ENM208 INTRODUCTION to MACHINING ANADOLU UNİVERSITY Industrial Engineering Department

Manufacturing Processes Spring 2005 Introduction To Machining Machining is the process of removing unwanted material from a workpiece in the form of chips. If the workpiece is metal, the process is often called Metal Cutting or Metal Removal. Machining is the most important of the basic manufacturing processes. Machining is capable of creating geometric configurations, tolerances, and surface finishes often unobtainable by any other manufacturing processes

Manufacturing Processes Spring 2005 Machining and Precision Because of the increased demand for high quality, precision machining is becoming common and hence the need for high accuracy measurement systems.

Manufacturing Processes Spring 2005 Examples of Machined Parts

Manufacturing Processes Spring 2005 Inputs to Machining Processes The machining process is complex because it has such a wide variety of inputs which are listed as follows: The machine tool selected to perform the process. The cutting tool selected (geometry and material). The properties and parameters of the workpiece. The cutting parameters selected (cutting speed, feed rate, and depth of cut). The workpiece holding devices or fixtures.

Types of Machining Operations

Manufacturing Processes Spring 2005 Turning Operations Turning is the process of machining external cylindrical and conical surfaces. The process uses a machine tool called a lathe.

Manufacturing Processes Spring 2005 Lathe Machine The Centre Lathe is used to manufacture cylindrical shapes from a range of materials

Swing - maximum diameter that can be rotated on the lathe. Maximum distance between centers Power of the lathe engine. Rotational speed range. Feed Rate range. Lathe Machine Characteristics Manufacturing Processes Lathe Machine Spring 2005

Manufacturing Processes Spring 2005 Lathe Operations Turning Operations To produce straight, conical, formed, or grooved workpieces such as shafts, spindles and pins

Manufacturing Processes Spring 2005 Lathe Operations Facing Operations To produce flat surface at the end of the part, which are useful for parts that are attached to other components.

Manufacturing Processes Spring 2005 Lathe Operations Boring Operations To enlarge hole or cylindrical cavity made by a previous process or to produce circular internal grooves

Manufacturing Processes Spring 2005 Lathe Operations Parting or Cutting off Operations To cut a piece from the end of a part

Manufacturing Processes Spring 2005 Lathe Operations Drilling To produce a hole, which may be followed by boring to improve its accuracy and surface finish

Manufacturing Processes Spring 2005 Lathe Operations Threading To produce external or internal threads

Manufacturing Processes Spring 2005 Lathe Operations Knurling Operations To produce a regularly shaped roughness on cylindrical surfaces

Manufacturing Processes Spring 2005 Cutting Tools for Lathe Operations Single Point Cutting Tools

Manufacturing Processes Spring 2005 Single Point Cutting Tool Geometry

Manufacturing Processes Spring 2005 Turning Tool Angles

Manufacturing Processes Spring 2005 Cutting-Tool Materials The selection of cutting-tool materials for a particular application is among the most important factors in machining operations The cutting tool is subjected to: (a) high temperatures; (b) contact stresses, and (c) sliding along the tool-chip interface and along the machined surface. A cutting tool material must possess the following characteristics: Hardness, so that the hardness, strength, and wear resistance of the tool are maintained at the temperature encountered in cutting operations. Toughness, so that impact forces on the tool or due to vibration during machining do not fracture the tool. Wear resistance, so that an acceptable tool life is obtained before the tool is indexed or replaced.

Manufacturing Processes Spring 2005 Cutting-Tool Materials Various cutting-tool materials with a wide range of mechanical, physical, and chemical properties are available. Tool materials are usually divided into the following general categories: 1- Carbon and medium-alloy steels. 2- High-speed steels. 3- Carbides (coated and uncoated). 4- Ceramics. 5- Diamond.

