Diamond turning of diffractive microstructures

• Diamond turning of complex diffractive structures using nickel silver alloys.
• Lead containing alloys yield better chips but surface defects increase.
• The feed direction influences the formation of burr on structure edges.
• Increasing the surface hardness by deep rolling enhances the structure accuracy.

Diamond machining is a suitable technology for manufacturing of diffractive optics with excellent surface finish. The machining result depends on the workpiece material to a large extent. Many materials are commonly applied in diamond machining. One material of particular interest is nickel silver, which offers a comparably higher hardness than aluminium or copper. Especially for machining of sharp edges this is an advantageous property. However, not all alloys are equally suited for machining. Therefore, this paper investigates the influences of different material properties on process forces, burr and chip formation, and most importantly the surface finish. The machining experiments demonstrate that burr and chip formation are predominantly influenced by the machining strategy. The process forces on the other hand, largely depend on the material composition, which also affects the surface finish, especially local surface defects. It was also found that an increasing surface hardness, which was generated by deep rolling, supports the reduction of plastic deformations of the machined microstructures.