project mmg.docx

Table of contents page 1.INTRODUCTION11.1. Subject11.2.Background12. FINDINGS31.1Resistance welding32.1.1. Processes of Resistance welding42.1.2. Applications of Resistance welding62.1.3. Advantages71.2Ultrasonic widing102.2.1. Processes of Ultrasonic welding102.2.2. Applications of Ultrasonic welding122.2.3. Advantages 132.3. Waterjet Cutting132.3.1. Processes of waterjet cutting132.3.2. Applications of waterjet cutting152.3.3. Advantages 152.4.Plasma Cutting 162.4.1. Processes of Plasma cutting162.3.2. Applications of Plasma cutting182.4.3. Advantages 183. CONCLUSION193. BIBLIOGRAPHY20

1. INTRODUCTION From the early years until the present, industrial processes and live has improved because inventors has found new ways to cut materials. According to Calabrese D.M (2011:49), Dr. Norman Franz was the first person to have studied water jetting in the early 1970s. The first commercial use was for the automotive industry to cut glass in 1983. Soon after, various types of materials were cut with the water-jet cutting machine. The water jet cutting process is used now more because it is fast and effective also less work.

2. FINDINGS2.1. RESISTANCE WELDINGResistance welding is fundamentally a heat squeeze process, Brumbaugh (1981:317). When the parts to be welded are raised to the fusion temperature by the passage of heavy electric current through the junction, pressure is applied mechanically to accomplish the welding. Examples of resistance welding include spot, seam, projection and flash welding.A form of electric pressure welding in which the necessary heat is produced by a flow of current through the parts to be welded and sufficient pressure to make the weld is applied simultaneously with the flow of current2.1.1. Processes of resistance welding2.1.1.1. RESISTANCE SPOT WELDINGAccording to Brumbaugh (1981:332), Resistance spot welding is a form of resistance welding in which the two surface are joined by spots of fused metal caused by heating the small areas of metal between suitable electrodes under pressure. Resistance spot welding is done either with hand spot welders or machine spot welders(Figure.2.1).

FIGURE: 2.1 SPOT WELDING (Indiana Dental Academy, 2002)

2.1.1.2. RESISTANCE SEAM WELDINGThe seam welding is similar to spot welding, except that a circular rolling electrode is used to produce the effect of a continuous seam, it is a series of continuous overlapping spots produced by the rotating electrode and a regularly interrupted current.

Figure : 2.2 Seam welding (Jones, 2009)2.1.1.3. PROJECTION WELDINGBrummbaugh (1981:342-343) explains resistance projection welding as a resistance welding process in which the position of the weld is established by the predetermined design of a projection on one of the two metal surfaces to be joint. Projection weld (Figure 2.2) is when the electric current flows through the electrode, causing the projrction metal to melt and fuse the two metal surfaces together.

FIGURE: 2.3. PROJECTION WELDING

The three types of projection used in resistance welding are:1. The cone type2. The spherical type3. The button type2.1.1.4. RESISTANCE FLASH WELDINGFlash welding is a resistance welding process in which the heat is applied before the two parts are pressed together. When the pressure is applied, molten metal is squeezed out of the weld, and the period which this activity takes place is known as the flashing time.The figure below shows how the resistance flash welding operates.

According to (Oates. J, 1968) during resistance welding, part heat generated is lost to the surroundings, by conduction heat transfer through solids, convection heat lost fromexposed surfaces by air cooling, and radiationdoes not require a medium.Heat balance is a function of part material andgeometry, electrode material and geometry, polarity, and the weld schedule. The goal of good resistance welding is to focus the heat generated close to the weld interface at the spot where the weld is desired. Figure 1 below, shows how the resistance welding is used in industry.The weld is made by a combination of heat, pressure and time. Electrical resistance of the materials to be welded causes localized heating at the interface of metals to be joined. Pressure is exerted by tongs and tips. Time refers to how long the current ows in the joint, which is determined by the material thickness and type, amount of the current and cross-sectional area of the welding tips and contact surfaces. The process is used in preference to mechanical fasteners, such as rivets or screws, when disassembly for maintenance is not required. Steel is widely used inautomotive industry. It is important for its performance features as a material used either for auto-mobile body or structural pieces such as chassis and wheels. Steels provide very valuable economic and technologic benets such as easy forming, even more strength after process of forming, low and delayeddeformation osculation(James. A, 1968).

