金工实习英文讲义-磨工
《金工实习》课件 《金工实习》第十章PPT
的安装方法基本相同。
2)卡盘安装 工件较长且只有一端有中心孔时应采用卡盘安装。安装方法与车床的安装方法基本 相同,如下左图所示
3)心轴安装 盘套类空心工件常用心轴安装。心轴的安装与车床的安装方法相同,不同的是磨削 用的心轴精度要求更高些,且多用锥度(锥度为1/5 000~1/7 000)心轴,如下右 图所示。
磨削硬材料时选用软砂轮。
10.3.2 砂轮的种类
为了适应各种加工条件和不同类型的磨削结构,砂轮分为平形砂轮、单面凹形 砂轮、薄片形砂轮、筒形砂轮和双斜边形砂轮等,如图所示。
(a)平形
(b)单面凹形
(c)薄片形
(d)筒形
平形砂轮:主要用于磨外圆、内圆和平面等。 单面凹形砂轮:主要用于磨削内圆和平面等。
纵向进给运动是指工作台带动工件所做的直线往复运动。纵向进给量 是指工件相对 于砂轮沿纵向运动方向上的移动量,单位为mm/r。
4.横向进给运动及横向进给量
横向进给运动是指砂轮沿工件径向上的移动,横向进给量 是指工作台每往复行 程(或单行程)一次,砂轮相对于工件径向移动的距离,单位为mm/r。
10.1.2 磨工的加工范围
1—工件转动变速旋钮;2—工件转动点动按钮; 3—工作头架;4—工作台;5—工作台手动手轮; 6—床身;7—工作台左、右端停留时间调整旋钮;
8—工作台自动及无级调速旋钮; 9—砂轮横向手动手轮;10—砂轮启动按钮; 11—砂轮引进、工件转动、切削液泵启动旋钮; 12—液压油泵启动按钮;13—电器操纵板;14—
1—砂轮横向手动手轮;2—磨头;3—工作台;4— 工作台手动手轮;5—床身;6—工作台自动及无级 调速手柄;7—砂轮自动进给(断续或连续)旋钮; 8—砂轮升降手动手轮;9—砂轮垂向进给微动手柄; 10—总停按钮;11—液压油泵启动按钮;12—砂轮 上升点动按钮;13—砂轮下降点动按钮;14—电磁 吸盘开关;15—电器操纵板;16—切削液泵开关; 17—砂轮高速启动按钮;18—砂轮停止按钮;19— 砂轮低速启动按钮;20—电源指示灯;21—砂轮修 整器;22—砂轮横向自动进给换向推拉手柄;23—
金工实习英文讲义-焊接
Mechanical Engineering TrainingWeldingName:Student NO.:Date:1. Introduction to WeldingWelding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material (the weld pool) that cools to become a strong joint, with pressure sometimes used in conjunction with heat, or by itself, to produce the weld. This is in contrast with soldering and brazing, which involve melting a lower-melting-point material between the workpieces to form a bond between them, without melting the work pieces.2. Types of Welding MethodsSome of the best known welding methods include:Shielded metal arc welding (SMAW) - also known as "stick welding", uses an electrode that has flux, the protectant for the puddle, around it. The electrode holder holds the electrode as it slowly melts away. Slag protects the weld puddle from atmospheric contamination. And this will be the focus of this training course.Gas tungsten arc welding (GTAW) - also known as TIG (tungsten, inert gas), uses a non-consumable tungsten electrode to produce the weld. The weld area is protected from atmospheric contamination by an inert shielding gas such as Argon or Helium.Gas metal arc welding (GMAW) - commonly termed MIG (metal, inert gas), uses a wire feeding gun that feeds wire at an adjustable speed and flows an argon-based shielding gas or a mix of argon and carbon dioxide (CO2) over the weld puddle to protect it from atmospheric contamination.Flux-cored arc welding (FCAW)- almost identical to MIG welding except it uses a special tubular wire filled with flux; it can be used with or without shielding gas, depending on the filler.Submerged arc welding (SAW) - uses an automatically fed consumable electrode and a blanket of granular fusible flux. The molten weld and the arc zone are protected from atmospheric contamination by being "submerged" under the flux blanket.Electroslag welding (ESW) - a highly productive, single pass welding process for thicker materials between 1 inch (25 mm) and 12 inches (300 mm) in a vertical or close to vertical position.3. The Shielded Metal Arc Welding ProcessShielded metal arc welding (SMAW) is one of the most common types of arc welding is; it is also known as manual metal arc welding (MMA) or stick welding. Electric current is used to strike an arc between the base material and consumable electrode rod, which is made of filler material (typically steel) and is covered with a coating flow that protects the weld area from oxidation and contamination by producing carbon dioxide (CO2) gas during the welding process. The electrode core itself acts as filler material, making a separate filler unnecessary.As can be seen from Figure 1, when the electrode rod contacts the base material, an arc will be stricken, which generates so much heat that the rod fuses. The coating flow on the external side of the rod will then produce CO2 to protect the weld area, while the fusedelectrode core will become the weld metal to put the base materials together. And the weld metal will be covered with a layer of solidified slag, which should be removed with a hammer when it cools down.1. Coating Flow2.Rod3.Shield Gas4.Fusion5.Base Material6. Weld Metal7.Solidified SlagFigure 1 The SMAW processThe process is versatile and can be performed with relatively inexpensive equipment, making it well suited to shop jobs and field work. An operator can become reasonably proficient with a modest amount of training and can achieve mastery with experience. Weld times are rather slow, since the consumable electrodes must be frequently replaced and because slag, the residue from the flux, must be chipped away after welding. Furthermore, the process is generally limited to welding ferrous materials, though special electrodes have made possible the welding of cast iron, nickel, aluminum, copper, and other metals.Figure 2 A worker carrying out the SMAW processFigure 2 shows a worker carrying out the SMAW process. We can see that he is wearing a helmet, a pair of thick gloves and a protection suit. And these will also be what you are supposed to be wearing when you are taking the training practice. During the process, there will be very strong lights that may make you feel dizzy and lose your sight for a while if you watch the light directly. So the helmet is used to protect your eyes from the strong light. Also, there will be quite a lot of sparks, the protection suit and gloves will protect you from being burnt.4. Training PracticeIn this training course, you are supposed to use SMAW to weld two separate iron plates together. First the teacher will give you a demonstration, you should watch carefully and pay attention to the details. Then each student will have to take the welding practice. Your scores will be given according to the quality of the weld joint.5. Safety Rules(1) Do remember to wear the helmet, gloves and the protection suit before you startwelding.(2) Keep the helmet always on when welding, do not use your eyes to look at thelights directly.(3) There is electricity in both the rod and the workbench, so do not use your barehand to touch either of them.(4) Do not point the rod to others or sway the rod around in case you or other peopleget hurt.。
金工实习英文讲义-线切割
Mechanical Engineering Training Electrical Discharge MachiningName:Student NO.:Date:1. Introduction to Electrical Discharge MachiningElectric discharge machining (EDM), sometimes colloquially also referred to as spark machining, spark eroding, burning, die sinking, wire burning or wire erosion, is a manufacturing process whereby a desired shape is obtained using electrical discharges (sparks). Material is removed from the workpiece by a series of rapidly recurring current discharges between two electrodes, separated by a dielectric liquid and subject to an electric voltage. One of the electrodes is called the tool-electrode, or simply the "tool" or "electrode", while the other is called the workpiece-electrode, or "workpiece".When the distance between the two electrodes is reduced, the intensity of the electric field in the volume between the electrodes becomes greater than the strength of the dielectric (at least in some point(s)), which breaks, allowing current to flow between the two electrodes. This phenomenon is the same as the breakdown of a capacitor (condenser). As a result, material is removed from both electrodes. Once the current stops, new liquid dielectric is usually conveyed into the inter-electrode volume, enabling the solid particles (debris) to be carried away and the insulating properties of the dielectric to be restored. Adding new liquid dielectric in the inter-electrode volume is commonly referred to as "flushing". Also, after a current flow, the difference of potential between the electrodes is restored to what it was before the breakdown, so that a new liquid dielectric breakdown can occur.2. Types of Electrical Discharge MachiningSinker EDMSinker EDM, also called cavity type EDM or volume EDM, consists of an electrode and workpiece submerged in an insulating liquid such as, more typically, oil or, less frequently, other dielectric fluids. The electrode and workpiece are connected to a suitable power supply. The power supply generates an electrical potential between the two parts. As the electrode approaches the workpiece, dielectric breakdown occurs in the fluid, forming a plasma channel, and a small spark jumps.Figure 1 Sinker EDM machineThese sparks usually strike one at a time because it is very unlikely that different locations in the inter-electrode space have the identical local electrical characteristics which would enable a spark to occur simultaneously in all such locations. These sparkshappen in huge numbers at seemingly random locations between the electrode and the workpiece. As the base metal is eroded, and the spark gap subsequently increased, the electrode is lowered automatically by the machine so that the process can continue uninterrupted. Several hundred thousand sparks occur per second, with the actual duty cycle carefully controlled by the setup parameters. These controlling cycles are sometimes known as "on time" and "off time", which are more formally defined in the following.The on time setting determines the length or duration of the spark. Hence, a longer on time produces a deeper cavity for that spark and all subsequent sparks for that cycle, creating a rougher finish on the workpiece. The reverse is true for a shorter on time. Off time is the period of time that one spark is replaced by another. A longer off time, for example, allows the flushing of dielectric fluid through a nozzle to clean out the eroded debris, thereby avoiding a short circuit. These settings can be maintained in microseconds. The typical part geometry is a complex 3D shape, often with small or odd shaped angles. Vertical, orbital, vectorial, directional, helical, conical, rotational, spin and indexing machining cycles are also used. Figure 1 shows the photo of a sinker EDM machine. Wire EDMFigure 2 Wire cutting processAs is shown in Figure 2, in wire electrical discharge machining (WEDM), also known as wire-cut EDM and wire cutting, a thin single-strand metal wire, usually brass, is fed through the workpiece, submerged in a tank of dielectric fluid, typically deionized