DESIGN OF SUPPORT BRACKET TACK WELDING FIXTURE

ABSTRACT: Welding Fixture:

A Welding fixture is a device for ensuring that a hole to be drilled, tapped or reamed in a work piece will be machined in a proper co-ordinate or PCD. Thus instead of laying out the position of a hole on each work piece with the aid of a square, straight edge, scriber and centre punch, the operation uses a welding fixture to guide the drill into the proper place. Basically it consists of a clamping device to hold the part in the position under hardened steel bushings through which the drill passes during operation. The drill is guided through bush. If the work piece is of simple construction, the welding fixture may be clamped on the work piece. In most cases however the work piece is held by the welding fixture and the welding fixture is arranged so that the work piece can be quickly inserted and quickly removed after machining operation is performed. Welding is usually used for mass production jobs or precision jobs.

The aim of the project is to design a welding fixture for drilling machine to perform drilling operation accurately for yoke. While making holes on the yoke lot of problems encountered such as inaccuracy, misalignment etc. These problems cause rejection of finished jobs productivity losses more time consumption etc.

In this project an attempt has made to design a drill welding fixture and use the same during the holes on work pieces, which eliminates the problems faced during conventional drilling. This procedure helps in increasing the production rate, accuracy, perfect alignment, reducing operators fatigue etc. In this procedure a drill welding fixture will guide the drill bit to the correct position on the workpiece. With implementation of SOLID EDGE, the modeling of each component of a welding fixture is designed.

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Department of Mechanical engineering P.E.S.C.E

DESIGN OF SUPPORT BRACKET TACK WELDING FIXTURE

THE PROJECT WAS CARRIED OUT IN 4 PHASES

DESIGN OF FIXTUREThe fixture design was carried out in a systematic manner, with the inputs given by AAL. Based on the date given by AAL, the design was conceptualized using CAD. Here an interactive process was followed to come up with the suitable design according to the specification provided by AAL.

CONVERTING OF 2-D MODELBased upon the findings obtained in the design process, we have converted the 2D model to 3D model using the modelling software SOLID EDGE V19. This helps in the fabrication purpose of the design.

SELECTION OF MATERIALSMaterials selection is a step in the process of designing any physical object. In the context of product design, the main goal of material selection is to minimize cost while meeting product performance goals. Systematic selection of the best material for a given application begins with properties and cost of candidate materials. For example, a thermal blanket must have poor thermal conductivity in order to minimize heat transfer for a given temperature difference or a load bearing member should have resistance to deformation. The materials which are selected for this setup are Mild steel, EN8, EN24, EN353

COST ESTIMATIONIn this stage the cost of the design is to be optimized. Based on the results of the analysis and modification, a suitable material was chosen which would meet the industrial standards

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Department of Mechanical engineering P.E.S.C.E

DESIGN OF SUPPORT BRACKET TACK WELDING FIXTURE

AXLE

An axle is a central shaft for a rotating wheel or gear. Axles are an integral component of most practical wheeled vehicles. In a live-axle suspension system, the axles serve to transmit driving torque to the wheel, as well as to maintain the position of the wheels relative to each other and to the vehicle body. The axles in this system must also bear the weight of the vehi-cle plus any cargo. A non-driving axle, such as the front beam axle in heavy duty trucks and some 2-wheel drive light trucks and vans, will have no shaft, and serves only as a suspension and steering component. 

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Department of Mechanical engineering P.E.S.C.E

DESIGN OF SUPPORT BRACKET TACK WELDING FIXTURE

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Department of Mechanical engineering P.E.S.C.E

SUPPORTBRACKET

DESIGN OF SUPPORT BRACKET TACK WELDING FIXTURE

PRINCIPLES OF FIXTURE DESIGN

1. LOCATION Ensure that work is given desired constraints. Place the locators so that swarf will not cause misalignment. Make the location points adjustable if a rough casting or a for-

ging is being formed. Introduce fool proofing devices such as fouling pins, projections

etc. to prevent incorrect positioning of the work piece. Make all location points visible to the operator from his working

position. Make location progressive.

