Spatter Reduction Report

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PROJECT REPORT

MARUTI SUZUKI INDIA LIMITED

SPATTER REDUCTION

Submitted by

ABHISHEK MITTAL

Roll No. - 101108003

Under the Guidance of

Mr. Supreet Bhullar Arun K Kumar

Associate Professor Deputy Manager(L-12)

Department of Mechanical EngineeringTHAPAR UNIVERSITY, PATIALA

June 2014


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DECLARATION

I hereby declare that the project work entitled SPATTER REDUCTION is an authentic

record of my own work carried out at MARUTI SUZUKI INDIA LIMITED as requirements

of six months project semester for the award of degree of B.E. (Mechanical Engineering),

Thapar University, Patiala, under the guidance of Mr. Supreet Bhullar and ER. Arun Kumar ,

during January to June, 2014.

ABHISHEK MITTAL

101108003

Date: ___________________

Certified that the above statement made by the student is correct to the best of our knowledge

and belief.

Mr. Supreet Bhullar Arun Kumar K

Associate Professor Deputy Manager(L-12)


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ACKNOWLEDGEMENT

I take this opportunity to express my profound gratitude and deep regards tomy guide Mr. Arun Kumar K.(Deputy Manager, Weld shop -3 MSIL), forhis exemplary guidance, monitoring and constant encouragement throughoutthe course of this project

The blessing, help and guidance given by him time to time shall carry me along way in the journey of life on which I am about to embark.

I also take this opportunity to express a deep sense of gratitude to Mr.Gobinath T(Assistant Manager, Weld shop - 3) and Mr.J.Edison (SeniorManager Process Engineering cell MSIL), for his cordial support, valuableinformation and guidance, which helped me in completing this task through

various stages.

I am obliged to staff members of MSIL for the valuable informationprovided by them in their respective fields. I am grateful for theircooperation during the period of my assignment.

ABHISHEK MITTAL

101108003


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CONTENTS

Declaration 2

Acknowledgement 3

Summary 5

About MSIL 6

Weld shop 24

Spatter Reduction 25

Procedure 29

Implementation Training Module 36

Weld Information Collection System 41

Spot checking 52

Parameter Determination 55

Automation System 70

Result 77

conclusion 78

References 79


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SUMMARY

Reduction of spatter in Ertiga line by maintain proper production process such as avoidingimproper face cutting, tip alignment, zero touch up and keeping parameters such as weld

time, current and pressure to acceptable limit. Spatter causes huge monetary, productivity,quality losses.

The project involves parameter determination which is a dominant factor in weld spatter.Also a concept was developed to automate the spatter reduction activities which were earlier

done manually.


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Maruti Suzuki India Limited (MSIL) is engaged in the business ofmanufacture, purchase and sale of motor vehicles, automobile components

and spare parts (automobiles).

The other activities of the Company consist of facilitation of pre-ownedcar sales, fleet management and car financing. The Companys portfolio

includes the Maruti 800, Alto 800, Alto K10, A-star, Estilo, WagonR, Ritz,

Swift, Swift DZire, SX4, Omni, Eeco, Kizashi, Grand Vitara, Gypsy,

Ertiga and Stingray.

The Companys services include Finance, Insurance, Maruti Genuine

Accessories, Maruti Genuine Parts, Maruti Driving School and Autocard.The Companys subsidiaries include Maruti Insurance Business Agency

Limited, Maruti Insurance Distribution Services Limited, True Value

Solutions Limited, Maruti Insurance Agency Network Limited, Maruti

Insurance Agency Solutions Limited, Maruti Insurance Agency Services

Limited, Maruti Insurance Logistic Limited and Maruti Insurance Broker

Limited.

Listed in SENSEX ,BSE:532500 AND NSE:MARUTI


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Earlier known as Maruti Udyog Limited, it was incorporated as a Public sector company on

24 Feb,1981with the following objectives: -

Modernization of Indian automobile industry.

Production of fuel-efficient vehicles to conserve scarce resources.

Production of large number of vehicles which was necessary for economic growth.

Transfer of Technology

Every minute two vehicles roll out of the Maruti Plant. It is therefore imperative that the

transfer of contemporary technology from our partner Suzuki is a smooth process. Great

stress is laid on training and motivating the people who man and maintain the equipment,

since the best equipment alone cannot guarantee high quality and productivity. From the

beginning it was a conscious decision to send people to Suzuki Motor Corporation for on-the-

job training for line technicians, supervisors and engineers. This helps them to imbibe the

culture in a way that merely transferring technology through documents can never replicate.At present 20% of our workforce have been trained under this program.

Maruti Code Of Conduct

A code has been developed to assist all the employees in their dealings with those with whom

the company does business i.e., customers, dealers, and suppliers and with each other. The

code is not a subst itute for the judgment and discretion of individual employee in day-to-day

work. Neither is it a replacement for company policies, which will continue to apply. The

code contains advice for making decisions in situations where there are no precedents, so that

a common set of norms of business behavior can grow throughout the company.

Following are the important points:

Integrity

Trust

Image


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Consumer Orientation

Ethics

Positive Attitude

MSILS GURGAON PLANT

The manufacturing plant, located about 25-km south of New Delhi in Gurgaon, has an

installed capacity of 5,00,000 units per annum. The total area of the plant is 12,02,256 m2

with a total covered area of 2,95,293 m2. The average daily production is around 2500

vehicles a day.

The whole production facility has been divided into 3 plants: -

1. Plant I (M800, Omni, Eeco, Ritz, Wagnon R)

2. Plant II ( Zen ESTILO, Swift Dzire)3. Plant III (Alto)

The other activities include research & development and utilities (captive power plant, water

and effluent treatment plant, compressor house, boiler house, air washers and incinerator

facilities.


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`Technician

Supervisor

Executive

Asst. Manager

Deputy Manager

Manager

Department Manager(DPM)

Deputy Divisional

Manager(DDVM)

Divisional Manager(DVM)

Director

Joint Managing Director(JMD)

Managing Director (MD)


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The Various divisions in Maruti Udyog Limited are:

Marketing & Sales

Spares

Engineering

Quality Assurance

Services

Production

Production Engineering

Materials

Information Services

Finance

Personnel and Administration


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Modern manufacturing includes all intermediate processes required for the production and

integration of a product's components. Some industries, such

assemiconductor andsteel manufacturers use the termfabricationinstead.

