Introduction to Six Sigma

ELIMINATION OF BRAKE ASSEMBLY FAILURE AT CUSTOMER END 2015-2016

ABOUT THE ORGANISATION

Established in 1981, Automotive Axles Limited (AAL) is a joint venture of Kalyani Group and

Meritor Inc., USA. With manufacturing facilities located at Mysore (Karnataka), the company is

currently the largest independent manufacturer of Rear Drive Axle Assemblies in India. The

company has also expanded its footprints in North India with its plants at Pantnagar and Jamshedpur.

Over the past 30 years, it has successfully been manufacturing reliable & long-life Medium & Heavy

duty Drive axles, Front Steer axles, Non-Drive axles, Axles for Defence & Off-Highway

applications and Drum & Disc Brakes. Recently it has forayed into manufacturing of Light duty

Drive axles.

Established : April 21, 1981

Equity Share

i. Meritor : 35.52%

ii. Kalyani : 35.52%

iii. Public : 28.96%

Land Size : 202,343.5 Sqm

Location : Mysore, India

Total Employees : 2000+

Manufacturing

Plants

:Mysore, Pantnagar, Jamshedpur

DEPARTMENT OF MECHANICAL ENGINEERING Page - 1


Over the years, AAL has developed an impressive domestic OEM clientele that includes Ashok Leyland, Tata

Motors, Asia Motor Works, Daimler India, Volvo India, SML Isuzu Ltd., Volvo Eicher Commercial Vehicles,

Vehicle Factory-Jabalpur, BEML, MAN Trucks Pvt. Ltd., Mahindra Trucks & Buses, CAT, Escorts, TIL and

Sonalika. AAL also exports axle parts to USA, France, Italy, China, Brazil and Australia.

VISION:To be a world class quality manufacturer of axles, providing innovative solutions to customer at

competitive price that enhance mobility, safety & environment and retain leadership.



ABSTRACT

Brake adaptor or brake flange is a plate on which brake assembly is mount. These flanges are

welded on the axle housing or the spindle. Most spindles have these welded on at the factory with

specialized jigs and higher precision welding equipment that what even experienced do-it-yourselves

have.

The flange needs to be welded on concentric and square. Square meaning the flange must be a

true 90 degrees from the spindle and concentric meaning the gap around the spindle must be the same

360 degrees around. If not, the brakes will not wear evenly and will cause reduced braking

performance. If not at the right depth the brakes will not be as effective and again, wear unevenly. If

the flange is not welded square to the spindle then there are the chances for un-machined surface to

appear on flange during flange turning process due to improper orientation.

The uneven surface formed will have an effect on bake assembly mounting failure. The uneven

surface leads to uneven distribution of load over the flange. This may gradually lead to brake failure

due to varying cyclic loads.

Our aim is to find out root cause for the error causing the orientation problem. Since the

manufacturing process responsible for creating the problem is unknown. We have to find out the

process responsible for the error. Hence six sigma technique is used to analyse the problem and to find

out a solution to eliminate the unclear surface on the brake flange.



CHAPTER 1

INTRODUCTION

1.1 AXLE

An axle is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle

may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels

rotating around the axle. In the former case, bearings or bushings are provided at the

mounting points where the axle is supported. In the latter case, a bearing or bushing sits

inside a central hole in the wheel to allow the wheel or gear to rotate around the axle.

Sometimes, especially on bicycles, the latter type axle is referred to as a spindle.

On cars and trucks, several senses of the word "axle" occur in casual usage, referring

to the shaft itself, it’s housing, or simply any transverse pair of wheels. Strictly speaking, a

shaft which rotates with the wheel, being either bolted or splinted in fixed relation to it,

is called an "axle" or "axle shaft". However, in looser usage an entire assembly including

the surrounding "axle housing" (typically a casting) is also called an "axle".

Fig 1.1: MS08-120 Single Reduction Hypoid Solo Drive Axle.

