Spot Weld - Pres

8/3/2019 Spot Weld - Pres

1/96


2/96

WHAT IS WELDING?

Welding is the process of joining metas

HEATJOINING

OF METAL

MELTING

OF METAL

FILLER MATERIAL

NO FILLER MATERIAL1. E. CURRENT2 GAS

3 CHEMICAL

REACTION


3/96

HOW MANY TYPES

WELDING ARE THERE?

1. ARC WELDING

2. RESISTANCE WELDING

3. GAS WELDING

4. LASER BEAM WELDING

5. THERMIT WELDING ETC.


4/96

TYPES OF WELDING POWER SUPPLIES

1.A.C Welding power supply

2.Capacitor-Discharge power supply

3.Transistor power supply

4.Frequency Inverter power supply

5.A.C Inverter welding power supply


5/96

TYPES OF RESISTANCE

WELDING

1. SPOT WELDING

2. PROJECTION WELDING

3. FLASH WELDING

4. SEAM WELDING

5. BUTT WELDING


6/96

WHAT IS RESISTANCE WELDING?

In this process, an electrical

current flows through resistive

circuit to generate enough heatbetween two pieces of sheet

metal so that the metal reaches

molten stage.The resistance to

the flow of current is provided

by the work piece.Themaximum heat is generated at

the point of maximum

resistance.


7/96

Principles of Resistance welding

A spot welding is made by pressing two or more overlapping piece

together while an electrical current is passed through a localized

contact area. The heat in the welding zone should be generated rapidly

so that only minimum heat is dissipated by conduction to cooler area.

The current is high but the voltage is very low and there is no danger

of an electric shock.

Resistance Welding is suitable for low cost and mass production and

is widely used in the automotive and electronics parts industries.


8/96

MAJOR ELEMENTS OF SPOT WELDING

* WELD CURRENT

* WELD TIME

* PRESSURE

* RESISTANCE

* ELECTRODE SHAPE (CURRENT DENSITY)


9/96

Current Is the rate of flow of a given no of electrons

through a particular cross section of a

conductor

The unit of current is amps ( A )


10/96

WELD TIME CONTROL FOR SPOT WELDING

1 . SQUEEZE TIME TIME REQUIRED FOR THE ELECTRODE

TO CLOSE ON METAL AND APPLY PROPER PRESSURE. IT

VARIES WITH THE GAP BETWEEN THE ELECTRODES .

2. UPSLOPE TIME TIME TAKEN FOR THE CURRENT TO

REACH FROM ZERO THE PEAK VALUE.

3. WELD TIME TIME REQUIRED FOR PEAK

CURRENT TO FLOW AND HEAT THE METAL4. DOWN SLOPE TIME TIME TAKEN FOR THE

CURRENT TO CUT OFF I.e, FROM PEAK TO ZERO


11/96

WELD TIME CONTROL FOR SPOT WELDING

5. HOLD TIME TIME TAKEN BY THE ELECTRODES TO

HOLD THE SHEETS TOGETHER AFTER THE CURRENT

FLOW STOPS. PRESSURE STILL APPLIED TO ALLOW

THE MOLTEN METAL TO SOLIDIFY.

6. OFF TIME IT IS THE TIME BETWEEN THE END OF ONE

SPOT SEQUENCE TO START OF NEXT SPOT SEQUENCE


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WELDT

IMECO

NTROL

FOR

SPOTWELDINGT

IM

E

CURRENT

SQEEZE

UP SLOPE

WELD

DN SLOPE

HOLD

OFF


13/96

TIMER CONTROLLER


14/96

WELDING CURRENT FEATURES AND MEASUREMENT

WHY CURRENT CAN NOT MEASURE WITH AMETER

In spot welding ,large current flows for very short time (0.02 sec -0.5 sec ), AMETER cannot

respond so quickly.

HOW TO MEASURE THE CURRENT

In spot welding current is measured with Toroidal coil

When high current flows it generates magnetic

field and magnetic flux interlink with the coil

generate Electromotive force in proportion to rate of change

of current to time V = K di/dt K is constant

Coil output V is in proportion to the coil

area and nos. of turns This type of sensor can measure any large current in differential value To

get absolute value it is interlink with electronic circuit.

Flux

Current

iCoil

Electromoti

ve force

Vi


15/96

How to check current?

