Welding Fixture and Checking Gauge Design for Clutch Pedal 检查离合器踏板焊接夹具和量具的设计.doc

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1、【精品文档】如有侵权，请联系网站删除，仅供学习与交流Welding Fixture and Checking Gauge Design for Clutch Pedal 检查离合器踏板焊接夹具和量具的设计.精品文档.CHAPTER 1: INTRODUCTION1.1 IntroductionThe first manufactured products were made one at a time. Early artisans started with little more than raw materials and a rough idea of the finished prod

2、uct. They produced each product piece by piece, making each part individually and fitting the parts into the finished product. This process took time. Moreover, the quality and consistency of products varied from one artisan to the next. As they worked, early manufacturing pioneers realized the need

3、 for better methods and developed new ideas. Eventually, they found the secret of mass production: standardized parts. Standard parts not only speeded production, they also ensured the interchangeability of parts. The idea may be obvious today, but in its time, it was revolutionary. These standard p

4、arts were the key to enabling less-skilled workers to replicate the skill of the craftsman on a repetitive basis. The original method of achieving consistent part configuration was the template. Templates for layout, sawing, and filing permitted each worker to make parts to a standard design. While

5、early templates were crude, they at least gave skilled workers a standard form to follow for the part. Building on the template idea, workers constructed other guides and work holders to make their jobs easier and the results more predictable. These guides and work holders were the ancestors of toda

6、ys jigs and fixtures. Yesterdays work holders had the same two basic functions as todays securely holding and accurately locating a work piece. Early jigs and fixtures may have lacked modern refinements, but they followed many of the same principles as todays work holder designs.The project is to de

7、sign a fixture for Clutch pedal. The part is machined in two more industries increasing the cost and machining time of the part. To eliminate outsourcing of the part the company has designed a fixture. The project is to design a fixture which will perform the remaining operation.Fixture is designed

8、to hold the object during its operation to avoid any errors in the dimension and for mass production. In any industry the accuracy is much important. Any error in the product may be harmful or dissatisfactory to the customer. In order to avoid this checking fixture is essential. Checking fixture che

9、cks whetherthe product is dimensionally correct or not. If there is any error in the structure or dimension the product gets rejected.Welding fixtures are normally designed to hold and support the various components (workpieces) to be welded. It is necessary to support them in a proper location whic

10、h is capable of preventing distortions in workpieces during welding. For this the locating elements need to be placed carefully, clamping has to be light but firm, placement of clamping elements has to be clear of the welding area and the fixture has to be quite stable and rigid to withstand the wel

11、ding stresses. There is no limit of designing a welding fixture. Its design depends on and driven by the hard facts that are what you want, and how to overcome the problems appearing with the current fixture. Keeping the defect free fast production rate as major target. The famous saying “Necessity

12、is the mother of invention” hold perfectly true in case of welding fixture design.1.2 Project DirectivesObjectives: The main purpose of our project is to design a welding fixture and checking gauge to manufacture Clutch Pedal for Mahindra & Mahindra M-star tractor as per requirements of inspection a

13、nd testing department. This is done to provide fast mechanism to manufacture Clutch pedal as per requirement of client and also at minimum cost.Scope of work: Design is the major and important factor in determining efficiency and work ability of the machine. Working capacity, precision, rate of prod

14、uction etc. are the factors affecting the basic designing of Clutch pedal. This project is an endeavor towards sophisticating ways of designing the given component to increase the accuracy and production rate of the work. This project will give us the exposure to different technical ideas regarding

15、operation, design software and difficulties while operating them.Constraints: The main constraints are Critical Characteristics and Significant Characteristics which are mentioned in 2D Product Drawings, Any failure in archiving Significant Characteristics may led to fouling or the part may not fit

16、properly in vehicle and any failure in archiving in Critical Characteristics may led even led to accidents. So Design Constraints must be archived within tolerance limit. This is mainly manufacturing based project hence the main constraints is to achieve this at minimum cost and with required flexib

