DESIGN CONCEPT OF A TURNING FIXTURE FOR OIL TANK · PDF fileDESIGN CONCEPT OF A TURNING...

@IJRTER-2016, All Rights Reserved 34

DESIGN CONCEPT OF A TURNING FIXTURE FOR OIL TANK

COVER MGB

Sunil Kumar K 1, Srinivasa Chari V 2, Lakshiminarayana T H 3,Kumarswamy j 4

1 Asst prof, Mechanical Engineering Department, RLJIT, Doddaballapur Karnataka 2 Asst prof, Mechanical Engineering Department, Atria IT, Bangalore Karnataka

3 Asst prof, Mechanical Engineering Department, RLJIT Doddaballapur Karnataka 4 Asst prof, Mechanical Engineering Department, RLJIT Doddaballapur Karnataka

Abstract— The word “tooling” refers to the hardware necessary to produce a particular product. A

considerable amount of tooling is the result of work performed by the tool designer. Tooling, as

viewed by the tool designer consist of vast array of cutting devices, fixtures, dies, gauges etc., used

in normal production. Tool design is concerned with design and development of machines and

special tooling, methods and techniques required by today’s high speed mass manufacturing at high

efficiency and productivity. Concept generation, getting the ideas, is the most critical step in the

engineering design process.in this project we designed few concepts for improved productivity of a

turning fixture for oil tank cover MGB in helicopter manufacturing.

Keywords—Design, MGB (Main Gear Box), Concept, Turning fixture, Oil Tank.

I. INTRODUCTION

1.1 Tool Design

Tool design is the specialized phase of tool engineering. Tool engineer in addition to his duties in

manufacturing may perform tool design functions, or a tool design specialist who devotes his entire

working time to tool design may perform them. The word “tooling” refers to the hardware necessary

to produce a particular product. A considerable amount of tooling is the result of work performed by

the tool designer.

Tooling, as viewed by the tool designer consist of vast array of cutting devices, fixtures, dies,

gauges etc., used in normal production. Tool design is concerned with design and development of

machines and special tooling, methods and techniques required by today’s high speed mass

manufacture at high efficiency and productivity. Its main objective is to produce component at a

competitive price, maintaining its quality and increased production.

The basic task of the tool designer is to provide drawings of a tool or set of tools to produce the

work piece. So, will be provided with a blue print of the work piece to be manufactured. The name

and specifications of the machine to produce the work piece and the number of work piece required.

In order to complete his task the tool designer may have to produce complete set of drawings

showing.

1. An Assembly drawing

2. Detailed drawing of each part

3. Complete list of parts needed to make the tool

4. One or more assemblies, if the design is complex

A mastery of drafting techniques is as essential to the designer as ability to read and write. His ideas

are valueless unless they can be expressed in a manner the tool makers can understand. All drawings

must be clear, complete, and exact and easily understand and must be genuine help to the tool

maker. The designer cannot rely on verbal instruction or on the previous experience of the

toolmakers.

International Journal of Recent Trends in Engineering & Research (IJRTER) Volume 02, Issue 11; November - 2016 [ISSN: 2455-1457]


1.1.2 Original Directions for Design

Engineers responsible for manufacturing planning must write down there plan in some form that can

be calculated and used by many people to fulfill their individual roles in total manufacturing

operation.

The documents describing all steps in manufacture of a given product is a “Route Sheet”. This

usually states that raw material, standard components or supplies required and every step of

procedure to create the finished item to be inspected again a part print.

It identifies all machinery required at each step and special tooling such as fixtures, dies and gauges

or special items; either existing or that may require new design.

An order of same kind is usually originated directing procurement of all such items and conveying

some ideas to design wanted, as at least required function of tooling, all directives of this sort are the

first step in design and must be clearly stated and well-coordinated in order to get the design started

right.

The design of tools and special items requires a routing, a part print, instruction sheet, master

processes sheet and jigs and tool order. Basically planner must visualize the part and be also to

understand how the items to be designed fit into the development of that part during the

manufacturing processes. The planner generally does not design the tools, but he should direct

procurement in writing and by means of sketches that clearly indicate what he wants.