Four Stages of resistance welding1. Heat increase, when the weld pool has not yet been created. Electrode force and the elevated temperature smooth the surface roughness of the work piece and transfer resistance decreases. In case of galvanized material, zinc melts and recedes from between the sheets at this stage, before the parent metal melts.

2. Rapid growth of weld nugget diameter. The weld pool is created and the molten metal diameter and nugget penetration increase rapidly. The resistance of molten metal is higher than that of solid metal, which increases total resistance.

3. The growth of the weld nugget slows down. The weld size growth slows down significantly. The growth of the weld pool is restricted by cooling electrodes and the increasing surface area of the weld pool.

4. Splash. The weld pool size increases so much that electrode tips can no longer contain the molten metal between the sheets, and therefore expulsions occur. A significant amount of molten metal splashes from the weld.

2.1.2. APPLICATIONS OF RESISTANCE WELDING

Resistance welding is a commonly used method for joining steel sheets. No filler metal is needed and the heat required for the weld pool is created by means of resistance when a high welding current is directed through the welded work pieces. An electro-conductive contact surface is created between the work pieces by pressing them together. Contact is made using the shape of either the welded surfaces of the work pieces or the shape of the electrodes. Water-cooled electrodes made of alloyed copper are used in resistance welding.Electrodes convey a pressing force to the joint and direct the welding current to the joint in the appropriate manner. After welding, the electrodes rapidly cool down the welded joint. Work stages in resistance welding are very fast. The surfaces to be welded do not usually require grinding or post heating. The resistance welding process can be easily automated need to be cleaned before welding, in addition to which the weld does not usually (Brumbaugh. J, 1998).The greatest total thickness of work pieces in spot, roller seam and projection welding is 6 mm. When joining work pieces of different thicknesses, the welding current is chosen according to the thinnest sheet. Lap joints can also be made by joining several sheets at the same time. Resistance welding is a very useful way of joining galvanized steel sheets. When making lap joints, the zinc layer melts before the parent metal in the joint and is directed away from the weld. Therefore, the actual weld consists of the parent metal and the zinc coating remains intact in the electrode contact point and at the edges of the weld between the contact surfaces.2.1.3. Advantages of resistance weldingResistance welding is one of the simplest, lowest costs, surest means of metal joining. An understanding of the resistance welding process is basic to making good welds. The machines, controls and fixtures are only the tools necessary to help make the weld. The process is doing the real work.DisadvantagesThe equipment is very large, expensive and individually designed to perform specific tasks. They require more electrical energy than the power supply is capable of delivering. The electrodes have to be able to reach both sides of the pieces of metal that are being joined together. A particular spot welding machine will be able to hold only a certain thickness of metal usually 5 to 50 inches and although the position of the electrodes can be adjusted, there will be only a limited amount of movement in most electrode holders.

The size and shapes of the electrodes will determine the size and strength of the weld. The join forms only at the spot where the electrodes are in contact with the metal. If the current is not strong enough, hot enough or the metal is not held together with enough force, the spot weld may be small or weak.Warping and a loss of fatigue strength can occur around the point where metal has been spot welded. The appearance of the join is often rather ugly, and there can be cracks. The metal may also become less resistant to corrosion.

2.2. ULTRASONIC WELDING Ultrasonic welding is a solid-state welding process in which coalescence is produced at the faying surfaces by the application of high frequency vibratory energy while the work pieces are held together under moderately low static pressure. According to Brumbaugh (1983:411-412), the friction that causes the two metal surfaces to become welded together is produced by acoustic vibration operating in a frequency range extending from 10,000 to 175,000 Hz (cycle per second). It is commonly used for plastics, especially for joining dissimilar materials.2.2.1. Processes of ultrasonic weldingThe pressure provided when clamping the surfaces to be welded should only be enough to prevent slippage of the two pieces. Excessive clamping may result in deformation of the surface, on the other hand inadequate clamping can result in damage to the transducer-coupler. Ultrasonic welding equipment is designed to convert electrical energy to mechanical (vibratory) energy; the vibratory energy is transferred to the surfaces to be joined by sonotrode tip oscillating approximately parallel to the plane of the interface between the two surfaces, this is basically shear type vibratory force. An ultrasonic welding system will generally consist of the following components:1. A frequency converter,2. A transducer-coupling system,3. An anvil,4. A clamping mechanism.

