface texture can affect performance, appearance, and wear. Essentially, Ra provides a standardized way to quantify surface finish, helping to ensure quality and consistency in materials and products.