INTRODUTION TO JIGS AND FIXTURES

INTRODUCTION TO JIGS & FIXTURES

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I. INTRODUCTION

Today the Latest techno & modern industrial world, Products or components Has to be produced by fast & easier way and with good quality & less cost far the Satisfaction of customer needs

When products or components are to be produced m large quantities with a High degree of accuracy and inter change ability at a competitive cost some specially designed tooling are used. ·These tooling consist of tools (cutting and Measuring), Jigs and fixtures and gauges etc. The object of designing such special Tooling is primarily economic, i.e., to ensure economy of manufacture by reducing manufacturing costs and increasing of. Industrial efficiency

When using of such tooling, which has been specially designed for a particular Job. reduces the fatigue of the operator as such operations e g marking out are usually eliminated and can get better accuracy as well as an increase in the output Further the use of specially designed tooling will lead to an improvement of accuracy and thereby the quality of the product and this will conform satisfaction of the consumer and community 

JIGS AND FIXTURES

Jigs and fixtures have become such a necessary part of modern manufacturing that an understanding of the principles involved, as well as examples of those, which have proved successful, is a necessity m every machine shop.

Jigs and fixtures are manufacturing equipments, which make hand or machine work easier or even possible the majority of them are additional equipments to machine tool, which have to fix and locate the work-piece and sometimes also guide the cutting tool.

DEFINITION OF JIG

A JIQ is a device m which a work piece / component is held and located for a specific operation In such a way, that it will guide one or more Cutting tools to the same zone of machining A JIQ also control limits one or more cutting tools m some cases 

DEFINITION OF FIXTURE

A fixture is a work holding device used to locate accurately and to hold securely one or more work-piece so· that the required machining operations can be performed A fixture should be securely fastened lo the table of the machine upon which the work is done The main purpose of a fixture is to locate the work quickly and accurately support ii properly, and hold securely Fixtures vary in design from relatively simple tools to expensive, complicated devices

FUNCTION OF JIG & FIXTURE

The main function of jig and fixture is it hold locate and guide the tool so as to produce work m case of Jig and it hold and locate the pieces in their proper position for carrying the various machining operation in case of fixture that is interchangeable within the tolerances set ty manufacturing requirements.

As work-holding devices fixtures help to simplify metalworking operations performed on special equipment as well as on nearly all of the standard machine tools a fixture merely holds and locates II work piece/component for a specific manufacturing operation but ii does not guide the cutting tool AJIQ may be a plate, box or a structure usually of metal. Fixtures are generally classified according to the kind of operations for which they are used, e.g., milling fixtures, welding fixtures grinding fixtures etc.

DIFFERENCE BETWEEN JIGS & FIXTURES

SL. NO	JIGS	FIXTURES
1	It is a work holding device. Which holds and positions the work piece and guides the cutting tools to the work piece	It is a work holding device. Which holds and positions the work piece and does not guide & locate the cutting tool
2	It has not fixed to the machine table	It is usually fixed to the machine table
3	It has usually light in construction	It has usually heavier in construction
4	It is used for machining operation	Other than machining operation, It ls also used !or assembly and inspection operation

WHY THE JIGS AND FIXTURES ARE USED?

1. To reduce the cost of production, as their use eliminates the laying out of work and setting up of tools
2. To increase the production
3. To ensure high accuracy of the part
4. To provide for interchangeability
5. To enable heavy and complex shaped parts to b& machined by being held nicely to a machine
6. Reduced quality control expenses.
7. Increased versatility of machine tool
8. Unskilled labor
9. Saving labor
10. Their use partially automates the machine tool
11. Their use improves the Safety a: work there by lowering the rate of accidents.

ADVANTAGES OF JIGS & FIXTURES

The use of Jigs and fixtures provides the followings·

• Eliminates the laborious marking out of each work-piece before machining so the cost of setting up according to the marking lines on machine tool beds can be reduced
• Increases machining accuracy and ensures inter change ability because the work-piece is automatically located without aligning on the machine tool and because the cutting tool is guided.
• Increases productivity due to increase in the speeds, feeds and depth of cut this becomes possible ii a Jl9 or fixture due to high clamping rigidity.
• Increases productivity .due to increasing the work-piece simultaneously machined or the number of cutting tools operating simultaneously as well as due lo the reduction in handing lime associated with set up and aligning the work-piece on the machine tool
• Saves operation labor
• Makes the use lower skilled labor possible.
• Decreases expenditure on quality control of the machine part
• Widens the technological capacity of the machine tools, I e.: increases the versatility of the machine
•  Either fully or partly automates the machine tool
•  Facilitates the assembly and also helps future up keep due to uniformity of manufacturing tolerances and promotes interchangeability

ECONOMY AND COST

The cost of the tool and the number of parts to be produced are other factors in determining the design if a small quantity of parts is to be produced. a simple, low­ cost tool may be satisfactory The necessity of keeping the manufacturing cost of a new article as low as possible or reducing the present cost of an existing article usually determines the type of Jig or fixture that IS to be made In some instances the cost of an operation may be reduced by using a more efficient though more expensive tool.

Increased accuracy and interchangeability secured through the use of a more elaborate tool frequently warrants i's jig or a fixture must be thought only after Justifying the cost of the component by using jig or fixture in comparison· of other process of making the component

The cost per component using Jig or fixture and the cost per component using Standard tools can be found oil by the method shown below.

Let

K1 = cost per piece without a jig or fixture

K2 = cost per piece with a Jig or fixture.

T1 = Oost of tooling (standard or simple)

T2 = cost of Jig or fixture.

n = number of pieces to be made

Then total cost without tooling = X1 = n x K1 + T1

Total cost with special tooling = X2 = n x K2 + T2

For economy of employing a /19 or fixture the condition must be that X1 must be less than X2.

i.e.  n x K2 + T2 must less than n x K1 +T1

The minimum number of component required for the production can be found out from the above equation.

Then X1 = X2

nxK1+T1 =nxK2+T2

NxK1-nxK2 =T2-T1

n (K1 - K2) = T2- T1

T2- T1

N= -------------------

K1 - K2