MARUTI SUZUKI MANUFACTURING PROCESS

Blanking is the cutting of a sheet metal part along a closed contour in one step. The piece cut

out is called a blank and may be further processed. Many blanks are often continuously cutout of a sheet or strip. Blanking will waste a certain amount of material. When designing a

sheet metal blanking process, the geometry of the blanks should be nestled as efficiently aspossible to minimize material waste. A distinction should be made between the two sheetmetal cutting processes of blanking and punching, since essentially they are the same process.

In punching, the piece cut out is waste. In blanking, the piece cut out is the work and is kept.

It is possible to employ fine blanking for many sheet metal cutting operations, particularlythose involving lower total sheet thickness. Fine blanking is an advanced precision

pressworking process that can create cuts having close tolerances and straight smooth edges,without shaving or other secondary processes.

A press forces a pressure pad on the sheet metal, holding the work tightly between the lower

die and the pressure pad. Close to, outside and all around the edge of the cut, a v-shaped ring

projecting from the bottom of the pressure pad impinges the work piece. This further securesthe work from movement and restricts metal flow. The cutting punch for this operation has a
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very small clearance with the lower die, usually 1%. As pressure is applied to the work, thepunch cuts through the metal at a s low rate. Simultaneously, another punch app lies force to

the other side of the sheet in the opposite direction. The secondary punch delivers less forcethan the cutting punch. Its purpose is to help with the cut and to prevent warping of the bank,

a common problem in sheet metal blanking operations. The force of the support punch is less

than and in the opposite direction of the cutting punch, therefore the summation of bothvectors indicates that the total force, (and hence the movement), will be in the direction

dictated by the cutting punch.

The press shop can be regarded as the starting point of car manufacturing process. Centrally

located between weld1, weld2 and weld3 supplies components to all the three plants.

The press shop has a batch production system whereas the plants have a line production

system. The press shop maintains an inventory of at least two days. The weld shops as per

their requirements pick the finished body parts. These may be divided as A, B & C. A


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components are large outer components e.g. roof, door panels, front hood etc. These

components are manufactured in the press shop at maruti due to design secrecy and huge

investment requirements. B & C components are manufactured by joint ventures or

bought from vendors.

The press shop can be explained under following headings

Raw Material

Blanking Line

Stamping Line

RAW MATERIAL

The raw material is in the form of cold rolled steel coils. It is specified in terms of steel grade

and width of coil required. The coils weigh about 15000kg.

BLANKING LINE

There are two blanking lines; ROSL (Rotary Oscillatory Shear Line) for rectangular sheets

and the other employing die cutting, for irregular shapes.

The rectangular sheets are obtained on ROSL while dies are employed to obtain the required

shape sheets.

The sequences of operations on the blanking line are as following: -

Uncoiling


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Cleaning

Leveling

Measuring

Shearing/cutting

Piling/stacking

STAMPING LINE

There are six presses of capacity varying from 1500 tones to 4000 tones.

Of these five are transfer presses and one is a semi-automatic press line, wherein the

loading is manual. The dies can be changed to obtain different body components. The

sequence of operations is as following: -

Destacking

Cleaning

Drawing

Trimming

Bending

Punching


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a "filler metal" into the joint to act as a binding agent. Other methods rely on pressure

to bind metal together, and still others use a combination of both heat andpressure.

Unlike soldering and brazing, where the metal pieces being joined remain unaltered,

the process of welding always changes the work pieces.

This is restricted area and I could not get permission to go inside. A single particle of dust if

embedded onto the body the paint would chip off. Hence the entry of non-factory personnel isrestricted in order to avoid the entry of dust particles.


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However the information regarding the process outline in the paint shop gathered from other

sources is as following: -

I. Pre-treatment:The body is thoroughly washed to remove dirt and oil scales.

II. ED coat:This is done by electric deposition method. After applying the ED coat body

is baked in ovens.

III.Intermediate coat:This is done by spray painting method. After applying the coat,

the body is dried in the oven.

IV.Final coat: For metallic coating, double coats are applied and aluminum flakes

provide the shine to metallic paint. This is also done by spray painting

method. The PBOK, i.e. Paint Body OK is sent to the assembly shop.


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Painting process I/C

& Top Coat painting

Painting process Final

Inspection


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The assembly shop receives PB-OK i.e. paint body OK from the paint shop. Here the body is

loaded on a conveyor on jigs. As the conveyor moves the fitments are made on the body at

various stations.The sequencing of models is done by PLC i.e. Program Logic Control. In Plant-1 there are

separate assembly lines for each model as compared toPlant-2which has only one U type

plant layout for different models. Altering the speed of the conveyor can alter the capacity of

shop. The Plant-3 conveyor runs at 2.7m/min. The conveyor belt can run at a maximum speed

of 4 m/min.

Assembly shops havecontinuous production system. The assembly line can be further

subdivided as following: -

Trim

Chassis

Final

TRIM

Tr im can be further subdivided as fol lowing: -

1. Trim 1

2. Trim 2

3. Trim 3

Trim 1:This is the beginning of the assembly line conveyor. Here amongst the first tasks

done is attaching the hydraulic supporters for the boot. The assembly line check sheet is put

inside the body.

.


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Trim 2:It starts with the head light fitting. Other operations done here are vacuum booster/

brake master cylinder fitment, seat belts, fuse box, wiper sprayer and motor, accelerator,

clutch, brake pedals, door glasses and a/c panel fitment. Trim 2 ends with the fitment of the

instrument panel, which is received from an instrument panel, sub assembly. This sub

assembly involves the fitting of the speedometer console, ashtray and stereo system. Besides

all these ignition coil for Car800.

Trim 3:The fittings done here are rear inside cover for boot, back door glass and windshield,

quarter glasses and connecting pipe between fuel lid and fuel tank. Car800's front coil spring

is also fitted here. Steering gear is mounted. For comedienne application on the windshield,

Motoman robots are employed.

There is a process check at the end of trim line wherein the points in the check sheet are

verified and marked ok.

CHASSIS

The chassis receives a trim up body. Here underbody fitments are made; hence body is loaded

on overhead jigs. Chassis can be subdivided as following: -

1. Chassis 1

2. Chassis 2

Chassis 1:Various fitments made here are rear shock absorbers, brake pipes, front coil spring

with knuckle, steering wheel, tie rods, rear suspension, fuel pipes, fuel tank and rear brake

drum. There is a knuckle sub assembly that feeds the line with knuckles for the front

suspension system. On front wheels disc brakes are used whereas on rear wheels drum

brakes are used. There is a process check at the end of chassis 1.