water. Wire-cut EDM is typically used to cut plates as thick as 300mm and to make punches, tools, and dies from hard metals that are difficult to machine with other methods. The wire, which is constantly fed from a spool, is held between upper and lower diamond guides. The guides, usually CNC-controlled, move in the x–y plane.On most machines, the upper guide can also move independently in the z–u–v axis, giving rise to the ability to cut tapered and transitioning shapes (circle on the bottom, square at the top for example). The upper guide can control axis movements in x–y–u–v–i–j–k–l–. This allows the wire-cut EDM to be programmed to cut very intricate and delicate shapes. The upper and lower diamond guides are usually accurate to 0.004 mm, and can have a cutting path or kerf as small as 0.021 mm using Ø 0.02 mm wire, though the average cutting kerf that achieves the best economic cost and machining time is 0.335 mm using Ø 0.25 brass wire. The reason that the cutting width is greater than the width of the wire is because sparking occurs from the sides of the wire to the work piece, causing erosion. This "overcut" is necessary, for many applications it is adequatelypredictable and therefore can be compensated for.The wire-cut process uses water as its dielectric fluid, controlling its resistivity and other electrical properties with filters and de-ionizer units. The water flushes the cut debris away from the cutting zone. Flushing is an important factor in determining the maximum feed rate for a given material thickness.Figure 3 Wiring cutting EDM machineFigure 3 shows a typical Wire Cutting EDM machine. Wire-cutting EDM is the focus of this training course.3. Applications of EDMPrototype productionThe EDM process is most widely used by the mold-making tool and die industries, but is becoming a common method of making prototype and production parts, especially in the aerospace, automobile and electronics industries in which production quantities are relatively low. In sinker EDM, a graphite, copper tungsten or pure copper electrode is machined into the desired (negative) shape and fed into the workpiece on the end of a vertical ram.Coinage die makingFor the creation of dies for producing jewelry and badges, or blanking and piercing (through use of a pancake die) by the coinage (stamping) process, the positive master may be made from sterling silver, since the master is significantly eroded and is used only once. The resultant negative die is then hardened and used in a drop hammer to produce stamped flats from cutout sheet blanks of bronze, silver, or low proof gold alloy. For badges these flats may be further shaped to a curved surface by another die. This type of EDM is usually performed submerged in an oil-based dielectric. The finished object may be further refined by hard or soft enameling and/or electroplated with pure gold or nickel. Softer materials such as silver may be hand engraved as a refinement.Coinage die makingSmall hole drilling EDM is used in a variety of applications.On wire-cut EDM machines, small hole drilling EDM is used to make a through hole in a workpiece in through which to thread the wire for the wire-cut EDM operation. A separate EDM head specifically for small hole drilling is mounted on a wire-cut machine and allows large hardened plates to have finished parts eroded from them as needed and without pre-drilling.Small hole EDM is used to drill rows of holes into the leading and trailing edges ofturbine blades used in jet engines. Gas flow through these small holes allows the engines to use higher temperatures than otherwise possible. The high-temperature, very hard, single crystal alloys employed in these blades makes conventional machining of these holes with high aspect ratio extremely difficult, if not impossible.4. Advantages and Disadvantages of EDMAdvantages of EDM include machining of:∙Complex shapes that would otherwise be difficult to produce with conventional cutting tools.∙Extremely hard material to very close tolerances.∙Very small work pieces where conventional cutting tools may damage the part from excess cutting tool pressure.∙There is no direct contact between tool and work piece. Therefore delicate sections and weak materials can be machined without any distortion.∙ A good surface finish can be obtained.∙very fine holes can be drilled.Disadvantages of EDM include:∙The slow rate of material removal.∙Potential fire hazard associated with use of combustible oil based dielectrics.∙The additional time and cost used for creating electrodes for ram/sinker EDM.∙Reproducing sharp corners on the workpiece is difficult due to electrode wear.∙Specific power consumption is very high.∙Power consumption is high.∙"Overcut" is formed.∙Excessive tool wear occurs during machining.∙Electrically non-conductive materials can be machined only with specific set-up of the process.[27]5. Training Practice with Wire EDMIn this training course, you are supposed to use a software called CAXA Manufacturing Engineer® to design a drawing yourself, generate the G-code for the drawing and import the G-code to the wire cutting EDM machine to cut the drawing on a steel sheet.The computer room is on the third floor of the training center, where you can use the software. The software is in Chinese, but don’t worry, the teacher and TA there will tell you how to use the functions in English. Once you have completed your drawing, you will have to upload it on the server so that you can download it on the computer where the wire cutting EDM machine is. After the training, you can take the finished workpiece away as a souvenir.In designing the drawing, there are some rules to follow. The lines or curves you draw must be continuous, without any break points, crosses or discontinuities. The distance between two lines or curves should be more than 0.2mm to allow the wire to pass through.6. Safety Rules(1) Stay away from the machine when it is working to avoid being injured by the sparks.(2) Wait until the workpiece cools down before you take it out from the machine.(3) Always remember to setup the protective cover before you start the machine.。
金工实习英文讲义-激光切割
Mechanical Engineering TrainingLaser CuttingName:Student NO.:Date:1. Introduction to Laser CuttingLaser cutting is a technology that uses a laser to cut materials, and is typically used for industrial manufacturing applications, but is also starting to be used by schools, small businesses, and hobbyists. Laser cutting works by directing the output of a high-power laser most commonly through optics. The laser optics and CNC (computer numerical control) are used to direct the material or the laser beam generated. A typical commercial laser for cutting materials would involve a motion control system to follow a CNC or G-code of the pattern to be cut onto the material. The focused laser beam directed at the material, which then either melts, burns, vaporizes away, or is blown away by a jet of gas, leaving an edge with a high-quality surface finish. Industrial laser cutters are used to cut flat-sheet material as well as structural and piping materials.In 1965, the first production laser cutting machine was used to drill holes in diamond dies. This machine was made by the Western Electric Engineering Research Center. In 1967, the British pioneered laser-assisted oxygen jet cutting for metals. In the early 1970s, this technology was put into production to cut titanium for aerospace applications. At the same time CO2 lasers were adapted to cut non-metals, such as textiles, because, at the time, CO2 lasers were not powerful enough to overcome the thermal conductivity of metals.2. Working Principle of Laser Cutting ProcessFigure 1 Structure of a laser cutterFigure 1 shows the structure of a laser cutter. Inside the cutter, generation of the laser beam involves stimulating a lasing material by electrical discharges or lamps within a closed container. As the lasing material is stimulated, the beam is reflected internally bymeans of a partial mirror, until it achieves sufficient energy to escape as a stream of monochromatic coherent light. Mirrors or fiber optics are typically used to direct the coherent light to a lens, which focuses the light at the work zone. The narrowest part of the focused beam is generally less than 0.0125 inches (0.32 mm) in diameter. Depending upon material thickness, kerf widths as small as 0.004 inches (0.10 mm) are possible. In order to be able to start cutting from somewhere else than the edge, a pierce is done before every cut. Piercing usually involves a high-power pulsed laser beam which slowly makes a hole in the material, taking around 5–15 seconds for 0.5-inch-thick (13 mm) stainless steel, for example.The movement of the cutter is controlled by a CNC device through G-code commands. The G-code can be manually programmed or be automatically generated with certain CAM (Computer Aided Manufacturing) software. In this training course, you are supposed to use a software called CAXA to design a drawing yourself, generate the G-code for the drawing and import the G-code to the laser cutting machine to cut the drawing on a wood sheet.3. Advantages of Laser CuttingAdvantages of laser cutting over mechanical cutting include easier workholding and reduced contamination of workpiece (since there is no cutting edge which can become contaminated by the material or contaminate the material). Precision may be better, since the laser beam does not wear during the process. There is also a reduced chance of warping the material that is being cut, as laser systems have a small heat-affected zone. Some materials are also very difficult or impossible to cut by more traditional means.4. Types of Lasers Used in Laser CuttingThere are three main types of lasers used in laser cutting. The CO2 laser is suited for cutting, boring, and engraving. The neodymium (Nd) and neodymium yttrium-aluminium-garnet (Nd-YAG) lasers are identical in style and differ only in application. Nd is used for boring and where high energy but low repetition are required. The Nd-YAG laser is used where very high power is needed and for boring and engraving. Both CO2 and