In rear wheel drive cars and trucks, the engine turns a drive shaft (also called a

propeller shaft or tail shaft) which transmits rotational force to a drive axle at the rear of the

vehicle. The drive axle may be a live axle, but modern rear wheel drive automobiles

generally use a split axle with a differential. In this case, one half-axle or half-shaft connects

the differential with left rear wheel, and second one does the same with the right rear wheel;

thus the two half axles and the differential constitute\ the rear axle.


http://en.wikipedia.org/wiki/Spindle_(tool)

http://en.wikipedia.org/wiki/Bicycle

http://en.wikipedia.org/wiki/Bushing_(bearing)

http://en.wikipedia.org/wiki/Bearing_(mechanical)

http://en.wikipedia.org/wiki/Gear

http://en.wikipedia.org/wiki/Wheel

http://en.wikipedia.org/wiki/Rotation

http://en.wikipedia.org/wiki/Shaft


1.2 TYPES OF AXLES1.2.1 BASED ON STRUCTURAL FEATURES

STRAIGHT AXLE:

A straight axle is a single rigid shaft connecting a wheel on the left side of the vehicle

to a wheel on the right side. The axis of rotation fixed by the axle is common to both

wheels. Such a design can keep the wheel positions steady under heavy stress, and can

therefore support heavy loads. Straight axles are used on trains (that is locomotives and

railway wagons), for the rear axles of commercial trucks, and on heavy duty off-

road vehicles. The axle can optionally be protected and further reinforced by enclosing the

length of the axle in housing.

SPLINT AXLE:

In split-axle designs, the wheel on each side is attached to a separate shaft. Modern

passenger cars have split drive axles. In some designs, this allows independent suspension of

the left and right wheels, and therefore a smoother ride. Even when the suspension is not

independent, split axles permit the use of a differential, allowing the left and right drive

wheels to be driven at different speeds as the automobile turns, improving traction and

extending tire life.

TANDEM AXLE:

A tandem axle is a group of two or more axles situated close together. Truck designs will

use such a configuration to provide a greater weight capacity than a single axle. Semi

trailers usually have a tandem axle at the rear.

1.2.2 BASED ON THE WORKING

DRIVE AXLE:

An axle that is driven by the engine or prime mover is called a drive axle.

Modern front wheel drive cars typically combine the transmission (i.e. gearbox and

differential) and front axle into a single unit called a transaxle. The drive axle is a split

axle with a differential and universal joints between the two half axles. Each half axle

connects to the wheel by use of a constant velocity (CV) joint which allows the wheel

assembly to move freely vertically as well as to pivot when making turns.

In rear wheel drive cars and trucks, the engine turns a driveshaft (also called a propeller

shaft or tail shaft) which transmits rotational force to a drive axle at the rear of the



vehicle. The drive axle may be a live axle, but modern rear wheel drive automobiles

generally use a split axle with a differential. In this case, one half- axle or half-

shaft connects the differential with the left rear wheel, and second one does the same

with the right rear wheel; thus the two half-axles and the differential constitute the rear

axle.

Some simple vehicle designs, such as leisure go-karts, may have a single driven wheel

where the drive axle is a split axle with only one of the two shafts driven by the engine, or

else have both wheels connected to one shaft without a differential (kart racing).

However, other go-karts have two rear drive wheels too.

Fig2.1: Drive Axle

DEAD AXLE(LAZY AXLE) :

A dead axle, also called lazy axle, is not part of the drive train but is instead free-

rotating. The rear axle of a front-wheel drive car is usually a dead axle. Many trucks and

trailers use dead axles for strictly load-bearing purposes. A dead axle located immediately in

front of a drive axle is called a pusher axle. A tag axle is a dead axle situated behind a drive

axle. Dead axles are also found on semitrailers, farm equipment, and certain heavy

construction machinery serving the same function. On some vehicles (such as motor



coaches), the tag axle may be steerable. In some designs the wheels on a lazy axle only come

into contact with ground when the load is significant, thus saving unnecessary tire we

LIFT AXLE:

Some dump trucks and trailers may be configured with a lift axle (also known as airlift

axle or drop axle), which may be mechanically raised or lowered. The axle is lowered to

increase the weight capacity, or to distribute the weight of the cargo over more wheels, for

example to cross a weight restricted bridge. When not needed, the axle is lifted off the ground

to save wear on the tires and axle, and to increase traction in the remaining wheels. Lifting an

axle also alleviates lateral scrubbing of the additional axle in very tight turns, allowing the

vehicle to turn more readily. In some situations removal of pressure from the additional axle

is necessary for the vehicle to complete a turn at all.

