Jigs and FixturesJigs and Fixtures

AGENDAAGENDA

IntroductionIntroductionResearch ObjectivesResearch ObjectivesMethodologyMethodologyTaxonomyTaxonomyWelding Jigs & FixturesWelding Jigs & FixturesDesign ConsiderationDesign ConsiderationAdvantages Advantages ConclusionConclusion

INTRODUCTIONINTRODUCTION

DEFINITIONDEFINITIONFIXTURE: FIXTURE: a device used to hold, position a device used to hold, position

and/or align a work piece for an operation or and/or align a work piece for an operation or process. Shipyard uses include assembly, process. Shipyard uses include assembly, subassembly, foundation and part fabrication.subassembly, foundation and part fabrication.

JIG: JIG: a device used to guide a tool; a template.a device used to guide a tool; a template.

Shipyard uses include pin tables and other Shipyard uses include pin tables and other devices for assembly of foundations, devices for assembly of foundations, bulkheads, assemblies and parts. Jigs are often bulkheads, assemblies and parts. Jigs are often incorporated into fixtures.incorporated into fixtures.

Jigs and fixtures are production tools used to Jigs and fixtures are production tools used to accurately manufacture , duplicate and accurately manufacture , duplicate and interchangeable parts interchangeable parts

Jigs and fixtures are specially designed so that Jigs and fixtures are specially designed so that large numbers of components can be machined large numbers of components can be machined or assembled identically, and to ensure or assembled identically, and to ensure interchange ability of components. interchange ability of components.

jigs and fixtures position components jigs and fixtures position components accurately and hold components rigid and accurately and hold components rigid and prevent movement during working in order to prevent movement during working in order to impart greater productivity and part accuracy impart greater productivity and part accuracy

DIFFERENCE BETWEEN JIGS AND DIFFERENCE BETWEEN JIGS AND FIXTURESFIXTURESJIGS: JIGS: Jigs are used to Jigs are used to holdhold the work piece and the work piece and

also to also to guideguide the tool while performing the the tool while performing the operation.operation.

Jigs are mostly used for Jigs are mostly used for drilling operationdrilling operation FIXTURES: FIXTURES: Fixtures are used Fixtures are used only to hold only to hold the the

work piece and it won’t guide the tool.work piece and it won’t guide the tool.

Fixtures are mostly used for Fixtures are mostly used for milling operationmilling operation

ELEMENT OF JIGS AND ELEMENT OF JIGS AND FIXTUREFIXTUREJigs and fixture consist of three elements : Jigs and fixture consist of three elements :

Locating elementLocating element Clamping element Clamping element Tool guiding and setting elementTool guiding and setting element

Contd…Contd… LOCATING ELEMENT :LOCATING ELEMENT : These These positionposition the work piece the work piece

accurately wrt. the tool guiding or setting element in the accurately wrt. the tool guiding or setting element in the fixture fixture

CLAMPING ELEMENT : CLAMPING ELEMENT : These These holdhold the work piece the work piece securely in the located position during operation.securely in the located position during operation.

TOOL GUIDING AND SETTING ELEMENT :TOOL GUIDING AND SETTING ELEMENT : These guiding or setting the tools in the correct position with These guiding or setting the tools in the correct position with

respect to the work piece .respect to the work piece . Drill bushes Drill bushes guide the drill accurately to the work piece.guide the drill accurately to the work piece. Milling fixture Milling fixture use setting for correct positioning of milling use setting for correct positioning of milling

cutters with respect to the work piece.cutters with respect to the work piece.

RESEARCH OBJECTIVESRESEARCH OBJECTIVES

Research ObjectivesResearch Objectives Increased 1st time quality = Lower CostsIncreased 1st time quality = Lower Costs accuracyaccuracy fairnessfairness gap minimizationgap minimization Increased Productivity = Lower CostsIncreased Productivity = Lower Costs less man-hoursless man-hours increase throughputincrease throughput lessen skilled labor requirementlessen skilled labor requirement

