27-05-2014, 01:49 PM
ADVANCED FINE FINISHING PROCESSES
ADVANCED FINE FINISHING.docx (Size: 509.14 KB / Downloads: 27)
ABSTRACT:
The technology is really spice of life. This project is all about latest technology which is useful for finishing materials with very high precision. These are the latest processes are called as Advanced Fine Finishing Processes. In this seminar we are going to take a overlook on some of these processes.
With the demand of stringent technological and functional requirements of the parts from micro- to nano-meter range, evolution of ultra precision finishing processes became obvious need of the manufacturing scientists and engineers. The traditional finishing processes of this category have various limitations, for example complex shapes, Miniature sizes, and 3-D parts can not be processed & finished economically and rapidly. This led to the development of advanced finishing techniques like Abrasive Flow Machining, Magnetic Abrasive Finishing, Magnetic Float Polishing, Magneto-rheological Abrasive Finishing, and Ion Beam Machining. In all these processes except Ion Beam Machining, abrasion of the work piece takes place in a controlled fashion such that the depth of penetration in the work piece is a fraction of micrometer so that the final finish approaches towards the nano range.
DEFENITION:
Advanced fine finishing is a metalworking process that improves surface finish and work piece geometry. This is achieved by removing just the thin amorphous surface layer left by the last process with an abrasive stone; this layer is usually about 1 μm in magnitude.
INTRODUCTION:
The developments in the material science have led to the evolution of difficult-to machine, high strength temperature resistant materials with many extraordinary qualities.
Nano- materials and smart materials are the demands of the day. To make different products in various shapes and sizes, many times, the traditional manufacturing techniques do not work. One needs to use non-traditional or advanced manufacturing techniques in general and advanced machining processes in particularly [IJ. Later includes both, bulk material removal advanced machining processes as well as advanced fine finishing processes. Further, the need for high precision in manufacturing was felt by manufacturers world over, to improve interchangeability of components, improve quality control and longer wear / fatigue life [2,3]. Achieving controlled surface finish on such components is equally important.
Traditionally, abrasives either in loose or bonded form whose geometry varies continuously in an unpredictable manner during the process are used for final finishing purposes.
Nowadays, new advances in materials syntheses have enabled production of ultra fine abrasives in the nanometer range without the need for comminution (a process by which brittle materials are reduced in size).
CONVENTIONAL MACHINING :
The three principal machining processes are classified as turning, drilling and milling. Other operations falling into miscellaneous categories include shaping, planing, boring, broachingand sawing.[5][6][7]
Turning operations are operations that rotate the workpiece as the primary method of moving metal against the cutting tool. Lathes are the principal machine tool used in turning.
Milling operations are operations in which the cutting tool rotates to bring cutting edges to bear against the workpiece. Milling machines are the principal machine tool used in milling.
TYPES OF MACHINING OPERATION:
There are many kinds of machining operations, each of which is capable of generating a certain part geometry and surface texture.
In turning, a cutting tool with a single cutting edge is used to remove material from a rotating work piece to generate a cylindrical shape. The speed motion is provided by rotating the work piece, and the feed motion is achieved by moving the cutting tool slowly in a direction parallel to the axis of rotation of the work piece.
Drilling is used to create a round hole. It is accomplished by a rotating tool that typically has two or four helical cutting edges. The tool is fed in a direction parallel to its axis of rotation into the work piece to form the round hole.
In boring, a tool with a single bent pointed tip is advanced into a roughly made hole in a spinning work piece to slightly enlarge the hole and improve its accuracy. It is a fine finishing operation used in the final stages of product manufacture.
In milling, a rotating tool with multiple cutting edges is moved slowly relative to the material to generate a plane or straight surface. The direction of the feed motion is perpendicular to the tool's axis of rotation.
The cutting tool
A cutting tool has one or more sharp cutting edges and is made of a material that is harder than the work material. The cutting edge serves to separate chip from the parent work material. Connected to the cutting edge are the two surfaces of the tool:
The rake face; and The flank.
The rake face which directs the flow of newly formed chip, is oriented at a certain angle is called the rake angle "α". It is measured relative to the plane perpendicular to the work surface. The rake angle can be positive or negative. The flank of the tool provides a clearance between the tool and the newly formed work surface, thus protecting the surface from abrasion, which would degrade the finish. This angle between the work surface and the flank surface is called the relief angle. There are two basic types of cutting tools:
Single point tool; and Multiple-cutting-edge tool
A single point tool has one cutting edge and is used for turning, boring and planning. During machining, the point of the tool penetrates below the original work surface of the work part. The point is sometimes rounded to a certain radius, called the nose radius.
Multiple-cutting-edge tools have more than one cutting edge and usually achieve their motion relative to the work part by rotating. Drilling and milling uses rotating multiple-cutting-edge tools. Although the shapes of these tools are different from a single-point tool, many elements of tool geometry are similar.