17、ility by using existing equipment available in the workshop.CHAPTER 2: LITRATURE SURVEY2.1 WeldingThe term welding refers to the process of metallurgical joining of two similar or dissimilar metals by heating them to their melting temperature and causing the molten metal to flow together with or wit

18、hout application of pressure, with or without use of filler material.Welding is widely used by metalworkers in the fabrication, maintenance, and repair of parts and structures. While there are many methods for joining metals, welding is one of the most convenient and rapid methods available. Welding

19、 is not new. The earliest known form of welding, called forge welding, dates back to the year 2000 B.C. Forge welding is a primitive process of joining metals by heating and hammering until the metals are fused (mixed) together. Although forge welding still exists, it is mainly limited to the blacks

20、mith trade. Today, there are many welding processes available. The primary differences between the various welding processes are the methods by which heat is generated to melt the metal. The most common types of welding are oxy-fuel gas welding (OFW), arc welding (AW), and resistance welding (RW).Fi

21、g. 2.1.1: MIG Welding2.2 Welding Process Involved Fig. 2.2.1: Typical Arrangement of MIG Welding Process Company uses MIG (Metal Inert gas welding) welding process This process is also popularly known as CO2 Welding process because shielding inert gas used contains 80% Argon & 20% CO2, Also called a

22、s GMAW (Gas Metal Arc welding). Metal electrode used is consumable and made of Copper Material It is a Fusion Welding process 2-4 mm of gap is maintained between workpiece and electrode No special flux material is required Direct Current Reverse Polarity (DCRP) connection is used (negative terminal

23、connected to work and positive terminal connected to electrode)Fig. 2.2.2: MIG Welding Machine2.3 Welding ParameterTable 2.3.1: Welding ParametersSr. No.ParameterValue1Voltage25 35 V2Current140 150 Amp3Gas Flow10 12 dm3/min4Wire Speed12 17 m/min5Wire Diameter0.8 mm2.4 FixtureA fixture is a work hold

24、ing or support device used in the manufacturing industry. What makes a fixture unique is that each one is built to fit a particular part or shape. The main purpose of a fixture is to locate and in some cases hold a work piece during either a machining operation or some other industrial process. A ji

25、g differs from a fixture in that it guides the tool to its correct position in addition to locating and supporting the work piece.Fixtures are devices which are used to increase the production rate of similar parts and reduce human efforts. Fixture varies in design from relatively simple tools to ex

26、pensive, complicate devices.The primary purposes of fixtures are: Reduce the cost of production Maintain consistent quality Maximize efficiency Fixture is device whichi. Locates job.ii. Clamps job.iii. But does not guide/locate tool used for operationFixture serves to reduce production time and prod

27、uction cost. It assures high accuracy for job, safety in work is archived. With the help of fixture operations such as marking, measuring, laying out are totally eliminated. Some basic elements of fixture are a. Bodyb. Locating Elementsc. Clamping Elementsd. Setting Elementse. Positioning Elementsf.

28、 Indexing ElementsFixtures are basically of two types viz.1) Permanent Fixture 2) Modular Fixture.Modular fixture is a work holding device that uses standard reusable to construct and customize work holding device. Modular fixtures are just like permanent fixture with some key differences they are a

29、s follows: Modular Fixtures can be assembled entirely from off the shelf components without machining. Many modular components are adjustable and universal. Specially designed tooling plates and blocks with standard grid pattern are foundation of good modular fixture Tooling plates and blocks are ma

30、in structural elements of any modular fixture system.Any fixture should be designed such that it maintains a proper workpiece control. Several theories and techniques to maintain work piece control are as follows:1. Equilibrium theories 2. Concept of location 3. Geometric control4. Dimensional contr

31、ol 5. Mechanical control6. Alternate location theories2.4.1 Classification of fixture: There are many ways to classify fixture:1) Classification according to the operation These are drilling, milling, boring, assembly, inspection, transfer, welding, spraying fixture etc.2) Classification based on th

32、e mode of working Hand or manually operated fixture, pneumatic fixture, hydraulic fixture, automatic fixture etc.3) Universal fixtures Devices in this class can hold any job within their design capacity eg. Mechanical vise is a universal fixture, which can hold any jobs in the jaws.A three jaw self