METHODOLOGYMETHODOLOGY

MethodologyMethodology

1.1. Survey and ClassifySurvey and Classify

2.2. Preliminary Design New System of Jigs or Preliminary Design New System of Jigs or FixturesFixtures

3.3. Economic AnalysisEconomic Analysis

4.4. Final Design New System of Jigs or FixturesFinal Design New System of Jigs or Fixtures

5.5. Documentation and DisseminationDocumentation and Dissemination

TAXONOMYTAXONOMY

Why Complete a Taxonomy ?Why Complete a Taxonomy ? It involves a relatively exhaustive searchIt involves a relatively exhaustive searchRelationships between different jigs and Relationships between different jigs and

fixtures are highlightedfixtures are highlightedThrough understandingThrough understandingPlan for ImprovementPlan for Improvement

TaxonomyTaxonomy

Jigs & Fixtures

Portable Fixtures

Stationary Fixtures

Guiding Jigs

Restraining Jigs

PORTABLE FIXTURESPORTABLE FIXTURES

Portable Fixtures

Portable Platen

Shaft Fixture w/ Rollers

Portable PlatenPortable Platen

This platform can be This platform can be

relocated by truckrelocated by truck..

It is metal and creates a nonpermanent workspace.

Shaft Support with RollersShaft Support with Rollers

This fixture supportsthe shaft in position andoccasionally rotates toprevent sagging of theshaft.

STATIONARY FIXTURESSTATIONARY FIXTURES

Stationary Fixtures

Burn Table

Cradle

Metal Columns

Mocks

BURN TABLEBURN TABLE

This metal table madeof a grid frameworkallows slag to fallthrough the spaces.

CRADLECRADLE

Large wooden cradles are used to support and maintain the shape of the hull during the erection stage.

METAL COLUMNSMETAL COLUMNS

Round Pipe supports, fixed in height provide adequate room for a crawler to drive under.

Wooden chocks and wedges are used where necessary to level the unit.

Threaded Adjustable Rudder Threaded Adjustable Rudder Mock Mock

Support for the Rudder unit hasbeen constructed to match the unit shape. It is used only once for a single hull design.

This fixture holds the rudderwhile bearings are installedduring assembly of the rudder.

SHELL MOCKSHELL MOCK

This mock resemblesa mold of the inner bottom shell plating.The shape is maintained while stiffeners are welded.

GUIDING JIGSGUIDING JIGS

Guiding Jigs

Pin Jigs

Pipe Jigs

Wireways

PIN JIGSPIN JIGS

Unique shaped panels can beformed over the Pin Jigs.

Threaded pipes are positioned in a grid and pins are used to adjust their heights.

PIPE SUPPORTSPIPE SUPPORTS

Pipe supports are used to holdirregular shaped units in position while being outfitted.

They may also be used during unit erection.

WIREWAYSWIREWAYS

These trees help to guide ductwork or gas lines so that access can be maintained during construction.

RESTRAINING JIGSRESTRAINING JIGS

Restraining Jigs

Cable and Stay

Chains

Clamps

Pipe Supports

CABLE & STAYCABLE & STAY

Cable and stays are used to maintain vertical alignment prior to welding.

This cable and stay is adjustable via the use of a ratcheting come along.

GRIPPING CHAINGRIPPING CHAIN

Chains are used in the Pipe shop to restrain or fasten pipes to the work table.

CLAMPSCLAMPS

Clamps are used to hold the work piece in fixed position for the intended work to be performed.

ADJUSTABLE PIPE ADJUSTABLE PIPE SUPPORTSSUPPORTS

Pipe support on wheels help make the work piece movement easier than use of a crane and hold the work piece in position.

DOWN SELECT PROCESSDOWN SELECT PROCESS

Translate Discussions to Translate Discussions to Customer RequirementsCustomer Requirements

Establish Production Establish Production NeedsNeeds

Translate to RequiredTranslate to RequiredAttributesAttributes

ParticipantsParticipants• • PlanningPlanning

• • Mold LoftMold Loft

• • Pipe ShopPipe Shop

• • Machine ShopMachine Shop

• • Unit AssemblyUnit Assembly

• • Accuracy Accuracy ControlControl

• • Ship ErectionShip Erection

• • Package UnitsPackage Units

• • MaintenanceMaintenance

PIN JIG CONCERNSPIN JIG CONCERNS

Rust and CorrosionDesire Manual AdjustmentMust Manage Horizontal ComponentJig Must Not Distort Work Piece underLoad

WELDING JIGS & FIXTURESWELDING JIGS & FIXTURES

WHY ???WHY ???To minimize distortion caused by heat of To minimize distortion caused by heat of

welding.welding.To permit welding in a more convenient To permit welding in a more convenient

position.position.To increase welding efficiency and To increase welding efficiency and

productivity.productivity. To minimize fit-up problems. To minimize fit-up problems.

