Manufacturing Technology 1: Machining Part PDF

12/9/2024 Manufacturing Technology 1: Machining Part Non Traditional Machining Processes (NTMP) 1 1 Machining processes are classified as traditional (conventional) and nontraditional (nonconventional) processes. 2 2...

12/9/2024 Manufacturing Technology 1: Machining Part Non Traditional Machining Processes (NTMP) 1 1 Machining processes are classified as traditional (conventional) and nontraditional (nonconventional) processes. 2 2 1  12/9/2024 Traditional machining process (TMP) is the manufacturing process by which parts can be produced to the desired dimensions and surface finish from a blank by gradual removal of the excess material in the form of chips with the help of a sharp cutting tool (single point tools, drills, milling cutters, grinding wheels, etc.). Almost 90% of the all engineering components are subjected to some kind of machining during manufacture. 3 3 4 4 2  12/9/2024 5 5 The recent increase in the use of hard, high strength and temperature resistant material in the applications has necessitated the development of newer machining techniques.  A few of such Materials are ceramics, composites, tungsten, stainless steel, tantalum, Inconel, uranium, beryllium and some high strength steel alloys.  The increasing utility of such materials in modern industry has forced the researcher to develop newer machining methods, so as to have full advantage of these costly materials. 6 6 3  12/9/2024 Nontraditional machining process (NTMP) is the manufacturing process by which parts can be produced to the desired dimensions and surface finish from a blank by gradual removal of the excess material in the form of atoms or molecules individually or in groups with the help of different kinds of energy (electrical, chemical, electrochemical, thermal, mechanical, etc.). 7 7 Why NTMP? NTMP have several specific advantages over TMP.  These processes are not limited by hardness of WP materials.  These processes are not limited by stiffness, and brittleness of WP materials.  Slender WP could be machined.  Complex shape could be produced by theses processes.  Higher degree of accuracy and surface finish could be obtained.  These processes are economical, fast and highly efficient. However NTMP are not substitutes for TMP, but are only 8 complementing them. 8 4  12/9/2024 The common NTMP are the followings:  Electrical discharge machining.  Electron beam machining.  Plasma arc machining  Laser beam machining  Ion beam machining  Electro-chemical machining  Electro-chemical grinding  Ultra sonic machining  Water jet machining  Abrasive water jet machining 9 9 Classification of NTMP  NTMP may be classified on the basis of type of energy used. 10 10 5  12/9/2024 1. Electro-Chemical Machining (ECM)  This process is developed on the principles of Faraday and ohm.  An electrolytic cell is formed by the anode (WP) and the cathode (reshaped tool) in the midst of a flowing electrolyte. 11 11  The principle: Due to electrolysis process, hydroxyl (- ve charged) ions are released which combine with the metal ions of anode to form insoluble metal hydroxides. Thus the metal is removed. 12 12 6  12/9/2024 13 13 14 14 7  12/9/2024 15 15 16 16 8  12/9/2024  The amount of mass dissolved (removed by process) is directly proportional to the current and time.  The current density (may be reached to more than 2000A/ 1 cm2 of WP) is proportional to the applied voltage, concentration of pumped electrolyte and gap between the electrodes (0.05 to 0.1 or 0.2 mm).  No spark is produced and the temp. generated are low which do not cause metallurgical changes in the properties of WP material. 17 17  Electrode (tools) materials should be machinable and good conductor of electricity. They are most commonly made of copper, brass, stainless steel and titanium. Copper and brass are preferred except for thin tools requiring greater stiffness.  Electrolytes most commonly used are water solutions of sodium chloride, potassium chloride, sodium nitrite and sodium hydroxide.  WP material to be machined should be good conductor of electricity. 18 18 9  12/9/2024 Advantages of ECM process  Complex shape could be produced.  No cutting force are involved in the process.  WP of very thin section could be produced.  There is no significant tool wear since there is no tool-WP contact.  Metal removal rate is quite high in comparison to TMP, specially in respect WP material of high strength.  It is an accurate process and close tolerance of the order of 0.05 mm could be easily obtained. 19 19 Disadvantages of ECM process  Materials which are non-conductors of electricity cannot be machined.  The huge amount of energy is consumed (about 100 times that required for turning or milling steel).  Required initial investment is quite high.  Because the electrolyte is pumped through the gap at high pressure, special fixtures must be used to hold the WP in place.  Because the electrolyte is pumped through the gap at high pressure , corrosion of WP, machine tool, fixture, etc. 20 20 10  12/9/2024 Applications ECM process  Machining of hard materials (exceed 42 RC) could be produced.  Machining of blind and through holes could be produced.  Machining of small deep holes could be produced.  It machines WP without tool rotation, so machining of pockets of any shape could be produced. 21 21 22 22 11  12/9/2024 2. Electrical Discharge Machining (EDM)  It is also known as spark erosion machining.  The principle: WP and tool (electrode) are immersed in dielectric fluid and separated by a gap (0.005 mm to 0.05 mm). When a difference of potential is applied between two conductors (WP - tool), the fluid will ionized. If the potential difference is maintained, then the spark will 23 be developed. 