mfg tooling -07 jig design

8/3/2019 Mfg Tooling -07 Jig Design

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Manufacturing Tooling5. Jig Design

Nageswara RaoPosinasetti

February 12, 2008 Nageswara Rao Posinasetti 2

Fixture

A fixture is a means through which apart is securely fastened to themachine tool table to accurately locate,support and hold the part during themachining operation.


Jig

A jig is a special class of fixture, whichin addition to provide all the functions

as above, also guides the cutting toolduring machining.

This is generally used for theoperations such as drilling, boring,reaming, tapping, counter boring, etc.


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Typical jig used for boring operation



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Drill Jigs

Provide methods forCorrectly locate the workpiece with

respect to the tool

Securely clamp and rigidly support theworkpiece during the operation

Guide the tool

Position and/or fasten the jig on amachine


Drill Jigs

Advantages

Minimize tool breakage

Minimize the possibility of human error

Permit the use of less skilled labor

Reduce manufacturing time

Eliminate retooling for repeat orders


Machine Considerations

Horsepower

Size limitations

Weight limitations

Cutting Tools

Special Machinery


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Process Considerations

Type of Operations (drilling,reaming,other)

Number of Operations

Similar vs. different

Sequential vs. simultaneous

Sequence

Inspection Requirements


Jig Bushes

To position and guide the cutting toolfor cutting.

Materials

Hardened steel

Carbide

Bronze

Stainless steel


Headless Bush

Most popular andleast expensive

Light axial load isexpected


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Clearance between Bush and Part


Headed Drill Bush

Jig plate can be thinner



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Slip Renewable Bush

Used for multipleoperations such asDrilling followed by

reaming


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Drill bushing position for angular drill entry


Fig. 5.43 Drilling irregular work surfaces


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Jig Components

Locators

Clamps

Jig plate with bushes

Jig body

Other elements as required

Supports

Jig feet


Types of Jigs

Template jigs

Plate jigs

Universal jigs

Leaf jigs

Channel and tumble jigs

Indexing jigs

Miscellaneous jigs


Template jigs

No clamping arrangement

Plates with bushing to guide the tool

Directly placed on the part

Simple

Least expensive


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Nesting Template Drill Jigs



Template jigs

Disadvantages

Not as foolproof as other types

Orientation of the hole pattern toworkpiece datums may not be as accurateas other types

They are usually not practical whenlocating datums are dimensioned


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Plate jigs

A template jig with workpiece clampingsystem


Plate Jig


Plate Drill Jig


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Fig. 5-7 Plate jigs


Fig. 5-7 Plate jigs


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Fig. 5-7 Plate jigs




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Fig 5-8 Angle plate jigs


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Fig 5-8 Angle plate jigs




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Universal jigs

Also called as Pump jigs

Universal that can be used for anygiven part by adding the necessarylocators and bushes



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Leaf jigs

Small

Hinged leaf with bushes which alsoapplies the clamping force



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Channel and tumble jigs

For drilling in more than one surface

Complicated and expensive



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The example illustrated was designed to drill 4holes equi-spaced around the tapered hub of ahand-wheel at right angles to the hub diameter.



Indexing jigs

To drill holes in a pattern

Indexing arrangement


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Miscellaneous jigs




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Drill Jig with R H Component


Drill Jig with L H Component


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Drill Jig with R H Component unassembled


Drill Jig with R H and L H Componentssimultaneously



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Pot Drill Jig


Pot Drill Jig



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Jig Design Guidelines

Drill Jigs should be of lightconstruction, consistent with rigidity tofacilitate handling, especially when jigshave to be turned over so that holescan be drilled from more than one side.

All unnecessary metal should be coredout of the jig body.



A jig which is not bolted to the machine tableshould be provided with feet, preferably four,opposite all surfaces containing guidebushings, so that it will 'rock' if not standingsquare on the table and so warn theoperator.

Clearance holes or burr slots should beprovided in the jig to allow for the burrformed when the drill breaks through thecomponent and for swarf clearance,particularly from locating faces.



Make all component clamping devices asquick acting as possible.

Design the jig fool-proof by the use of foulpins and similar devices, that is arrange it sothat the component, tools or bushes cannotbe inserted except in the correct way.

Make some locating points adjustable whenthe component is a rough casting and maybe out of alignment.


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Locate clamps so that they will be in the bestposition to resist the pressure of the cuttingtool when at work.

If possible, make all clamps integral parts ofthe jig and avoid the use of loose parts.

Avoid complicated clamping and locatingarrangements which are liable to wear orneed constant attention.



Place all clamps as nearly as possibleopposite some bearing point of thecomponent to avoid springing thecomponent and in accessible positions.

All sharp edges should be removed from thevarious detail parts of the jig.

Provide handles or other devices whereverthese will make the handling of the jig more

convenient.



If possible, place all tool guide bushingsinside the geometrical figure formed by

connecting the points of location of the feet. Make, if possible, all locating points visible to

the operator when placing the component inposition in the jig so that the component canbe seen to be correctly located. The operatorshould also be able to have an unobstructedview of the clamps.


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Before using the jig in the machine shop forcommercial purposes, test all jigs as soon asthey are made.

The location points, which are hardened ifnecessary, are established withconsiderations to machining operations, ifany, to follow and that any mating parts arelocated from the same datum surface.



Locating and clamping arrangements aredesigned to reduce idle time to a minimumby using simple clamps which are easy andquick to operate and also operate withoutdamaging the component.

Springs should be used whenever possibleto elevate the clamps clear of the componentwhilst being loaded or unloaded.



Clamps should be positioned abovethe points supporting the component,

in order to avoid distortion and shouldbe strong enough to hold thecomponent without bending.

Generally clamps should not be reliedupon for holding the work against the

pressure exerted by the cutting tool.


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Locating and supporting surfacesshould, whenever possible, berenewable.

Such surfaces should be of hard material.



The process of inserting andwithdrawing the component from the jigshould be as easy as possible.

Ample space should be left between thejig body and the component for handmovements.

Some means of ejection should exist torelease the component if it sticks in the jig.



The design of the jig must be safe.

Handles or levers should be large enough

to clear adjacent parts so that pinchedfingers are avoided.


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If necessary, make provision for theuse of coolant.

Position locations at places wherethere is no flash or burr on thecomponent.



If possible, eliminate spanners by theuse of levers.

If spanners have to be used, make onespanner fit all the clamp operating boltsand nuts.

Consideration should be given at thedesign stage to the use of standardisedjig components.


Power requirement for Drilling

d = drill diameter, in

K, A, B, E - Constants

8.18.0, dfAKMTorque =

28.08.02, dEKdfBKTThrust +=


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Basic Design Steps

1. Method of locating the part identify thestandard components required for locatingpurpose.

2. Design the clamping method. Make aproper choice of clamps C-washer, swingwasher, nut, strap clamp, toggle clamp, etc.

3. Design any supports required

4. Design the jig bushes required.

5. Design the jig body.


Design Study Drill Jig

1. Method of locating the part Thecentral hole which helps in locating aswell as indexing for the hole.

2. Clamping can be done with a nut

and a C-washer

Indexing will have to be done with aplunger type retracting.


For locating 5/8 inhole

Forlocatingin the jigbody


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For locating 5/8 inhole

Forlocatingin the jigbody




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mfg tooling -07 jig design

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