Manufacturing Processes Spring 2005 Characteristics of Cutting-tool Materials

Manufacturing Processes Spring 2005 Workholding on a Lathe 1- The work center line must be accurately centered along the axis of the lathe spindle. 2- The work must be held rigidly while being turned. 3- The work must NOT be sprung out of shape by the holding device. 4- The work must be adequately supported against any deflection caused by its own weight and against springing caused by the action of the cutting tool. You cannot perform accurate work if the workpiece is improperly mounted. The requirements for proper mounting are as follows:

Manufacturing Processes Spring 2005 Workholding on a Lathe There are four general methods of holding work in the lathe: (1)between centers, (2) In a chuck, (3) on a mandrel, and (4) on a faceplate.

Manufacturing Processes Spring 2005 Turning Parameters 1- Cutting Speed (V) is the primary cutting motion, which relates the velocity of the cutting tool relative to the workpiece. It is generally given in units of (m/min). 2- Feed (f) is the amount of material removed per revolution or per pass of the tool over the workpiece. In turning, feed is in millimeter per revolution (mm/r), and the tool feeds parallel to the rotational axis of the workpiece. 3- Depth of Cut (d) It is the distance the tool is plunged into the surface. In turning, it is half the difference between initial and final diameters given in (mm).

Manufacturing Processes Spring 2005 Selection of Cutting Speed Selection of Cutting Speed depends on three factors: 1- Operation Type. 2- Workpiece Material 3- Tool Material

Manufacturing Processes Spring 2005 Selection of Feed Rate Selection of Feed Rate depends on three factors: 1- Operation Type. 2- Workpiece Material 3- Tool Material

Manufacturing Processes Spring 2005 Roughing and Finishing Cuts In machining the general procedure is to (a) Perform one or more roughing cuts at low speed, fast feed rate and large depth of cut (little consideration of dimensional tolerances and surface finish), and (b) Follow it with a finishing cut a higher speed, slower feed rate and smaller depth of cut for a good surface finish. V f d

Manufacturing Processes Spring 2005 Summary of Turning Parameters and Formulas

Manufacturing Processes Spring 2005 Drilling and Related Hole Making Operations

Manufacturing Processes Spring 2005 Hole Making Processes Various Types of Drilling and Reaming Operations

Manufacturing Processes Spring 2005 Drilling Sequence The Most Accurate holes are produced by the following sequence of operations: 1- Center drilling. 2- Drilling. 3- Boring, and 4- Reaming.

Manufacturing Processes Spring 2005 Drilling Operation Drilling is the process of producing or enlarging a hole. This is accomplished by rotating the tool and/or workpiece.

Manufacturing Processes Spring 2005 Reaming Reaming - Enlarging an existing hole with a multi- edged tool (reamer) for dimensional accuracy and/or surface finish

Manufacturing Processes Spring 2005 Countersinking Operation Countersinking - operation for producing a tapered feature at the end of a hole. Most popular application is a feature for a flathead screw (82 degrees).

Manufacturing Processes Spring 2005 Counterboring Operation Counterboring - Enlarging of an existing hole at one end. This enlarged hole is concentric with the existing hole and is flat at the bottom. One application of this process is a feature to set the head of a bolt below a surface.

Manufacturing Processes Spring 2005 Center Drilling Center Drilling – is an operation used to start a hole at the desired location on a surface or to produce the hole at the end of a piece of stock so that it may be mounted between centers in a lathe.

Manufacturing Processes Spring 2005 Tapping Tapping – an operation used to produce internal thread in workpieces.

Manufacturing Processes Spring 2005 Drilling Machines

Manufacturing Processes Spring 2005 Drilling Tools Most Commonly used

Manufacturing Processes Spring 2005 Reamer

Manufacturing Processes Spring 2005 Drilling Parameters - Given hole diameter, D (mm), - Given hole length, L (mm), - Select cutting speed, V (m/min), - Select feed, f (mm/r), Rotational speed, (rpm) Feed speed, Machining time, Metal removal rate, (mm/min) (min) (mm 3 /min)

Manufacturing Processes Spring 2005 Recommended speeds and feeds

Manufacturing Processes Spring 2005 Workholding in Drilling Vise Angle plate Jig Clamp to table of drill press Workholding devices for drilling are important to ensure that the workpiece can be located properly.