Chassis 2:The various fitments made here exhaust system (silencer and catalytic converter),

engine cum transmission case assembly, gear shift rod, front and rear bumpers, stabilizer bars

and tyres. Radiator of Car800 is fitted here. The tie rod and drive shafts are connected to the

knuckle to complete the front suspension system. There is a process check at the end of

chassis 2.


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FINAL

Since all the fitments have been made, we will refer the body as vehicle from now onwards.

The vehicle is loaded on the conveyor. It can be further subdivided as: -

Final 1

Final 2

Final 1: The fitments made here are Spare wheel cover, ID plate, scuff, seats, roof trim and

carpet, boot carpet, battery and air cleaner. Clutch cable and parking brake connections are

made. Brakes are evacuated and brake oil is filled. Coolant is also filled.

Final 2:Five liters of petrol is filled in the vehicle. A/C evacuation and charging is done

here, the refrigerant used here is R134a (400 gm +- 50). Door gaps are checked and adjusted,

front grill of Car800 is fitted.

There is a process check at the end of this line. Here the vehicle is checked for the following

as per the check sheet: -

Final-Engine room

Final-Cabin

Final-Pit

Final-Side body

Final-Engine room:Engine oil, brake oil and coolant level. Electrical connections, viz.

ignition coil to distributor, battery terminals, and wiper motor connections. Air cleaner

fitment, radiator hoses &clamp tightening, fuel hoses clamping, radiator mtg. bolt fitments,

clutch cable connection, accelerator pedal play &choke cable play are checked.

Final-Cabin: All lamps viz. head lamp high/low, parking lamp, cabin lamp, wiper water

spray, reverse lamp, ac cooling, blower etc. are checked here.

Mirror view, clutch pedal play and brake pedal play & operation of parking

levers are checked here. Steering shaft column and shaft nuts and bolts are tightened.


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Final-pit: The vehicle is checked for brake oil leakage, coolant leakage, fuel leakage etc.

And these are marked OK on the check sheet.

Final-side body:All door fitments checked. Spare wheel fitment and rear seat fitments are

checked. Seat adjustments are checked.

The vehicle is said to be AB-OK now. It is sent to vehicle inspection dept.

The assembly check sheet is removed. A new check sheet is added to vehicle carrying AB-

OK stamps. The vehicle is called FC-ON i.e. final check on.

Work-pieces are held together under pressure exerted by electrodes. Typically the

sheets are in the 0.5 to 3 mm (0.020 to 0.118 in) thickness range.

The process uses two shapedcopperalloyelectrodesto concentrate welding current

into a small "spot" and to simultaneously clamp the sheets together.

Forcing a large current through the spot will melt the metal and form the weld. The

attractive feature of spot welding is that a lot of energy can be delivered to the spot in

a very short time (approximately 10 - 100 milliseconds).
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That permits the welding to occur without excessive heating of the remainder of the

sheet.

The amount of heat (energy) delivered to the spot is determined by the resistance

between the electrodes and the magnitude and duration of the current.

The amount of energy is chosen to match the sheet's material properties, its thickness,

and type of electrodes.

Applying too little energy will not melt the metal or will make a poor weld. Applying

too much energy will melt too much metal, eject molten material, and make a hole

rather than a weld.

Another feature of spot welding is that the energy delivered to the spot can be

controlled to produce reliable welds.

Weld spatter occurs when small liquid molten metal particles are expelled from thesurface of the materials while welding, due to pressure and heat.


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WHY WE NEED TO CONTROL SPATTER ? ??

Deterioration of quality due to metal dust and burrs caused by spatter

Spatter can leave marks and also makes spots weak which degrades quality of

production.

Damage of costly PLS , Limit switches , and other sensors in automation line.

Lots of high cost equipments are installed in automation line,spatter can hinder in the

working of these instruments and in extreme case can lead to failure of these

instruments also.

Increased down time due breakdowns related to LS & Sensor damage

For company like MSIL ,completing their production targets in time is most important

requirement, but spatter can lead to breakdown ,so it is important to control spatter.

Health and safety implications for employees


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For MSIL safety comes first and for this we need to control spatter as it can harm eyesand skin .

Higher electrical power usage

Spatter can be because of wrong parameters like current. Generating more current on spotthen required means improper usage of costly resources.

FFaaccttoo rrss CCoo nnttrriibbuuttee ttoowwee llddssppaattttee rr!!

Tip alignment and mismatch problem

One of the most common factor that contributes to spatter, mismatch of tip of guns i.e

movable and stationary gun.Abnormal Zero touchup

Absence of zero touch between body to be welded and stationary gun can make way forspatter because of air gap.

Abnormal dressing condition

Improper dressing or grinding can also produce spatter because it leads to improper dressingtip.

Abnormal gun pressure and welding current.

Too low gun pressure or to high current contributes to spatter.Improper location of weld spot

Another factor that contributes due to incorrect location of weld spot ,which can be because

of overlapping of spots etc.


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1stStepis collect initial data, follow these steps:

a. Collect the data at standard condition

Use standard format for this purpose.

2ndStepis Tip alignment & matching Checking and correction of

Shank alignment

Cap Tip alignment

Tip matching

* Tip alignment and matching to be done in new tip, after dressing* If wear down value is NG then gun mastering to be done

3rd

Stepis Welding Current & pressure calibration

Checking of welding current output vs Input ( by weld checker & Turn ratio setting)

Pressure calibration (by pressure checker )

4thStep is Dresser Check

Dresser mounting check

Dresser cutter and holder condition check


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Air blow and cutter rotation direction check

Tip condition after Tip Dressing

5

th

Step is Zero touch up Checking and correction of

- Zero touch up with body surface

6thStep is pressure setting correction

Checking and correction of

- Weld pressure as per standard

7th

Stepis Dressing time and dressing frequency setting

Checking and correction of

- Dressing frequency

- Dressing timeOther than the above procedures following factors also affect thewelding condition:

Excessive dust on the welding surface

Gap and mismatch of comp. in jigs

Vibrations in Servo gun & Robot


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The aim of the project is to reduce spatter and improve welding

process. Spatter free weld shop was motto of this project.

Reduced power consumption

Better weld quality and less rework

Reduced maintenance costs

Safer and cleaner environment

Lower consumable costs

Increased production up-time


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A team was formed including expertise, line supervisor,summer

trainee. A proper checksheet was designed to record daily spatterdata. The project started with aim of reducing spatter in YL8 line

.During initial data collection spatter percentage was found out to be

42%which was way above acceptable level.A proper procedure to control spatter was followed as discussedabove and the results obtained were commendable. The spatter

percentage of Left side body was reduced from 40%to 5%.

