M. Ibbotson - Professional english in use engineering (794233), страница 14
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, which has(4) ................................ edges. This is designed to(5) ................................ screwdrivers, which (6) ................................into it.The top edge of the screw head is (7) ................................ .This avoids having a sharp edge, which couldcause cuts.The tapered side of the head allows the screw to be(8) ···-··························· . The advantage of this is that thescrew head can be fully (9) ................................ within thematerial surrounding the screw, making the screwhead (10) ................................ with the surface of thematerial.The top part of the screw shaft is smooth and has a(11) ................................ diameter.The lower part of the screw is (12) ................................
.The close-up picture shows that the(13) ................................ forming the outer part of thethread is not pointed, but (14) ................................ .Ov~r ..f-o11ou •Describe the 3D feat ures of some components or assemblies you know about.Professional English in Use Engineering51r!J Machining 1-Machining and CNCMachining is the use of machines to cut pieces of material (called workpieces) and shapethem into components. The tools used in machining, to make holes, grooves, threads, etc.,are called machine tools. Metal is often machined. As it is cut, waste is produced, called swarfor chips.
During machining, a liquid called cutting fluid may be pumped onto the workpieceto act as a coolant, keeping the workpiece cool.In manufacturing, machining is usually guided by computers called computer numericalcontrol (CNC) systems. Often, design information (on shapes and sizes of components) isfed directly into CNC systems from computer aided design I computer aided manufacturing(CAD/CAM) software.Note: CAD/CAM is said as two words: /'kred ,krem/.-Machining with cutting toolsBelow are the most common machining techniques which use cutting tools.Milling is cutting done by a milling machine, often using toothed cutting discs (wheels withteeth that have sharp edges).
When a workpiece is milled, it is held in a fixed position onthe machine, and is shaped by cutting tools which rotate (spin) while being moved over thesurface of the workpiece.Turning is a technique for cuttingcomponents that have a circularcross-section. The workpiece isturned by a machine called a lathe,which rotates the workpiece.A fixed machine tool is then movedagainst the rotating workpiece tocut material from it.Turning using a latheSawing is cutting using a blade (a thin, sharp piece ofmetal), which usually has teeth, to remove a thicknessof material slightly wider than the blade.
The gap leftby the blade, along the line of the cut, is called a kerf.Machines that use toothed blades include circular saws,which have rotating circular blades, band saws, andpower hacksaws. A hacksaw has a blade with very smallteeth, for cutting metal. Saws may also use abrasivewheels - that is, thin, circular cutting wheels with rough,hard surfaces - often made of industrial diamond.A band sawDrilling is a technique for cutting circular holes. A machine called a drill is fitted with atool called a drill bit (or bit).
The bit rotates and drills into the material. Holes with largediameters can be cut using holesaws- hollow cylinders with teeth, which saw circular cutsand remove a core (a solid cylinder) of material. When used to drill into concrete, thistechnique is also called core drilling, or diamond drilling, as the holesaws have industrialdiamond edges. Usually, drilling refers to making new holes. In machining, enlarging a hole(making it wider) is called boring.Grinding is removing material across a surface area, using abrasive wheels. The machinesused to grind materials with abrasive wheels are called grinders.52Professional English in Use Engineering23.1Match the two parts to make correct sentences. Look at A and B opposite to help you.A drill bit is an example of2 Material being machined is called3 The waste metal produced during machining is called4 Metal gets hot during cutting, so cutting fluid can be used as5 A computer that guides a machining process is called6 Drawings can be produced and transferred to the machining process usinga CAD/CAM software.b a CNC system.c a machine tool.d a workpiece.e swarf or chips.f a coolant.23.2Complete the descriptions below the photos using the words in the box.