Figure: 1.1 Principles of ultrasonic welding(Bown,2000)Ultrasonic Welding Step by StepThe basic process of ultrasonic welding can be described by the following steps: The parts to be welded are placed in the anvil or fixture. The horn, which transfers ultrasonic energy, contacts the parts to be welded. Pressure is applied to keep the horn in contact with the welded materials and to hold them together. The horn delivers ultrasonic vibrations to heat up the materials. The vibrations move less than a millimeter either up-and-down or side-to-side. The materials are welded together. The horn gets retracted and the welded materials can be removed from the anvil.

Figure: 1.2 ultrasonic processesThis vibration energy is transmitted through the upper layer of thermoplastic to the interface of the two surfaces where localized frictional heat develops. Brown (2000:152) states Teflon with low coefficient of friction and high melting temperature is impossible to weld using this process. Friction causes the molded ridge (energy director) to melt and fuse with surface against which is pressed. Figure 1 below illustrates an ultrasonic step joint.

Figure1: An ultrasonic welding step joint(Eric, J. and Wang, K. 1976)2.2.2. Applications of ultrasonic weldingEric, J. & Wang, K (1968:163) states that: The process is particularly suited to the welding of the thin metal sections, using lap joints as in resistance welding and cold pressure welding. Almost every metal can be welded by the ultrasonic process, but soft metals or those with low coefficients of friction are the most difficult to weld unless of extremely tgin foil section. A fast, clean, efficient and repeatable process, Ultrasonic welding is ideal for joining just about any plastic parts for many applications. Some uses of ultrasonic include the following: The applications of ultrasonic welding are extensive and are found in many industries including electrical and computer, automotive and aerospace, medical, and packaging. Whether two items can be ultrasonically welded is determined by their thickness. If they are too thick this process will not join them. This is the main obstacle in the welding of metals. In the automotive industries, ultrasonic welding tends to be used to assemble large plastic and electrical components such as instrument panels, door panels, lamps, air ducts, steering wheels, upholstery and engine In electronic appliances like switches, sensors and data storage keys are fabricated using ultrasonic welding. Ultrasonic welding is also used to make medical parts like filters, catheters, medical garment and masks. Ultrasonic welding is also applied in the packaging of dangerous materials such as explosives, fireworks and other reactive chemical blister packs, pouches, tubes, storage containers. In the electrical and computer industry ultrasonic welding is often used to join wired connections and to create connections in small, delicate circuits. 2.2.3. Advantages of ultrasonic welding Fast, economical and easily automated. Mass production, up to 60 parts per minute is possible. Increased flexibility and versatility Possibility to join large structures. Used in health care industries due to clean welds. Produce the high strength joints consistently.

2.3. WATER JET CUTTING PROCESS2.3.1. PROCESS OF WATER JET CUTTINGWater jet cutting is a process where water at high pressure is used to cut a large variety of materials.There are two types ofwater jet cutting a) Pure water jet cutting andb) Abrasive water jet cutting

A. Pure water jet cuttingThere is a fundamental difference between pure water jet and abrasive water jet cutting. Pure water jet cutting are used on softer materials, according to Olsen (2010) ranging from fabrics to rubber and a wide variety of food products. Below is a picture of how the inside of a pure water jet looks like.

Figure 1. Inside of a pure waterjet cutter(Anon, 2008)

A. Abrasive water jet cutting Abrasive water jet cutting cuts the harder materials like metals, ceramics and most plastics. Olsen (2010) states the abrasive waterjet cutting mechanism is similar to a grinding wheel. The abrasive particles are moved by the water jet rather than the wheel and chip out small pieces just like the abrasive particles in the wheel does. By using a hard abrasive such as garnet, an abrasive waterjet can cut a very wide range of metals and other hard materials and thus become a useful technology for machine and fabricating shops. In abrasive waterjet cutting, the abrasive does the cutting and not the water as in pure water jet cutting. According to Olsen (2010), the role of the water is to entrain the abrasive particles that are introduced at the nozzle and accelerate enough of them to a high enough speed to cut effectively. Faster cutting is achieved by increasing the speed of the particles and/or by increasing the number of particles entrained in the water stream. The picture below is the inside of an abrasive water jet cutter.