A view of spatter control checksheet can be seen below which is

updated for each and every robot in welding shop and stepwisesequence was followed to achieve desired results.

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W1 Jan 14 W2 Jan 14 W3 Jan 14 W4 Jan 14

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Period

YL8 Ertiga - LH Side body Spatter

control progress


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And now after 4 monthsthe current spatter and the difference thathas been made can be seen in below bar graph:

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YL8 LINE SPATTER STATUS AS ON 28.04.2014

YL8 Line Feb'14

YL8 Line Mar'14

YL8 Line Apr'14


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A standardized process for recording data was formulated which

includes summary sheet of a particular area, supervisor check sheet,monthly data graph which is updated on regular basis. It helps us to

analyze spatter data of a particular area and decide next course ofaction. Given below are the examples of data collection sheets to give

the insight of how things work.

Monthly Spatter status update sheet which give us the monthly

spatter status.

Individual robot wise check sheet updated on regular basis to

know the current spatter status of particular robot.(Supervisor

check sheet.)

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Jan'14 Feb'14 March'14 April'14

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YL8 LSB Line Spatter Status


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Area wise Summary sheet updated on regular basis :


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Zero touch up and dressing training module was made for line superviser and workers.


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Below is the step by step instruction for Fanuc robot to conduct zero touch up procedure.


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WELD INFORMATION CONTROL SYSTEM

INTRODUCTION

As we know, the spots of a car are the most prcised work done on a car as their failure can

cause accident. So, the company prefers to check the spots of car as it directly refer us to the

company quality. But, it was not possible for the company to check the spots of every car as

it was a very time consumable process as the processes done to check the spots were

hammering test and peeling test. Till now, Maruti Suzuki India Limited was checking the

spots of every export car and every 10th import car. But this does not give assurance to the

customer for the best quality car as there was no tool for analysis of weld spot quality. So,

there was a need to implement a method which would help the company in providing the best

quality car. Due to this reason, weld information control system came to being in use.

WELD INFORMATION CONTROL SYSTEM

Weld information control system is a non-destructive testing technique to check the spots. In

this technique, a spot id is given to every spot of the car. The datas of welding parameters

are noted. These data have been fed to the PLC (programmable logic controller). IT

department has implemented a server which would be directly linked with the PLC. PLC

provides a graphical characteristic of every spot in computer screen with the help of server

from which we could ensure defective spots on line. Also, the robot line would stop in which

problem has occurred i.e. if the spots does not have the same characteristics as provided to

the PLC, the robot would stop working itself and show faults on computer screen. So that, we

can correct the spot by taking counter measure. Also, this technique will help us in having a

control on NG welding flow.


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NG Welding Flow

NG welding flow occurs at a point where the robot is not able to weld the spot correctly i.e.

the weld does not took properly due to following reasons:-

a) Spatter control

b) Spot Miss

c) Gun alignment NG

d) Tip / Tip Dressing NG

e) Half spot

f) Spot out of position

g) Gun shunting

h) Part deformation (part mismatch)

W.I.C.S. FUNCTIONALITY

Prevents NG Welding Flow

Accurate Detection of Faults

a) Spatter controlb) Spot Miss

c) Gun alignment NG

d) Tip / Tip Dressing NG

e) Half spot

f) Spot out of position

g) Gun shunting

h) Part deformation (part mismatch)

Analysis of every weld spot

Storage of weld spot parameters (upto 10 years)


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W.I.C.S. METHODOLOGY

The methodology on which W.I.C.S. depends is to study about the resistance waves as the

reason for the spot failure could be known by this methodology.

RESISTANCE WAVES

Resistance waves are the graphical representation between resistance values and the weld

time to show that the nugget formed is absolutely correct.

Fig. 3.2. Principle of Resistance Waves

As we can see from the above figure 3.2, the resistance value first decreases but as the temp.

of base metal is raised the resistance value climb up and form a nugget and as the nugget

expansion takes place with the increase in electrical path, the resistance value again decline.


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BENEFITS FOR OBSERVING RESISTANCE WAVES

Resistance wave profile is full spot welding, white body check.

Detect the abnormal conditions early. Prevent NG Welding Flow.

RESULTS OBTAINED BY OBSERVING RESISTANCE WAVES

By observing the resistance waves, we could get to know the various methods because of

which the NG Welding Flow occurs.

1. Fault due to get out of parts position.

Fig. 3.3. Fault seen due to get out of parts position


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From the above fig. 3.3, we can clearly see that the nugget formation takes place at any other

position than required.

2. Fault due to bend parts.

Fig. 3.4. Fault seen due to bend parts

From the above fig. 3.4, we can clearly see that the nugget formation does not took place

correctly as the parts in which the spot was to be applied was bent.


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3. Fault due to get out of position.

Fig. 3.5. Fault due to get out of position seen

From the above fig. 3.5, we can clearly see that the nugget formation was formed slightlyside from its position due to which spot was not formed as required.


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FAULTS RELATED TO RESISTANCE WAVES

E79 Resist wave fault

Fault occurs due to low quantity of heat, Tip diameter expansion, Lack or 2sets of work, Shift

of weld position, Gun touch, terrible expulsion etc.

Fig. 3.6. Fault of E79 resistance waves

-Reset possible at reset box

-Be cautious that when same control no. and same condition has been used continuously,

judgment will not be done.

NG body dont stop, even if no check and reset.

When you returns weld points before more than 1 weld point by manual operation and you

re-welded the weld points, it is possibility existence to stop by fault again.

E85 Wave Resist Frequent

Fault occurs due to tip dress, etc.

-Timers output E85, when weld points more than thresholds of a warning level occurred

frequently in res. decrease width or aver. res.

-Reset possible in reset box

E80 High Resistance

Faults occur due to dust between the tip, power cable break etc.


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Fig. 3.7. Fault of E80 high resistance waves

-Timers output E80 when it detect resistance value ahead of a threshold of high resistance

and it doesnt send weld current according to the setting value.

-Discontinue the power supply at the detection of the fault

- Measures are the basically same as low current fault.

- We can reset the fault at a reset box, but it occurs again till the fault state is removed

GRAPHICAL REPRESENTATION OF RESISTANCE WAVES

Fig. 3.8, shows the graphical representation of resistance values at the time of welding.


