Introduction The EBM technique is used for cutting fine holes and slots in any material. In a vacuum chamber, a beam of high-velocity electrons is focused on a work piece. The kinetic energy of the electrons, upon striking the work piece, changes to heat, which vaporizes minute amounts of the material. The vacuum prevents the electrons from scattering, due to collisions with gas molecules.
Need to achieve extreme surface smoothness. for high melting capacity and high productivity extremely fast and accurate beam control that allows several melt pools to be maintained simultaneously to get stress relieved components with material properties better than cast and comparable to wrought material. to achieve precise welding and surface modification, as well as brazing.
Working Principle Electron beam machining uses high velocity electrons that strike the work surface to generate heat. As the electrons strike the work piece with high velocity, their kinetic energy is transformed into thermal energy which melts and vaporizes the material. The production of free electrons ( negatively charged particles) are obtained by electron gun.
Process parameters Beam potential:50000 volts to 200000volts speed:50% to 80% of speed of light Current heat:110w/cm2 beam deflection signal
Application of EBM Drilling of holes in pressure differential devices used in nuclear reactors, aircraft engine. Machining of wire drawing dies having small cross sectional area. EBM is used for cutting holes as small as 0.001 inch (0.025 millimetre) in diameter or slots as narrow as 0.001 inch in materials up to 0.250 inch (6.25 millimetres) in thickness.
Advantages of EBM There is no mechanical contact between tool and work piece, hence no tool wear. Very small holes can be machined in every type of material with high accuracy Drilling of extremely small diameter holes down to 0.002 in. Drilling holes with high depth/diameter ratios,greater than 100:1.
Disadvantages of EBM Cost of equipment is high. Rate of material removal is low. It can used for small cuts only. Vacuum requirements limits the size of work piece.
Introduction Ultrasonic machining, also known as ultrasonic impact grinding. It is a machining operation in which a vibrating tool oscillating at ultrasonic frequencies is used to remove material from the work piece aided by an abrasive slurry that flows freely between the work piece and the tool. It differs from most other machining operations because very little heat is produced. The tool never contacts the work piece and as a result the grinding pressure is rarely more than 2 pounds, which makes this operation perfect for machining extremely hard and brittle materials, such as glass, sapphire, ruby, diamond and ceramic s
Working Principle The process is performed by a cutting tool, which oscillates at high frequency, typically 20-40 kHz, in abrasive slurry. The tool is gradually fed with a uniform force. The high-speed reciprocations of the tool drive the abrasive grains across a small gap against the work piece The impact of the abrasive is principally responsible for material removal in the form of small wear particles that are carried away by the abrasive slurry. The tool material, being tough and ductile, wears out at a much slower rate The shape of the tool corresponds to the shape to be produced in the work piece.
Process parameters Frequency of tool :20 khz to 40 khz Amplitude of oscillations:0.013mm to 0.1mm Abrasive particles grain size:280 mesh size
Need USM is primarily targeted for the machining of hard and brittle materials may be dielectric or conductive such as boron carbide, ceramics, titanium carbides, rubies, quartz etc. USM is a versatile machining process as far as properties of materials are concerned. This process is able to effectively machine all materials whether they are electrically conductive or insulator.
Applications Drilling Grinding Coining Piercing of dies Welding operations on all materials which can be treated suitably by abrasives. Used for machining hard and brittle metallic alloys, semiconductors, glass, ceramics, carbides etc. Used for machining round, square, irregular shaped holes and surface impressions.
Advantages Machining any materials regardless of their conductivity USM apply to machining semi-conductor such as silicon, germanium etc. USM is suitable to precise machining brittle material. USM does not produce electric, thermal, chemical abnormal surface. Can drill circular or non-circular holes in very hard materials Less stress because of its non-thermal characteristics
Disadvantages USM has low material removal rate. (3- 15mm3/min) Tool wears fast in USM. Machining area and depth is restraint in USM.
Introduction It is the material removal process where the material is removed by high velocity stream of air/gas or water and abrasive mixture. An abrasive is small, hard particle having sharp edges and an irregular shape. High velocity jet is aimed at a surface under controller condition.
Working Principle High pressure water starts at the pump, and is delivered through special high pressure plumbing to the nozzle. At the nozzle, abrasive is introduced & as the abrasive/water mixture exits, cutting is performed. Once the jet has exited the nozzle, the energy is dissipated into the catch tank, which is usually full of water & debris from previous cut.
Process parameters Pressure of gas Pressure or water Velocity of gas/water Nozzle-tungsten:dia-(.05mm to 1mm) Stand off distance-0.7mm to 1mm Abrasive size-10 to 50 um
Need Pure cuts soft materials – corrugated cardboard, tissue papers, automotive interiors Very thin stream (0.004-0.010mm dia) Extremely detailed geometry Can cut thick, soft, light materials like fiberglass insulation, brittle materials
Applications Used mostly to cut lower strength materials such as wood, plastics, and aluminium. When abrasives are added, stronger materials such as steel, and even some tool steels can be cut. For circuit boards, water jet cutting is mostly used to cut out smaller boards from a large piece of stock Woodworking is another application that abrasive water jet machining can be used for.
Advantages Extremely fast setup & programming No start hole required There is only one tool Low capital cost Less vibration No heat generated in work piece Environmentally friendly
Disadvantages Low metal removal rate Due to stay, cutting accuracy is affected Abrasive powder cannot be reused Tapper is also a problem