2. CLAMPING Position the clamps to give best resistance to cutting forces without

causing deformation of the work piece. If possible make the clamps integral with fixture body. Make all clamping and location methods easy and natural to perform.

3. CLEAFRANCE Allow sample clearance to allow for variations of work piece size and

operator’s hand.Ensure that there is sample swarf clearance and clearance to enable the work piece to be removed after machining, when burns will be present.

4. STABILITY AND RIGIDITY Make the fixture as rigid as required for operation. Provide means of positioning and bolting the equipment to machine

table. Provide four feet so that uneven seating will be obvious and ensure

that the forces on the equipment act within area enclosed by a line joining points.

5. HANDLING Make the component as light as possible and easy to handle, and en-

sures that no sharp corners are present and provide lifting points, if it is heavy.

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Department of Mechanical engineering P.E.S.C.E

DESIGN OF SUPPORT BRACKET TACK WELDING FIXTURE

6. GENERAL Keep the design simple in order to minimize the cost, and avoid break

down caused by over contraction. Utilize the standard and proprietary parts as much as possible.

7. PROVISION FOR COOLANT The jig or fixture most have adequate arrangement for the supply of

coolant to the cutting edge of the tool, so that the tool is cooled and at the same time the swarf of the chips produced are washed away so that, operator does not waste his time in adjusting the coolants flow and cleaning the chips.

ELIMINATE FINISHING OPERATIONS Finishing operations should never be performed for cosmetic purposes. Making a fixture look better often can double its cost.

KEEP TOLERANCES AS LIBERAL AS POSSIBLE The most cost effective tooling tolerance for a locator is approximately 30% to 50% of the work piece’s tolerance. Tighter tolerances normally add extra cost to the tooling with little benefit to the process. Where necessary ,tighter tolerances can be used, but tighter tolerances do not necessarily result in a better fixture , only a more expensive one.

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Department of Mechanical engineering P.E.S.C.E

DESIGN OF SUPPORT BRACKET TACK WELDING FIXTURE

STEPS OF FIXTURE DESIGN

Step 1: DEFINE REQUIREMETSTo initiate the fixture design process, clearly state the problem to be solved or needs to be met. State these requirements as broadly 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 productions? If improving an existing job, is the goal greater accuracy ,faster cycle times ,or both? Is the tooling intended for one part or an entire family of parts?

Step 2: GATHER INFORMATION Collect all relevant data and resemble 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 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 able 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.

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Department of Mechanical engineering P.E.S.C.E

DESIGN OF SUPPORT BRACKET TACK WELDING FIXTURE

Step 3: DEVELOP OPTIONS This phase of the fixture-design process requires the most creativity. A typical work piece can be located and the clamped several different ways. The natural tendency is to think of one solution, then develop and refine it while blocking out other, perhaps better solutions. A designer should brainstorm for several good tooling alternatives ,not just choose one path right away. During this phase ,the designer’s goal should be adding options ,not discarding them. In the interest of economy, alternative designs should be developed only far enough to make sure they are feasible and to do a cost estimate.

Step 4: CHOOSE THE BEST OPTIONThe fourth phase of the tool-design process is a cost/benefit analysis of different tooling options. Some benefits, such as greater operator comfort and safety, are difficulty to express in dollars but are still important. Other factors, such as tooling durability, are difficult to estimate.To evaluate the cost of any work holding alternative, first estimate the initial cost of the fixture .To make this estimate, draw an accurate sketch of the fixture. Number and list each part and component of the fixture. Number and list each part and component of the fixture individually.First list the cost of each component, them itemize the operations needed to mount, machine and assemble that component. Once those steps are listed, estimate the time required for each operation for each component, and then multiply by the labour rate.

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Department of Mechanical engineering P.E.S.C.E

DESIGN OF SUPPORT BRACKET TACK WELDING FIXTURE

WELDING USING FIXTURE:

• Initially the fixture is located in its position on the housing.• The next operation involves the proper placement of the TOP PAD BRACKET fol-

lowed by its clamping.• Once the clamping is done, tack welding is done.• After tack welding fixture is unclamped and the bracket is fully welded.