Nd/ Nd-YAG lasers can be used for welding.5. Laser Cutting MethodsThere are many different methods in cutting using lasers, with different types used to cut different material. Some of the methods are vaporization, melt and blow, melt blow and burn, thermal stress cracking, scribing, cold cutting and burning stabilized laser cutting. Vaporization cuttingIn vaporization cutting the focused beam heats the surface of the material to boiling point and generates a keyhole. The keyhole leads to a sudden increase in absorptivity quickly deepening the hole. As the hole deepens and the material boils, vapor generated erodes the molten walls blowing ejecta out and further enlarging the hole. Non melting material such as wood, carbon and thermoset plastics are usually cut by this method. Melt and blowMelt and blow or fusion cutting uses high-pressure gas to blow molten material fromthe cutting area, greatly decreasing the power requirement. First the material is heated to melting point then a gas jet blows the molten material out of the kerf avoiding the need to raise the temperature of the material any further. Materials cut with this process are usually metals.Thermal stress crackingBrittle materials are particularly sensitive to thermal fracture, a feature exploited in thermal stress cracking. A beam is focused on the surface causing localized heating and thermal expansion. This results in a crack that can then be guided by moving the beam. The crack can be moved in order of m/s. It is usually used in cutting of glass.Stealth dicing of silicon wafersThe separation of microelectronic chips as prepared in semiconductor device fabrication from silicon wafers may be performed by the so-called stealth dicing process, which operates with a pulsed Nd:YAG laser, the wavelength of which (1064 nm) is well adopted to the electronic band gap of silicon (1.11 eV or 1117 nm). gReactive cuttingAlso called "burning stabilized laser gas cutting", "flame cutting". Reactive cutting is like oxygen torch cutting but with a laser beam as the ignition source. Mostly used for cutting carbon steel in thicknesses over 1 mm. This process can be used to cut very thick steel plates with relatively little laser power.6. Training PracticesIn this training course, you are supposed to use a software called CAXA to design a drawing yourself, generate the G-code for the drawing and import the G-code to the laser cutting machine to cut the drawing on a wood sheet.The computer room is on the third floor of the training center, where you can use the software. The software is in Chinese, but don’t worry, the teacher and TA there will tell you how to use the functions in English. Once you have completed your drawing, you will have to upload it on the server so that you can download it on the computer where the laser cutting machine is. After the training, you can take the finished workpiece away as a souvenir.7. Safety RulesOne thing you have to pay attention to in this training course is that, do not put any part of your body in the laser cutting machine when it is still working. The powerful laser may burn the skin and cause injury.。
金工实习报告模板英语
IntroductionThis report aims to document my experiences during the Golden Workshop internship, which provided me with hands-on training in various metalworking techniques. The internship took place at [Company Name], a renowned institution for metalworking and engineering education. Through this internship, I gained valuable skills, insights, and a deeper understanding of the metalworking industry.Objective of the InternshipThe primary objective of my internship was to:1. Learn and apply fundamental metalworking techniques.2. Gain practical experience in the manufacturing process.3. Understand the importance of precision, safety, and quality in metalworking.4. Develop problem-solving and teamwork skills.Internship Duration and LocationThe internship lasted for [duration] weeks, from [start date] to [end date]. It was conducted at [Company Name], located at [Company Address].Daily RoutineMy daily routine during the internship involved the following activities:1. Morning Meeting: A brief meeting with the workshop instructor to discuss the day's tasks and any safety precautions.2. Lecture: A theoretical session on the topic of the day, covering concepts, principles, and safety guidelines.3. Hands-On Training: Practical application of the learned techniques under the supervision of experienced instructors.4. Lunch Break: A break to relax and rejuvenate.5. Afternoon Work: Continuation of hands-on training and problem-solving activities.6. Reflection and Documentation: Writing down observations, experiences, and reflections at the end of the day.Learning and Skills GainedDuring the internship, I learned and honed the following skills:1. Basic Metalworking Techniques: I gained proficiency in basic metalworking techniques such as sawing, filing, grinding, bending, and welding.2. Precision Measurement: I learned how to use various measuring tools like calipers, micrometers, and rulers to ensure precision in my work.3. Safety Protocols: I was trained in safety protocols to ensure a safe working environment, including the use of personal protective equipment (PPE).4. Problem-Solving: I developed problem-solving skills by identifying and addressing issues that arose during the manufacturing process.5. Teamwork: I collaborated with my peers to complete tasks efficiently and effectively.Key Projects and ActivitiesHere are some of the key projects and activities I participated in during the internship:1. Manufacturing a Metal Frame: I was responsible for designing and manufacturing a metal frame using welding and bending techniques.2. Creating Metal Components: I created various metal components for a prototype, including bolts, nuts, and brackets.3. Assembling a Metal Structure: I assembled a metal structure using焊接 and riveting techniques.4. Participation in a Team Project: I worked with a team to design and manufacture a metal gadget, which required coordination and effective communication.Reflections and InsightsThe internship has been a transformative experience for me. Here are some of my reflections and insights:1. Appreciation for Precision: I realized the importance of precision in metalworking and how it directly impacts the quality of the final product.2. Safety is Non-Negotiable: The emphasis on safety during theinternship reinforced the idea that safety should always be a toppriority in any workplace.3. Problem-Solving Skills: The challenges I faced during the internship helped me develop critical thinking and problem-solving skills.4. Value of Teamwork: Working in a team taught me the importance of collaboration and communication in achieving common goals.ConclusionIn conclusion, my internship at [Company Name] has been an invaluable learning experience. It has equipped me with the necessary skills and knowledge to excel in the field of metalworking. I am grateful for the opportunity to have gained practical experience and for the guidance and support provided by the instructors and my peers. I look forward to applying the skills and insights gained during the internship in my future endeavors.References- [Company Name]. (Year). [Company Name Manual]. [Location].- [Instructor Name]. (Year). [Lecture Notes on Metalworking Techniques]. [Location].- [Textbook Author]. (Year). [Textbook Title]. [Publisher].Appendices- Photos of the metalwork projects completed during the internship. - Diagrams of the metal components designed and manufactured.- Reflections and self-assessment of the skills acquired during the internship.。
金工实习英文讲义-铸造
Mechanical Engineering TrainingSand CastingName:Student NO.:Date:1. Introduction to CastingCasting is a manufacturing process by which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process. Casting materials are usually metals or various cold setting materials that cure after mixing two or more components together; examples are epoxy, concrete, plaster and clay. Casting is most often used for making complex shapes that would be otherwise difficult or uneconomical to make by other methods. Casting is a 6000 year old process. The oldest surviving casting is a copper frog from 3200 BC.In this training course, considering the availability of required equipment in the training center, we will focus on the training of metal casting methods.2. Metal Casting and Its Common MethodsMetal casting is one of the most common casting processes. Metal patterns are more expensive but are more dimensionally stable and durable. Metallic patterns are used where repetitive production of castings is required in large quantities. Common metal casting methods include Sand Casting, Die Casting and Evaporative-pattern Casting.Sand CastingSand casting, also known as sand molded casting, is a metal casting process characterized by using sand as the mold material. The term "sand casting" can also refer to an object produced via the sand casting process. Sand castings are produced in specialized factories called foundries. Over 70% of all metal castings are produced via a sand casting process. As the most widely used metal casting methods, it is the main focus of this training course and will be talked about in detail in the following sections.Figure 1 Sand CastingSand casting is relatively cheap and sufficiently refractory even for steel foundry use. In addition to the sand, a suitable bonding agent (usually clay) is mixed or occurs with the sand. The mixture is moistened, typically with water, but sometimes with other substances, to develop strength and plasticity of the clay and to make the aggregate suitable for molding. The sand is typically contained in a system of frames or mold boxes known as a flask. Themold cavities and gate system are created by compacting the sand around models, or patterns, or carved directly into the sand. A demonstration of sand casting is shown in Figure 1.Die CastingDie casting is a metal casting process that is characterized by forcing molten metal under high pressure into a mold cavity. The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process. Most die castings