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Fig. 3.8. Graphical representation of resistance values

This representation shows us the difference in the resistance decreasing width. This is shownby the line arrays of red, ye llow and blue colour in above fig.

METHOD FOR OBSERVING RESISTANCE WAVEFORM

To measure the transition of resistance value in every 0.5 cycle in welding, we have to

calculate the parameter 1 to 4 and supervise them. The parameter to be calculated are as

follows:-

1. Resistance width decrease: - Max. resistance valuefinal resistance value

2. Average resistance value:- Average of resistance value between 2.5cyc and weld time

(setting time) -0.5cyc

3. 3.Max resistance value:- Max value between setting time and weld time (setting time)

-1.5cyc

4. Final resistance value:- Resistance Value of weld time (setting time) -0.5cyc


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Fig. 3.9 Resistance waveform

SETTING OF RESISTANCE LIMIT

Resistance limits refers us to a position after which alarm would rang. Resistance limits are

classified in two levels: -

1. Alarm Level: - When the nugget formation does not take properly, limit of alarm level

is reached and the alarm rang so that the worker or engineer could take the counter

measure.

2. Fault level: - When the engineer or worker does not take counter measure after the

alarm, then the line would automatically spot.


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PROBLEMS OCCURING IN OBSERVATION

There is a case when there is not a change of resistance. In this case, only the thin

sheet side is weld NG on sheet combination such as thin- thick-thick sheets and in the

case of sheet combination of thin-thin sheets. Therefore, there is the case that NG

points cannot stop.

Whether fault stops or not depend on a limit setting. Misjudgment occur a lot of

times, when limit setting is too rigorous. But it cannot detect weld NG, when limit

setting is too indulgent.

Now, we set limits from average and unevenness of the present data which WICS

system collect.


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WELD SPOT CHECKING PROCESS STANDARDIZATION

Maruti Operation Standard Inspection

MOS I is known as Maruti Operation Standard Inspection sheet in which a list of all the spots

are made and their robots are mentioned which apply these spots. Cycles are divided

according to the application of spots. This sheet has a full spot detail of a car and the copy of

every sheet is listed in the file on the line so that any engineer could go on the line and with

this sheet could know about the inspection of this spot. The sheet is divided according to

main body, main body pit, white body, cowl box, etc. and their cycles.

DESCRIPTION OF MOS I

The first thing that an engineer should know in welding department is the layout of

department.

He should know that which robot is working on which car.

He should know which spots can be checked and which cannot be checked.

He should know how many men are needed for checking the spots in a given

component.

For this, MOS I has been made so that the engineer have a list of all the spots being

implemented on the components of the car.

OBJECTIVES OF MOS I

1. To mark the spots with different colours of different robots working on the

component.

2. To mark the G.A. spots and Maru - A spots of the component.

3. To mark the cycle so that we could know how many men are needed for checking the

spots? No. of cycles is equal to no. of men needed to check the spots.


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4. To know how many robots are doing welding in a given component and how many

spots are there in the given component.

METHODOLOGY ADOPTED

A MOS I sheet was made in which the picture of component with the spots was

printed.

The robots which are applying those spots in a given component were noted down

along with their spots.

Maru- A spots and G.A. spots were seen and marked on it.

The men working on a given component to check the spots were noted and cycles

were made according to their work.

Modified MOS I of Main body checked at white body area


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CONCLUSIONS

Easy for engineer to trace back the broken spot robot

Easy to find out the component details with the help of index.


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PARAMETER DETERMINATION

Parameters such as tip pressure, weld current, squeeze time and weld time affects weldquality and expulsions. Low pressure, high current and weld time were found to be main

reasons for weld expulsions.

METHODOLOGY

Stage 1 - calculating pressure at particular current, time, hold time, sheet thickness ratio,material

stage 2 - determining current and weld time combination through lobe diagram

stage 3 - verifying by peel test nugget size,depth, shear strength

stage 4 - spot sample

PRESSURE CALCULATION

Expulsion in welding is determined by many factors involving electrical, thermal,metallurgical, and mechanical processes.

Although there are many complicated causes of expulsion, its basic process can be describedby the interaction between the forces from the liquid nugget and its surrounding solidcontainment. Major forces acting on a weldment during welding are illustrated in Fig. 3.

They include the squeezing force provided by the electrodes (FE,applied) and the force fromthe liquid nugget (FN) onto its solid containment, which is generated by the pressure (P) in

the molten metal and a compressive force between the workpieces. There is also a resistanceto sheet separation provided by solid diffusion (corona bonding) at the faying interface. Thisforce is usually much smaller than the others and can be neglected in the analysis, as this

model considers extreme expulsion conditions only.

Expulsion occurs when the force from the liquid nugget (FN) onto the solid containment

equals or exceeds the effective electrode force (FE), i.e., FN FE.

In practice, the applied electrode force is rarely collinear with the total force from the liquid

nugget because of complications in electrode geometry such as wearing, electrode alignment,and part fitup. Therefore, the applied electrode force, in many cases, is not the same as theone used to contain the liquid nugget from expulsion. The effective electrode force is

introduced in this situation to accurately represent the force used to suppress the force fromthe liquid nugget.

EVALUATION OF EFFECTIVE ELECTRODE FORCE

An effective electrode force, which is usually a portion of the total applied electrode force, isused to balance the force from the liquid nugget.


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FE,appliedis the applied electrode force, FNis the total force from the liquid nugget against thesolid containment, and Fxis a force imposed by the other workpiece. FEis the effective

electrode force, which will be explained in the following. In Fig. 5, d is the distance betweenthe total nugget force and the electrode force; r is the distance between FNand the edge of the

nugget (it is the radius in the case of a round weld); x is the distance between force FxandFE,applied. Moment equilibrium with respect to the acting point of Fxproduces the following

relationship between FE,appliedand FN:

FE,appliedx = FN (d + X)

An offset between the applied electrode force and that from the

nugget, which is created by an angular misalignment of electrodes.


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Before metal melts, x = 0 because FN= 0, and FE,appliedand Fxhave to be collinear. As the

liquid nugget grows, FNgets larger (FNis proportional to the area of the nugget at the fayingsurface) so Fxgets smaller because Fx+ FN= FE,appliedassuming FE,applied= constant.

