Diamond Turning - The Machine Tool

The Machine Tool

For best possible quality natural diamonds are used as single-point cutting elements during the final stages of the machining process. A CNC SPDT lathe rests atop a high-quality granite base with micrometer surface finish quality. The granite base is placed on air suspension on a solid foundation, keeping its working surface strictly horizontal. The machine tool components are placed on top of the granite base and can be moved with high degree of accuracy using a high-pressure air cushion or hydraulic suspension. The machined element is attached to an air chuck using negative air pressure and is usually centered manually using a micrometer. The chuck itself is separated from the electric motor that spins it by another air suspension.

The cutting tool is moved with nanometer precision by a combination of electric motors and piezoelectric actuators. As with other CNC machines, the motion of the tool is controlled by a list of coordinates generated by a computer. Typically, the part to be created is first described using a CAD model, then converted to G-code using a CAM program, and the G-code is then executed by the machine control computer to move the cutting tool. The final surface is achieved with a series of cutting passes of decreasing depth.

Alternative methods of diamond machining in practice also include diamond fly cutting and diamond milling. Diamond fly cutting can be used to generate diffraction gratings and other linear patterns with appropriately contoured diamond shapes. Diamond milling can be used to generate aspheric lens arrays by annulus cutting methods with a spherical diamond tool.