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Department of Mechanical engineering P.E.S.C.E

DESIGN OF SUPPORT BRACKET TACK WELDING FIXTURE

SELECTION OF MATERIALS

SELECTION OF MATERIAL BASED ON THE JOB AND HEAT TREATMENT

Material selection is a step in the process of designing any physical object. In the context of product design, the main goal of material selection is to minimize cost while meeting product performance goals. Systematic selection of the best material for a given application begins with properties and costs of candidate materials. For example, a thermal blanket must have poor thermal conductivity in order to minimize heat transfer for a given temperature difference or a load bearing member should have resistance to deformation. The materials which are selected for this setup are Mild steel, ENS, EN24, EN353.

MILD STEEL

It is the most common form of steel often used when large amounts of steel are needed. Mild steel is a carbon steel typically with a maximum of 0.25% Carbon and 0.4%-0.7% manganese, 0.1%-0.5% Silicon and some traces of other elements such as phosphorous, it may also contain led or sulphur. Mild steel have good strength and low to medium Carbon content and can be bent, worked or can be welded into an endless variety of shapes for uses from vehicles to building materials. Though mild steel is a strong as most steels, and corrodes quickly in moist environments, but is cheap and readily available and hence is used the most worldwide.

Different types of steel have different properties that make them useful for specific things. Steel’s property comes from the way that it was made. Steel with more carbon will be harder yet more brittle. Sometimes,

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Department of Mechanical engineering P.E.S.C.E

DESIGN OF SUPPORT BRACKET TACK WELDING FIXTURE

Stress strain diagram for mild steel

Graph of stress as a function of strain can be constructed from data obtained in any mechani-cal test where load is applied to a material, and continuous measurement of stress and strain are made simultaneously. It is constructed for compression, tension and torsion tests.

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Department of Mechanical engineering P.E.S.C.E

DESIGN OF SUPPORT BRACKET TACK WELDING FIXTURE

EN8: EN8 is an unalloyed carbon steel with good tensile strength. The material also requires heat treatment for hardening of the component to avoid failure during operation.Tensile properties may vary but are usually between 500-800 N/mm^2

Chemical Composition Typical analysis in %

C Si Mn S P

0.40% 0.25% 0.80% 0.015% 0.015%

Application : Components of small cross section, requiring low tensile strength, as well as heavy forging in the normalized condition for automotive and general engineering such as axles, clutch shafts, presses and punches parts, piston rods and gear rods.

Heat treatment: The material also requires heat treatment for hardening of the component to avoid failure during operation. The heat treatment carried out for EN8 steel is as depicted below.

Hardening temperature Quenching medium Tempering tempera-ture

750-900 oil 150-200

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Department of Mechanical engineering P.E.S.C.E

DESIGN OF SUPPORT BRACKET TACK WELDING FIXTURE

EN24It is a high quality, high tensile, alloy steel. Usually supplied readily machine able. It combines high tensile strength, shock resistance, good ductility and resistance to wear. EN24 is available from stock in round bar, flat bar and plate. EN24 comes treated in the condition to 850/1000 N/mm^2, EN24 is a popular grade of through hardening alloy steel due to its machinability. EN24 is used in components such as gears, shafts, studs and bolts. EN24 can be further surface-hardened to create components with enhanced wear resistance by induction or nitrating processing.

In addition to the above, EN24 is capable of retaining good impact values at low temperatures, hence it is frequently specified for harsh offshore applications such as hydraulic bolt tensioners and ship borne mechanical handling equipment. It is therefore recommended that larger sizes are applied in the annealed (softened) condition and that quenching and tempering is carried after initial stock removal. This should achieve better mechanical properties towards the core.