33、centering chuck can hold any cylindrical job in it jaws and a four jaw chuck can hold the job having an irregular cross section. A part having a machine tool bedplate is also a universal fixture on which any job can be clamped using T-slots on it. An indexing head is universal holding and positionin

34、g fixture. It can hold on a chuck or plate.Following are the purpose and advantages of fixtures: It reduces or sometimes eliminates the efforts of marking, measuring and setting of workpiece on a machine and maintains the accuracy of performance. The workpiece and tool are relatively located at thei

35、r exact positions before the operation automatically within negligible time. So it reduces product cycle time. Variability of dimension in mass production is very low so manufacturing processes supported by use of jigs and fixtures maintain a consistent quality. Due to low variability in dimension a

36、ssembly operation becomes easy, low rejection due to les defective production is observed. It reduces the production cycle time so increases production capacity. Simultaneously working by more than one tool on the same workpiece is possible. The operating conditions like speed, feed rate and depth o

37、f cut can be set to higher values due to rigidity of clamping of workpiece by jigs and fixtures. Operators working become comfortable as his efforts in setting the workpiece can be eliminated. Semi-skilled operators can be assigned the work so it saves the cost of manpower also. There is no need to

38、examine the quality of produce provided that quality of employed fixtures is ensured.2.4.2 General requirement of fixtureIn order to maintain the workpiece stability during a machining process, an operational fixture has to satisfy several requirements to fully perform its functions as a workholding

39、 device. The following constraints must be observed while designing a viable fixture: Deterministic location: A workpiece is said to be kinematically restrained when it cannot move without losing contact with at least one locator. The workpiece is constrained by a set of appropriately placed locator

40、s so that it is presentable for the machining operation. Locating errors due to locators and locating surfaces of the workpiece should be minimized so as to accurately and uniquely position the workpiece within the machine coordinate frame. Total constraint: A workpiece should be fully constrained a

41、t all times to prevent any movement. Clamps should provide locking forces to hold the workpiece in place -once it is located. A totally restrained part should be able to remain in static equilibrium to withstand all possible processing forces or disturbance. A necessary and sufficient condition to w

42、arrant workpiece stability is to satisfy the condition of force closure. Contained deflection: Workpiece deformation is unavoidable due to its elastic/plastic nature, and the external forces impacted by the clamping actuation and machining operations. Deformation has to be limited to an acceptable m

43、agnitude in order to achieve the tolerance specifications.Geometric constraint:Geometric constraint guarantees that all fixturing elements have an access to the datum surface. They also assure that the fixture components do not interfere with cutting tools during a machining operation. In addition t

44、o these requirements, a fixture design should have desirable characteristics such as quick loading and unloading, minimum number of components, accessibility, design for multiple cutting operations, portability, low cost, etc.2.5 Checking GaugeFixture is designed to hold the object during its operat

45、ion to avoid any errors in the dimension and for mass production. In any industry the accuracy is much important. Any error in the product may be harmful or dissatisfactory to the customer. In order to avoid this checking gauge is essential. Checking gauge checks whether the product is dimensionally

46、 correct or not. If there is any error in the structure or dimension the product gets rejected. 2.5.1 Points to be considered while designing checking gauge:1) Measuring places of part: Checking gauge should be applicable for inspecting the places indicated by Plan sheet and Quality list the followi

47、ng places should be inspected generally.a) Assembled surface with other parts.b) Gap surface or gap line (parting line) between other parts.c) Touching surface (mainly with weather strip)d) Flushing line (joint area, touching place)e) Surface on stepped touching area, joggling linef) Fastening hole

48、for screwg) Inserting hole for parth) All other holes (Holes with unnecessary for inspection can be excluded, such as drain holes obvious for its position)i) Trim linej) Locator position2) Panel settinga) Panel with datum hole should be located by the datum hole.b) Place a panel on a datum face and setting surface, and the surface should be clamped basically. Datum face means the surface with coordinate holes and the surface indicated on quality list setting surface means as followed. The place on wh