Manufacturing Processes(IM 212)

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Arab Academy for Science, Technology, and Maritime Transport Manufacturing Processes(IM 212) Department of Industrial & Management Engineering College of Engineering and Technology Lecture 1 :

1 Arab Academy for Science, Technology, and Maritime Transport Manufacturing Processes(IM 212) Department of Industrial & Management Engineering College of Engineering and Technology Lecture 1 : Introduction to Manufacturing Processes 1 Course Contents 1. Introduction to Manufacturing Processes 2. Mechanics of Chip Formation 3. Cutting Tools for Machining 4. Tool Wear and Tool Life 5. Economics of Machining 9. Broaching and Shaping 10. Grinding 11. Finishing Operations 12. Numerical Control of Machine Tools 13. Nontraditional Machining 6. Turning 7. Drilling and Reaming 8. Milling 2

2 Course Assessment 7 th Week Examination : 30 ( ) 12 th Week Examination: 20 ( ) Weeks 1-15 : 10 Final Examination : 40 Total Marks : 100 Reference: Fundamentals of Machining Processes: Conventional and Nonconventional Processes Author: Hassan El-Hofy, Alexandria University, Egypt Publisher: CRC Taylor and Francis, Boca Raton, Florida, USA Cat. #: 7288 ISBN: Publication Date: Number of Pages: Course Objectives At the end of this course, student should be aware of the following: 1. Classification of the machining technologies. 2. The material removal mechanism of each process. 3. Machining system components. 4. Economics of machining. 5. Effect of the different variables on the process behavior. 6. Selection of the proper machining process for any application. 4

3 Overview of Manufacturing Processes Manufacturing is the process of converting raw materials into products. Manufacturing represents 20-30% of the value of all goods and services produced in industrialized countries. Machining activities constitute ~ 20% of the manufacturing activities in the USA. Classification of Manufacturing Processes 5 Classification of Machining Processes Machining: is the removal of the unwanted material (Machining Allowance) from the workpiece in order to obtain a finished product of the desired size, shape, and surface quality. 6

4 Classification of Machining Processes Cutting: machining allowance is removed in the form of visible chips. Abrasion: machining allowance is removed in the form of minute and invisible chips by hard, tiny, and randomly oriented abrasive grit (bonded or loose) of indefinite number and shape. Erosion: machining allowance is removed in the form of successive surface layers as a result of dissolution, melting and vaporization of the material being machined. Cutting Abrasion 7 Machining by Cutting The tool is penetrated into the workpiece by a depth of cut. Cutting tools have definite number of cutting edges of a known geometry. The machining allowance is removed in the form of visible chips. The shape of the workpiece produced depends on the tool-workpiece relative motion. Chip Depth of Cut Tool Cutting Speed Cut Surface Workpiece 8

5 Tool and Workpiece Motions Workpiece Tool Stationary Linear Rotary Spiral Stationary Shaping Broaching Drilling Linear Planing Milling Rotary Turning Spiral Hobbing 9 Classification of Cutting Processes Based on Number of Cutting Points/Edges Machining by Cutting Single Point Turning Boring Shaping Planing Multi point Drilling Reaming Milling Broaching Hobbing Sawing Filing Based on Cutting Kinematics Machining by Cutting Form Generation Form & Generation Shaping Planing Drilling Form Turning Form Milling Turning Shaping Planing Pocket Milling Contour Milling Thread Cutting Slot Milling Gear Hobbing 10

6 Classification of Cutting Processes Generation Cutting Form-Generation Cutting Form Cutting 11 General Aspects of Machining Technology General Aspects of Machining Technology 12

Main Elements of Machining by Cutting t Main

Formation During metal cutting three different

7 Main Elements of Machining by Cutting t Main Elements of Machining by Cutting 13 Chip Formation During metal cutting three different types of chip are formed that affects the product accuracy and surface roughness. Thetypeofchipformeddependsontheworkpiecematerialandthemachining conditions. Discontinuous (Segmented) Chip Continuous Chip Continuous Chip with Built-Up Edge (BUE) 14

8 Discontinuous (Segmented) Chip Discontinuous chips are produced when brittle materials such as Cast Iron and Bronze are cut. As the cutting tool contacts the metal, some compression stresses occur, and the chip begins to flow along the chip-tool interface. The metal compresses until rupture which occurs at the shear plane and the chip separates from the workpiece. Chip Cutting Speed Tool Workpiece 15 Discontinuous (Segmented) Chip This type of chip causes: Variations of the cutting forces that result in vibrations. Loss of product accuracy. Poor surface quality. Extensive tool wear. Machining conditions producing this type of chip: 1. Materials that contains hard inclusions and impurities. 2. Very low/very high cutting speeds. 3. Large depth of cuts. 4. Very small or -ve rake angles. 5. Low stiffness of the machine tool. 6. Lake of the effective cutting fluid. 16

9 Continuous Chip Fractures or ruptures do not occur because of the ductile nature of the metal. Although continuous chip is considered an ideal for better surface finish, low power consumption and longer tool life, they are not always desirable as they tend to tangle around the tool holder. Hence, machining operation has to be stopped to clear away the chips. Chip breakers are therefore used to break chips but they increase cutting tool cost and raise cutting forces and power. Chip Cutting Speed Tool Workpiece 17 Continuous Chip Machining conditions producing this type of chip: 1. Ductile/soft materials (Mild Steel, Copper, and Aluminum). 2. High cutting speeds (>60 m/min). 3. Small depth of cut. 4. Small feed rate. 5. Sharp cutting edge. 6. Tool material of low coefficient of friction. 7. Efficient cutting fluid. 8. Large (+ve) rake angles. 18

10 Chip Breakers Chip breakers are used to split the chips. The use of chip breakers increases cutting tool cost and raises cutting forces and power. Types of chip breakers: 1. Groove Type. Chip Breaker Land Width Chip Breaker Depth 19 Chip Breakers 2. Obstruction Type: Chip Breaker Height Chip Breaker Distance Chip Breaker Wedge Angle Chip Breaker Height Chip Breaker Distance a) Attached b) Integrated 20

11 Continuous Chip with Built-Up Edge (BUE) The local high temperature, the high pressure and the frictional resistance to the flow of the chip cause the work material to adhere to the cutting edge of the tool forming the Built-Up Edge (BUE). The rest of the material randomly adheres to the workpiece cut surface resulting in: Poor surface finish. Changes the geometry of the cutting tool. Causes failure of the cutting tool. BUE Fragments Welded to Chips Cutting Speed BUE Welded to Machined Surface BUE 21 Continuous Chip with Built-Up Edge (BUE) Machining conditions producing this type of chip: 1. Ductile materials such as Mild Steel, Copper, and Aluminum. 2. Low cutting speed (<60 m/min). 3. Large depth of cut. 4. Large feed rate. 5. Dull (not sharp) cutting edge. 6. High friction at the chip-tool interface. 7. Insufficient cutting fluid. 8. Small (+ve) rake angles. 22

12 Factors Affecting Cutting Processes 23

THEORY OF METAL CUTTING

THEORY OF METAL CUTTING INTRODUCTION Overview of Machining Technology Mechanism of chip formation Orthogonal and Oblique cutting Single Point and Multipoint Cutting Tools Machining forces - Merchant s