Weld checker

Toroidal coil


16/96

Resistance weldingRelation between Current and time

B

C

Time

Current

A

A: Strong current and short time

C: Small Current and long time

B:Medium current and medium time

A :- WILL HAVELESS WORK DISTORTION

LESS OXIDATION

GOOD WELDABILITY


17/96

Change in Current Density


18/96


19/96

PROPERTIES AND FUNCTION OF ELECTRODESREQUIREMENT OF ELECTRODES

1. ELECTRODES CENTERED AND FIXED SECURILY TO ELECRODES HOLDER

2. FREE MOVEMENT ALLOWING FOR CONSITTENT PRESSURE REPEATABILITY

3. QUICK RESPONSE OF THE ELECTRODE ARM ALLOWS FOR PRESSURE TO BE MAINTAINED DURING

WELDING

4. ELECRODES MUST HAVE LOW NATURAL RESITANCE, HIGH HEAT CONDUCTIVITY AND

MAINTAINED HARDNESS EVEN AT HIGH TEMPERATURES

5. HIGH CONDUCTIVITY ELECTRODES ARE USED FOR LOW CONDUCTIVE MATERIALS AND LOW

CONDUCTIVE ELECTRODES BEING USED FOR HIGH CONDUCTIVE MATERIAL

FUNCTIONS OF ELECTRODES

1. THEY SUPPLY THE SUFFICIENT WELDING CURRENT TO THE WORK ( GOOD ELECTRICAL CONDUCTOR )

2. THEY HELP DISSIPATE THE THE HEAT FROM THE WELD ZONE (HIGH THERMAL CONDUCTIVITY)

3. THEY TRANSMIT THE REQD. FORCE TO THE WORK (GOOD MECHANICAL STRENGTH )

SHAPE OF ELECTRODES

1. AS TIP OF THE ELECRODE DETERMINE THE WELDING AREA ON THE WORK PIECE IT IS NECESSARY

TO MAINTAIN THE CONTANT SHAPE FREE FROM WEAR

2. MANY TYPES OF SHAPES ARE USED IN ELECTRODES

F - TYPESCR - TYPES

CF - TYPESR - TYPESP - TYPES

THE MOST COMMONLY USED ELECTRODES SHAPES ARE P AND CR TYPES.


20/96

Electrode tip length

The endurance life of electrode tips depends from the

length of the copper part of the electrode tip besides the

material.


21/96

Resistance welding

Relation between Current and Pressure

CurrentA:High Current and High Pressure

B:Medium current and medium Pressure

C: Small Current and High Pressure

ExplosionSmall

Large

Nugget Dia

(Strength)

No NuggetSplash

B - will have

Good Weld

Less Spatters

Optimum Nugget Dia


22/96

How to check pressure?

Pressure gauge

Electrode


23/96

Resistance

Is the internal opposition a material offers to the flow ofelectrical current.

The unit is Ohms (:)( when very small value is referred, resistance is often represented using micro ( Q:) = 10-6

Ohms

The Magnitude depends on the material and varies as the lengthchanges, but inversely proportional to the cross sectional area ofthe conductor.

R=V( L/A)V=resistivity , L= Length, A= Cross section

Resistance also changes as the temperature of the material

changes.RT= R20 (1+E(T-20))

RT= Resistance at T0C, R20= Resistance at 20

0C

E=Temperature coefficient of the material


24/96

Contact Resistance


25/96

Impedence

When an alternating current passes through a conductor, aninductive reactance will oppose the flow of current. ( X)

The combination of the inductance and the resistance is

called the impedence ( Z )

Z= (R

2

+ X

2

)

1/2


26/96

Generation of heat Heat energy is generated when ever

electrical current is passed through an

electrical resistance.

Q=I2RtQ= watt-seconds or joules

I=Current in amperesR=Resistance in Ohms

t= Time in cycles ( 1 cycle = 20 milli sec )


27/96

Temperature gradient


28/96

Temperature gradient


29/96

Change in Contact Resistance during Welding


30/96

Heat Zone


31/96

PSW WELDING SYSTEM

Welding gun Transformer Controller ELCB

ELCB


32/96

TYPES OF SPOT WELDING GUNS

1. Portable spot welding (PSW ) gun

2. IT spot welding gun

3. SSW(Stationary Spot Welder)

4. Servo gun

5. Fixture gun


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PSW (X TYPE GUN)


34/96


35/96

Gun Body


36/96

PARAMETER FOR SELECTION OF TIPS

Tip Dia Sheet

thickness

Conditions

12 0.4 ~0.8 Used in PSW and SSW

13 0.4 ~ 0.8Used generally in Cap tip in

PSW

16 0.6 ~ 2.0Used both as Cap and normal

in PSW &SSW

Tip Material should be ( CRM 16-CuCr 1Zr)

Cr 0.4 - 1 % , Zr 0.02 -0.1 % & Cu - Bal.Properties

Conductivity:- 75 ~ 80

Hardness :- 130~170 Brinel


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38/96

Electrode cooling


39/96

Why cooling? The electrodes with its tips are tightly on a work piece made of steel that temperature must be

that high to melt its material. The electrodes must be cooled for protection and endurance live

purposes Increases the temperature of the secondary circuit from 20C up to 80C, in that case increases

the resistance in the secondary circuit. Copper parts increase their resistance by 6 x 4% = 24%,brass parts by 6 x 1,5% = 9%.