are made from non-ferrous metals, specifically zinc, copper, aluminum, magnesium, lead, pewter and tin based alloys. Depending on the type of metal being cast, a hot- or cold-chamber machine is used.The casting equipment and the metal dies represent large capital costs and this tends to limit the process to high volume production. Manufacture of parts using die casting is relatively simple, involving only four main steps, which keeps the incremental cost per item low. It is especially suited for a large quantity of small to medium sized castings, which is why die casting produces more castings than any other casting process. Die castings are characterized by a very good surface finish (by casting standards) and dimensional consistency.Figure 2 shows a die casting machine. In later sessions of the training course, you will have the chance to see the die casting process and make an aluminum model of a fighter yourself with the machine.Figure 2 Die Casting MachineEvaporative-pattern CastingEvaporative-pattern casting is a type of casting process that uses a pattern made from a material that will evaporate when the molten metal is poured into the molding cavity. The most common evaporative-pattern material used is polystyrene foam.The two major evaporative-pattern casting processes are:(1) Lost-foam casting(2) Full-mold castingThe main difference is that lost-foam casting uses an unbonded sand and full-mold casting uses a bonded sand (or green sand). Figure 3 shows patterns and according products made from the patterns in evaporative-pattern casting. Please pay attention tothe materials of the pattern and product.Figure 3 Pattern and Product of Evaporative-pattern casting3. Components of Sand CastingFigure 4 Structure of Sand Casting ProcessFigure 4 shows the structure of a sand casting process, from which we can see that the structure is mainly composed of the flasks, a mold cavity, a core, the ventilation system and the gating system.PatternsFrom the design, provided by an engineer or designer, a skilled pattern maker builds a pattern of the object to be produced, using wood, metal, or a plastic such as expanded polystyrene. Sand can be ground, swept or strickled into shape. The metal to be cast will contract during solidification, and this may be non-uniform due to uneven cooling. Therefore, the pattern must be slightly larger than the finished product, a difference known as contraction allowance. Patterns also have core prints that create registers within the molds into which are placed sand cores. Such cores, sometimes reinforced by wires, are used to create under-cut profiles and cavities which cannot be molded with the cope and drag, such as the interior passages of valves or cooling passages in engine blocks.Paths for the entrance of metal into the mold cavity constitute the runner system and include the sprue, various feeders which maintain a good metal 'feed', and in-gates which attach the runner system to the casting cavity. Gas and steam generated during casting exit through the permeable sand or via risers, which are added either in the pattern itself, or as separate pieces.Molding Box and MaterialsA multi-part molding box (known as a casting flask, the top and bottom halves of which are known respectively as the cope and drag) is prepared to receive the pattern. Molding boxes are made in segments that may be latched to each other and to end closures. For a simple object—flat on one side—the lower portion of the box, closed at the bottom, will be filled with a molding sand. The sand is packed in through a vibratory process called ramming, and in this case, periodically screeded level. The surface of the sand may then be stabilized with a sizing compound. The pattern is placed on the sand and another molding box segment is added. Additional sand is rammed over and around the pattern. Finally a cover is placed on the box and it is turned and unlatched, so that the halves of the mold may be parted and the pattern with its sprue and vent patterns removed. Additional sizing may be added and any defects introduced by the removal of the pattern are corrected. The box is closed again. This forms a "green" mold which must be dried to receive the hot metal. If the mold is not sufficiently dried a steam explosion can occur that can throw molten metal about. In some cases, the sand may be oiled instead of moistened, which makes possible casting without waiting for the sand to dry. Sand may also be bonded by chemical binders, such as furane resins or amine-hardened resins.CoresTo produce cavities within the casting—such as for liquid cooling in engine blocks and cylinder heads—negative forms are used to produce cores. Usually sand-molded, cores are inserted into the casting box after removal of the pattern. Whenever possible, designs are made that avoid the use of cores, due to the additional set-up time and thus greater cost.With a completed mold at the appropriate moisture content, the box containing the sand mold is then positioned for filling with molten metal—typically iron, steel, bronze, brass, aluminum, magnesium alloys, or various pot metal alloys, which often include lead, tin, and zinc. After filling with liquid metal the box is set aside until the metal is sufficiently cool to be strong. The sand is then removed revealing a rough casting that, in the case of iron or steel, may still be glowing red. When casting with metals like iron or lead, which are significantly heavier than the casting sand, the casting flask is often covered with a heavyplate to prevent a problem known as floating the mold. Floating the mold occurs when the pressure of the metal pushes the sand above the mold cavity out of shape, causing the casting to fail.After casting, the cores are broken up by rods or shot and removed from the casting. The metal from the sprue and risers is cut from the rough casting. Various heat treatments may be applied to relieve stresses from the initial cooling and to add hardness—in the case of steel or iron, by quenching in water or oil. The casting may be further strengthened by surface compression treatment—like shot peening—that adds resistance to tensile cracking and smooths the rough surface.4. Basic Process of Sand CastingFigure 5 Sand Casting ProcessAs can be seen in Figure 5, the process can be summarized into 6 steps:(1) Place a pattern in sand to create a mold.In this step, first of all, put the pattern in the center of the flask. Two locators are needed here for you to identify the relative position and orientation of the pattern after it is covered by sand. Then fill the flask with sand, the sand should be filled over and around the pattern and the locators. After certain amount of sand is filled in, a procedure called ramming should be done, during which the sand is tightened under the continuous ramming of a hammer, until the tightened sand reaches the top of the flask. Note that in this procedure, please pay attention to the locations of the pattern and the locators so that you can avoid changing their location when ramming the sand.(2) Incorporate the pattern and sand in a gating system.The gating system is used to guide the molten metal into the mold cavity. So in the creation of the mold, the gating system should be considered. The gating system can be divided into sprue gate, cross gate and ingate according to their position in the system. The sprue gate guides the molten metal vertically down from the casting head, while thecross gate spreads the metal so that it can fully cover the space to be filled and the ingate guides the metal into the cavity.(3) Remove the pattern.Remember to be very careful when removing the pattern, any movement in the wrong direction may damage the mold cavity. When doing so, first use a brush dipped with water to moisten the joints of the pattern with the sand, so that the sand may not easily collapse. Then, slightly knock the pattern so that clearances occur between the pattern and the cavity to facilitate removal. Finally, carefully remove the pattern in the vertical direction. If damages do happen during the removal, you should try to restore its original shape. (4) Fill the mold cavity with molten metal.The molten metal comes from a furnace that melts the metal in very high temperature. You can use a casting ladle to transfer the molten metal, in which the metal shouldn’t occupy over 80% of the full capacity of the ladle. You should be very careful when transferring the metal because any drop of the molten metal can cause permanent damage to human skin if it accidentally splash on the body.(5) Allow the metal to cool.In this step, wait patiently for the metal to cool down and solidify and never touch the metal with bare hand.(6) Break away the sand mold and remove the casting.When the metal cools down, break the sand mold and get the casting out with a clamp, then dip the casting in water for more than 10 seconds before you can touch it with your hands.5. Safety Rules(1) Place the tools you use in order and remember to clean your position before youleave.(2) Do not make loud noise or quarrel during the training.(3) Remember to wear protection suits to protect yourself from injury when you aretrying to get the molten metal out of the furnace.(4) Do not use your hands to touch the casting before it cools down. When cleaningthe casting, remember to take care of the people around in case the tools you use hurt them.。
金工实习心得体会磨工范文2篇
金工实习心得体会磨工范文金工实习心得体会磨工范文精选2篇(一)实习期间,我在一家金工公司担任磨工的实习生,通过与同事的合作和指导老师的指导,我在这段时间里学到了许多宝贵的经验和知识。
首先,我学会了如何正确使用金工工具和设备。
在实习期间,我接触到了各种各样的磨工工具,例如磨具、砂轮和砂带等。
通过学习和实践,我逐渐掌握了这些工具的正确使用方法和注意事项。
我学会了如何正确调整和安装砂轮,并且了解了不同类型的砂轮的用途和特点。
同时,我还学会了如何根据加工要求选择合适的砂带,并且学会了正确安装和调整砂带的方法。
这些知识和技能对于我今后的金工工作将非常有帮助。
其次,我学到了如何进行有效的磨削加工。
磨削加工是金工中最常用的处理方法之一,也是最为复杂的一种加工方式。
在实习期间,我通过观摩和实践,学会了如何根据工件的材质和形状进行合理的磨削加工。
我了解了不同材料在磨削过程中的磨损规律和磨削参数的设置。
我还学会了如何正确掌握磨削力和磨削温度的控制,以避免对工件造成不良影响。
这些经验对于我今后的金工加工能力提升有很大的帮助。
最后,我学到了在金工实践中的注意事项和安全知识。
金工是一项高风险的工作,任何一丝不慎都可能导致严重事故的发生。
在实习期间,我通过实践和培训了解了金工工作中的各种安全规定和操作规程。
我学会了正确佩戴和使用个人防护装备,并且学会了如何正确处理和储存金工液体和化学品。
同时,我还了解了金工操作中的常见问题和故障排除方法。
这些安全知识对于我今后的金工实践和工作生活都有着重要的意义。
通过这段实习经历,我不仅学到了许多实用的金工知识和技能,也锻炼了自己的动手能力和职业素养。
