chapter  15
28 Pages

Metal Cutting and Machining Technology

Metal cutting and machining technology is the most common and necessary technology to enable the aerospace industry to manufacture series of components of an aircraft. There have been tremendous amount of improvements made, developing from simple metal cutting machines with manual controls to very special purpose numerically controlled (NC) machines to meet the requirements of the aerospace customers. For aerospace applications, NC machines have been developed ranging from small to very large sizes, which are hard to imagine, if not personally witnessed to manufacture mainly the wing components of large aircraft. The major aerospace input structural raw materials are produced mainly by rolling, extrusion, forging, and other forming operations as discussed in Chapter 4. The geometry and the dimensions of the initial raw stock materials are selected based on the nal geometry of the part after machining to satisfy various engineering requirements; mainly structural strength, toughness, fatigue, and the aircraft weight and also the ease of manufacturing. For manufacturing major structural components, quite a substantial amount of machining is required to nish the part per geometry and dimensional tolerances from the original wrought products received from the metal manufacturers. The buy-to-y ratio (weight ratio between input raw material used and the weight of the nal component installed in the aircraft), a term commonly referred to within the aerospace community, is an important factor to be considered owing to various reasons including energy used, capital, tool, labor costs, etc. Generally, the lower the ratio, the more economical it is to produce the parts and nally reduce the overall manufacturing cost of the aircraft. The metal cutting processes used in manufacturing aircraft components are dependent on many factors including the type of material, the size and shape of the part, the dimensional tolerances, surface characteristics, and nally the production economics. The cost of machining is very much dependent on total machining time and the type of material being machined, which determines the life of a cutter and the capital cost of the machine. To meet the manufacturing and economic needs of the aircraft parts of various metals including aluminum, titanium, steels, and super alloys, various machining centers have been developed in the last few years. Similarly, huge varieties of cutting tools have been developed to satisfy the requirements of the machining centers as well as the life of the cutting tools. This chapter illustrates the fundamentals of metal-cutting principles and machining technology as the author learnt from his undergraduate course of Workshop Technology [1], and Principles of Machine Tools [2] in India during 1972. This chapter also illustrates machining of most common aircraft metals including aluminum, titanium, steel, and composite materials used for

This section describes the basic concepts of metal-cutting principles to help understand some important aspects of metal cutting including metal-cutting methods, cutting tool nomenclature, mechanics of chip formation, kinematics and dynamics of metal cutting, and thermodynamics of metal cutting.