辽宁石油化工大学：《数控加工技术》课程PPT教学课件（英文版）第二章 金属切削原理与刀具 Principles of Metal Cutting and Cutting Tools

遼字石油化工大學⊙ Chapter Two Principles of Metal Cutting and Cutting Tools

Chapter Two Principles of Metal Cutting and Cutting Tools

遼字石油化工大學⊙ Instructional objectives 1. Understand the meaning of cutting motion, cutting parameters and the type of tool 2. Understand the properties and categaries of tool materials 3. Understand the chip formation process, chip types and control. Understand the phenomenon of bue 4. Understand the cutting force, cutting power, cutting force measurement and empirical formula of it Master the influencing factors of cutting force

Instructional objectives 1.Understand the meaning of cutting motion, cutting parameters and the type of tool; 2.Understand the properties and categaries of tool materials. 3.Understand the chip formation process, chip types and control. Understand the phenomenon of BUE. 4.Understand the cutting force, cutting power, cutting force measurement and empirical formula of it. Master the influencing factors of cutting force

遼字石油化工大學⊙ Instructional objectives 5. Understand the generation and conduction of cutting heat, the measurement of cutting temperature. Master the main factors affecting the cutting temperature. Understand the cutting fluid. Master the influence of cutting temperature on the workpiece tool and the cutting process 6. Understand the form and reason of tool wear Understand the process of tool wear and blunt standards, the empirical formula of tool life, grasp the concept of tool life, tool life factors 7. Understand the machinability of metals and master the selection principle of cutting parameters

5.Understand the generation and conduction of cutting heat, the measurement of cutting temperature. Master the main factors affecting the cutting temperature. Understand the cutting fluid. Master the influence of cutting temperature on the workpiece tool and the cutting process. 6.Understand the form and reason of tool wear. Understand the process of tool wear and blunt standards, the empirical formula of tool life, grasp the concept of tool life, tool life factors. 7.Understand the machinability of metals and master the selection principle of cutting parameters. Instructional objectives

遼字石油化工大學⊙ This chapter is an introduction to the fundamentals of the machining proces-ses and presents the basic concepts relevant to all machining operations The chapter opens with a discussion of the cutting tools, mechanics of chip formation in machining and the calculation of force and power in the machining Temperature rise in chip cutting tool are then dicussed Mechanisms of tool tear and failure follow. with flank wear characterized by th-e Taylor tool-life equation Crater wear nose wearand other forms of wear are also described The chapter ends with a discssion of surface finish, the integrity of parts produced by machining, and the factors involved in the machinability of various metallic materials

This chapter is an introduction to the fundamentals of the machining proces-ses and presents the basic concepts relevant to all machining operations. The chapter opens with a discussion of the cutting tools,mechanics of chip formation in machining and the calculation of force and power in the machining. Temperature rise in chip cutting tool are then dicussed. Mechanisms of tool tear and failure follow,with flank wear characterized by th-e Taylor tool-life equation. Crater wear,nose wear,and other forms of wear are also described. The chapter ends with a discssion of surface finish,the integrity of parts produced by machining,and the factors onvolved in the machinability of various metallic materials

遼字石油化工大學⊙ 2.1 Introduction of the Cutting tools A Cutting Processes Cutting processes remove material form the surface of a workpiece by producing chips. Some of the more common cutting processes, illustrated in the Figs as follows Depth of fa) staight turnng (b) Cutin ott Chip fe) Slab IAE Ia.I Some examples of common machining HGURE 13.2 Schematic illustration of the turning operation, showing, various features

2.1 Introduction of the Cutting Tools A.Cutting Processes: Cutting processes remove material form the surface of a workpiece by producing chips.Some of the more common cutting processes,illustrated in the Figs as follows:

遼字石油化工大學⊙ O turning in which the workpiece is rotated and a cutting tool removes a layer of material as the tool moves to the left, as in right Fig. shows OCutting off, in which the cutting tool moves radially inward and separates the right piece from the bulk of the blank SLab milling in which a rotating cutting tool removes a layer of material from the surface of the workpiece CEnd milling, in which a rotating cutter travles along a certain depth in the wo-rkpiece and produces a cavity