我深刻体会到了金工实习对于专业能力的重要性,以及对于自我价值的提升。
我将以这段实习经验为契机,不断提升自己的技能和知识水平,为将来的职业发展打下坚实的基础。
金工实习心得体会磨工范文精选2篇(二)在金工实习的这段时间里,我深刻体会到了实践的重要性和对知识的运用能力的锻炼。
金工实习英文讲义-表面保护
Mechanical Engineering Training ManualName:Student NO.:Date:Edited by Christopher ZhuHeat Treating1. Introduction to Heat TreatingHeat treating is a group of industrial and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also used in the manufacture of many other materials, such as glass. Heat treatment involves the use of heating or chilling, normally to extreme temperatures, to achieve a desired result such as hardening or softening of a material. Heat treatment techniques include annealing, case hardening, precipitation strengthening, tempering and quenching. It is noteworthy that while the term heat treatment applies only to processes where the heating and cooling are done for the specific purpose of altering properties intentionally, heating and cooling often occur incidentally during other manufacturing processes such as hot forming or welding.2. Effects of Composition, Time and Temperature in Heat TreatingThe specific composition of an alloy system will usually have a great effect on the results of heat treating. If the percentage of each constituent is just right, the alloy will form a single, continuous microstructure upon cooling. Such a mixture is said to be eutectoid. However, if the percentage of the solutes varies from the eutectoid mixture, two or more different microstructures will usually form simultaneously. A hypoeutectoid solution contains less of the solute than the eutectoid mix, while a hypereutectoid solution contains more. Figure 1 shows the phase diagram if and iron-carbon alloying system, which reveals the composition of alloy under different temperatures.Figure 1 Phase diagram of an iron-carbon alloying system Proper heat treating requires precise control over temperature, time held at a certain temperature and cooling rate.Figure 2 Time-temperature transformation (TTT) diagram for steel With the exception of stress-relieving, tempering, and aging, most heat treatments begin by heating an alloy beyond the upper transformation (A3, see Figure 1) temperature. This temperature is referred to as an "arrest" because, at the A3 temperature nothing happens. Therefore, the alloy must be heated above the temperature for a transformation to occur. The alloy will usually be held at this temperature long enough for the heat to completely penetrate the alloy, thereby bringing it into a complete solid solution.Because a smaller grain size usually enhances mechanical properties, such as toughness, shear strength and tensile strength, these metals are often heated to a temperature that is just above the upper critical temperature, in order to prevent the grains of solution from growing too large. For instance, when steel is heated above the upper critical temperature, small grains of austenite form. These grow larger as temperature is increased. When cooled very quickly, during a martensite transformation, the austenite grain-size directly affects the martensitic grain-size. Larger grains have large grain-boundaries, which serve as weak spots in the structure. The grain size is usually controlled to reduce the probability of breakage.In Figure 2, lines in different colors signify the control of temquencperature and time in different heat treating methods.3. Types of Heat TreatingComplex heat treating schedules, or "cycles," are often devised by metallurgists to optimize an alloy's mechanical properties. In the aerospace industry, a superalloy may undergo five or more different heat treating operations to develop the desired properties. This can lead to quality problems depending on the accuracy of the furnace's temperature controls and timer. These operations can usually be divided into several basic techniques. AnnealingAnnealing is a rather generalized term. Annealing consists of heating a metal to a specific temperature and then cooling at a rate that will produce a refined microstructure. The rate of cooling is generally slow. As is shown in Figure 1, Annealing is most often used to soften a metal for cold working, to improve machinability, or to enhance properties like electrical conductivity.Figure 3 A hilarious example showing the effect of annealing In ferrous alloys, annealing is usually accomplished by heating the metal beyond the upper critical temperature and then cooling very slowly, resulting in the formation of pearlite. In both pure metals and many alloys that cannot be heat treated, annealing is used to remove the hardness caused by cold working. The metal is heated to a temperature where recrystallization can occur, thereby repairing the defects caused by plastic deformation. In these metals, the rate of cooling will usually have little effect. Most non-ferrous alloys that are heat-treatable are also annealed to relieve the hardness of cold working. These may be slowly cooled to allow full precipitation of the constituents and produce a refined microstructure.Ferrous alloys are usually either "full annealed" or "process annealed." Full annealing requires very slow cooling rates, in order to form coarse pearlite. In process annealing, the cooling rate may be faster; up to, and including normalizing. The main goal of process annealing is to produce a uniform microstructure. Non-ferrous alloys are often subjected to a variety of annealing techniques, including "recrystallization annealing," "partial annealing," "full annealing," and "final annealing." Not all annealing techniques involve recrystallization, such as stress relieving.NormalizingFigure 4 Difference between Normalizing and AnnealingNormalizing is a technique used to provide uniformity in grain size and composition throughout an alloy. The term is often used for ferrous alloys that have been austenitized and then cooled in open air. Normalizing not only produces pearlite, but also bainite sometimes martensite, which gives harder and stronger steel, but with less ductility for the same composition than full annealing. Figure 4 shows the difference between normalizing and annealing in temperature and cooling rate.QuenchingQuenching is a process of cooling a metal at a rapid rate. This is most often done to produce a martensite transformation. In ferrous alloys, this will often produce a harder metal, while non-ferrous alloys will usually become softer than normal.To harden by quenching, a metal (usually steel or cast iron) must be heated above the upper critical temperature and then quickly cooled. Depending on the alloy and other considerations (such as concern for maximum hardness vs. cracking and distortion), cooling may be done with forced air or other gases, (such as nitrogen). Liquids may be used, due to their better thermal conductivity, such as oil, water, a polymer dissolved in water, or a brine. Upon being rapidly cooled, a portion of austenite (dependent on alloy composition) will transform to martensite, a hard, brittle crystalline structure. The quenched hardness of a metal depends on its chemical composition and quenching method. Cooling speeds, from fastest to slowest, go from fresh water, brine, polymer (i.e. mixtures of water + glycol polymers), oil, and forced air. However, quenching a certain steel too fast can result in cracking, which is why high-tensile steels such as AISI 4140 should be quenched in oil, tool steels such as ISO 1.2767 or H13 hot work tool steel should be quenched in forced air, and low alloy or medium-tensile steels such as XK1320 or AISI 1040 should be quenched in brine.However, most non-ferrous metals, like alloys of copper, aluminum, or nickel, and some high alloy steels such as austenitic stainless steel (304, 316), produce an opposite effect when these are quenched: they soften. Austenitic stainless steels must be quenched to become fully corrosion resistant, as they work-harden significantly. TemperingFigure 5 Typical quench and temper cyclesUntempered martensitic steel, while very hard, is too brittle to be useful for most applications. A method for alleviating this problem is called tempering. Most applications require that quenched parts be tempered. Figure 5 shows typical quench and temper cycles. Tempering consists of heating steel below the lower critical temperature, (oftenfrom 400 to 1105 ˚F or 205 to 595 ˚C, depending on the desired results), to impart some toughness. Higher tempering temperatures (ma y be up to 1,300 ˚F or 700 ˚C, depending on the alloy and application) are sometimes used to impart further ductility, although some yield strength is lost.Tempering may also be performed on normalized steels. Other methods of tempering consist of quenching to a specific temperature, which is above the martensite start temperature, and then holding it there until pure bainite can form or internal stresses can be relieved. These include austempering and martempering.4. SpecificationsUsually the end condition is specified instead of the process used in heat treatment. Case hardeningCase hardening is specified by hardness and case depth. The case depth can be specified in two ways: total case depth or effective case depth. The total case depth is the true depth of the case. For most alloys, the effective case depth is the depth of the case that has a hardness equivalent of HRC50; however, some alloys specify a different hardness (40-60 HRC) at effective case depth; this is checked on a Tukon microhardness tester. This value can be roughly approximated as 65% of the total case depth; however the chemical composition and hardenability can affect this approximation. If neither type of case depth is specified the total case depth is assumed.For case hardened parts the specification should have a tolerance of at least ±0.005 in (0.13 mm). If the part is to be ground after heat treatment, the case depth is assumed to be after grinding.The Rockwell hardness scale used for the specification depends on the depth of the total case depth, as shown in the Table 1. Usually hardness is measured on the Rockwell "C" scale, but the load used on the scale will penetrate through the case if the case is less than 0.030 in (0.76 mm). Using Rockwell "C" for a thinner case will result in a false reading.For cases that are less than 0.015 in (0.38 mm) thick a Rockwell scale cannot reliably be used, so file hard is specified instead. File hard is approximately equivalent to 58 HRC. When specifying the hardness either a range should be given or the minimum hardness specified. If a range is specified at least 5 points should be given.Through hardeningOnly hardness is listed for through hardening. It is usually in the form of HRC with at least a five point range.AnnealingThe hardness for an annealing process is usually listed on the HRB scale as a maximum value. It is a process to refine grain size, improve strength, remove residual stress and affect the electromagnetic properties.5. Use of Rockwell Scale in Hardness MeasurementIn this training course, in order to quantify the effect of heat treatment on the hardness of the work piece, the Rockwell scale is used for the measurement of hardness.The Rockwell scale is a hardness scale based on indentation hardness of a material. The Rockwell test determines the hardness by measuring the depth of penetration of an indenter under a large load compared to the penetration made by a preload. There are different scales, denoted by a single letter, that use different loads or indenters. The result is a dimensionless number noted as HRA, where A is the scale letter. Table 2 shows various Rockwell scales.Figure 6 Force diagram of Rockwell testThe determination of the Rockwell hardness of a material involves the application of a minor load followed by a major load. The minor load establishes the zero position. The major load is applied, then removed while still maintaining the minor load. The depth of penetration from the zero datum is measured from a dial, on which a harder material gives a higher number. That is, the penetration depth and hardness are inversely proportional. The chief advantage of Rockwell hardness is its ability to display hardness values directly,thus obviating tedious calculations involved in other hardness measurement techniques.Figure 7 A digital Rockwell testerFigure 7 shows a digital Rockwell tester that could automatically conduct the Rockwell test and give the result of the hardness. In this training course, we will also use such a device to measure the hardness of the finishing workpiece6. Training PracticeIn this training course, you are supposed to learn about the basic knowledge about heat treatment, including understanding of the phase diagram of the iron-carbon alloy system and the TTT diagram for steel. You should also master how different heat treatment methods are applied and their advantages.After that, you will have the chance to take a training practice on Quenching. Here, first the workpiece will be put into a furnace and be heated to three different temperatures, then be cooled down in water for a strict amount of time to realize the quenching process. Then the hardness of the workpiece heated under different temperatures will be measured in a digital Rockwell tester and the result will be compared to see the different effects that temperature has on the finished workpiece.7. Safety Rules(1) The temperature in the furnace will be more than 800℃, so do not stay too close tothe furnace and use gloves and a clamp to put the workpiece in and out of the furnace.(2) When cooling the workpiece in water, remember to swirl it instead of simply dipping itin water. And the time for cooling should be strictly followed.。
金工实习英文讲义-锻造
Mechanical Engineering Training Forging and PressingName:Student NO.:Date:Forging and Pressing1. Introduction to Forging and PressingForging is a manufacturing process involving the shaping of metal using localized compressive forces. The blows are delivered with a hammer (often a power hammer) or a die. Forging is often classified according to the temperature at which it is performed: cold forging (a type of cold working), warm forging, or hot forging (a type of hot working). For the latter two, the metal is heated, usually in a forge. Forged parts can range in weight from less than a kilogram to hundreds of metric tons. Forging has been done by smiths for millennia; the traditional products were kitchenware, hardware, hand tools, edged weapons, and jewelry. Since the Industrial Revolution, forged parts are widely used in mechanisms and machines wherever a component requires high strength; such forgings usually require further processing (such as machining) to achieve a finished part. Today, forging is a major worldwide industry.Stamping (also known as pressing) is the process of placing flat sheet metal in either blank or coil form into a stamping press where a tool and die surface forms the metal into a net shape. Stamping includes a variety of sheet-metal forming manufacturing processes, such as punching using a machine press or stamping press, blanking, embossing, bending, flanging, and coining. This could be a single stage operation where every stroke of the press produces the desired form on the sheet metal part, or could occur through a series of stages. The process is usually carried out on sheet metal, but can also be used on other materials, such as polystyrene. Stamping is usually done on cold metal sheet. See Forging for hot metal forming operations.This training course will be divided into two parts. In the first part, you will learn about the working principle of Numerical Control (NC) Pressing Machines and learn to program with G-code that drives the machine to work. Then you are supposed to design a drawing yourself and write down the G-code according to the coordinates of the drawing so that the pressing machine can work out the drawing on a sheet metal following the G-code. In the second part, you will learn about the most traditional forging method, namely the open-die forging, in which you will be grouped in pairs to work out a workpiece following the guidance of the teacher.2. Types of Forging ProcessMetal casting is one of the most common casting processes. Metal patterns are more expensive but are more dimensionally stable and durable. Metallic patterns are used where repetitive production of castings is required in large quantities. Common metal casting methods include Sand Casting, Die Casting and Evaporative-pattern Casting. Drop ForgingDrop forging is a forging process where a hammer is raised and then "dropped" onto the workpiece to deform it according to the shape of the die. There are two types of drop forging: open-die drop forging and closed-die drop forging. As the names imply, the difference is in the shape of the die, with the former not fully enclosing the workpiece, while the latter does.Open-die drop forgingOpen-die forging is also known as smith forging. In open-die forging, a hammer strikes and deforms the workpiece, which is placed on a stationary anvil. Open-die forging gets its name from the fact that the dies (the surfaces that are in contact with the workpiece) do not enclose the workpiece, allowing it to flow except where contacted by the dies. Therefore the operator, or a robot, needs to orient and position the workpiece to get the desired shape. The dies are usually flat in shape, but some have a specially shaped surface for specialized operations.Open-die forgings can be worked into shapes which include discs, hubs, blocks, shafts (including step shafts or with flanges), sleeves, cylinders, flats, hexes, rounds, plate, and some custom shapes. Open-die forging lends itself to short runs and is appropriate for art smithing and custom work. A demonstration of open die forging is shown in Figure 1.Figure 1 Open-die ForgingImpression-die forgingImpression-die forging is also called closed-die forging. In impression-die forging, the metal is placed in a die resembling a mold, which is attached to the anvil. Usually, the hammer die is shaped as well. The hammer is then dropped on the workpiece, causing the metal to flow and fill the die cavities. The hammer is generally in contact with the workpiece on the scale of milliseconds. Depending on the size and complexity of the part, the hammer may be dropped multiple times in quick succession. Excess metal is squeezed out of the die cavities, forming what is referred to as flash. The flash cools more rapidly than the rest of the material; this cool metal is stronger than the metal in the die, so it helps prevent more flash from forming. This also forces the metal to completely fill the die cavity. After forging, the flash is removed. A demonstration of impression die forging is shown in Figure 2.Figure 2 Impression-die forgingPress forgingPress forging works by slowly applying a continuous pressure or force, which differs from the near-instantaneous impact of drop-hammer forging. The amount of time the dies are in contact with the workpiece is measured in seconds (as compared to the milliseconds of drop-hammer forges). The press forging operation can be done either cold or hot.Press forging can be used to perform all types of forging, including open-die and impression-die forging. Impression-die press forging usually requires less draft than drop forging and has better dimensional accuracy. Also, press forgings can often be done in one closing of the dies, allowing for easy automation.Roll forgingRoll forging is a process where round or flat bar stock is reduced in thickness and increased in length. Roll forging is performed using two cylindrical or semi-cylindrical rolls, each containing one or more shaped grooves. A heated bar is inserted into the rolls and when it hits a stop the rolls rotate and the bar is progressively shaped as it is rolled through the machine. The piece is then transferred to the next set of grooves or turned around and reinserted into the same grooves. This continues until the desired shape and size is achieved. The advantage of this process is there is no flash and it imparts a favorable grain structure into the workpiece.Examples of products produced using this method include axles, tapered levers and leaf springs.3. G-code programmingIn this part of training, you are supposed to design a drawing yourself and learn to use G-code to program