1.1.3 Tool Design Objectives:

The main objective of tool design is to lower manufacturing costs while maintaining quality and

increased production. To accomplish this, the tool designer must satisfy the following objectives.

1. Provide simple, easy to operate tools for maximum efficiency.

2. Reduce manufacturing expenses by producing parts at the lowest possible cost.

3. Design tools which consistently produce parts of high quality.

4. Increase the rate of production with existing machine tools.

5. Design the tool to make it fool proof and to prevent improper use.

6. Select the material which will give adequate tool life.

7. Provide protection in the design of tools for maximum safety of the operator.

1.1.4 Tool Design Manufacturing As an important aspect of manufacturing tool design occupies a position between product and

production. First the need for a product is determined. Then drawings and specifications are

developed. The product designers forward this information to the process planning engineer. The

process planning engineer working with the product designers and the tool designers, plans the

methods which will be used to produce the part. Occasionally, the product designer changes or

modifies design to simplify or speed up production. Normally, the product designers sets the

production rate and the part design, chooses the machine tools, schedules the deadlines and a budget

is setup. The tool designer must plan within this frame work.

1.1.5 Planning the design: The amount of planning in a toll design greatly affects its success or

failure. This is an orderly process. All the information and specifications pertaining to the proposed

design are evaluated so that the most efficient and cost effective tool design can be selected. During

this phase, the tool designer carefully studies part drawing and production plan. The tool designer

must understand the parts of the manufacturing process.

1.2 Fundamental Design Principle: It is taken for granted that the designer is familiar with the

standard drafting procedures. However, tool room drafting differs in some respect from standard



practice. A tool drawing is generally used once and not referred to again unless the tool is

redesigned for better performance.

In a very large company, a set of tool room drawings, to make possible several people to work on

the same tool, each making its own parts, which will eventually be assembled in the desired tool.

There are some rules that will result in saving of design time and will aid in making the drawing.

1. Use only those views absolutely necessary to convey all the necessary information. Descriptive

notes on drawing in many instances can replace an entire set of lines, dimensions and

sometimes entire views. Avoid repeating details in various views.

2. If the shape of the parts can be described, it may be unnecessary to draw the part. Standard

parts should be outlined on a tool drawing to show their location and possibly, a location

dimension included. Thus standard detailed parts such as screws, washers etc., need not be

dimensioned particularly if they are listed and dimensioned.

3. Convections are to be followed to represent the threaded parts, gear teeth etc., to save the time.

4. Avoid repeating dimensions in different views. Errors can be made so that the dimensions are

consistent.

5. Tool drawing should carry critical size dimensions and location dimensions. This vital that tool

maker not be required to make any calculations in order to determine critical size or location

dimensions. The location of the screw, locator pins and dowel should be indicated and but not

dimensioned.

6. Ballon leader lines should be at an angle with dimension lines so that they are not confused

with dimension lines. Ballons should be in order between or next to views so that they can be

easily found.

7. The designer should outline the work piece in red for which the tool, jig, fixture or die is to be

made. This not only helps the designer but in most instances help the tool maker or any one

reading the print.

1.3 Degrees of Freedom:

Fig1.1:- Degrees of freedom

The location refers to establishment of desired relationship between work piece and jig or fixture.

Correct location influences the accuracy of the finished product. The jigs and fixture are so designed

that all possible movements of components must be restricted. The determination of the locating

points and clamping of work piece serve to restrict the movements of the components in any

directions, while setting it at the correct position relative to the figure.



The locating points are determined by first finding out the possible degrees of freedom of the work

piece, which are then restricted by suitable arrangements which serve as location.

The principle of determining locating points is described below.

A body in space has twelve degrees of freedom i.e., it is capable of moving into space in the twelve

precise ways and for successful location, the necessary degrees of freedom as consistent with the job

requirement should be constrained or restricted.

The twelve degrees of freedom are

1. Six movements of translation i.e., axial movements in either direction along the axis X-X, Y-Y

and Z-Z direction as shown in the figure.

2. Six rotational movements i.e., rotation of the body about the axis X-X, Y-Y and Z-Z in either

clockwise or anticlockwise direction.