● Turuning in which the workpiece is rotated and a cutting tool removes a layer of material as the tool moves to the left,as in right Fig. shows. ●Cutting off,in which the cutting tool moves radially inward and separates the right piece from the bulk of the blank. ●Slab milling,in which a rotating cutting tool removes a layer of material from the surface of the workpiece. ●End milling,in which a rotating cutter travles along a certain depth in the wo-rkpiece and produces a cavity

遼字石油化工大學⊙ In order to analyze this process in detail, a two-dimensional model of it is presented in Fig. 2.2. In this idealized model, a cutting tool moves to the left along the workpiece at a constant elocity, v, and a depth of cut t. a chip is prouced ahead of the tool by plastically deforming and shearing the material continuously along the shear plane This phenomenon can be demonstrated Rough surface Shiny surface by slowly scraping the Rake face Chip Tool surface of a stick of Shear plane Rake anal butter lengthwise with a Flank face sharp knife and Relief or clearance observing the formation Workpiece of a chip Shear angle

In order to analyze this process in detail,a two-dimensional model of it is presented in Fig.2.2.In this idealized model,a cutting tool moves to the left along the workpiece at a constant elocity,v,and a depth of cut t. A chip is prouced ahead of the tool by plastically deforming and shearing the matearial continuously along the shear plane. This phenomenon can be demonstrated by slowly scraping the surface of a stick of butter lengthwise with a s h a r p k n i f e a n d observing the formation of a chip

遼字石油化工大學⊙ B Cutting Factors The factors that influence the cutting process are outlined in Table 2.1 In order to appreciate the contents of this table,lets now identify the major independent variables in the cutting prcess. (atool materials and coatings (b)tool shape, surface finish, and sharpness (c)workpiece material and con-dition (dcutting speed, feed, and depth of cut (e)cutting fluids, (characteristics of the machine tool (g working holding and fixturing

B.Cutting Factors The factors that influence the cutting process are outlined in Table 2.1. In order to appreciate the contents of this table,let’s now identify the major independent variables in the cutting prcess: (a)tool materials and coatings; (b)tool shape,surface finish,and sharpness; (c) workpiece material and con-dition; (d)cutting speed,feed,and depth of cut; (e)cutting fluids; (f )characteristics of the machine tool; (g)working holding and fixturing

遼字石油化工大學⊙ TABLE 2.1 Factors Influencing Machining Operations Parameter Influence and interrelationship Cutting speed, depth of cut Forces, power, temperature rise, tool life, type of chip, feed, cutting fluids surface finish and integrity Tool angles As above; influence on chip flow direction; resistance to tool wear an nd chipping Continuous chir Good surface finish; steady cutting forces; undesirable, especially in automated machinery Built-up edge chip Poor surface finish and integrity; if thin and stable, edge can protect tool surfaces Discontinuous chip Desirable for ease of chip disposal; fluctuating cutting forces: can affect surface finish and cause vibration and chatter Temperature rise Influences tool life, particularly crater wear and dimensional accuracy of workpiece; may cause thermal damage to workpiece surface Tool wear Influences surface finish and integrity, dimensional accuracy, temperature rise, forces and power Machinability Related to tool life, surface finish, forces and pe d type of chip

TABLE 2.1

遼字石油化工大學⊙ Dependent variables in cutting are those that are influenced by changes in the independent variables listed above, and include (a type of chip produced; (b)force and the chip (c temperature rise in the workpiece, the tool, and the chip; (dtool wear and failure (e)surface finishi and surface integrity of the workpiece

Dependent variables in cutting are those that are influenced by changes in the independent variables listed above,and include (a) type of chip produced; (b) force and the chip; (c) temperature rise in the workpiece, the tool, and the chip; (d)tool wear and failure; (e)surface finishi and surface integrity of the workpiece