C Si Mn Ni Cr Mo

0.40% 0.30% 0.60% 1.50% 1.20% 0.25%

EN353 Steel En353 is a case hardened steel which is carburized with carbon percentage of up to 0.2%. It is the most widely used industrial application which produces a hard ware resistance surface layer on low carbon and low alloy steels. The chemical composition of the EN353 is listed below

C Si Mn Cr Mo Ni

0.10-0.20

0.35 0.50-1.00 0.75-1.25 0.80-0.15 1.00-1.50

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Department of Mechanical engineering P.E.S.C.E

DESIGN OF SUPPORT BRACKET TACK WELDING FIXTURE

2D DRAWING

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Department of Mechanical engineering P.E.S.C.E

DESIGN OF SUPPORT BRACKET TACK WELDING FIXTURE

OBJECTIVE OF THE PROJECT:

1) To Save the Machining hour rate of Support pad by providing a new welding fixture

2) To Accommodate the job better and increase the production on Welding Machine

3) Higher utilization of available resources

SCOPE OF THE PROJECT:

The project plays very important role in an industry for increasing the productivity by decreasing the set up time by decreasing the machine hour rate.

METHODALOGY (PROCEDURE):

1) Product lay out drawing2) Conceptual drawing to make Fixture design

How Fixture will work?

1) Fixture will locate in Brake Flange holes on housing & it will rest on Housing Box section

2) Fixture will be clamped to the Flange3) Support Pad will be located in the Fixture.4) Tack welds the Support pad to the housing.5) De clamp the fixture6) Inspect the component ( Tack welded Housing)7) Repeat the same on other side.

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Department of Mechanical engineering P.E.S.C.E

DESIGN OF SUPPORT BRACKET TACK WELDING FIXTURE

ADVANTAGE:

It eliminate the marking out measuring and other setting method before machining

It enable identical parts which are interchangeable, this facilitates the assembly operation

It increases the machining accuracy because the work piece is automatically located and the tool guided without making manual adjustment .

APPLICATION:

Support Bracket will be welded on the housing & machining will be done (Milling, drilling & Tapping)Plummer Block will be mounted on this bracket &it will support to Brake cam shaft to be aligned in one axis.

CONCLUSION:

The newly designed welding fixture helps to simplify the operation and reduces the risk of the operator during loading and unloading. Therefore even unskilled workers can operate the machine to produce accurate welding on the work piece. The replacement of skilled workers also proves cost effective. It welds the housing with accurate alignment and hence loss of rejections will be minimized. It also protects the work piece surface free from scratches, damages etc.

This fixture helped in achieving more positional accuracy and precision in welding the bracket.

Time taken to carry out the welding process using the welding fixture was reduced while compared to conventional method.

The fixture allows objective of using a fixture to reduce the cycle time and production cost is achieved.

ADVANTAGES OF NEWLY DESIGNED WELDING FIXTURE FOR TOP PAD BRACKET:

The advantages of the welding fixture are as follows: This kind of welding fixture uses the simple clamping mechanism.

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Department of Mechanical engineering P.E.S.C.E

DESIGN OF SUPPORT BRACKET TACK WELDING FIXTURE

EASE OF OPERATION: The welding fixture for mounting TOP PAD bracket provides a flexible design, which results in skill reduction.

COST REDUCTION: Higher production, reduction in scrap and saving in labour costResults in substantial reduction in cost of Axle housing with TOP PAD Produced using fixtures.

This design provides the great flexibility of welding TOP PAD bracket without marking, whereas in conventional method, welding is preceded by marking the component.

REPEATABILITY: It is the variation in the measurement taken by a single person or instrument on the same item and under the same conditions.

The design saves a lot of time, avoiding the marking process.

The welding fixture also incorporates fool-proof mechanism, which pre-vents the miss alignment time of the component.

FIT TO USE: The newly designed fixture is ready to use without much al-terations.

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Department of Mechanical engineering P.E.S.C.E

DESIGN OF SUPPORT BRACKET TACK WELDING FIXTURE

Student's Signature 1.

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Mr.Rudresh Addamani Asst professor Department Of Mechanical Engineering PESCE, Mandya

Signature of Guide

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Department of Mechanical engineering P.E.S.C.E