Thus, for designing rotation facilities it is to be ensured that arrangements are provided for positive

restraints as well as ensure the surface relationship necessitated by the job i.e., natural location

relationships between the surface points and lines.

1.4 Locations

In the design of jigs and fixtures, the location the component is of important aspect as the correct

location influence the accuracy of the finished product and particularly in the reference to the

positional relationship with other surfaces on the component. Further, the location arrangements are

closely related to other aspects of Jig applications as for example, the faulty method of clamping

may cause the component to lift away from the locating surface though the perfectly satisfactory

method of location might have been employed.

1.4.1 Basic Rules for Locating:

Part locators, for restricting the movement of a part and its proper positioning requires skill and

planning. They must be planned into the tool design and never be installed as an afterthought.

The basic rules for locating are

1. A tool designer must always ensure that locators are positioned to contact.

2. Work on a machined surface. This essential for accurate placement of the part in the tool and to

ensure the repeatability jig or fixture.

3. The locators should be spaced as apart as possible, thus using fewer locators and ensuring

complete contact over the locating surface.

4. The tool tolerance should be between 20 to 50% of part of tolerance in order to maintain the

required precision.

5. Use of duplicate locators, which is costly and also causes in accuracy should be avoided. Once

the reference surface for location is decided there should not be other locator to cause

interference in location with Reference to the reference surface. For instance, locating a part

both from its outside edge and the hole can create problems.

1.4.2 Locating devices: Locating devices usually made case hardened steel and separate from jig

and fixture, accurately ground and accurately positioned in jig or fixture of body. The typical

locating devices used for jog and fixtures are:

1. Locating buttons

2. Adjustable locators

3. Locating pins

4. Conical locators

5. Diamond and pin locators

6. Profile locators



In and fixture design, it not always possible to clamp the work directly to either the base or one of

the walls of the fixture For example, the surface may not be machined at those places where it is

most convenient to effect the clamping. Further the presence of chips between the mating surfaces

can cause misalignment. Further if the locating faces are inclined at more than then the

misalignment error will be more than the thickness of the chip adhering between the inclined

surfaces. In such cases, when the reamed or finely finished holes are available, locating pins may be

used for positioning purposes. In the pins, the location pins, the location diameter is made a push fit

with the hole with it engages.

The shank of the pin is driven or pressed into the jig or fixture body and the locating diameter

should always be larger than the shank in order to prevent pin from being pushed into the jig or

fixture body.

1.5 Clamping Devices: The purpose of clamping devices is to hold work in the correct relative position in the fixture and to

ensure that the job is not displayed under cutting forces. The most efficient scheme of clamping

means that the clamping should be adequate and at the same time, the clamping device design

should be such that the operating time of jig or fixture is minimum. Thus for high rates of

production, quick acting clamps are essential where as simple clamps may be adequate for small

batches of work. In the design of efficient clamping devices, the following points are to be

considered. The rotary or reciprocating movement of clamp should be avoided as far as possible. If

however the movement of clamp is necessary then only positively guided movement should be

employed. Arrangement should be made to lift the clamp away from work, or otherwise clear

it, when the clamping load is released this can be achieved by employing compression springs.

1.5.1 Basic Rules of Clamping:

Clamping prevents the part from shifting or being pulled from the Jig or fixture during machining.

1. Clamp should always contact the work at its most rigid point to avoid bending or damage of

part by the clamping force. If the clamping force at any point could bend the part, it must be

supported at that point.

2. Clamp should be positioned such that it does not interfere with the operation of machine tool

and enable operator to work easily and safely.

3. Tool forces generated by cutting action should help in holding the work piece instead of lifting

or tilting it. The tool forces should be directed towards de solid part of the tool body.

4. The type and amount of clamping force(force required to hold a part against The

locator) needed to hold a part is usually determined by the tool forces working on the part and

the way the part is positioned in the tool clamping Pressure should only be enough to hold the

part against the locators.

5. The locators should resist the bulk of the thrust, clamps must never be expected to hold all the

thrust. Tool designer should choose the clamp which is simpler and easier to use and most

efficient.