Look at B oppositeto help you.coresdiamondbladecircularabrasivebitdrilldrillinggrinderhacksawholesawsawtoothedwheel-3 a ............................. for aa .............................5 a thick ............................ ............................ on a ...........................for metal4 a .............................
blade for a2 a ............................ .6 ............................. of concretebeing removed by23.3Complete the sentences using the words in the box. Look at B opposite to help you.I drillgrindmillturnsawI1 Lathes are designed to ................................ workpieces.2 Different bits are designed to ................................ into different types of material.3 When you ................................
a workpiece, the cutting blade removes a thickness of material toform a kerf.4 Abrasive wheels ................................ material.5 On some machines, toothed cutting wheels can be used to ................................ any part of aworkpiece, in order to form its final shape.Ove.,r .f-o tjotc'I'Think about a specific metal component made by machining. What machine tools andmachining techniques do you think were used to make it?Professional English in Use Engineering53Machining 2Guillotining and punchingThin materials can be cut by applying pressurein order to shear them - that is, cut themwith a scissoring force (in engineering, calleda shear force). Sheets of metal can be shearedusing a machine called a guillotine, which hasa long blade. Usually, sheets are guillotinedwhen long, straight cuts are required .sheetA guillot ineA punchSmall shapes, such as circles, can be shearedfrom sheets using a machine called a punch,which pushes a die (a shaped tool) throughthe sheet.
The shaped piece of metal that ispunched from the sheet is called a blank. If theblank is the finished product, this process iscalled blanking. If the sheet itself, with holesmade in it, is the finished product, the processis called piercing.High-temperature metal cutting techniquesFlame-cutting generally uses oxygen (02) and acetylene (C2H2). The two gases are blownthrough a torch - basically a tube - as a mixture called oxyacetylene. The acetylene burns inthe oxygen to produce a flame hot enough to melt steel.Electrical discharge machining (EDM) - also called spark erosion - involves passing a tightlength of wire through a workpiece, similar to the way thin wire is used to cut cheese.However, the wire does not actually touch the workpiece.
Instead, a high-voltage currentproduces an electric arc, which 'jumps' across a small gap between the wire and theworkpiece. As the current arcs, it generates heat, which melts the metal ahead of the wire.Plasma cutting uses a plasma torch to blow out gas at high pressure. The gas argon (Ar)is often used. At the same time a high-voltage current is passed through the plasma torch,and arcs between the torch and the workpiece. This ionizes some of the atoms in the gas,changing it to plasma.
As the plasma is heated by the arc, it reaches an extremely hightemperature - much hotter than would be possible for a gas that had not been ionized.Not e: When atoms are ionized, their electrons - tiny negatively charged particles that are normallyattached to the atom - break away and float freely within the gas.Laser cutting and UHP waterjetsLaser beams (concentrated light) can cut materials accurately, in small quantities, by meltingthem. Laser cutting is especially suitable for plastics.Ultra-high-pressure (UHP) waterjets- jets of water fired at extremely high pressure- cancut almost any material, including metal. An advantage of UHP waterjet cutting is that theedge quality of workpieces is high- that is, the cut edges are smooth.
This means that nosecondary operations- further processes to smooth rough edges- are required. Also, becauseUHP waterjets are cold, they do not leave a heat-affected zone (HAZ) on the workpiecethat is, an area near the cut edge whose properties have been changed by heat.54Professional English in Use Engineering24.1Match the cutting processes (1-4) to the descriptions (a-e).
You wiU need to use some of thedescriptions more than once. Look at A opposite to help you.1blanking2 guillotining3 piercing4 punchingabcde24.2shearing materialapplying pressureapplying pressureapplying pressureapplying pressuretotototoaaaablade to make long, straight cutsdie to make small, shaped (not straight) cutsdie to produce workpieces with holes in themdie to cut small, shaped workpieces from sheetsComplete the descriptions of the photos using words from B and C opposite.This torch burns (1) ................................
(C 2 H 2 ) ina flow of (2) ................................ -a mixture called(3) ................................. The torch can be used for(4) ................................-................................ .24.3This machine is used for (5) ................................................................-................................ waterjet cutting.It produces workpieces with very smoothedges. Because of this high (6) ............................... ...
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