TOOL DESIGNTOOL DESIGN

JIGS AND FIXTURES

PRESS TOOLS

GAUGES CUTTING TOOLS

Introduction to semi-automatic and single spindle automatic screw lathes, Design of cams for automatsscrew lathes, Design of cams for automats

O C OO O CPRODUCT DESIGN

PROCESS PLANNING

TOOL DESIGN

PRODUCT PRODUCTION

Books:Jigs and Fixtures by P H Joshi

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Tool Design by Donaldson, LeCain, Goold

PURPOSE OF TOOL DESIGN

Tool design is the process of designing andd l i th t l th d d t h ideveloping the tools, methods and techniquesnecessary to improve manufacturing efficiency andproductivityproductivity.

It gives the industry the machine and special toolingd d f t d ’ hi h d hi h lneeded for today’s high speed, high volume

production. Ensures level of quality and cost. Since no single tool or process can serve all forms

of manufacturing, tool design is an ever changing,growing process of creative problem solving.

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TOOL DESIGN OBJECTIVES

Provide simple, easy to operate tools for maximumefficiency.y

Reduce manufacturing expenses by producing partsat the lowest possible cost.p

Design tools which consistently produce parts ofhigh quality.g q y

Increase the rate of production with existing machinetools.

Design the tool to make it foolproof and preventimproper use.p p

Select materials which will give adequate tool life. Provide protection in the design of the tools for Provide protection in the design of the tools for

maximum safety of the operator.3

PLANNING THE DESIGN

All of the information and specifications pertainingto the proposed product are evaluated so that theto the proposed product are evaluated, so that themost efficient and cost effective tool design can beselectedselected.

The tool designer must understand the part and thef imanufacturing processes.

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PART DRAWINGS

When analyzing the part drawing, the tool designermust consider several general factors which directlyinfluence the design choices. These factors are: Overall size and shape of the part. Type and condition of the material used for the part.ype a d co d t o o t e ate a used o t e pa t Type of machining operation to be performed. D f i d Degree of accuracy required. Number of pieces to be made. Locating and clamping surfaces.

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JIG AND FIXTURE DESIGNJIG AND FIXTURE DESIGN

INTRODUCTION The accuracy achieved during machining process

depends upon the precision with which the tool andp p pthe work-piece are mounted.

Chucks, vises etc. are suitable for general purposeg p pbut for mass production set up and clamping timebecomes unacceptable.

Hence separate jigs and fixtures are to be designedfor specific applications.

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IMPORTANT CONSIDERATIONS WHILE DESIGNING

Study of work-piece and finished component size andgeometry.

Extent of automation of machine. Provision of locating devices in the machine. Available clamping arrangements in the machine. Available indexing devices, their accuracy.g , y Rigidity and of the machine tool under consideration. Study of ejecting devices safety devices etc Study of ejecting devices, safety devices, etc. Required level of the accuracy in the work and quality to

be producedbe produced.

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• Production Devices which are generally workg yholders with / without tool guiding / settingarrangement. These are called jigs and fixtures.g j g

JIGFIXTURE

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JIGS Jigs are production devices which are used to hold,

support and locate the work-piece moreover it alsosupport and locate the work piece moreover it also guides the cutting tool.

The most common application of jigs are for all hole The most common application of jigs are for all hole making operations.

Types of jigs:yp j gdrilling, boring, reaming etc.Open jig, closed or box jigTemplate jig, plate jig, table jig, sandwich jig, angleplate jig, modified angle plate jig, tumble jig, channel jig,l f ji i d i ji t i ji ji lti t tileaf jig, indexing jig, trunnion jig, pump jig, multi-stationjig

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FIXTURES Fixtures are the production devices which are used

f l ti h ldi d ti th k ifor locating, holding and supporting the work-piecehowever unlike jigs they are not used for guiding thecutting toolcutting tool.

Used for much wider applications than jigs involvingall other machining processesall other machining processes.

Due to the increased tool forces, fixtures are builtt d h i th ji ld b f thstronger and heavier than a jig would be for the

same part. Fi t ll l ifi d b th t f Fixtures are normally classified by the type of

machine on which they are used.