the path of the drawing so that the pressing machine could follow the G-code to work out the drawing on a sheet metal.G-code (also RS-274), which has many variants, is the common name for the most widely used numerical control (NC) programming language. It is used mainly in computer-aided manufacturing for controlling automated machine tools. G-code is sometimes called G programming language.In fundamental terms, G-code is a language in which people tell computerized machine tools how to make something. The how is defined by instructions on where to move, how fast to move, and through what path to move. The most common situation isthat, within a machine tool, a cutting tool is moved according to these instructions through a toolpath, cutting away excess material to leave only the finished workpiece. The same concept also extends to noncutting tools such as forming or burnishing tools, photo-plotting, additive methods such as 3D printing, and measuring instruments.In the following, we will talk about the grammar of the G-code programming language. The code is composed of a series of variables specifying the commands to be executed and numbers specifying the coordinates, lengths or diameters. Table 1 and Table 2 shows the meanings of variables in G-code and some common used G-code commands.An example of G-code ProgrammingFigure 3 A complete G-code commandFigure 3 shows a complete G-code command. In this command, I, J and K are used specially in G02 and G03 commands to signify the incremental coordinate of arc center relative to the starting point of the arc.Figure 4 An exemplary drawingAs said above, you have to design a drawing yourself. The drawing could be drawn on a coordinate paper, which you can buy at the supermarket near the gate of the campus. The drawing you design should be better a simple one with only straight lines, circles or arcs, so that you can write the G-code easily. Other shapes like curves, splines are very difficult for manual programming. Figure 4 shows an exemplary drawing composed of two straight lines and two semi-circles.Before programming, you have to identify the coordinates of some main points on the drawing. In the example, six points are identified, in which A, B, C and D are the ends of the two straight lines while E and F are the centers of the semi-circles. Suppose we start from point C and set C as the origin, the coordinates of all the other points could be determined.Figure 5 shows the G-code for the exemplary drawing. Following the instructions, you can write the G-code for your own drawing.4. Open-die forging trainingIn the second part of this training course, you are supposed to take the open-die forging training. You must have seen from movies what a smith do in old times. In order to make swords or arrows, they put raw iron materials into a furnace with high temperature until the iron becomes very hot and turns soft. Then they take the glowing iron out with a clamp and use hammers to punch the iron to change its size and shape until it finally has the shape of what they want. And what you are going to do is very similar to that.By the time, all of you will be divided into small groups, with three students in each group. One student will be watching the furnace to see if the iron is hot enough to be takenout, another student will be working with the hammer to punch the iron while the last student will be stabilizing the iron with the clamp and checking the shape of the iron. Since the iron will become hard if it cools down, you have to pay attention if the iron is still glowing, if not, put it back in the furnace and repeat the process when it glows again.5. Safety Rules(1) Remember to wear gloves when working the hammer and clamp.(2) The furnace is very hot, so the student beside the furnace must wear protectionsuits to avoid injury.(3) Do not play with the hammer or use the hammer to hurt people around.(4) Students working with the clamp should hold the clamp at its end instead of themiddle, so that the iron could be stabilized and you won’t get hurt.。
003-金工实习指导书-磨工
磨工实习一、教学基本要求1、基本知识要求:(1)了解磨削加工特点、加工范围、加工精度和表面粗糙度;(2)了解常用磨床的种类、用途;(3)了解磨床的组成、功用及磨床的运动。
(4)了解砂轮的种类、特点及选用;(5)了解普通磨削的加工方法和工件安装方法。
(6)了解磨削加工安全操作技术。
2、基本技能要求:简单的磨床操作。
二、磨工实习安全技术要求1、 操作者必须穿工作服,戴安全帽,长发须压入帽内,不能戴手套操作,以防发生人身事故。
2、 多人共用一台磨床时,只能一人操作并注意他人的安全。
3、 开车前,检查各手柄的位置是否到位,确认正常后才准许开车。
4、 砂轮是在高速旋转下工作的,禁止面对砂轮站立。
5、 砂轮启动后,必须慢慢引向工件,严禁突然接触工件。
吃刀量不能过大,以防切削力过大将工件顶飞发生事故。
6、 砂轮未停稳不能卸工件。
7、 发生事故时,立即关闭机床电源。
8、 工作结束后,关闭电源,清除切屑,认真擦净机床,加油润滑,以保持良好的工作环境。
三、教学内容及进度安排第一部分 基本知识介绍课题 磨削加工基本知识(2小时)1、指导教师讲解部分。
1.1讲述磨削加的工特点、加工范围、加工精度和表面粗糙度。
1.2讲述磨床的种类(平磨、外圆磨、内圆磨)及用途。
1.3以M1412为例讲述外圆磨的型号、组成及磨削运动。
以M7130为例讲述平面磨床的组成。
1.4讲述砂轮的特性、选择及使用方法。
1.5讲述磨削外圆时工件装夹方法(顶尖安装、卡盘安装、芯轴安装),磨削平面时工件的装夹方法(电磁吸盘装夹)。
2、指导教师演示部分。
2.1演示参观外圆磨床和平面磨床的基本操作方法。
第二部分 基本操作练习(2小时)1、 指导教师讲解和演示部分(1小时)。
1.1示范讲解外圆磨床基本操作方法。
a)磨外圆 b) 磨内孔 c )磨平面a)磨螺纹 b) 磨齿轮 c )磨刀具磨削加工类型1.2示范讲解平面磨床基本操作方法。
2、学生操作练习部分(1小时)。
《金工实习Ⅰ》教学大纲课程名称金工实习课程英文名称Practiceof
《金工实习Ⅰ》教学大纲课程名称:金工实习课程英文名称:Practice of Metal Machining课程类别:集中实践教学环节学时数:2W 其中实验学时数:2W 课外学时数:0学分:2使用专业:自动化一、实习性质与任务金工实习是一门实践性的技术基础课。
金工实习以实践教学为主,课堂教学与自学为辅。
学生必须进行独立操作。
二、实习基本要求1. 知识了解机械制造的一般过程。
熟悉机械零件的常用加工方法及其所用主要设备的工作原理与典型结构﹑工夹量具的使用以及安全操作技术。
了解机械制造工艺知识和一些新工艺、新技术在机械制造中的应用。
2. 能力具备对简单零件初步具有选择加工方法和进行工艺分析的能力.在主要工种上应具有独立完成简单零件加工制造的实践能力。
3. 素质在质量和经济意识、安全与环保意识、创新意识、理论联系实际和科学作风等工程技术人员应具有的基本素质方面受到培养和锻炼。
三、相关课程材料成型技术基础、机械制造技术基础四、教学过程1. 教学方法:课堂讲授为辅,现场辅导为主教学2. 学时分配3. 学习方法:多媒体演示+现场实操讲解。
4. 考核方式:总评成绩=平时成绩+实操成绩+实习报告成绩。
五、教材及主要参考资料教材:霍仕武主编. 《金工实训教程》华中科技大学出版社.2015参考资料:[1] 康力主编.《金工实训》.同济大学出版社.2009.6[2] 郭术义主编.《金工实训》.清华大学出版社.2011.1六、课程教学内容的基本要求、重点和难点第一章铸造实训1. 教学内容(1)砂型铸造生产过程及特点;(2)了解砂型的基本造型方法、造型工具的使用;2. 教学基本要求:了解零件、模型和铸件的区别;初步学会使用造型工具,完成简单手工整模造型、分模造型、挖砂造型的操作。
3. 重点和难点:整模造型中分型面的选择第二章焊接实训+铣、刨、磨工实训1. 教学内容(1)手工电弧焊的操作方法、热处理及表面处理方法;(2)铣削、刨削、磨削加工的基本操作过程;2. 教学基本要求:能够进行简单的手工电弧焊操作,完成平焊焊缝。
金工实习教学大纲
金工实习教学大纲课程名称:金工实习英文名称:Metals craft practice学时: 2 周学分:3 分开课学期:第一、二学期适用专业:1机械类专业 2非机械类参照执行开课系、教研室:机械系工程实训中心一、实习的目的和要求1.目的:金工实习是机制类专业学生熟悉冷热加工生产过程、培养实践动手能力、学习《机械制造技术基础》等后续课程的实践性教学环节,是必修课。
通过实习,使学生熟悉机械制造的一般过程,掌握金属加工的主要工艺方法和工艺过程,熟悉各种设备和工具的安全操作使用方法;了解新工艺和新技术在机械制造中的使用;掌握对简单零件冷热加工方法选择和工艺分析的能力。
2.实习教学的基本要求(一)安全要求在实习全过程中,始终强调安全第一的观点,进行入厂安全教育,宣传安全实习守则,教育学生遵守劳动纪律和严格执行安全操作规程。
(二)实习要求金工实习是重要实践教学环节,其基本要求是:完成车工、钳工、焊工和铸工等工种的基本操作和学习相关金属工艺基础知识,使学生了解机械制造的一般过程,熟悉机械零件常用加工方法及所用设备结构原理,工具、量具的操作,具有独立完成简单零件加工能力;使学生通过简单零件加工,巩固和加深机械制图知识及其应用,学会对工艺过程的分析能力;培养学生的劳动观点,理论联系实际的工作作风和经济观点,实习报告是实习质量考核的形式之一。
(三)能力培养要求加强对学生专业动手能力的培养;促使学生养成发现问题、分析问题、运用所学过的知识和技能独立解决问题的能力和习惯。
二、实习内容(一)铸工实习(1天半,12学时)1.基本知识要求:(1)铸造生产过程及特点;(2)型砂及芯砂的性能及配置;(3)了解铸型结构,零件、模型和铸件的区别;(4)型芯的作用,芯盒的结构,型芯的出气,涂料及芯骨的作用,型芯的定位;(5)各种造型方法,造型工具的使用;2.基本技能要求:(1)完成手工两箱等造型作业;(2)了解型芯制作;(3)对铸件进行造型工艺方法的分析;(4)识别常见缺陷、分析其产生原因和防止方法。
金工实习报告总结磨工(2篇)
金工实习报告总结磨工实践是检验真理的唯一标准,作为一名机械专业的在读本科生,在谙熟了专业基础课的内容后,于大二上学期在百忙的学习中抽空开始了金属工艺学实习,开始了理论结合实践学习的途径。
根据学院的安排,机类专业实习为期四周,第一周为钳工(焊工、热处理);第二周为铣工(铸工、磨工),第三周为数控机床实习(分为计算机自动编程数控铣、手动编程数控车、线切割);第四周为车工。
第一周上午先进行岗前安全培训,使我们懂得了基本的车间安全操作规程;其中:机床工作过程中必须有人值守;测量和对工件进行重新装卡必须停车操作两点车间安全纪律特别值得注意。
另外,对于车床,开车前用于卡紧工件用的三抓卡盘上的扳手必须去下。
钳工实习开始,我们在技师的指导下,拿起锯子,端起锉刀;按图样的要求加工锤头。
锤头的加工分为划线、锯断、锉削三种操作。
将长条六面体的两端锉平后,图上龙胆紫溶液,在划线平台上用划线尺进行划线,划线时紧靠在直角方砖上以保证垂直。
锯切起锯时,左手拇指抵住划线处,起锯角____~____度,保证垂直,轻轻用力起锯。
起锯完成后,改平。
推进式用力,会拉时应尽量轻,速度不宜过快。
断锯时,更应轻慢。
最磨洋工的要数锉削了。
推锉时,左脚在前,身体倾斜____度。
右手握刀靠腰,左手抵住端平。
身体顺势向前推锉的同时,下压力从左手渐渐过渡到右手保持平整。
在锤头的两个主要面上,需花费将近两天的时间才得以完成,然后是“表面功夫”,用小锉刀和砂纸进一步将表面修平,擦光。
钳工的实习,让我明白了吧铁杵磨成绣花针需要多少工夫。
焊工的实习是电焊操作。
(由于气焊操作的危险性更大,未能被允许操作,我深感遗憾)绝缘手套和防护面罩是电焊工的基本安全防护用具。
带上手套,操作还算灵便;而戴上面罩,则眼前完全一片漆黑。
我们练习了焊条的装卡、起焊、平焊等工作。
要注意的有以下几点:1、每次焊完后,焊芯融化比药皮多,缩进药皮内部一段,而药皮本身不具有导电性,所以起焊时先应轻敲除去多余的药皮方能起焊。
金工加工实习报告磨工的内容摘要
金工加工实习报告磨工的内容摘要金工实习报告:磨工篇哎呀,说到金工实习,我就想起了那个磨床,那可真是个让人又爱又恨的家伙。
那天,老师让我们去练习磨削,我心里还暗暗想着:“这不是小菜一碟嘛!”结果,现实却是狠狠地打了我一巴掌。
刚开始,我还觉得挺简单的,就是把工件放在磨床上,然后让砂轮来回转啊转的。
可是,当我真正开始操作的时候,才发现这可不是那么回事。
我得控制好砂轮的速度,不能太快也不能太慢,否则磨出来的工件质量就会大打折扣。
而且,还得不停地调整砂轮的角度,以便能够磨到工件的每一个角落。
这可真是个技术活儿啊!我记得那天中午,我们班的同学都在食堂吃饭,而我还在车间里苦苦挣扎。
我边吃边想:“这磨床也真够讨厌的,整天让我在这里折腾。
不过,话说回来,这也算是一种锻炼吧。
就像那句话说的,‘磨刀不误砍柴工’,只有经过不懈的努力和锻炼,才能成为一个优秀的金工师傅。
”于是,我又开始了我的磨削之旅。
我一边磨,一边琢磨着怎么才能提高效率。
突然,我想到了一个办法:既然砂轮的速度和角度都很重要,那么为什么不把它们结合起来呢?于是,我开始尝试着用不同的速度和角度来磨削工件。
没想到,这个方法居然奏效了!我磨出来的工件不仅质量更好了,而且速度也大大提高了。
这并不是说我已经完全掌握了磨工的技巧。
毕竟,金工实习是一个漫长的过程,需要我们不断地学习和积累经验。
但是,我相信只要我努力下去,总有一天我会成为一个出色的金工师傅。
这次金工实习让我深刻地认识到了金工行业的重要性和艰辛。
虽然我在磨工方面还有很多不足之处,但是我相信通过不断地努力和学习,我会变得越来越好的。
就像那句话说的,“熟能生巧”,只要我们肯下功夫,就一定能够成为行业的佼佼者!好了,今天的报告就到这里啦!谢谢大家的聆听!下次实习再见啦!。
金工实习实训报告磨锤子
金工实习实训报告磨锤子一、实习目的和意义金工实习是金属工艺学课程的重要组成部分,通过金工实习的教学,配合金属工艺学课程的学习,使学生初步了解加工不同的工件所选取相应的工艺、加工相同的零件可选取不同的工艺以及使用所需要的机床设备的操作技术。
本次实习的重点在于金属切削工艺,以及对切削加工的设备和使用方法的了解。
钳工实习方面侧重于钳工工作中所需用的各类工具。
实习成果是用所给材料结合各种工艺做出实验室专用实验桌。
二、实习内容1.钳工实习在钳工实习中,我们主要是以团队的形式制作一个实验室的大铁桌。
在这个过程中,我们学会了如何使用各类工具,如锯子、锉刀等,以及如何按照图样要求加工锤头。
锤头的加工分为划线、锯断、锉削三种操作。
首先,我们将长条六面体的两端锉平,然后使用龙胆紫溶液在划线平台上进行划线。
划线时,要紧靠在直角尺上,以保证划线的准确性。
接下来,我们使用锯子将工件锯断,锯断时要注意安全,避免锯子反弹伤人。
最后,使用锉刀对工件进行锉削,使其达到图样要求的尺寸和表面质量。
2.磨工实习在磨工实习中,我们主要学习如何使用磨床对工件进行磨削加工。
磨削加工是一种高精度的表面加工方法,可以提高工件的尺寸精度和表面粗糙度。
首先,我们需要了解磨床的结构和原理,熟悉磨床的操作方法和注意事项。
在操作磨床时,要确保磨床的安全防护装置齐全有效,避免因操作不当造成人身伤害。
接下来,我们对工件进行装夹,选择合适的磨削参数,如磨削速度、进给量等。
在磨削过程中,要注意观察工件的磨削情况,如发现异常情况,应立即停止磨削,分析原因并采取相应措施。
最后,对磨削后的工件进行检验,确保其达到图样要求的尺寸和表面质量。
三、实习收获通过金工实习,我对金属切削工艺和钳工操作有了更深入的了解。
在钳工实习中,我学会了如何使用锯子、锉刀等工具,掌握了划线、锯断、锉削等基本操作技能。
在磨工实习中,我了解了磨床的结构和原理,熟悉了磨床的操作方法和注意事项。
通过实际操作,我掌握了磨削加工的基本技能,提高了工件的尺寸精度和表面粗糙度。
