3 - Abrasive machining processes

Abstract

Abrasive machining processes, also called machining with geometrically undefined cutting edges, are the natural choice for precision and high-precision manufacturing, machining, and finishing of hard materials and hardened surfaces. Abrasive machining processes are generally used as postmachining or final machining operations for precision, high-precision, and ultraprecision parts with tight dimensional and form tolerances and fine surface finishes. Conversely, abrasive blasting processes, such as abrasive water-jet machining, are a general exception to the abrasive machining processes used to produce precision parts. Abrasive blasting is used in applications that commonly do not require high precision or fine surface quality. Abrasive blasting is used in surface treatment, cutting, and trimming metal blanks and parts, composite material components, and hard and brittle materials such as ceramics. The microfabrication version of abrasive blasting, widely known as powder blasting, has been applied as a viable, low-cost option for fabricating microelectromechanical systems and microfluidic devices, especially with brittle materials. Abrasive machining processes employ hard granular particles (abrasives) in machining, abrading, or polishing to remove material and modify the shape and surface texture of manufactured parts. A substantially high number of undefined cutting edges with statistically distributed sizes and geometries, rather sharp negative rake angles, large contact and friction zones formed between the abrasive grains and workpiece material, and generally very small chip thicknesses, are the factors common to abrasive machining processes. The German standard (DIN standard 8589) divides abrasive machining processes, or machining processes with geometrically undefined cutting edges, into grinding, honing, lapping (polishing can be considered a special form of fine lapping), free abrasive grinding (such as tumbling), and abrasive blasting. Grinding, honing (which includes superfinishing), lapping, and polishing are considered precision machining processes. These four groups are discussed in detail in this chapter.