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FIXTURESThe following is a partial list of productionoperations that use fixturesoperations that use fixtures.

Assembling LappingBoringBroaching

MillingPlaning

DrillingForming

SawingShaping

GaugingGrinding

StampingTappingg

Heat treatingHoning

pp gTestingTurning

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HoningInspecting

TurningWelding

ADVANTAGES OF JIGS AND FIXTURES

Productivity I t h bilit Interchangeability Skill reduction Cost reduction Low variability and consistent quality Low variability and consistent quality

ELEMENTS OF JIGS AND FIXTURESELEMENTS OF JIGS AND FIXTURES

Locating elements Clamping elements Tool guiding and setting elements

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oo gu d g a d sett g e e e ts

PRESENTATION OF WORKPIECEPRESENTATION OF WORKPIECE

A jig or fixture drawing shows the workpiece in A jig or fixture drawing shows the workpiece inposition with the jig/fixture.

The workpiece should be discernible from the The workpiece should be discernible from thejig/fixture.

The workpiece is drawn in a chain-dotted line, The workpiece is drawn in a chain dotted line,preferably in colour (red, green or blue).

The workpiece is considered transparent.p p As the workpiece is transparent, it would not

obstruct or block the view of any part of thejig/fixture.

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LIMITS AND FITSRunning fit / clearance fitPush fit: transition fitPush fit: transition fitPress fitForce fit Interference fit

In tool making accuracy grades 7-11 have been found to be the

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In tool making, accuracy grades 7-11 have been found to be themost convenient. H7 holes are the most preferred which areobtained by careful reaming.

MATERIALS USED IN JIGS AND FIXTURESThis is a partial list of materials often used for making jigs, fixtures, press tools, collets, etc.

High speed steels (HSS)Die steels

Case hardened steelsHigh tensile steelsDie steels

Carbon steelsCollet steels (spring steels)

High tensile steelsMild steelCast ironCollet steels (spring steels)

Oil hardened non-shrinking tool steels

Cast ironNylon and fibrePhospher bronzetool steels Phospher bronze

Materials are chosen to resist wear of the tools, reducewear of the mating parts and prevent damage to theworkpiece.

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LOCATING PRINCIPLES

Workpiece requisites: The location has to meetdimensional requirements of the workpiece statedq pon the component drawing.

φ40φ80φ40

L D φ110

Accuracy: Location should be done on the most

L D φ110

Accuracy: Location should be done on the mostaccurate surface of the workpiece. A machinedsurface is preferable to an un-machined one.

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LOCATING PRINCIPLES

Constraints: Location should prevent linear androtary motion of the workpiece along and around therotary motion of the workpiece along and around thethree major axes X, Y and Z.

Motion economy: Location system should facilitatey yeasy and quick loading of the workpiece in thefixture.

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LOCATING PRINCIPLES

Redundant locators: redundant locators should beid davoided.

Fool proofing: The location system should positivelyprevent wrong loading of the workpiece in a fixtureprevent wrong loading of the workpiece in a fixtureby fool proofing.

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LOCATING METHODSLOCATING METHODS

A plane surface A profilep A cylindrical surfaceExamplesp

Cylindrical locators2-Cylindrical locators (for connecting rod)y ( g )Conical locatorAdjustable ‘V’ locatorsAdjustable V locators

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STANDARD LOCATING ELEMENTS(TYPES OF LOCATORS)

Pin and button locators Cylindrical locator Conical locator Jack pin locator Jack pin locator Drill bush locator Fixed ‘V’ locator Sliding ‘V’ locator

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LOCATING FROM A PLANE SURFACE Locating pins/pads Adjustable supports Adjustable supports Adjustable locators/spring loaded pads Wedge pin sed for height adj stment Wedge pin used for height adjustment Equalizing rocker location for square or rectangular

workpieceworkpiece

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SIX-POINT LOCATION (3-2-1 LOCATION PRINCIPLE)

Provide a rest to workpiece on Provide a rest to workpiece onthree points on the bottom x-ysurface.

Movement along z-axis, rotationwith respect to x-axis and y-axisrestricted.