Figure 2. Inside of an abrasive water jet cutter(Anon, 2008)

According to Anon (2013), The energy required for cutting materials is obtained by pressurizing water to ultra-high pressures and forming an intense cutting stream by focusing this high-speed water through a small, precious-stone orifice. There are two main steps involved in the water jet cutting process.The Electric Servo Pump generally pressurizes normal tap water at pressure levels above 50,000 psi; to produce the energy required for cutting.Water is then focused through a small precious stone orifice to form an intense cutting stream. The stream moves at a velocity of up to 3 times the speed of sound, depending on how the water pressure is exerted.The process is applicable to both pure water jets and abrasive jets. For abrasive cutting applications, abrasive garnet is fed into the abrasive mixing chamber, which is part of the cutting head body, to produce a coherent and an extremely energetic abrasive jet stream. To achieve these pressures, water is introduced into the unit by way of a booster pump and filter. This filtering process is very important as water must be clean before reaching ultra-high pressures in order to protect the high pressure parts and provide a consistent cutting stream. A water treatment system is sometimes needed to remove harmful minerals from the water. After being filtered, the water enters the high pressure cylinder where it is pressurized to the desired level. Below is a diagram of the operation of a water jet cutting machine.

Figure 3. Operation diagram of water jet cutting machineAnon,2011Materials that can cut with a water jetAlmost any material can be cut with a water jet, even food. From rubber, glass, foam and wood to steel, copper, titanium and even stone. There is absolutely every material that can be cut with a water jet cutter.

Picture GalleryBelow are pictures of some products that have been cut using either the abrasive or pure water jet cutting process.

Figure 4: Aluminium product Figure 5: Copper productAnon (2012) Anon(2012)

Figure 6: Metal products Figure 7: GlassAnon (2002) Anon (2012)

2.3.2. Applications of water jet cutting

Water jet cutting can be used in the following industries: Marine, Medical, Electronics, Aerospace, Automotive, Signs, Architecture, Art, Glass, Commercial, Military, Recreational, Tooling, Manufacturing, Paper, Computer Circuits, Food, Lumber, Plastics, Residential Housing, Stone, Tile and Marble, Rubber and many more industries. Water jet Cutting for Food Water jet Cutting Stone, marble and tile Water jet Cutting for Aerospace Water jet Cutting for Paper & Slitting Water jet Cutting for Glass Water jet Cutting for Composites Water jet Cutting for Automotive Water jet cutting other material2.3.3. Advantages of pure water jet cutting Very thin water stream Very little material wastage during cutting No heat is generated during cutting Applicable to both thin and thick materials Fast cutting Extremely low cutting force Very suitable for light and soft materials cutting

2.3.3.1. Advantages of an abrasive water jet cutter Extremely versatile process No heat is generated No mechanical stresses Thin stream Thin and thick material cutting Little cutting material wastage Low cutting force Little or almost no burr One jet setup is almost applicable for all abrasive jet jobs Quickly switch between abrasive waterjet to pure waterjet

2.4. PLASMA CUTTING

2.4.1. PROCESS OF PLASMA CUTTINGPlasma cutting is the process that uses high speed ionized gas that is delivered from a constricting orifice. Basically high velocity ionized gas is termed plasma, and it conduct electricity from the torch of the plasma cutter to the work piece (COLT, J 2011)The schematic labelled diagram is shown below of the cutting torch of the plasma cutter.