1.5.2 Types of Clamps: 1. Lever or strap clamp

2. Screw clamp

3. Hinged clamp

4. Two way clamp

5. Wedge operated clamp

6. Cam operated clamp



1.6 Design Principles for Jigs and Fixtures:

While designing the jigs and fixtures the following principles should be borne in the mind.

1. The method of location and clamping should be such that it should reduce idle time to a

minimum. For this purpose the aim of the designer should be to arrange in such a way that the

loading can take place on one batch of components while another is being machined. Location

and clamping influence the accuracy and of the component.

2. Process of loading and unloading the component should be as easy as possible and should be

foolproof so that a component can be loaded in only one correct position and it can't enter in

any position.

3. Work supports

(a) The number of fixed supports on any surface should not be more than three and they

should be as far apart as possible, because the component will sit on three points without

rocking.

(b) The area of supporting surface should be kept clean. Its surface should not take dust.

(c) The supports should be visible and accessible to the operator.

4. Jigs and Fixtures should be rigid enough as this fault is generally not realized in normal

working. For this purpose at least 4 legs should be provided on the jigs and suitable means

should be provided for clamping the fixture on the machine bed if possible, arrangements to

damp out and absorb the vibrations should also be provided.

5. For cleanliness and accuracy, the importance of providing good swarfand chips clearness

cannot be over emphasized Adequate should be provided to enable the metal chips to be blown

clear using compressed air.

6. Jigs and Fixtures should be foolproof. The design of jigs and fixtures should be such that it is

impossible for an operator to insert either the work piece or cutting tool in any position other

than the correct one.

7. Design should be as simple as possible. As far as possible standard Components or parts

should be used and similar operations should be grouped. Milling fixtures should be provided

with a setting piece so that a feeler gauge may be used for setting the fixture relative to the

cutters.

1.7 Design of Fixtures

i) Jig: - A jig is a device, which holds and locates a work piece and guides and controls one or more cutting

tools. It is not fastened to the machine on which it is used and may be moved around the table of the

drilling machine. By the use of a jig skilled workers are not required and the responsibility of

accuracy of the whole location is taken care by the jig.

ii) Fixture: - A fixture is a special tool used for location and firmly holding a work piece in the proper position

during a manufacturing operation. The name is derived from the fact that a fixture is always fastened

to a machine or bench in a fixed position. Fixtures always are economical means to produce

repetitive type of work by incorporating special work holding devices.

There are three types of fixture: -

1. Standard Fixture

2. Dedicated Fixture

3. Modular Fixture

iii) Standard Fixture: -

In the small-lot production, we have just one, or at the most, a small number of parts produced to a

given design. For the purpose of work holding, standard machine tool accessories such as three-jaw



chuck and machine vise are used. Here, a high degree of operator skill as well as considerable time

are needed to accomplish the location function.

iv) Dedicated Fixture: -

In the medium-lot –to- mass production, sufficiently large number of parts would be produced to a

given design to justify design and building of a special fixture. This fixture is referred to as a

“dedicated fixture’. The time and cost involved in making a dedicated fixture are distributed over

the large number of parts produced. Hence, the effect on one piece is minimal.

v) Advantages:

a) The work piece is located automatically in the fixture without requiring a high degree of

operator skill. Hence, cost of employing a highly skilled operator is saved. Also the time needed to

be spent on locating or setting up the work piece is greatly reduced thereby increasing productivity.

b) High levels of accuracy can be achieved on the produced part and interchangeability is

improved.

However, the main disadvantage is that a dedicated fixture can only be used for the particular part

design.

vi) Modular Fixture: - In Flexible Manufacturing, low volume and high part variety are the norm. In modular fixturing

approach, a large variety of the standard fixturing elements such as base plate, locators, clamps,

screws, cams, etc. are purchased from the market and stocked. Making use of some of these

elements, a fixture is constructed to suit the work piece design. Here the time required for the design

and production of the various fixturing elements is saved. However, as compared to a dedicated

fixture, higher degree of operator skill and longer time would be required for conceiving and

executing the fixture assembly.