23  A very high temperature of WP surface around 10000 ℃ causes the WP surface start to melt in the spark-surface contact area. 24 24 12  12/9/2024  The circulating dielectric carries away the eroded particles of metal and dissipated heat caused by spark. 25 25 26 26 13  12/9/2024 27 27 28 28 14  12/9/2024 29 29  Electrode (tools) materials should be machinable and good conductor of electricity. They are most commonly made of copper, brass, graphite and titanium. Copper and brass are preferred except for thin tools requiring greater stiffness.  WP material to be machined should be good conductor of electricity. 30 30 15  12/9/2024 Advantages of EDM process  Complex shape could be produced.  No cutting force are involved in the process.  WP of very thin section could be produced.  There is no significant tool wear since there is no tool-WP contact.  It is an accurate process and close tolerance of the order of ± 5 microns could be easily obtained. 31 31 Disadvantages of EDM process  Materials which are non-conductors of electricity cannot be machined.  Metal removal rate is slow, therefore this process should only be used where other TMP are not suitable as machining costs are high.  The huge amount of energy is consumed.  Surface cracking may take place. 32 32 16  12/9/2024 Applications of EDM process  This process is very useful in tool manufacturing due to the ease with which hard metals can be machined.  Machining of cavity of dies.  Hole as small as 0.1 mm in diameter can be made. 33 33 Wire Cut - Wire EDM 34 34 17  12/9/2024  EDM primarily exists commercially in the form of wire cutting m/c.  In this process, a slowly moving wire travels along a prescribed path and remove material from the WP.  The material is removed by a series of discrete discharges between the wire and WP in the presence of dielectric fluid in the gap.  The area where discharge take place is heated to extremely high temp. so that the surface is melted and removed.  The wire for wire EDM is made of brass, copper, tungsten, molybdenum. 35 35 36 36 18  12/9/2024 37 37 3. Laser Beam Machining (LBM)  The word laser stands for Light Amplification by Stimulated Emission of Radiation. 38 38 19  12/9/2024 Vision LWI IV Nd:YAG laser welding machine 39 Bystronic Bysprint 3015 Co2 laser cutting machine 40 20  12/9/2024 CAB laser marking machine 41 Industrial Laser 42 21  12/9/2024 3. Laser Beam Machining (LBM)  The word laser stands for Light Amplification by Stimulated Emission of Radiation.  When the focused laser beam impinges on the surface of the workpiece, the material partly vaporises.The resulting cutting kerf is surrounded by molten material which is continuously ejected during the cutting process by a stream of cutting gas. 43 43 44 44 22  12/9/2024  Gas is blown into the cut to clear away molten metals, or other materials in the cutting zone. in some cases, the gas jet can be chosen to react chemically with the WP to produce heat and accelerate the cutting speed.  The oxygen is the most common type, or carbon dioxide (CO2) 45 45 Advantages of LBM process  LBM could be used to drill micro holes with very large depth.  Laser operates in any transparent environment, including air, inert gas, vacuum and ever certain liquids.  The laser head need not be in close proximity for performing cutting and drilling operations in locations of difficult accessibility.  Any metal or non-metal can be machined. E.g. tungsten, ceramics, wood, paper.etc.  Work piece need not be electrically conductive.  A laser beam can be split into several beams, each beam can be used to perform same operations or different operations. 46 46 23  12/9/2024 47 47 48 48 24  12/9/2024 49 49 50 50 25  12/9/2024 51 51 Disadvantages of LBM process  Lasers are not very effective on metals such as aluminum and copper alloys due to their ability to reflect light as well as absorb and conduct heat.  The material being cut gets very hot, so in narrow areas, thermal expansion may be a problem.  Not suitable for machining blind holes in metal.  High capital investment.  The metal removal rate of 0.0065 cm3/hr in LBM is among the slowest as compared to other machining processes.  The holes produced by LBM may taper from entry to exit. The taper on one side of the hole can be as much as 0.05mm/mm. 52 52 26  12/9/2024 4. Water Jet Machining (WJM)  Water jet technology uses the principle of pressurizing water to high pressures, and allowing the water to escape through a very small opening called orifice (usually varies from 0.08 mm to 0.5 mm) to increase its speed (up to 920 m/sec).  These high velocity water jets can be used to cut soft materials like paper boards, wood, plastics, rubber, leather, fiberglass, frozen meat, etc. 53 53 54 54 27  12/9/2024 55 55 56 56 28  12/9/2024  The cutting ability of water jet machining can be improved by adding hard and sharp abrasive particles (silicon carbide or aluminum oxide) into the water jet which is known as abrasive water jet machining process (AWJM).  Almost any type of material This machining process is ranging from hard brittle ideal for cutting heat material such as ceramics, sensitive materials that metals and glass to extremely cannot be machined by soft materials such as foam and processes that produce heat rubber can be cut by AWJM. 57 while machining. 57 58 58 29  12/9/2024 59 59 Applications: AWJM is highly produced in aerospace, automotive and electronic industries. In aerospace industries, Titanium and aluminum bodies for military aircrafts, engine components and interior cabin parts are made using AWJM. In automotive industries, parts like head liners, door panels, bumpers are made by this process. In electronics industries, circuit boards and cables are made by this process. Disadvantages: High capital cost. High noise level during operation. 60 60 30  12/9/2024 61 61 62 62 31  12/9/2024 63 63 64 64 32  12/9/2024 65 65 66 66 33