Precision Parts Cutting Machining
Precision parts cutting machining primarily includes precision turning, mirror grinding, and lapping. Using finely ground single-crystal diamond tools on precision lathes, ultra-fine turning is performed with a cutting thickness of about 1 micron. This process is commonly used to machine high-precision, highly polished parts, such as spherical, aspherical, and planar mirrors made of non-ferrous metals. For example, an aspherical mirror with a diameter of 800 mm used in nuclear fusion devices can achieve a precision of 0.1 microns and a surface roughness of Rz 0.05 microns.
Special Processes for Precision Parts Machining
When the precision of parts machining targets nanometers or even atomic units (with atomic lattice spacing being 0.1 to 0.2 nanometers), conventional cutting methods become inadequate. Instead, special machining methods are employed. These methods utilize chemical, electrochemical, thermal, or electrical energy to surpass the bonding energy between atoms, thereby removing or altering atomic structures on the workpiece surface to achieve the desired precision. These special processes include:
- Mechanical and Chemical Polishing
- Ion Sputtering and Ion Implantation
- Electron Beam Exposure
- Laser Beam Machining
- Metal Evaporation and Molecular Beam Epitaxy
The key characteristic of these methods is the extremely fine control over the addition or removal of surface material. Achieving high precision still depends on advanced machining equipment and appropriate control systems, often using precise masks as intermediaries. For instance, in the fabrication of very-large-scale integrated (VLSI) circuits, an electron beam is used to expose a photoresist on a mask. The photoresist atoms polymerize (or decompose) under the impact of the electron beam, and a developer then dissolves the exposed or unexposed areas to create the mask. Electron beam exposure for mask fabrication requires precision machining equipment with a table positioning accuracy of ±0.01 microns.