1.8 Design Considerations

i) Location: -

a) Ensure that the work piece is given the desired constraint.

b) Position the locators so that swarf will not cause mal-alignment.

c) Make the location points adjustable if a rough casting or forging is being machined.

d) Introduce fool proofing devices such as fouling pins, projections etc. to prevent incorrect

positioning of the work piece.

ii) Clamping: -

a) Position the clamps to give best resistance to the cutting forces.

b) Position the clamps so that they do not cause deformation of the work piece.

c) Provide fiber or nylon pads where part surfaces are soft.

d) If possible, make the clamps integral with the fixture body.

e) Make all clamping and location motions easy and natural to perform.

iii) Clearance: -

a) Allow ample clearance to allow for variations of work piece size.

b) Allow ample clearance to the operators’ hands.

c) Ensure that there is ample swarf clearance, and clearance to enable the work piece to be removed

after machining, when burrs will be present.



iv) Stability and rigidity:-

a) Provide four feet so that uneven seating will be obvious and ensure that the forces on the

equipment act within the area enclosed by a line joining the seating points. If the base has large

resting area, suitably relieve to have better resting and to reduce machining cost.

b) Make the equipment as rigid as is necessary for the operation.

c) Provide the means positioning and bolting the equipment to the machine table or spindle if

required.

v) Handling: -

a) Make the equipment as light as possible and easy to handle, ensure that no sharp corners are

present, and provide lifting points if it is heavy.

b) Safety of men, material and machinery to be taken care of.

vi) General: - a) Keep the design as simple as possible in order to minimize cost, and to avoid breakdown caused

by over complication.

b) Utilize standard and proprietary as much as possible.

c) Check the work piece can be loaded into, and removed from the equipment; the design

technique where by the equipment is designed around the work piece, tends to make this a

common source of error.

1.9 Types of Fixture and its Industrial Application a) Vise Fixture

b) Milling Fixture

c) Facing Fixtures

d) Boring Fixture

e) Face Plate Fixture

f) Turning Fixture

g) Grinding Fixture

1. Milling Fixtures: A milling fixture holds the part in correct relation to the milling cutter so that

required shape of the work piece is obtained. It mainly consists of base, clamps, and rest

blocks, locating pins and gauging surfaces.

2. Turning Fixture: Turning fixture is used for facing, boring and turning operations. This fixture

mainly consists of locating and clamping devices as the axis of work piece must accurately

coincide with spindle axis. Most of the turning fixtures are special face plates designed to

facilitate quick loading, locating of work piece in mass production.

3. Grinding Fixture: A grinding fixture is used to give high degree of accuracy and high finish to

the product within the precise tolerances. Hence in this fixture, the work piece will be more

accurate and the fixture will be having greater rigidity compared to milling fixtures.

4. Broaching Fixture: In broaching fixture the work piece is held more accurately and broach is

guided accurately so that the built in precision of the broach is reproduced in the work pieces.

5. Welding and Assembly Fixture: This type of fixture contains usual locating and clamping

elements but while designing, the effects of heat during welding is also taken into account.

6. Lathe Fixture: Generally in lathe fixture, round work pieces are machined. in this type, many

attachments like 3-jaw chuck, 4-jaw chuck, collects are used to hold the work pieces.

II. CONCEPT GENERATION

Concept generation, getting the ideas, is the most critical step in the engineering design process.

Starting with a set of customer needs and target specifications, the process conclude with an array of

product alternatives from which a final design is selected.



2.1 An overview on product design process:

Product design is the process of fulfilling the needs of the customer or the market place in which the

generated product takes the value.

This can be achieved by following the stages of product design process:-

Figure 2.1:- Flowchart of product design

The following are the stages which represent the systematic approach for concept development as

shown in Figure 2.1.

1. Need identification of the new design and problem identification for redesign of a product.

2. Analysis of existing similar products and collection of relevant information on product of similar

nature. Literature on the subject should be reviewed.

3. Identification of the need of the users to know exactly what is wanted and to setup the objectives

of the product development and determined what is required to be incorporated into the product.

4. A research methodology should be setup on what could be done to fulfill the objectives,

including incorporation of user’s information.

5. Planned research elimination of portable hazards elimination and arrival at feature

specifications.

