Subject :- Manufacturing Processes - 1 Prepared by:- Nakum Pradipsinh( ) Guided By :Harshal Sir Bipin Sir

Metal Cutting Process

Manufacturing Manufacturing is the use of machines, tools and labor to produce goods for use or sale. The term may refer to a range of human activity, from handicraft to high tech, but is most commonly applied to industrial production, in which raw materials are transformed into finished goods on a large scale

Turning the raw material in finish goods

Selection process for manufacturing process Cost Material Functional aspects Rate of production Quality of product Safety, reliability and maintability requirements ITS CALLED AS BREAK EVEN ANALYSIS

BREAK EVEN ANALYSIS It is the responsibility of engineer to select the suitable manufacturing process which makes the required quality of product to the specifications and at lowest cost possible. Every company in market stands for making a profit. They have set of requirements regarding your product

CLASSIFICATION OF Manufacturing PROCESS Casting process Forming process Fabrication process Material removal process

Casting process Sand casting – 60% Investment casting – 7% Die casting – 9% Permanent mold casting – 11% Centrifugal casting – 7% Shell mold casting – 6%

Forming process Forging Rolling Extrusion Wire drawing

Material removal process Grinding Turning Drilling Shaping Milling Broaching Sawing

Fabrication process Gas welding Electric arc welding Electric resistance welding Thermit welding Cold welding Brazing Soldering

WHAT IS MACHINING……..? Machining is a term used to describe a variety of material removal processes in which a cutting tool removes unwanted material from a work piece to produce the desired shape. The work piece is typically cut from a larger piece of stock, which is available in a variety of standard shapes, such as flat sheets, solid bars, hollow tubes, and shaped beams. Machining can also be performed on an existing part, such as a casting or forging.

Machining

Cutting Tool Classification 1. Single-Point Tools One dominant cutting edge Point is usually rounded to form a nose radius Turning uses single point tools 2. Multiple Cutting Edge Tools More than one cutting edge Motion relative to work achieved by rotating Drilling and milling use rotating multiple cutting edge tools

Cutting Tools

Cutting Conditions in Machining Three dimensions of a machining process: Cutting speed v – primary motion Feed f – secondary motion Depth of cut d – penetration of tool below original work surface For certain operations, material removal rate can be computed as R MR = v f d where v = cutting speed; f = feed; d = depth of cut

Cutting Conditions for Turning

Four Basic Types of Chip in Machining 1. Discontinuous chip 2. Continuous chip 3. Continuous chip with Built-up Edge (BUE) 4. Serrated chip

Brittle work materials Low cutting speeds Large feed and depth of cut High tool ‑ chip friction (a) discontinuous Discontinuous Chip

Ductile work materials High cutting speeds Small feeds and depths Sharp cutting edge Low tool ‑ chip friction Figure (b) continuous Continuous Chip

Ductile materials Low ‑ to ‑ medium cutting speeds Tool-chip friction causes portions of chip to adhere to rake face BUE forms, then breaks off, cyclically Figure (c) continuous with built ‑ up edge Continuous with BUE

Cutting tool materials Selection of cutting tool materials is very important What properties should cutting tools have Hardness at elevated temperatures Toughness so that impact forces on the tool can be taken Wear resistance Chemical stability

Types of tool materials o Carbon + medium alloy steel o High speed steel (HSS) o Cast cobalt alloys o Carbides o Coated tools o Ceramics o Cubic boron nitride o invented by GE in 1969 o Silicon nitride o Diamond

Cutting fluid is a type of coolant and lubricant designed specifically for metalworking and machining processes. There are various kinds of cutting fluids, which include oils, oil-water emulsions, pastes, gels, aerosols (mists), and air or other gases Common exceptions to this are machining cast iron and brass, which are machined dry.

