ABSTRACT
This chapter presents chemical and electrochemical non-traditional and hybrid machine tools and operations. Chemical machining (CHM) depends on controlled chemical dissolution of the work material by contact with a strong etchant. The process is mainly used to produce shallow cavities of intricate shapes in materials independent of their hardness or strength. CHM embraces two main applications, namely, chemical milling and photochemical machining (PCM). Chemical milling has a special significance in the aircraft and aerospace industries, where it is used to reduce the thickness of plates enveloping walls of rockets and airplanes, with the aim of striving to improve the stiffness to weight ratio, whereas photochemical machining (PCM) (also called spray etching) is a variation of CH milling in which the resistant mask is applied to the workpiece by photographic techniques. Both processes use etchant to remove material by chemical dissolution (CD). The etch rate of PCM is five to ten times that achieved by CH milling.
In electrochemical machining (ECM), the workpiece is connected to the anode, while the tool is connected to the cathode of a DC source of 5 to 30 V. Both the tool and workpiece electrodes must be electrically conductive. They are separated by a narrow gap, into which an electrolyte is pumped rapidly to sweep away the sludge from the gap. The shape of the cavity formed in the workpiece is the female mating image of the tool shape. The tool advances axially toward the workpiece at a constant feed rate. ECM is well suited to mass production of complex shapes in conductive difficult-to-cut (DTC) materials. Finally, ECM-allied processes and EC-hybrid processes are also considered.