6. Creative design with alternatives.

7. Final design concept and prototype development.

8. Verification of its feasibility through feedback from portable users and experts.

9. Refinement of the design.

10. Final product design and prototype.

2.1.1: Concept development

In the concept development phase, the needs of the target market are identified, alternative product

concept are generated and evaluated and one or more concepts are selected for further development

and testing.

2.1.2: Concept selection

Concept selection is the activity in which various product concepts are analyzed and sequentially

eliminated to identify the most promising one. Concept selection is the process of evaluating

concepts with respect to customer needs and other criteria comparing the relative strengths and

weakness of the concepts and selecting one or more concepts for further investigation, testing or

development.

Requirement definition

Concept development

Detail design

Testing and refinement



2.1.3: Concept screening and concept scoring

There are two stages of concept selection, first stage is called concept screening and the second

stage is called concept scoring. Each is supported by decision matrixes, which are used to rate, rank

and select the best concept.

Concept screening, rough initial concepts are evaluated relating to a common reference concept

using the screening matrix. Concept scoring is used when increased resolution will better

differentiate among competing concepts.

2.1.4 Detailed design

In this stage of the design process, the chosen concept design is designed in detail with all

dimensions and specifications. The designer should also work closely with manufacture to ensure

that the product can be made.

2.1.5: Testing and Refinement

The testing and manufacturing phase involves the construction and evaluation of preproduction

version of the product. Prototypes are tested to determine whether the product will work as designed

and whether the product satisfies the user or key customer needs.

2.1.6: Product design specification

This is the most important stage of the design process. This stage includes the clear status of the

actual problem. It is important to know the customer needs and analyze the marketplace to produce a

list of requirements necessary to produce a successful product.

2.2 Concept generation

Concept 1

Fig 2.2 (a)



This is the initial basic model of turning fixture. To overcome milling fixture this turning fixture is

designed. Component cannot be fixed easily because it should be clamped to get reference point.

Design is complex.

Concept 2

Fig 2.2 (b)

This is second stage of concept design. The component can be fixed but exact reference point cannot

be obtained. Turning fixture is designed according to outer diameter. Component cannot be fixed

accurately due to vibration may occur.



Concept 3

Fig 2.2 (c)

This is the final model of the turning fixture which has exact reference point. The component can be

clamped easily. The fixture is provided with nut to fix the component tightly. It takes less time and

production is more. Less cost for designing the turning fixture compared to milling fixture. The

machining can be done in one rotation.

2.2.1 Casted oil tank



Fig 2.2.1:- Casted oil tank



2.2.2 Milling fixture:-

Fig 2.2.2:- Turning operation by using Milling fixture

III. CONCLUSION

The change in helicopter transmission system, the MGB was modified and subsequently the OIL

TANK housing also got modified. Therefore the modified housing machining was carried out in

house to meet the design as well as production requirement. To arrive at the design of fixture for the

fabrication of this component the project work has taken up. The present project work highlights the

method of designing of turning fixture for the manufacture of MGB oil tank

REFERENCES

1. Kline WA, DeVor RE, Lindberg JR(1982) The Prediction of cutting forces in end milling with application to

cornering cuts. Int J Mach Tool Des Res 22(1):7-22

2. Koeingsberger F, Sabberwal AJP(1982) An investigation into the cutting forces pulsations during milling

operations. Int J Mach Tool DesRes 1:15-33

3. TIEN-Ching Wu: Automatic turning head light Structure:Patent no. US6309089 B1, 30 oct 2001

4. Michael J.Barnes and Speak; Adjustable headlight, headlight adjusting and direction sensing control system and

method of adjusting head lights ; patent no; US5868488 A, 9 feb 1999.

5. Chian-yin Tseng; Direction adjustable device for an automobile with a steering linkage: Patent no. US6767119 B2,

27 jul 2004.

6. Chion-Dong Lin; steering wheel controlled car light piloting system, Patent no. US5416465 A; 16 may 1995.

DESIGN CONCEPT OF A TURNING FIXTURE FOR OIL TANK · PDF fileDESIGN CONCEPT OF A TURNING...

Documents

Transcript of DESIGN CONCEPT OF A TURNING FIXTURE FOR OIL TANK · PDF fileDESIGN CONCEPT OF A TURNING...