Economic Advantages Reduction of tool costs Reduce tool wear, tools last longer Increased speed of production Reduce heat and friction so higher cutting speeds Reduction of labor costs Tools last longer and require less regrinding, less downtime, reducing cost per part Reduction of power costs Friction reduced so less power required by machining

27 Heat Generated During Machining Heat finds its way into one of three places Work piece, tool and chips Too much, work will expand Too much, cutting edge will break down rapidly, reducing tool life Act as disposable heat sink

Characteristics of a Good Cutting Fluid 1. Good cooling capacity 2. Good lubricating qualities 3. Resistance to rancidity 4. Relatively low viscosity 5. Stability (long life) 6. Rust resistance 7. Nontoxic 8. Transparent 9. Nonflammable

Tool wear / Tool failure – After use of some time tool is subjected to wear. Cause of tool wear— Interaction between tool & chip. Cutting forces. Temperature increase during cutting

Tool wear / Tool failure *Effect of tool wear Tool wear changes tool shape, decrease efficacy. Tool wear induce loss of dimensional accuracy, loss of surface finish. It increases power consumption. *Classification of tool wear – Flank wear Crater wear on tool face Chipping Breakage Loss of hardness at high temperature

Flank wear It occurs on flank. It is due to friction between newly machined work piece surface & contact area of flank. The worn region at flank is called ’wear land’. The width of wear land (hf) is account as a measure of wear & it is determined by means of tool maker microscope. Causes — Feed of brittle material is less than 0.15 mm/rev. Abrasion by hard particles & inclusions in workpiece. Abrasion by fragment of built up edge. Shearing of micro welds between tool & work.

The small cavity is crated on the face of the tool. This small cavity is called ‘crater’ which develops at some distance from cutting edge. Causes— Pressure of chips when it is slide over face of tool. High temp at tool- chip interface. Some times it reaches to the melting temperature. Crater wear is more in case of continuous chips of ductile material. Lack of lubrication. Feed is less than 0.15 mm/rev. Low cutting speed. Crater wear on tool face

Tool life The length of time that a cutting tool can function properly before it begins to fail A measure of the length of time a tool will cut satisfactorily. Tool life generally indicates, the amount of satisfactory performance or service rendered by a fresh tool or a cutting point till it is declared failed.

Tool Life Expectancy The Taylor Equation for Tool Life Expectancy provides a good approximation. V c T n = C A more general form of the equation is where V c =cutting speed T=tool life D=depth of cut S=feed rate x and y are determined experimentally n and C are constants found by experimentation or published data; they are properties of tool material, workpiece and feed rate.

VC4 VC3 VC2 VC1 T1 T2T3 T4 Cutting velocity, VC (m/min) Tool life in min (T) Cutting velocity – tool life relationship

Tool Life Criteria in Production 1. Complete failure of cutting edge 2. Visual inspection of flank wear (or crater wear) by the machine operator 3. Changes in sound emitted from operation 4. Degradation of surface finish 5. Increased power 6. Work piece count 7. Cumulative cutting time

1. Shank. It forms the body of a solid tool and it is this part of the tool which is gripped in the tool holder. 2. Face. It is the top surface of tool between the shank and point of the tool. In the cutting action the chips flow along this surface only. 3. Point. It is the wedge shaped portion where the face and flank of the tool meet. It is cutting part of tool. It is also called nose, particularly in case of round nose tools. 4. Flank. Portion of tool which faces the work is term as flank. It is the surface adjacent to and below the cutting edge when tool lies in a horizontal position..

5. Base. It is actually the bearing surface of the tool on which it is held in a tool holder or clamped directly in a tool post. 6. Heel. It is the curved portion at the bottom of tool where the base and flank of the tool meet, as shown in Fig Nose radius. If the cutting tip (nose) of a single point tool carries a sharp cutting point the cutting tip is weak. It is, therefore, highly stressed during the operation may fail or lose cutting ability soon and produces marks on the machined surface

Tool Signature Convenient way to specify tool angles by use of a standardized abbreviated system is known as tool signature or tool nomenclature. It indicates the angles that a tool utilizes during the cut. It specifies the active angles of the tool normal to the cutting edge. This will always be true as long as the tool shank is mounted at right angles to the work-piece axis. The seven elements that comprise the signature of a single point cutting tool can be stated in the following order: Tool signature Back rake angle (0°) 2. Side rake angle (7°) 3. End relief angle (6°) 4. Side relief angle (8°) 5. End cutting edge angle (15°) 6. Side cutting edge angle (16°) 7. Nose radius (0.8 mm)

Orthogonal cutting: Orthogonal cutting (Fig.) is also known as two dimensional metal cutting in which the cutting edge is normal to the work piece. In orthogonal cutting no force exists in direction perpendicular to relative motion between tool and work piece.

2. Oblique cutting. Oblique cutting (Fig.) is the common type of three dimensional cutting used in various metal cutting operations in which the cutting action is inclined with the job by a certain angle called the inclination angle.

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