Figure 1:Plasma Torch (source: Torchmate,2013)Places where plasma cutting is usedThe use ofPlasma cuttersis very prevalent in manufacturing today, and is vital in metal fabrication operations. Industrial sectors across the board manufacture products that require precisely cut and formed metal components, and are therefore dependent on the manipulation of heavy metals.Plasma cuttersare extremely versatile and can be used for piercing, cutting, intricate design and bevelling metals of different types, sizes and thicknesses (DAVIS, D 2013)For more than 50 years,Plasma cuttershave been renowned as essential productivity enhancing tools. Their high cutting speed and superior quality deliverance results in higher productivity by saving both time and money, makingPlasma cuttersa superior option compared to more traditional cutting processes (COLT, J 2014). From a safety perspective, the plasma cutting machines have become more user-friendly and the process reduces operators exposure to some of the hazards and dangers associated with metal cutting and profiling (HUSSARY, N 2012, OTT, D 2012).The thickness of the material should be taken into consideration when trying to decide on what plasma cutting machine to buy. Amperage and thicknesses go hand in hand. So, if cutting thinner materials is what this machine is needed for then a lower amp machine will be perfect for the job. However if you usually mess with metal that is at least thick then one will want to look at the higher amp machines. The schematic labelled diagram is shown below of the cutting torch of the plasma cutter (SHUDA, D 2011)2

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Figure 3: The plasma cutter ( Cook, W 2010)1) Power supply2) Control panel3) Cutting torch4) Earth clam

Cutting Operation (CARLSON, A 2010)1) To begin cutting, place the tip of the torch on the work for drag cutting or from 1.5 mm to 3 mm form work for standoff cutting (Note: standoff cutting will increase the consumables life and allow for faster cutting speeds).

2) When starting at the edge of a piece of work, start with the torch at a 90 angle to the work.

Figure 4: Safety Trigger ( Hidden, S 2001)

3) Pull the trigger and the arc will start immediately.

4) Slowly start moving the torch across the metal insuring that the sparks are going through the metal. If sparks are not going through the cut slow the rate or the cut. Start cutting from the edge of the work piece.

5) For best results keeps the torch moving at a steady pace.

6) Finish the cut and release the trigger to stop the arc. (Note: Gas/Air will continue to flow for 20 seconds after the trigger is released).

a)

Lifts trigger safety lock.Press trigger.

b)

Avoid firing the torch when it is not in contact with the work piece.

c)

Figure 4.1:Safety TriggerIf the sparks are not visible at the bottom of the plate, the arc is not penetrating the metal. This can be caused if the torch is moved too quickly, have insufficient amperage, or fail to direct the plasma stream straight into the metal (JUSKO, J 2013)Travelling at the right speed produces a clean cut with less dross on the bottom of the cut and little or no distortion of the metal. Slow travel speeds can overheat the metal, causing dross to accumulate. To minimize dross, increase travel speed or reduce amperage (WHITING, T 2007)For an indication of how fast to move the torch, refer to the machine's cutting speed graph or check the speed for a rated cut. Dross also accumulates when we push a machine to cut a material at its maximum thickness. The only cure for this is a bigger machine (Thompson, S 2007).

2.4.2. APPLICATIONS OF PLASMA CUTTINGThe plasma transfer heat to the work piece, melting the material. The high speed stream of ionized gas mechanically blows the molten metal away, leaving the material with spaces or holes. In a plasma cutting torch, a cool gas such as air or nitrogen (N2) enters Zone B (Figure 2), where a pilot arc between the electrode and the torch tip heats and ionizes the gas (BOHNART, E 2005)The main cutting arc then transfers to the workpiece through the column of plasma gas in Zone C. By forcing the plasma gas and electric arc through a small orifice, the torch delivers a high concentration of heat to a small area. The stiff, constricted plasma arc is shown in Zone C (Figure 2). Direct current (DC) straight polarity is used for plasma cutting, as shown in the illustration. The cutting torch also uses a secondary gas (Zone A, Figure 2) which assists the high velocity plasma gas in blowing the molten metal out of the cut and allowing a fast, slag-free cut (McQuade, K 2009)The secondary gas also cools the torch. Compressed air, supplied by either a cylinder or plant air system, or CO2 is normally used as the secondary gas. The plasma gas flows into the torch through the positive lead, around the electrode, and out through the tip orifice. The secondary gas flows into the torch through the negative lead, down around the outside of the torch liner, and out between the tip and shield cup around the plasma arc (Heston, T 2012)When the torch is started a pilot arc is established between the electrode and cutting tip. This pilot arc creates a path for the main arc to transfer to the work. Because DC current alone is not sufficient to initiate and maintain the pilot arc, high frequency is superimposed on the direct current. DC power is also used for the main cutting arc. The negative output is connected to the torch electrode through the torch lead. The positive output is connected to the workpiece via the work cable and to the torch through a contactor and resistor. Workpiece