Meanwhile, x goes up as can be derived from a moment equilibrium with respect to theacting point of FE,applied: FNd = Fxx when assuming d = constant. Because the magnitude ofFN increases and that of Fx goes down, x has to get larger, or F xgets farther away from the

center of the nugget during nugget growth. It is reasonable to assume that when Fxmovesacross the right edge of the nugget (Point A), the solid loses its containment of the nugget.

Therefore, x = rd can be regarded as a critical condition for expulsion to happen.

Expulsion condition : FE = (rd)/r * FE,applied

The discrepancy d is usually created by asymmetric loading, such as in the case of electrodemisalignment (axial and angular misalignments), electrode wear, or improper workpiece

fitup. It can be approximated by the distance between the geometric center of the indentationmarks and that of the nugget. The force provided by the electrodesis fully used against thenuggetforce such that d = 0 and FE = FE,applied. Figure 6 shows a case with angular

misaligned electrodes. The nugget forms around the shortest electrical current path, which isnot the same as where the total electrode force is applied because of the angular

misalignment. As a result, an offset d is created between the applied electrode force and theforce from the nugget.The location of the applied electrode force is estimated from thesurface indentation and the nugget force is at the geometric center of the nugget.

A guideline for selecting an electrode force/welding schedule can be obtained by estimatingthe conditions of extreme cases. The force from the liquid nugget can be calculated with the

knowledge of its size and pressure.

Schematic diagram of simplified forces and their locations on one

workpiece at expulsion.


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PRESSURE AND FORCES IN LIQUID NUGGET

A volume increase occurs during heating in the solid state, solid to liquid phase

transformation, and heating in the liquid state. The volume change due to melting happens atthe melting point for pure metals and between solidus and liquidus temperatures for alloys

(except eutectic alloys). However, a free volume expansion of the nugget during resistancespot welding is not possible due to its surrounding solid containment and the squeezing ofelectrodes. As a result, pressure in the nugget may be significant because of the relatively low

compressibility of liquids. Another source of pressure in the liquid nugget is the pressure ofmetal vapors. Such pressure exists because at temperatures above the melting point, a closed

system tends to reach liquid/vapor equilibrium according to general thermodynamicprinciples. In add ition to metal vapor pressure, pressure from gases resulting from thermaldecomposition of surface agents should also be considered. Examples of surface agents are

lubricants on metal sheets, pretreatment agents, adhesives (in the case of weld-bonding), and

Forces acting on the weldment during resistance spotweldin in idealized

Schematic diagram of the balance of forces considered in themodel.FN is the force from the nugget due to liquid pressure and FE is theeffective

electrode force.


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adsorbed moisture or gases. The pressure can be evaluated by considering the type andamount of gaseous products, and their reactivity with, and solubility in, the liquid alloy.

So there are four major components of pressure in a liquid metal during resistance spot

welding: solid to liquid phase transformation (melting), expansion in the liquid state, vapors

from the liquid metal, and decomposition of surface agents.

P =Pmelt +Pexp +Pvapor +Pdecomp

PRESSURE DUE TO MELTING

As the result of melting a certain portion of the metal surrounded by the solid phase,

compression of the liquid takes place. The relationship between the volume V and pressurePin the liquid nugget at a given absolute temperature T can be described by the coefficient of

compressibility

V/P)T*1/ V

Therefore, for a small increment of volume, the resulting increase in pressure is

dP = d V*1/VSince the molten metal is not allowed to expand freely due to the containment of its solidsurrounding and electrode forces, the increase in pressure resulting from melting is

approximately the same as that from compressing the liquid metal from VLto VS. Thispressure can be obtained by integrating where VSand VLare molar volumes of solid and

liquid states, respectively, at the melting temperature. Therefore, the pressure due to meltingisPmelt= 1/ln(VL/ VS)

So a high volume change during melting results in a high pressure contribution.

PRESSURE CHANGE DUE TO LIQUID EXPANSION

A quantitative relationship between pressure and temperature under a constant volume can be

described by thermal pressure coefficient

= 1/P(P/T)v

Its value is unknown for most liquid metals. However, the partial derivative of P/T may be

presented as the product of two partial derivatives:

(P/T)v = - (V/T)p(P/V)vBy introducing a coefficient of volume thermal expansion,

= 1/V(V/T)r

and using compressibility coefficient , can be expressed by variables whose values can be

found in published metallurgical data sources:

= (1/P)(/


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Hence, for a small increment of temperature, the increase in pressure is: D

dP = (/dT

Integraing the above yields the contribution of pressure due to the expansion of the liquid

nugget in the range from melting point Tm to a given temperature Tat a constant volume inthe following form: de

Pexp = (/(TTmelt)

Because the contributions of vapor and surface agents to the total pressure are usually small,

they can be neglected in estimating liquid pressure and force from the nugget. Therefore

P = 1/ln(VL/ VS) + (/(TavgTmelt)

PROCEDURE FOLLOWED IN PRESSURE CALCULATIONS

Obtain material properties o f the maina lloying elements and surface contaminants.

Obtain information of temperature distributionand value, and dimensions of the nugget. Calculate pressure components and thetotal pressure.

Calculate forces in the directions of interest

CURRENT AND WELD TIME DETERMINATION

Weldability range (lobe) is the area where acceptable welds can be produced using a specificcombination of welding current and weld t ime. Welding range is limited by the minimumacceptable weld size and splash limit. In spot welding, weldability range is usually defined

using coordinate axes where weld time is located on one axis and welding current on theother. The electrode force used, electrode geometry and cleanness, and the consistency and

thickness of the welded material affect the shape and size of the weldabilityrange. Materials with good welding properties have a large weldability range, which meansthat welding parameters can be selected from a great number of different combinations. Cold

rolled metal sheets usually have a large weldability range. Welding current can vary from1.02.0.kA in common weld times. The alloying of the steel and thick zinc coat ing, in

particular, may decrease the weldability range. In this case, the correct use ofappropriate welding parameters is very important in terms of producing good spot welds.For a given combination of materials, electrodes, process conditions, and at a particular

electrode-force, the weld lobe describes a region of acceptable welding parameters.The parameter axes are generally weld time (duration) & weld current. The "lower" boundary

is the parameter combination that produces a weld button of minimum acceptabledimensions. The "upper" boundary is defined by expulsion conditions. Expulsion is a

probabilistic event, so one way to define the limit is to find the conditions that lead to (say)

50% of welds expelling. The area inside the lobe represents the "safe" welding window fornew electrodes. Generally the wider the better.