WELDING JIGSWELDING JIGSWelding jigs are specialized devices which Welding jigs are specialized devices which

enable the components being welded to be enable the components being welded to be easily and rapidly set up and held.easily and rapidly set up and held.

QUALITY REQUIRED:QUALITY REQUIRED: Rigid and strong since it has to stand Rigid and strong since it has to stand

contractional stresses without deforming.contractional stresses without deforming. Simple to operate, yet it must be accurate.Simple to operate, yet it must be accurate. Designed such that it is not possible to put the Designed such that it is not possible to put the

work in it the wrong way. work in it the wrong way. Faced with wear-resistant material to stand Faced with wear-resistant material to stand

continual wear.continual wear.

WELDING FIXTURESWELDING FIXTURESA welding fixture serves the same purpose as a A welding fixture serves the same purpose as a

welding jig; but, in addition, it permits the welding jig; but, in addition, it permits the changing of the position of the work during the changing of the position of the work during the actual welding, so as to place the welds in a actual welding, so as to place the welds in a plane convenient to the operator at all timesplane convenient to the operator at all times

This increases welding speed.This increases welding speed.Fixture CharacteristicsFixture Characteristics

Supporting Supporting Clamping Clamping Grounding and Grounding and Imparting movement (usually referred to as Imparting movement (usually referred to as

travel or traveling) to name but a fewtravel or traveling) to name but a few

Welding Fixture Classification Welding Fixture Classification Those that act on the work being welded: Those that act on the work being welded: clampclamp

the parts together while simultaneously the parts together while simultaneously supportingsupporting them, the objective being to effect a weld in the them, the objective being to effect a weld in the flat flat positionposition. hold the work . hold the work stationarystationary in which case the in which case the welding equipment moves or is traveled over it or may welding equipment moves or is traveled over it or may be mechanized and move the work under the stationary be mechanized and move the work under the stationary welding equipment. Includes welding equipment. Includes rotating positioners, power rotating positioners, power turning rolls, lathes, and mill type setups turning rolls, lathes, and mill type setups etc.etc.

Those that act on the welding equipment:Those that act on the welding equipment:

provide provide only stationary support only stationary support or both support and or both support and travel to the welding equipment. include the travel to the welding equipment. include the beam with beam with carriagecarriage, the , the self-propelled tractorself-propelled tractor, the , the spud welding unit spud welding unit and a variety of and a variety of boom type welding manipulatorsboom type welding manipulators..

Fixture SelectionFixture Selection In selecting fixtures for mechanized welding, In selecting fixtures for mechanized welding,

the engineer must evaluate considerations the engineer must evaluate considerations such assuch as

Production volumeProduction volume Joint geometryJoint geometry Movability of the welding head.Movability of the welding head.

Design of Good Welding Jigs and Design of Good Welding Jigs and FixturesFixtures

The fixture should be The fixture should be strong and light strong and light but but rigidrigid enough to enough to ensure ensure accurate alignmentaccurate alignment..

Whenever possible, a fixture should be Whenever possible, a fixture should be positionerspositioners, enabling all , enabling all welds to be brought to a convenient welds to be brought to a convenient welding positionwelding position..

The fixture should permit quick and easy positioning (by one The fixture should permit quick and easy positioning (by one hand, if possible). Thus, hand, if possible). Thus, balancingbalancing of the fixture may be of the fixture may be necessary.necessary.

Design should be as Design should be as simple and inexpensive simple and inexpensive as possible; as possible; accuracy and elaboration should be no greater than required. accuracy and elaboration should be no greater than required. Only Only essential dimensions essential dimensions should be controlled in a fixture. should be controlled in a fixture. AppearanceAppearance should be disregarded. should be disregarded.

The use of The use of light alloys light alloys for moving parts reduces weight. Air or for moving parts reduces weight. Air or electric motors should be used for electric motors should be used for revolvingrevolving, and air or , and air or hydraulic rams for hydraulic rams for tiltingtilting the fixture assembly. the fixture assembly.

