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

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1、 Welding Fixture and Checking Gauge Design for Clutch Pedal AssemblyCHAPTER 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 product. They produced each product piece by

2、 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 for better methods and developed new id

3、eas. 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 parts were the key to enabling less-skill

4、ed 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 early templates were crude, they at leas

5、t 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 todays jigs and fixtures. Yesterdays work ho

6、lders 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 design a fixture for Clutch pedal. The par

7、t 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 to hold the object during its operation

8、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 checks whetherthe product is dimensionally

9、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 which is capable of preventing distortions i

10、n 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 welding stresses. There is no limit of desi

11、gning 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 is the mother of invention” hold perfect

12、ly 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 and testing department. This is done to p

13、rovide 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 production etc. are the factors affecting th

14、e 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 operation, design software and difficult

15、ies 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 properly in vehicle and any failure in a

16、rchiving 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 flexibility by using existing equipment availa

17、ble 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 without application of pressure, with or wi

18、thout 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 is not new. The earliest known form of

19、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 blacksmith trade. Today, there are many weldin

20、g 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).Fig. 2.1.1: MIG Welding2.2 Welding Process

21、 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 as GMAW (Gas Metal Arc welding). Metal el

22、ectrode 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 connected to work and positive terminal

23、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 holding or support device used in the manuf

24、acturing 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 jig differs from a fixture in that it gui

25、des 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 expensive, complicate devices.The primary

26、 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 production cost. It assures high accuracy f

27、or 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. Indexing ElementsFixtures are basicall

28、y 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 as follows: Modular Fixtures can be asse

29、mbled 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 main structural elements of any modular f

30、ixture 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 control 5. Mechanical control6. Alternate lo

31、cation 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 the mode of working Hand or manually oper

32、ated 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 centering chuck can hold any cylindrica

33、l 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 positioning fixture. It can hold on a chuck or pl

34、ate.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 their exact positions before the operation

35、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 assembly operation becomes easy, low rej

36、ection 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 of cut can be set to higher values due t

37、o 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 examine the quality of produce provided

38、 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 device. The following constraints must

39、 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 locators so that it is presentable for the mac

40、hining 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 at all times to prevent any movement. Cl

41、amps 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 warrant workpiece stability is to satisf

42、y 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 magnitude in order to achieve the tolera

43、nce 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 to these requirements, a fixture design

44、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 operation to avoid any errors in the dimensio

45、n 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 correct or not. If there is any error

46、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 following places should be inspected generally

47、.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 for screwg) Inserting hole for parth) A

48、ll 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

49、 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 which panel is located by assembly jigs in following operation Fixed place with screws on loose parts (panel fixed with screws). Surface

50、 which have large effect on that part or on the other part the minimum places should be selected as setting surface most appropriate for setting the panel shape.c) Full examination is required for setting the loose parts. Fixed place with screws on loose parts as setting surface. Loose parts (Hood,

51、Door, Fender, etc.) should be provided on C/F by coordinate holes.2.6 Degree of Freedom A body in a space can have following motions or movementsa) Translation motion i. Along X-X Axisii. Along Y-Y Axisiii. Along Z-Z Axisb) Rotary motion iv. Along X-X Axisv. Along Y-Y Axisvi. Along Z-Z AxisThus a fr

52、ee body in space has three translation motion and three rotary motions. These are six degree of freedom of free body in space. The main purpose of this concept is that the workpiece in fixture is fully constrained with the help of locator and clamping device.Fig. 2.6.1: Degree of Freedom of Body in

53、Free SpaceDegrees of freedom are to be constrained in the fixture and checking gauge to serve the purpose of location.2.7 M Star Tractor Clutch Pedal Fig. 2.7.1: Clutch Pedal Figure above shows clutch pedal which is to be welded on welding Fixture. It has five basic parts viz.1. Clutch Pivot Assembl

54、y2. Clutch Pedal3. Foot Pedal4. Pedal Bush M-Star5. Support Gusset Clutch Pedal The Weld length is 306 mm. CHAPTER 3: DESIGN & MANUFACTURINGSuccessful fixture designs begin with a logical and systematic plan. With a complete analysis of the fixtures functional requirements, very few design problems

55、occur. When they do, chances are some design requirements were forgotten or underestimated. The workpiece, processing, tooling, and available machine tools may affect the extent of planning needed. Preliminary analysis may take from a few hours up to several days for more complicated fixture designs

56、.3.1 Five-step problem solving processFixture design is a five-step problem-solving process. The following is a detailed analysis of each step.Step 1: Define Requirements To initiate the fixture-design process, clearly state the problem to be solved or needs to be met. State these requirements as br

57、oadly as possible, but specifically enough to define the scope of the design project. The designer should ask some basic questions: Is the new tooling required for first-time production or to improve existing production? If improving an existing job, is the goal greater accuracy, faster cycle times,

58、 or both? Is the tooling intended for one part or an entire family of parts? The tooling designer must determine how much freedom and input there is on each project. If many choices regarding machine tools, operations, and cutting tools have already been made, the designers role will have a relative

59、ly narrow focus.Step 2: Gather/Analyze Information Collect all relevant data and assemble it for evaluation. The main sources of information are the part print, process sheets, and machine specifications. Make sure that part documents and records are current. For example, verify that the shop print

60、is the current revision, and the processing information is up-to-date. Check with the design department for pending part revisions. An important part of the evaluation process is note taking. Complete, accurate notes allow designers to record important information. With these notes, they should be a

61、ble to fill in all items on the Checklist for Design Considerations. All ideas, thoughts, observations, and any other data about the part or fixture are then available for later reference. It is always better to have too many ideas about a particular design than too few. Four categories of design co

62、nsiderations need to be taken into account at this time: workpiece specifications, operation variables, availability of equipment, and personnel. These categories, while separately covered here, are actually interdependent. Each is an integral part of the evaluation phase and must be thoroughly thou

63、ght out before beginning the fixture design.Workpiece specifications usually are the most important factors and have the largest influence on the fixtures final design. Typically, these considerations include the size and shape of the part, the accuracy required the properties of the part material,

64、the locating and clamping surfaces, and the size of the run. Operation variables include the type of operations required to make the part, number of operations performed, and sequence of operations, inspection requirements, and time restrictions. Availability of equipment required to machine, assemble, and inspect a part often determines whether the fixture is designed for a single part or multiple parts. A process engineer sometimes selects the equipment to machin