Figure 2: Theory of Operation ( Komatsu American Industries LLC, 2012)

2.4.3. Advantages

Cuts any type of electrically conductive metals including aluminium, copper, brass and stainless steel. Cuts faster up to 33.02 mm per minute on 0.0635 mm Steel. Does not require a pre-heat cycle which saves time and is more convenient Has a smaller heat affected zone which prevents the area around the cut from warping and minimizes paint damage. Plasma cutting requires only minimal operator training. The torch is easy to operate, and new operators can make excellent cuts almost immediately. Plasma cutting is more economical. Plasma cutting systems can yield quality cuts on both ferrous and nonferrous metals. Thickness from gauge to 0.762 mm can be cut effectively.(FLANDERS, P 2011)Disadvantages Noise when cutting thick sections. -Plasma cutting creates a large heat-affected zone in the area surrounding the cut. -Cutting materials under-water cutting minimizes the size of the heat-affected zone. -Dross, the re-solidified metal that forms at the bottom of the cut, is a potential issue for processors using plasma cutting since it frequently forms during plasma cutting. -High initial cost of the equipment -The moving parts in the cutting head are subject to wear which adversely affects the quality and accuracy of the shaping.

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CONCLUSIONCutting and welding are very important and useful processes in the industry. This has shown through the research and discussions in the report The Water jet cutting is a very accountable process which is very convenient and precise for cutting the products, methods for using water jet cutting is simple and unique.In conclusion, ultrasonic welding has many advantages over other welding techniques for many types of connections. These include speed, cost, reliability and many others. However, it should also be made clear that it is only ideal for a relatively small proportion of all of the possible joints. Ultrasonic is the term related to frequency, which above the 8000 Hz called ultrasonic. It is not depend up on heating, not high pressure and not large deformation. The body is accomplished in solid state and no need for external heat, filler metal.Water jet is a cutting process that can be used to cut almost any material and even food. It is more accurate than laser cutting and it just uses water and abrasive in some cases. Water jet cutting is an easy, accurate and fast cutting process that is being used in industries.

BIBLIOGRAPHYAnon, 2002. http://fbnmetal.com/waterjet.html [07 April 2015]

Anon, 2008.http://xinology.com:888/Glass-Processing-Equipments-Supplies-Consumables/glass-cutting/water-jet-cutting/overview/two-types-of-water-jet.html [27 March 2015]

Anon, 2011. http://www.reedmanssheetmetal.com.au/waterjet_cutting.html [27 March 2015]

Anon, 2012. http://www.headland.com.au/fabrication/what-materials-can-a-waterjet-cut/ [27 March 2015]

Anon, 2013. http://www.techniwaterjet.com/how-it-works/ [25 March 2015]Brown, 2000. Journal of Assembly Headquarters, 57(6):151153, JulyBrumbaugh, E. 1981 Engineering & Technology. Canada: Macmillan.

Calabrese D.M. 2011:49. The present and future of water jet cutting. New York: IWA publications.

Olsen D, January 22 ,2010. Waterjet vs. Abrasive Waterjet: Important differences.http://www.drolsenslab.com/abrasive-waterjet-technology/how-does-it-cut/ [28 March 2015]http://www.plasma-cutter.com/technical.htmhttp://www.thefabricator.com/?filter=article&category=plasmacuttinghttp://www.sentinelsteel.co.za/articles/plasma_cutting.html#.VSSKmNyUeh4http://www.thefabricator.com/article/cuttingweldprep/mechanized-plasma-cutting-developments-in-high-definition-technology-improve-versatilityEric, J. & Wang, K. 1976. Ultrasonic welding of thermoplastics. Cornell University: The Sibley School of Mechanical and Aerospace EngineeringSacks, Raymond; Bohnart, E. (2005). "17".Welding Principles and Practices(Third ed.). New York: McGraw_Hill. p.597.ISBN978-0-07-825060-6

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