Materials & Processes in Manufacturing

Size: px

Start display at page:

Download "Materials & Processes in Manufacturing"

Suzan Johns
5 years ago
Views:

1 2003 Bill Young Materials & Processes in Manufacturing ME 151 Chapter 21 Fundamentals of Chip Type Machining Processes 1 Materials Processing 2003 Bill Young 2 Introduction Machining is the process of removing unwanted material from a workpiece in the form of chips to obtain a finished product of the desired,, and Machining is the most important of the basic manufacturing processes Vast majority of manufactured products require machining at some stage in their production 7 Basic Chip Formation Processes Shaping / Planing Turning Milling Drilling Sawing Broaching Grinding (Abrasive Machining) 2003 Bill Young 3

2003 Bill Young 4 Machining Inputs & Outputs Figure 21-1 Page 481 Fundamental Cutting Parameters For all

velocity of workpiece relative to cutting tool (sfpm, in/min, m/m, m/sec) - Amount of material removed per

workpiece Figure 21-5 Page 485 2003 Bill Young 5 Basic Components for Machining 4 Basic components that

2 2003 Bill Young 4 Machining Inputs & Outputs Figure 21-1 Page 481 Fundamental Cutting Parameters For all metal cutting processes it is important to distinguish between: - Primary cutting motion and relates to velocity of workpiece relative to cutting tool (sfpm, in/min, m/m, m/sec) - Amount of material removed per revolution or per pass of tool over workpiece (in/rev, in/cycle, in/min, in/tooth) - Distance tool engages workpiece Figure 21-5 Page Bill Young 5 Basic Components for Machining 4 Basic components that makeup any machining process Machine Tool or Machining Center Workpiece Workholding Device Figure 21-3 Page Bill Young 6

2003 Bill Young 7 Process Input Parameters General guidelines are available in many types of reference handbooks Factors that

Tool Material & Geometry Turning w/carbide Tools Machining Reference Data Example Figure 21-4 Page 484 2003 Bill Young 8 Process

of material Material Removal Rate (MRR) - Volume of material removed over time Cutting Time (T m ) - Time required to perform

3 2003 Bill Young 7 Process Input Parameters General guidelines are available in many types of reference handbooks Factors that must be considered to machine a given material Cutting Speed, Depth of Cut, Feed Rate Process Material Type & Hardness Cutting Tool Material & Geometry Turning w/carbide Tools Machining Reference Data Example Figure 21-4 Page Bill Young 8 Process Cycle Times Determined using standard formulas based on type of process and recommended machining values for a particular type of material Material Removal Rate (MRR) - Volume of material removed over time Cutting Time (T m ) - Time required to perform cut Example Turning Process Cycle Times Volume of Cut MRR = Cutting Time T m = L + Allowance f r N s Figure 21-5 Page Bill Young 9

2003 Bill Young 10 Chip Formation Chip formation is generally explained using a 2-dimensional (orthogonal) model rather than a 3-dimensional (oblique) model Chip formation is based on a localized

tool geometry Edge Radius (Nose Radius) Back Rake Angle Interactions between the tool face & chip surface Interactions between the tool flank & material surface 2003 Bill Young 11 Effects of Work

4 2003 Bill Young 10 Chip Formation Chip formation is generally explained using a 2-dimensional (orthogonal) model rather than a 3-dimensional (oblique) model Chip formation is based on a localized process taking place over a narrow region Machining Models Machining models allow for understanding of: Behavior of the material during chip formation Influence of the most critical elements of the tool geometry Edge Radius (Nose Radius) Back Rake Angle Interactions between the tool face & chip surface Interactions between the tool flank & material surface 2003 Bill Young 11 Effects of Work Material Properties Properties of the workpiece are important in chip formation High strength materials require larger forces which increase deflection, friction, heat generation, operating temperature and require greater work input Structure and composition such as hard or abrasive constituents affect tool wear is important in determining type of chip produced Continuous Discontinuous (Segmented) 2003 Bill Young 12

5 2003 Bill Young 13 Heat & Temperature in Metal Cutting Power put into the process is largely converted to heat, which elevates the temperature of the: Chip Workpiece Tool Environment / Cutting Fluid Three main sources of heat: Figure Page 510 Shear Zone - Plastic deformation Tool / Chip Interface Contact Region - Plastic deformation & friction Tool Flank - Friction Types of Machining Operations Turning Drilling Grinding Grinding Boring Sawing Reaming Sawing Broaching Machining Cylindrical Surfaces Machining Holes Figure Page Bill Young 14 Types of Machining Operations Shaping Planing Milling Facing Broaching Grinding Machining Flat Surfaces Milling Sawing Figure Page Bill Young 15

6 2003 Bill Young 16 Chapter 21 - Fundamentals of Chip-Type Machining Processes Basic understanding of chip formation processes and major components of the process Basic concept of chip formation Effects of work material properties Effects of heating and temperature in metal cutting Review Questions:

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