Fig2.2:

Lift Axle



CHAPTER 2

LITERATURE REVIEW

A literature review is much more than a list of separate reviews of articles and books. They are common and very important in the sciences. A literature review is a critical, analytical summary and synthesis of the current knowledge of a topic. It should compare and relate different theories, findings, and so on, rather than just summarize them individually. It should also have a particular focus or theme to organize the review. It does not have to be an exhaustive account of everything published on the topic. But it should discuss all the more significant academic literature important for that focus.

2.1 Base Papers:

Review Paper-1:

Sawita D. Dongre1, Prof. U. D. Gulhane2, Harshal C. Kuttarmare3, Authors: M.Tech 3rd sem student1. Professor of Mechanical Department2. Assistant Professor of Mechanical Department3, S.S.P.A.C.E Wardha1. B.D.C.O.E. Sevagram2. D.M.I.E.T.R. Wardha3.

Title: Design and Finite Element Analysis of JIGS and Fixtures for Manufacturing of Chassis Bracket.

Publication: International Journal of Research in Advent Technology, Vol.2, No.2, February 2014 E-ISSN: 2321-9637.

Description: This project is about the design and analysis of Jigs and fixture which is used in the manufacturing of chassis bracket of Bajaj car RE60 (passenger car).The purpose of the jigs is to provide strength, holding, accuracy and interchangeability in the manufacturing of product. By performing analysis on jigs and fixtures we find out stress acting on jigs and fixtures and bracket. The jigs and fixtures are the economical ways to produce a component in mass. So jigs and fixtures are used and serve as one of the most important facility of mass production system. These are special work holding and tool guiding device. What makes a fixture unique is that each one is built to fit a particular part or shape. The main purpose of a fixture is to locate and in the cases hold a work piece during an operation. A jig differs from a fixture in the sense that it guides the tool to its correct position or towards its correct movement during an operation in addition to locating and supporting the work piece. So in this project we will design jigs and fixtures while manufacturing of chassis bracket and analyzing stress and strain developed in jigs and fixtures and chassis bracket. In this we will minimize the different problem of breakage of jigs and fixtures.



Review Paper-2:

G. Rajesh Babu and N. Amar Nageswara Rao Mechanical Engineering Department,Authors: Nimra College of Engineering & Technology, Ibrahimpatnam, Vijayawada Title: STATIC AND MODAL ANALYSIS OF REAR AXLE HOUSING OF A TRUCK.

Publication: International Journal of Mathematical Sciences, Technology and Humanities 7 (2011) 69 – 76

Description: Axle housing is one of the significant components that lead to great performance of the vehicle. It may be available in one-piece or has spilt type construction that is also known as banjo type construction. Axle housings are usually comprised of double lip seals and over size bearings. This results in more capacity and enhanced surface area contact over axle. Both the front and rear openings have centre housing. Differential carrier closes the front opening. On the other hand, spherical cover plate is used for closing the rear. This paper analysis the static and modal analysis of the rear axle housing. The geometry of axel housing is created in Pro-E-4.0 software as per the drawing. Then the model is imported to develop a mesh by using HyperMesh-10, through IGES format and then solid elements were created for axel housing. A converged mesh is generated and the meshed component is exported to Ansys-11 to evaluate the product strength and ability to withstand against all forces and vibrations .Finally the stresses, deflections and natural frequencies of the cast iron and mild steel models are carried out and compared.

Review Paper-3:

Roger G. Schroeder a,*, Kevin Linderman a,1, Charles Liedtke b,2, Adrian S. Choo c,3,a aCurtis L. Carlson School of Management, University of Minnesota, USAAuthors: bStrategic Improvement Systems, LLC Excelsior, MN, USA cLally School of Management and Technology, Rensselaer Polytechnic Institute, USA

Title: SIX SIGMA: DEFINITION AND UNDERLYING THEORY

Publication: Journal of Operations Management 26 (2008) 536–554

Description: Six Sigma has been gaining momentum in industry; however, academics have conducted little research on this emerging phenomenon. Understanding Six Sigma first requires providing a conceptual definition and identifying an underlying theory. In this paper we use the grounded theory approach and the scant literature available to propose an initial definition and theory of Six Sigma. Our research argues that although the tools and techniques in Six Sigma are strikingly similar to prior approaches to quality management, it provides an organizational structure not previously seen. This emergent structure for quality management helps organizations more rigorously control process improvement activities, while at the same time creating a context that enables problem exploration between disparate organizational members. Although Six Sigma provides benefits over prior approaches to quality management, it also creates new challenges for researchers and practitioners.