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CONSRUCTION OF LOBE CURVES

1. First you decide what is Cold, Hot, and OK. I use: Cold = undersize weld button when thecoupon is peeled apart, OK = greater than minimum acceptable size. Hot = expulsion

occurred during the weld.2. Select the proper tips, that have a contact size of at least the minimum button size required.3. Then setup the proper force for the job.4. Next you condition the tips with 25 welds, this is very important for coated materials.

5. Make a weld in a small coupon, record the current with an accurate weld current meter,along with the cycle time.

6. Peel the coupon apart, measure button size, length plus width, and divide by two. (Lengthand width are at a 90 degree axis)7. Classify the weld, OK, Hot, or Cold. Note, if you got expulsion, it is Hot, dont bother to

peel it.8. Enter the weld current under the appropriate column, there are four columns for OK, three

for Cold, and three for Hot, use whatever one you want.9. Continue with different current levels10. Then change cycle time to 4 cycles, and entered 7 more welds.

11. Then 6 cycles, then 7 cycles, then 3 cycles.As we fill in the area on the left, a chart is constructed on the right, that is our weld lobe. The

spreadsheet also finds which cycle time gave the widest acceptable current range, andannounces that is the cycle time to use, along with a current that is about 10% below theexpulsion level.


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Weld lobe data collection


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Electrode force = 200kgf/cm2

Elecrode force = 250 kgf/cm2

Elecrode force = 300 kgf/cm2


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SQUEEZE TIME SETTING

Figure 2 shows how the weld time can be started at different times relating to theforce cycle. In the middle example, the welding current comes on too early and the

squeeze time is too short to allow sufficient force to build up between componentsto produce a satisfactory weld. Many welding defects can be attributed to weldingwith too short a squeeze time.

The lower example shows a welding cycle where the current is applied late and the peak

force has been established for some time. Although acceptable welds may result from thissequence, time is wasted unnecessarily, and in volume production this can add significantcosts.

Examples of different squeeze times in resistance welding


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In the top figure, the squeeze time is adjusted so that the current is initiated just before thepeak welding force is achieved. This produces the best quality weld at the highest production

rate.

Modern programming systems for spot welding equipment enable the welding force current

value and the relevant time sequence to be programmed. On closer inspection theprogrammed sequence actually performed by the welding gun may differ from the intendedwelding cycle. This is because of delays in the control system due to mechanical inertia,

performance of the pneumatic force cylinder and other mechanical losses which modify the

intended time sequence. It is essential to calibrate not only the forge force and the weldingcurrent but also to set the squeeze time correctly.

The key forces are displayed on an illuminated bar on the Squeeze Analyser, shown

schematically in figure 2. Short squeeze times are indicated by a large gap between thesqueeze force and the peak force. Long squeeze times result in the squeeze force and the peakforce being identical so that no gap in the illuminated bar occurs. Ideal squeeze times show as

a small gap (one unlit light emitting diode) between squeeze and peak force. The simplevisual display of the Squeeze Analyser enables the supervisor quickly to assess the operatingvalues of a spot welding installation. In practice, it takes minutes to calibrate a gun correctly

for optimum operating conditions. The actual values of the forces are also indicated on thefront panel display.

PNUEMATIC VS SERVO GUN

Pneumatic or hydraulic cylinders actuate most spot welding guns. The electrodes move the

entire range of the cylinder when the gun opens and closes. Clamping force is normallyfixedby a pressure regulator, and there is usually no means to provide feedback regarding the

actual clamping pressure. The motor-controlled servo gun provides variable electrodeopenings and programmable regulated pressure.

Pneumatic guns often have two cylinders; one is used for short open and the other creates afull open space between electrodes. The servo gun (in position control) provides

programmable electrode opening anywhere between the full stroke of the gun. The electrodeopening can be programmed to move simultaneously with other axes of the robot.

Application flexibility cycle time savings are realized by the servo-gun's ability to open theelectrodes only a short distance, or a larger amount, to provide the exact clearance neededaround tooling or parts.

During the weld, the servomotor switches to torque control and provides a uniform calibratedclamping force. This is easily programmed in the robot control and is expressed as a unit of

force. The force can be stepped during an individual weld cycle or varied from weld to weldfor different material thickness stack-ups.

Pneumatic guns close at full clamping force, which creates high impact on the tips. Theservo gun controls the rate at which the electrodes close and ramps up to the clamping force.This controlled process extends the life of tips and is a major reason auto manufacturers have

been using them. The controlled clamp force also improves quality and cosmetics, allowingwelds to be made on Class A surfaces


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Hence squeeze time for pneumatic guns is set to 3-4 cycle whereas squeeze time for servoguns can be set to 0 as weld trigger is given only after the application of tip force.

SHEAR STRENGTH CALCULATION

The shear strength of a single spot weld can be calculatedas follows:Shear strength(N)= 2.6 t d Rm

where:t = sheet thickness, mmd = weld diameter, mmRm = tensile strength of the material, MPa

PEEL TEST

This test is conducted to determine nugget size and depth to ascertain the quality of spotweld.


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SPOT SAMPLE

For final verification spot samples were taken and their shear strength calculated by tensile-

shear testing machine in R&D lab.

Chisel test is conducted to check if spots are not broken

Spot sample jig


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Spot sample : 0.8-1.2mm sheet combination, current = 6.5, weld time = 15, pressure = 200




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AUTOMATIC DETECTION SYSTEM

There was a consistent problem of tip mis-alignment, improper face cutting and dresser not

rotating. As a result these problems were regularly checked by the maintenance and quality

department personnel. There was an urgent need to automate this process to avoid any

possibility of degradation in spot quality due to tip mis-alignment and face cutting.

TIP ALIGNMENT DETECTION

CONTRUCTION AND WORKINGThis device consists of a mild steel strip of dimension 30 X 100 resting on cast iron rods.

There is a pressure sensor below one of the rod. During tip dressing the tips will exert a

vertical force in opposite direction on the plate. Any misalignment will cause a moment in theplate which in turn would increase or decrease the force exerted by the rod on the pressure

sensor.

Tip separated by x

Mild steel strip

Cast iron hollow rods

Force sensor

Mx

R

R

F

FW


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TIP FORCE DETERMINATION

Usually for steel design, the yield strength is used with a factor of safety, or, alternatively, aload factor is applied to the design load, and bending stresses must not exceed the

yield stress.