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Mechanical Engineering TrainingGrindingName:Student NO.:Date:1. Introduction to GrindingGrinding is an abrasive machining process that uses a grinding wheel as the cutting tool.A wide variety of machines are used for grinding:(1) Hand-cranked knife-sharpening stones (grindstones)(2) Handheld power tools such as angle grinders and die grinders(3) Various kinds of expensive industrial machine tools called grinding machines(4) Bench grinders often found in residential garages and basementsGrinding practice is a large and diverse area of manufacturing and toolmaking. It can produce very fine finishes and very accurate dimensions; yet in mass production contexts it can also rough out large volumes of metal quite rapidly. It is usually better suited to the machining of very hard materials than is "regular" machining (that is, cutting larger chips with cutting tools such as tool bits or milling cutters), and until recent decades it was the only practical way to machine such materials as hardened steels. Compared to "regular" machining, it is usually better suited to taking very shallow cuts, such as reducing a shaft’s d iameter by half a thousandth of an inch or 12.7 μm.Grinding is a subset of cutting, as grinding is a true metal-cutting process. Each grain of abrasive functions as a microscopic single-point cutting edge, and shears a tiny chip that is analogous to what would conventionally be called a "cut" chip (turning, milling, drilling, tapping, etc.). However, among people who work in the machining fields, the term cutting is often understood to refer to the macroscopic cutting operations, and grinding is often mentally categorized as a "separate" process. This is why the terms are usually used in contradistinction in shop-floor practice, even though, strictly speaking, grinding is a subset of cutting.In this training course, considering the availability of required equipment in the training center, we will focus on the training of metal casting methods.2. Types of Grinding ProcessSelecting which of the following grinding operations to be used is determined by the size, shape, features and the desired production rate.Surface GrindingSurface grinding uses a rotating abrasive wheel to remove material, creating a flat surface. The tolerances that are normally achieved with grinding are ± 2 × 10−4 inches for grinding a flat material, and ± 3 × 10−4 inches for a parallel surface (in metric units: 5 μm for flat material and 8 μm for parallel surface).The surface grinder is composed of an abrasive wheel, a workholding device known as a chuck, either electromagnetic or vacuum, and a reciprocating table.Typical workpiece materials include cast iron and steel. These two materials do not tend to clog the grinding wheel while being processed. Other materials are aluminum, stainless steel, brass and some plastics. The photo of a surface grinding machine is shown in Figure 1. The machine you are going to use in this training course is the surface grinding machine. You will learn about the working principles of the machine and manipulate the machine to grind a workpiece according to a technical drawing.Figure 1 Surface grinding machineCylindrical GrindingCylindrical grinding (also called center-type grinding) is used to grind the cylindrical surfaces and shoulders of the workpiece. The workpiece is mounted on centers and rotated by a devise known as a drive dog or center driver. The abrasive wheel and the workpiece are rotated by separate motors and at different speeds. The table can be adjusted to produce tapers. The wheel head can be swiveled.The five types of cylindrical grinding are: outside diameter (OD) grinding, inside diameter (ID) grinding, plunge grinding, creep feed grinding, and centerless grinding.A cylindrical grinder has a grinding (abrasive) wheel, two centers that hold the workpiece, and a chuck, grinding dog, or other mechanism to drive the work. Most cylindrical grinding machines include a swivel to allow for the forming of tapered pieces. The wheel and workpiece move parallel to one another in both the radial and longitudinal directions. The abrasive wheel can have many shapes. Standard disk shaped wheels can be used to create a tapered or straight workpiece geometry while formed wheels are used to create a shaped workpiece. The process using a formed wheel creates less vibration than using a regular disk shaped wheel.Tolerances for cylindrical grinding are held within five ten-thousandths of an inch (+/- 0.0005) (metric: +/- 13 um) for diameter and one ten-thousandth of an inch (+/- 0.0001) (metric: 2.5 um) for roundness. Precision work can reach tolerances as high as fifty millionths of an inch (+/- 0.00005) (metric: 1.3 um) for diameter and ten millionths (+/- 0.00001) (metric: 0.25 um) for roundness. Surface finishes can range from 2 to 125 micro-inches (metric: 50 nm to 3 um), with typical finishes ranging from 8-32 micro-inches. (metric: 0.2 um to 0.8 um)Figure 2 shows a cylindrical grinding machine.Figure 2 Cylindrical grinding machine3. Working Principle of the Surface Grinding MachineFigure 3 Structure of a surface grinding machineAs can be seen in Figure 3, the surface grinding machine consists of a table with a fixture to guide and hold the work piece, and a power-driven grinding wheel spinning at the required speed. The speed is determined by the wheel’s diameter and manufacturer’s rating. The grinding wheel can travel across a fixed work piece, or the work piece can be moved while the grind wheel stays in a fixed position. The work piece is usually firmlyfixed on the table through electromagnetic power to make sure it won’t move under the rotatory force of the grinding wheel. So when we say the work piece moves, we actually mean the table that fixes the work piece moves.Fine control of the grinding head or table position is possible using a vernier calibrated hand wheel. From Figure 3, we can see there are three hand wheels, in which the Longitudinal Feed Hand Wheel controls the longitudinal movement of the table, the Cross Feed Hand Wheel controls the horizontal movement of the table while the Vertical Feed Hand Wheel controls the vertical movement of the grinding head. With the hand wheels, we can precisely control the amount of material to be removed and finally meet the technical requirement.Figure 4 The grinding processAs can be seen form Figure 4, the Grinding machine removes material from the surface of the workpiece by abrasion, which can generate substantial amounts of heat. To cool the work piece so that it does not overheat and go outside its tolerance, grinding machines incorporate a coolant. The coolant also benefits the machinist as the heat generated may cause burns. During the grinding process, the coolant is continuously supplied to the grinding wheel where it contacts the workpiece to remove the heat.4. Grinding WheelA grinding wheel is an expendable wheel that is composed of an abrasive compound used for various grinding (abrasive cutting) and abrasive machining operations. The wheels are generally made from a matrix of coarse particles pressed and bonded together to form a solid, circular shape. Various profiles and cross sections are available depending on the intended usage for the wheel. They may also be made from a solid steel or aluminum disc with particles bonded to the surface. Figure 5 shows the photo of a grinding wheel that is used in the surface grinding machine.Figure 5 Grinding wheelThe manufacture of these wheels is a precise and tightly controlled process, due not only to the inherent safety risks of a spinning disc, but also the composition and uniformity required to prevent that disc from exploding due to the high stresses produced on rotation.Common materials for manufacturing grinding wheels include: Aluminum Oxide, Silicon Carbide, Ceramic, Diamond and Cubic Boron Nitride. Grinding wheels with diamond or Cubic Boron Nitride (CBN) grains are called super-abrasives. Grinding wheels with Aluminum Oxide (corundum), Silicon Carbide or Ceramic grains are called conventional abrasives.5. Use of the MicrometerIn the training practice, you are supposed to grind the workpiece according to a technical drawing where size and tolerance of the finished workpiece are specified. Your finished workpiece must conform to all the specifications in the technical drawing. Therefore, in order to check if the workpiece is qualified, you have to learn about the use of the micrometer.A micrometer, sometimes known as a micrometer screw gauge, is a device incorporating a calibrated screw widely used for precise measurement of components in mechanical engineering and machining as well as most mechanical trades. Micrometers are usually, but not always, in the form of calipers (opposing ends joined by a frame), which is why micrometer caliper is another common name. The spindle is a very accurately machined screw and the object to be measured is placed between the spindle and the anvil. The spindle is moved by turning the ratchet knob or thimble until the object to be measured is lightly touched by both the spindle and the anvil. Figure 6 shows a micrometer.Figure 6 The micrometerBut how to read the micrometer? Let us see an example in Figure 7.Figure 7 Micrometer thimble reading 5.78mmThe spindle of an ordinary metric micrometer has 2 threads per millimeter, and thus one complete revolution moves the spindle through a distance of 0.5 millimeter. The longitudinal line on the frame is graduated with 1 millimeter divisions and 0.5 millimeter subdivisions. The thimble has 50 graduations, each being 0.01 millimeter (one-hundredth of a millimeter). Thus, the reading is given by the number of millimeter divisions visible on the scale of the sleeve plus the particular division on the thimble which coincides with the axial line on the sleeve.Suppose that the thimble were screwed out so that graduation 5, and one additional 0.5 subdivision were visible (as shown in Figure 7), and that graduation 28 on the thimble coincided with the axial line on the sleeve. The reading then would be 5.00 + 0.5 + 0.28 = 5.78 mm.6. Training PracticeIn this training course, you are supposed to grind the workpiece according to a technical drawing. The drawing will be given to you in class, so before you start working, first read the drawing carefully and make sure you have understood all the specifications on the drawing. Then following the guidance of the teacher, you can manipulate the grinding machine. When you have finished, use the micrometer to check if the workpiece meets the specifications, if not, you have to repeat the process until the specifications are all met.7. Safety Rules(1) The grinding wheel rotates in a very high speed, so do not try to use your hands totouch the wheel or workpiece when the machine is running.(2) Sparks may occur when the grinding machine is working, so you shall stay awayfrom the end of the machine to avoid being burnt.(3) After the workpiece is finished, do not try to pick it up with bare hand. Gloves areneeded in case you get your fingers injured by the heat from the workpiece.。