Spatter Reduction Report
-
Upload
aabhimittal -
Category
Documents
-
view
227 -
download
0
Transcript of Spatter Reduction Report
-
8/10/2019 Spatter Reduction Report
1/77
1 | P a g e
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
-
8/10/2019 Spatter Reduction Report
2/77
2 | P a g e
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)
-
8/10/2019 Spatter Reduction Report
3/77
3 | P a g e
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
-
8/10/2019 Spatter Reduction Report
4/77
4 | P a g e
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
-
8/10/2019 Spatter Reduction Report
5/77
5 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
6/77
6 | P a g e
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
-
8/10/2019 Spatter Reduction Report
7/77
7 | P a g e
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
-
8/10/2019 Spatter Reduction Report
8/77
8 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
9/77
9 | P a g e
`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)
-
8/10/2019 Spatter Reduction Report
10/77
10 | P a g e
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
-
8/10/2019 Spatter Reduction Report
11/77
-
8/10/2019 Spatter Reduction Report
12/77
-
8/10/2019 Spatter Reduction Report
13/77
13 | P a g e
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
http://en.wikipedia.org/wiki/Fabrication_(semiconductor)http://en.wikipedia.org/wiki/Fabrication_(metal)http://en.wikipedia.org/wiki/Fabrication_(metal)http://en.wikipedia.org/wiki/Fabrication_(semiconductor) -
8/10/2019 Spatter Reduction Report
14/77
14 | P a g e
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
-
8/10/2019 Spatter Reduction Report
15/77
15 | P a g e
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
-
8/10/2019 Spatter Reduction Report
16/77
16 | P a g e
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
-
8/10/2019 Spatter Reduction Report
17/77
-
8/10/2019 Spatter Reduction Report
18/77
18 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
19/77
19 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
20/77
20 | P a g e
Painting process I/C
& Top Coat painting
Painting process Final
Inspection
-
8/10/2019 Spatter Reduction Report
21/77
21 | P a g e
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.
.
-
8/10/2019 Spatter Reduction Report
22/77
22 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
23/77
23 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
24/77
24 | P a g e
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).
http://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Alloyhttp://en.wikipedia.org/wiki/Alloyhttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Alloyhttp://en.wikipedia.org/wiki/Copper -
8/10/2019 Spatter Reduction Report
25/77
25 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
26/77
26 | P a g e
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
-
8/10/2019 Spatter Reduction Report
27/77
27 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
28/77
28 | P a g e
-
8/10/2019 Spatter Reduction Report
29/77
29 | P a g e
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
-
8/10/2019 Spatter Reduction Report
30/77
30 | P a g e
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
-
8/10/2019 Spatter Reduction Report
31/77
31 | P a g e
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
-
8/10/2019 Spatter Reduction Report
32/77
32 | P a g e
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.
40
22
5
0
5
10
15
20
25
3035
40
45
W1 Jan 14 W2 Jan 14 W3 Jan 14 W4 Jan 14
S
p
a
t
t
e
r
%
Period
YL8 Ertiga - LH Side body Spatter
control progress
-
8/10/2019 Spatter Reduction Report
33/77
33 | P a g e
And now after 4 monthsthe current spatter and the difference thathas been made can be seen in below bar graph:
0
5
10
15
20
25
30
35
40
S
P
A
T
T
E
R
%
YL8 LINE SPATTER STATUS AS ON 28.04.2014
YL8 Line Feb'14
YL8 Line Mar'14
YL8 Line Apr'14
-
8/10/2019 Spatter Reduction Report
34/77
34 | P a g e
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.)
40
6.6 9 6
0
5
10
15
20
25
30
35
40
45
Jan'14 Feb'14 March'14 April'14
S
P
A
T
T
E
R
%
Period
YL8 LSB Line Spatter Status
-
8/10/2019 Spatter Reduction Report
35/77
35 | P a g e
Area wise Summary sheet updated on regular basis :
-
8/10/2019 Spatter Reduction Report
36/77
-
8/10/2019 Spatter Reduction Report
37/77
37 | P a g e
Zero touch up and dressing training module was made for line superviser and workers.
-
8/10/2019 Spatter Reduction Report
38/77
38 | P a g e
-
8/10/2019 Spatter Reduction Report
39/77
39 | P a g e
-
8/10/2019 Spatter Reduction Report
40/77
40 | P a g e
Below is the step by step instruction for Fanuc robot to conduct zero touch up procedure.
-
8/10/2019 Spatter Reduction Report
41/77
41 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
42/77
42 | P a g e
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)
-
8/10/2019 Spatter Reduction Report
43/77
43 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
44/77
44 | P a g e
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
-
8/10/2019 Spatter Reduction Report
45/77
45 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
46/77
46 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
47/77
47 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
48/77
48 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
49/77
49 | P a g e
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
-
8/10/2019 Spatter Reduction Report
50/77
50 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
51/77
51 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
52/77
52 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
53/77
53 | P a g e
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
-
8/10/2019 Spatter Reduction Report
54/77
54 | P a g e
CONCLUSIONS
Easy for engineer to trace back the broken spot robot
Easy to find out the component details with the help of index.
-
8/10/2019 Spatter Reduction Report
55/77
55 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
56/77
56 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
57/77
57 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
58/77
58 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
59/77
59 | P a g e
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)(/
-
8/10/2019 Spatter Reduction Report
60/77
60 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
61/77
61 | P a g e
-
8/10/2019 Spatter Reduction Report
62/77
62 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
63/77
63 | P a g e
Weld lobe data collection
-
8/10/2019 Spatter Reduction Report
64/77
64 | P a g e
Electrode force = 200kgf/cm2
Elecrode force = 250 kgf/cm2
Elecrode force = 300 kgf/cm2
-
8/10/2019 Spatter Reduction Report
65/77
65 | P a g e
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
-
8/10/2019 Spatter Reduction Report
66/77
66 | P a g e
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
-
8/10/2019 Spatter Reduction Report
67/77
67 | P a g e
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.
-
8/10/2019 Spatter Reduction Report
68/77
68 | P a g e
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
-
8/10/2019 Spatter Reduction Report
69/77
69 | P a g e
Spot sample : 0.8-1.2mm sheet combination, current = 6.5, weld time = 15, pressure = 200
Spot sample : 1.2-1.2mm sheet combination, current = 6.5, weld time = 18, pressure = 250
Spot sample : 1.4-1.2mm sheet combination, current = 6.5, weld time = 20, pressure = 300
-
8/10/2019 Spatter Reduction Report
70/77
70 | P a g e
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
-
8/10/2019 Spatter Reduction Report
71/77
71 | P a g e
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) -
8/10/2019 Spatter Reduction Report
72/77
72 | P a g e
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
-
8/10/2019 Spatter Reduction Report
73/77
73 | P a g e
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] ;
-
8/10/2019 Spatter Reduction Report
74/77
74 | P a g e
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: ;
-
8/10/2019 Spatter Reduction Report
75/77
-
8/10/2019 Spatter Reduction Report
76/77
76 | P a g e
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/
-
8/10/2019 Spatter Reduction Report
77/77