CHAPTER 3

NEED OR SCOPE OF PROJECT

The following are some of the factors which improves the performance and reduces the cycle time of the manufacturing process carried out.

1. The main reason for break assembly mounting failure is the un-machined surface left out on the brake flange. The brake flanges with unclear surfaces are not accepted by the customers. Hence the main aim of the project is to eliminate the un-machined surface.

2. Straightening and load testing of the axle is done to remove the run-out, centre shift and face height defects. So, these defects can be eliminated at the stage in which they are generated.

3. If these defects are eliminated at respective stages then the energy required to drive the hydraulic press straightening system will be reduced.

4. The amount of material removed during the flange turning can be further reduced if there is no error in the orientation of the flange.

5. It reduces the chance of rework to be done if there is no unclear surface.

6. The defect causing manufacturing process can be replaced or altered or repaired.

7. Proper clamping and fixtures can be provided in the manufacturing process if necessary



CHAPTER 4

INTRODUCTION TO SIX SIGMA [6σ]:

Six Sigma seeks to improve the quality of the output of a process by identifying and removing

the causes of defects and minimizing variability in manufacturing and business processes. It uses a set

of quality management methods, mainly empirical, statistical methods, and creates a special

infrastructure of people within the organization, who are experts in these methods. Each Six Sigma

project carried out within an organization follows a defined sequence of steps and has specific value

targets, for example: reduce process cycle time, reduce pollution, reduce costs, increase customer

satisfaction, and increase profits.

Methodologies

Six Sigma projects follow two project methodologies inspired by Deming's Plan-Do-Check-Act

Cycle.

These methodologies, composed of five phases each, bear the acronyms DMAIC and DMADV.

DMAIC is used for projects aimed at improving an existing business process.

DMADV is used for projects aimed at creating new product or process designs.

Methodology

The six sigma technique used to resolve the problem is DMAIC. i.e. Define Measure Analyse Improve

and Control

DMAIC

The DMAIC project methodology has five phases:

The five steps of DMAIC

Define the system, the voice of the customer and their requirements, and the project goals,

specifically.

Measure key aspects of the current process and collect relevant data; calculate the 'as-is’

Process Capability.

Analyse the data to investigate and verify cause-and effect relationships. Determine what the

relationships are, and attempt to ensure that all factors have been considered. Seek out root

cause of the defect under investigation.



Improve or optimize the current process based upon data analysis using techniques such as

design of experiments, pokayoke or mistake proofing, and standard work to create a new,

future state process. Set up pilot runs to establish process capability.

Control the future state process to ensure that any deviations from the target are corrected

before they result in defects. Implement control systems such as statistical process control,

production boards, visual workplaces, and continuously monitor the process.

Any organisation’s main initiative is to improve the current Process and thereby enhancing the

production rate.

There are two methods in Process improvements.

Problem Solving [Defect Reduction].

Process optimisation [Cost and Cycle time Reduction].

Selection of improvement projects

For each improvement projects identified we have to do the following

Categorize whether the problem is generic or specific.

Departmental/ Functional level projects are called Generic problems. Process level projects are

called specific defects or specific problems. The specific problems are technically clear.

Identify the category of specific problem

KNOWN UNKNOWN

CAUSE

For type 1, 2 & 3 problem, we have to do only improve & control.


KNOWN UNKNOWNSOLUTION2

Cause known

Solution unknown

4Cause unknown

Solution unknown

1Cause known

Solution known

3Cause unknown

Solution known


For type 4 problem, entire DMAIC is applicable

Fig: Category identification for Specific problem





PROCESS OBSERVATION

FIG: PROCESS OBSERVATION FLOW CHART

Some of the main processes to be observed is as follows

1. Tack welding

2. Seam welding

3. Bore and Face housing banjo

4. Ring and cover welding

5. Swaging

6. Friction weld spindles to housing

7. Tack and full weld brake flanges

8. Cooling

9. Straightening and Load testing

10. Grinding bearing dia



11. Curl turn and flange turnig

KEY WORDS

HOUSING

SPINDLE

BRAKE FLANGE

RUN OUT

FACE HEIGHT


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Introduction to Six Sigma

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