The bending stiffness is equal to the product of the elastic modulus E and the area moment ofinertia I of the beam cross-section about the axis of interest. In other words, the bending

stiffness is EI . According to elementary beam theory, the relationship between the appliedbending moment M and the resulting curvature K of the beam is

M = EIK

The flexure of the plate depends on:

1. The plate thickness

2. The elastic properties of the plate

3. The applied load or forceAs flexural rigidity of the plate is determined by the Young's modulus, Poisson's ratioand

cube of the plate's elastic thickness, it is a governing factor in both (1) and (2).

Flexural Rigidity,

D = (Ehe3)/12(1v2)

E = Young's Modulus

he = elastic thickness (~1015 km)

v = Poisson's Ratio

Flexural rigidity of a plate has units ofPam3

, i.e. one dimension of length less from the onefor the rod, as it refers to the moment per unit length per unit of curvature, and not the totalmoment. I is termed as moment of inertia.J is denoted as 2nd moment of inertia/polarmoment of inertia

Factor of safety for mild steel = 3

Bending stress b = (MY)/I

Where M(X) = Bending Moment at X

Y = Maximum distance from the neutral axis

Ix= second moment of area= (bh3)/12 = 6.86* 10-12

Sheet thickness = 1.4, length = 100 mm, breadth = 30 mm

x = Maximum distance between misaligned weld tips in X direction = 15 mm = 1.5*10-2

Bending moment ,M(Nm) = F(50)F(50 + X)

Y = 1.4/2 = 0.7 mm = 7* 10-4 m

Maximum bending stress will be at the bottom most point.

b = (Fx*7* 10-4)/I

=( F*1.5*10-2*7* 10-4)/( 6.86* 10-12)

F = b /1.53*106
http://en.wikipedia.org/wiki/Pascal_(unit)http://en.wikipedia.org/wiki/Pascal_(unit)http://en.wikipedia.org/wiki/Pascal_(unit)http://en.wikipedia.org/wiki/Pascal_(unit)


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Bending stress has to be less than allowable tensile stress

Allowable tensile stress = Youngs modulus(E)/FOS

E for mild steel = 420 Mpa

Allowable stress , t = 420/3 = 140 Mpa

F = 140*106/1.53*106

= 93 N

MISALIGNMENT CALIBRATION

Mx = 0

0 = 50(1500)1500(50+X)RB(100)RB = 15x

RB can be determined from the load cell reading. Accordingly x is calculated to determine thedegree of misalignment.

Tips can be adjusted using L keys. 5 full rotation moves the tip 1mm towards the fixed tip.

FACE CUTTING DETECTION

Proper dress ing is required to bring the tip diameter to the required level. This is necessary so

that the required current density is maintained. It is also necessary to remove any carbondeposits that may obstruct the flow of current during welding.The device consists of component locating pin which is paced at the top of the metal strip.

The Robot gun travels a certain perpendicular distance from a datum until the gun tip touches

the locating pin. The distance is recorded to determine whether there is any hole at the tip

centre due to improper dressing.

To check the tip diameter after dressing the tip is made to exert certa in force over the gauge

pressure sensor. If the tip diameter is less pressure exerted would be high and hence improper

dressing would be detected.

X

Datum

Locating


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The material used is cast iron. Since the minimum force detectable from the load cell is veryless available cone with tip diameter 1.5 mm is feasible. The compressive stress developed

would be very less.ROBOT PROGRAMMINGTip dressing programm was modified in accordance with the sensor requirement. For e.g.

programm was made for the additional path robot follows after dressing, giving differentpressure schedule during testing and logic was given to check the conditions for proper

process in macro module.

1: !*** 371A TIP DRESS *** ;2: ;

3: UTOOL_NUM = 1 ;4: UFRAME_NUM = 0 ;5: $USEUFRAME = 0 ;

6: PAYLOAD[1] ;7: ;

8: !*** IO_RESET *** ;9: CALL IO_RESET ;10: ;

11: !*** AROUND HOME POSITION*** ;

12:L PR[2] 2000mm/sec FINE ;13: ;14: Reset Tip Wdn ;

15: ;16: LBL[1] ;

17: R[17] = 0 ;18: DO[213] = ON ;19: ;

20:L P[3] 2000mm/sec FINE ;21: ;

22: !*** BEFORE DRESS POSITION*** ;23:L P[4] 2000mm/sec FINE ;

24: ;25: DO[221] = ON ;

26: R[99] = $MCR.$GENOVERRIDE ;27: OVERRIDE = 100% ;28: ;

29: !*** DRESS POSITION *** ;

30:L P[5] 200mm/sec FINEPRESS_MOTION P=[99,89] ;


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31: ;32: WAIT 0.50(sec) ;

33: WAIT DI[203] = ON ;34: ;

35: !*** BEFORE DRESS POSITION

*** ;36:L P[4] 300mm/sec CNT0 ;

37: ;38: DO[221] = OFF ;

39: DO[213] = OFF ;41: ;42:L P[3] 1000mm/sec CNT10 ;

43: ;44: CALL TWD ;

45: ;46:L P[3] 1000mm/sec CNT10 ;

47: ;48: DO[210] = ON ;49: ;

50: !*** Tip Change Request *** ;51: IF DI[210] = ON,JMP LBL[10] ;52: ;

54: ;55: DO[210] = OFF ;

56: WAIT 0.50(sec) ;57: ;58: CALL WDN_CHK ;

59: ;60:L PR[2] 2000mm/sec CNT100 ;

61: ;62: CALL IO_RESET ;63: ;

64: !*** HOME POSITION *** ;65:L PR[1] 2000mm/sec FINE ;

66: ;67: !*** IO_RESET *** ;68: CALL IO_RESET ;

69: ;70: IF R[17] = 1,JMP LBL[1] ;

71: ;72: END ;73: ;

74: LBL[10] ;75: ;

76: ;77: !*** Tip Change Position *** ;78:L P[9] 2000mm/sec FINE ;

79: ;

80: Reset Tip Wdn ;81: ;


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CONCLUSION

Spatter reduction activities were a huge success. We reached our target of 5 % in 4 weld areas

in Ertiga line. Parameter determination for different sheet combination helped us achieve the

required spot quality at low current and weld time.

REFERENCES

1. Expulsion Prediction in Resistance Spot Welding by J. SENKARA, H. ZHANG,

AND S. J. HU2.

Spot Weld Properties When Welding With ExpulsionA Comparative Study by M.

Kimchi3. Ruukki-Resistance-welding-manual4.

Miller Handbook for Resistance Spot Welding

5.

http://www.updatetechnology.com/


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Documents

Spatter Reduction Report