CONTD…CONTD… should be should be built built around the work and should around the work and should locatelocate and and

clamp components in position so that assembly, clamp components in position so that assembly, tacking, and welding may be carried out in one fixture. tacking, and welding may be carried out in one fixture.

should permit freedom of movement in one plane to should permit freedom of movement in one plane to avoid residual stress in the completed weldment. avoid residual stress in the completed weldment. Design should permit Design should permit heat dissipation heat dissipation to to release, release, rather than bindrather than bind, the assembly being welded., the assembly being welded.

JointsJoints must be readily must be readily accessibleaccessible for welding. By slots for welding. By slots or other means, the fixture should readily present or other means, the fixture should readily present seams on the reverse side of the objectseams on the reverse side of the object

FixturesFixtures should be should be kept cool kept cool enough to handle air, enough to handle air, water, fins or insulated handles can be used.water, fins or insulated handles can be used.

Parts should be prebent in the fixture, if necessary, for Parts should be prebent in the fixture, if necessary, for final accuracy.final accuracy.

CONTD…CONTD… Clamps must Clamps must operateoperate quicklyquickly. Screws and moving parts . Screws and moving parts

should be protected against should be protected against weld spatterweld spatter.. Either integral or separate Either integral or separate copper backing bars copper backing bars should should

be used in cases of poor fit or for light plate.be used in cases of poor fit or for light plate. Use of Use of nuts and boltsnuts and bolts, , wrencheswrenches, , C-clampsC-clamps, , wedgeswedges and and

hammers and hand screws hammers and hand screws should be should be minimumminimum.. Methods of Methods of grounding the work grounding the work are important are important

considerations in fixture design, since they affect arc considerations in fixture design, since they affect arc action, quality of weld, and speed at which welds are action, quality of weld, and speed at which welds are produced. The ground must make good contact with the produced. The ground must make good contact with the work through the medium of copper, copper graphite work through the medium of copper, copper graphite brushes, sliding shoes etc.brushes, sliding shoes etc.

CONTD…CONTD… A good fixture design avoids the A good fixture design avoids the problem of arc blow problem of arc blow by by

taking following measures:taking following measures:

(a) (a) All All steelsteel other than being welded should be kept .at other than being welded should be kept .at least least 25 mm from the arc25 mm from the arc..(b) (b) Clapping fingers Clapping fingers may be made from a may be made from a non-magneticnon-magnetic material.material.(c) (c) The The ground connection ground connection should be made directly with should be made directly with the work and not with the backing bar. The point of the work and not with the backing bar. The point of connection should be as far from the arc as possible. connection should be as far from the arc as possible. The ground can be split to offset arc blow.The ground can be split to offset arc blow.(d) (d) When possible, the fixture should be built from When possible, the fixture should be built from low low carbon steelcarbon steel, large masses of steel should be normali-, large masses of steel should be normali-zed to minimize residual magnetism.zed to minimize residual magnetism.(e) (e) When When horn type fixtures horn type fixtures are used, the welding should are used, the welding should be toward the closed end.be toward the closed end.

CONTD…CONTD… The fixture should be designed for The fixture should be designed for ease of ease of

accessibility to the welding headaccessibility to the welding head when when procedure adjustments and servicing are procedure adjustments and servicing are necessary. Accessibility is also necessary in necessary. Accessibility is also necessary in the positioning of welding controls.the positioning of welding controls.

The design of fixture should be such that the The design of fixture should be such that the weldment weldment can be can be easily and quickly removed easily and quickly removed from the fixture.from the fixture.

TYPES OF JIGS AND TYPES OF JIGS AND FIXTURESFIXTURES A A C-clampC-clamp is good enough for most welding jobs. It can is good enough for most welding jobs. It can

be quickly and cheaply made in the shop.be quickly and cheaply made in the shop. A simple, but effective A simple, but effective ‘V’ rest ‘V’ rest for supporting short bars for supporting short bars

or pieces of pipe for tacking or welding on the benchor pieces of pipe for tacking or welding on the bench Rotating fixtures Rotating fixtures for making for making circumferential welds circumferential welds or for or for

building up rollers, rings, valves, drilling bits and axles building up rollers, rings, valves, drilling bits and axles are very valuable, as they speed up the job and make are very valuable, as they speed up the job and make for neater welds with less waste.for neater welds with less waste.