Rest the workpiece on two pointsof side surface (x-z), to fix themovement of workpiece along ymovement of workpiece along y-axis and rotation with respect to z-axis.

Six-point location in a jig Provide a support at one point of

the adjacent surface (y-z) that willfix other remaining free

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gmovements.

LOCATING FROM A PROFILE For simple components, a sighting plate can be used. The workpiece can be positioned on the sighting platep p g g p

in such a way that there is equal margin on all thesides.

The profile of the workpiece can be located byconfining the profile with cylindrical locating pinsconfining the profile with cylindrical locating pins.

When there is considerable variation in workpiecedi i f b t h t b t h t i l tdimensions from batch to batch, an eccentric locatorcan be used.

Workpieces with little variation can be locatedprecisely with nesting plates with suitable provision forloading and unloading.

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LOCATING FROM CYLINDER Spigots used for locating bores should have ample

lead for easy entry and their length should be shortlead for easy entry and their length should be shortto prevent jamming of the workpiece.

Long locators for fragile workpiece should be Long locators for fragile workpiece should berelieved at the centre.

Location posts, which are also used for clampingp , p gmust be retained by a nut or a grub screw.

When two location pins are used, the less importantone should be made diamond-shaped.

Rough cored holes and bosses are located byfconical locators, which often have integral clamping

arrangement and drill bush.

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LOCATING FROM CYLINDER Fixed V blocks are used to locate approximately the

outside surface of a cylinderoutside surface of a cylinder. For precise location, an adjustable guided V block is

necessary. The V block can be adjusted by a screwnecessary. The V block can be adjusted by a screw or a cam.

The V block should be positioned in such a way that p ythe variation in the workpiece would not affect the location for the operation. For drilling central holes, th t li f V h ld b ti lthe centre line of V should be vertical.

Clearance grooves should be provided at flash line of cast forged and moulded workpiecesof cast, forged and moulded workpieces.

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LOCATOR FOR PLANE SURFACE

Fig.1 Fig.2 Fig.3

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LOCATOR FOR PLANE SURFACE In fig 1 undercut is provided at the bottom where two

perpendicular surfaces intersect each other This isperpendicular surfaces intersect each other. This ismade for swarf clearance.

Th fi 2 h fl t h d d b tt t l t The figure 2 shows flat headed button type locator.There is no need to made undercut for swarfl Th b b dj d d idclearance. The button can be adjusted to decide very

fine location of the workpiece. There can be a vertical button support shown in

figure 3, which is a better arrangement due to itscapacity to bear end load and there is a provision forswarf clearance automatically.

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CYLINDRICAL LOCATORSCYLINDRICAL LOCATORS

For locating componentshaving drilled holes.

The cylindrical componentto be located is gripped by acylindrical locator fitted tothe jig’s body and insertedthe jig s body and insertedin the drilled hole of thecomponent.p

The face of the jig’s bodyaround the locator isundercut to provide spacefor swarf clearance.

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CONICAL LOCATORS

For locating the workpiecehaving cylindrical hole

The workpiece is located byp ysupporting it over the conicallocator inserted into thedrilled hole of the workpiece.

Degree of freedom along z- Degree of freedom along z-axis can also be restrainedby putting a template with theby putting a template with thehelp of screws

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JACK PIN AND V LOCATORSJACK PIN AND V LOCATORS

Thi i d f l ti thThis is used for locating thecircular and semi-circulartype of workpieces

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type of workpieces.

‘V’ LOCATORS This is quick and effective method of locating the

workpiece with desired level of accuracy. This isworkpiece with desired level of accuracy. This isused for locating the circular and semi-circular typeof workpiecesof workpieces.

The main part of locating device is Vee shapedblock which is normally fixed to the jigblock which is normally fixed to the jig.

The fixed type locator is normally fixed on the jig andadjustable locator can be moved axially to provideproper grip of Vee band to the workpiece.

This locator can be of two types fixed Vee locatorand adjustable Vee locator.

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Screw adjusted V-locator Female locator

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Cam operated V-locator Quick action V-locator

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p Q

C t iti f V W iti f VCorrect position of V Wrong position of V

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