A few A few clampsclamps for sheet or plate joints for sheet or plate joints To To turn over very large pieces turn over very large pieces of work for positioning in of work for positioning in

welding, it is often useful to build welding, it is often useful to build adaptersadapters which bolt which bolt or clamp to the work and contain the trunnions. or clamp to the work and contain the trunnions.

A A roller bed roller bed for welding pressure vessels, containers for welding pressure vessels, containers and other cylindrical objects. and other cylindrical objects.

DESIGN CONSIDERATIONDESIGN CONSIDERATION

DESIGN PRINCIPLEDESIGN PRINCIPLE

The 3-2-1 Principle of Jig Fixture DesignThe 3-2-1 Principle of Jig Fixture Design For a fixture designer, the major portion of design time For a fixture designer, the major portion of design time

is spent deciding how to locate the work piece in the is spent deciding how to locate the work piece in the fixture. fixture.

You know that any free body has a total of twelve You know that any free body has a total of twelve degrees of freedom as below:degrees of freedom as below:

6 translational degrees of freedom: +X, -X, +Y, -Y, +Z, -Z6 translational degrees of freedom: +X, -X, +Y, -Y, +Z, -Z 6 rotational motion(3 clockwise & 3 anticlockwise) 6 rotational motion(3 clockwise & 3 anticlockwise)

about respective axes.about respective axes. It must required to fix all the 12 degrees of freedom It must required to fix all the 12 degrees of freedom

except the three transitional degrees of freedom (-X, -Y except the three transitional degrees of freedom (-X, -Y and -Z) in order to locate the work piece in the fixture. and -Z) in order to locate the work piece in the fixture. So, 9 degrees of freedom of the work piece need to be So, 9 degrees of freedom of the work piece need to be fixed.fixed.

But, how?But, how? Rest the work piece on three non-collinear points of the Rest the work piece on three non-collinear points of the

bottom surface (XY), and you will be able to fix the +Z, bottom surface (XY), and you will be able to fix the +Z, CROT-X, ACROT-X, CROT-Y and ACROT-Y degrees of CROT-X, ACROT-X, CROT-Y and ACROT-Y degrees of freedom.freedom.

Now, rest the work piece at two points of side surface Now, rest the work piece at two points of side surface (XZ), and you will be able to fix the +Y and ACROT-Z (XZ), and you will be able to fix the +Y and ACROT-Z degrees of freedom.degrees of freedom.

Now, rest the work piece at one point of the adjacent Now, rest the work piece at one point of the adjacent surface (YZ), and you will be able to fix the +X and surface (YZ), and you will be able to fix the +X and CROT-Z degrees of freedom.CROT-Z degrees of freedom.

So, you can successfully fixate 9 required degrees of So, you can successfully fixate 9 required degrees of freedom by using the 3-2-1 principle of fixture design.freedom by using the 3-2-1 principle of fixture design.

DESIGN CONSIDERATION FOR JIGS AND DESIGN CONSIDERATION FOR JIGS AND FIXTUREFIXTURE

Design consideration for jigs and fixture Design consideration for jigs and fixture depends upon following three factors.depends upon following three factors.

Tooling costTooling cost Tooling detail andTooling detail and Tooling operationTooling operationThese design consideration are independent of These design consideration are independent of

each other.each other.

TOOLING COSTSTOOLING COSTSThe total cost of any jig or fixture is frequently the The total cost of any jig or fixture is frequently the

major area of consideration many work holder major area of consideration many work holder designs.designs.

Permanent fixtures have distinct advantages in the Permanent fixtures have distinct advantages in the production of high-volume and high-precision parts.production of high-volume and high-precision parts.

It reduce machine setup time, machine cycle time It reduce machine setup time, machine cycle time and the level of operator skill required to produce and the level of operator skill required to produce satisfactory quality outputsatisfactory quality output

General-purpose work holders are more expensive General-purpose work holders are more expensive than temporary tools in most cases, but their utility than temporary tools in most cases, but their utility and flexibility often allow these work holders to be and flexibility often allow these work holders to be regarded as a capital cost to be amortized over a regarded as a capital cost to be amortized over a period of time without regard to actual usage.period of time without regard to actual usage.

CONTD…CONTD…Modular fixturing is typically a capital investment to Modular fixturing is typically a capital investment to

be amortized over a set lifespan, with an average cost be amortized over a set lifespan, with an average cost assigned to usage for each anticipated job.assigned to usage for each anticipated job.

Modular fixturing is typically a capital investment to Modular fixturing is typically a capital investment to be amortized over a set lifespan, with an average cost be amortized over a set lifespan, with an average cost assigned to usage for each anticipated job.assigned to usage for each anticipated job.

General-purpose tools are reused extensively, but General-purpose tools are reused extensively, but still incur some costs for maintenance and storage.still incur some costs for maintenance and storage.

Modular fixtures will be disassembled, and the Modular fixtures will be disassembled, and the components maintained, stored, and reused components maintained, stored, and reused frequently.frequently.

TOOLING DETAILSTOOLING DETAILSIt is the overall construction characteristics and It is the overall construction characteristics and

special features incorporated into the jig or fixture.special features incorporated into the jig or fixture.depends upon depends upon the type and complexity of the the type and complexity of the

individual tooling elements, the extent of secondary individual tooling elements, the extent of secondary machining and finishing operations on the tool, the machining and finishing operations on the tool, the tool-design process, and the amount of detail in the tool-design process, and the amount of detail in the work holder drawings. Permanent work holders are work holder drawings. Permanent work holders are designed and built to last longer than temporary designed and built to last longer than temporary work holders.work holders.

Permanent work holders contain different Permanent work holders contain different commercial tooling components based on expected commercial tooling components based on expected tool usage.tool usage.

Contd….Contd…. Permanent jigs intended for a high-volume drilling Permanent jigs intended for a high-volume drilling

operation.operation. The secondary operations normally associated The secondary operations normally associated

with tooling include hardening, grinding, and with tooling include hardening, grinding, and similar operations to finish the work holdersimilar operations to finish the work holder

permanent work holders are hardened and permanent work holders are hardened and ground to assure their accuracy over a long ground to assure their accuracy over a long production run.production run.

TOOLING OPERATIONS TOOLING OPERATIONS The performance of any work holder is critical The performance of any work holder is critical

to the complete usefulness of the tool.to the complete usefulness of the tool.he performance of a permanent, modular, or he performance of a permanent, modular, or

general-purpose work holder is considered, general-purpose work holder is considered, several factors about the machine tools must several factors about the machine tools must be known.be known.

These factors include the type, size, and These factors include the type, size, and number of machine tools needed for the number of machine tools needed for the intended operations.intended operations.

Figure 1-6 shows a typical temporary work Figure 1-6 shows a typical temporary work holder for drilling and milling operations on the holder for drilling and milling operations on the same partsame part

ADVANTAGEADVANTAGE

ADVANTAGES OF JIGS & ADVANTAGES OF JIGS & FIXTURESFIXTUREScost savings cost savings precise and accurate precise and accurate increase productivity increase productivity Interchangeability Interchangeability less skill requirement less skill requirement Time savingTime savingAlignment of a part or work piece.Alignment of a part or work piece.Securing the part or work piece. Securing the part or work piece. Duplication of a process. Duplication of a process.

Contd…Contd… Maintain or improve part quality. Maintain or improve part quality. Reduce cost of production. Reduce cost of production.

Improve overall safety to the part, the operator, Improve overall safety to the part, the operator, and the machine. and the machine.

CONCLUSIONCONCLUSION

CONCLUSIONCONCLUSIONBoth the jigs and the fixtures are used to Both the jigs and the fixtures are used to

reduce the nonproductive time of any mass reduce the nonproductive time of any mass production process.production process.

The 3-2-1 method is the fundamental principle The 3-2-1 method is the fundamental principle for all types of fixture design.for all types of fixture design.

There are varieties of jigs & fixtures are used in There are varieties of jigs & fixtures are used in shipyards for different purposesshipyards for different purposes

It should be standardized at part and assembly It should be standardized at part and assembly level to reduce tooling and manufacturing level to reduce tooling and manufacturing costs.costs.