It can be assumed that the resistances of secondary circuits are dominated 90% by copperparts.

In the case the welding current in the secondary circuit at a temperature of 20Current is 10kA then

Does the temperature of the secondary circuit rise up to 80C:

The welding current falls down to 8 kA. To keep the welding current constant, the secondarycircuit must be cooled.

With rising temperature the electrodes get less hard. The danger of deformation occurs and thecontacting areas of the tips get larger. Therefore the welding current density reduces and thewelding spot quality gets worse.

Well cooling makes the endurance life of the electrode tips longer. Good cooling of thesecondary circuit secures a constant welding current and a constant current density!


40/96

EFFECT OF WATER COOLING

Water Flow Rate in PSW Should be 20~25 Ltr/Min

Water temp for circulation should be 25 deg C

Less Water flow result inHigh consumption of Tip

Bigger nugget Dia

Low strength of Welds


41/96

Preparation for MS Spot welding*Material to be welded should be free from Dust, Rust, Paint,

Grease & Acid substance*The Electrode should be of RWMA CLASS - II (Conductance

75% & Hardness 130 ~170 Brinnel

*Min Pitch is to be maintained as per table to avoid the

*Shunting of current due to adjacent spots.It can also be

corrected by increasing current with due consideration of

shunting current

* If the lap between two plates goes less , it will reduce the

strength and lead to undulation and Distortion

*In case of welding 2 sheets of different thickness ,condition

of thinner sheet is applicable.However in principle ratio

should be kept max between 1:3. In case of three or more

sheet,Total sheet thickness should not exceed the 4 times of

thinner sheet. Condition for mean value is applicable


42/96

USE OF COATED SHEET

Flange width

Welding condition has to be raised for welding coated sheets. As the heat disspating capacity of dia 13 tip

is less as compared to dai 16 tip ( volume ratio is 1:1.6) , life of dia 13 tip will be reduced requiring large

no. of changeovers as comapred to dia 16 tip and also it needs more time to weld same quantity of spots

as compared to dia 16 tip as shown in the table .

There is a difference of 1:1.6 in the volume ratio of the tips and this controls the weldability greatly

For instance, when you weld the steel board of t0.7 mm

Uncoated Coated

2 sheets 7.8KA, 14 cycles 9.2 KA, 14 cycles

Dia 16 tip 54 spots/min or less 39 spots/min or less

Dia 13 tip 21spots/min or less 15 spots/min or less

3 sheets 8.2 KA, 14 cycles 9.7 KA, 14 cycles



Lets take the case of YD2 weldingline

There are 1805 respot ( about 70% of total spots) and on an average operator can weld about 25spots/min

and the tact time is 2.55 min

Incase of Dia 16 tip, 29 welding guns will be needed whereas in case of dia 13 tip, 48 welding guns will

be needed thus requiring more investment and space ( asuming 2 nos. coated sheets).


43/96

Direction of Flange

As for zinc that is the surface treatment material of the coated sheet, the melting point is relieved by the

dispersion of low straightening spatter. As a result, it becomes a pockmarked pattern on externals and the

decrease in the quality is caused in the part where zinc is relieved.Moreover, the steel sheet might get transformed by receiving heat from spatter from the short distance and

causes irregularity. It doesn't completely return to the original shape though finish is required in both cases.

Moreover, the plated layer given with great pains as the result is peeled off. In the design of the body,

consideration where the skin is not located in the welding flange extension is necessary.

USE OF SUPER DEEP DRAWING MATERIALDecrease in strength

Incase of deep drawing material like SPCX, ultimate tensile strength is less as compared to the normal

material like SPCC. Due to heat affected zone, strength falls further resulting in degradation of strength

by about 15% as comapred to normal steel.

Minimum welding pitch ; Standard for minimum welding pitch is 20mm

In case the spot pitch is reduced more than this, the strength of each spot will decrease so this minimum

pitch has to be secured. Incase more spots are needed to secure proper strength, spots should be

staggered as shown belowAs staggering of spots require more flange width, this has to be checked in the drawing.

20


44/96

REFERENCE FOR MS SPOT WELDING

(A-class )

Thickness(mm) Rank

0.9 1

0.91.2 2

1.21.6 3

1.6 4

Thickness rank table

Thic

knes

srank

Weld

Time(cyc)

Weld

Curre

nt(kA)

Electrod

e

Force(kN)

Thic

knes

srank

Wel

d

Tim

e(cyc)

Weld

Curre

nt(kA)

Electrod

e

Force(kN)

Thi

ckn

ess

rank

Wel

d

Tim

e(cyc)

Weld

Curren

t(kA)

Electrode

Force(kN)

Thicknessrank

Wel

d

Tim

e(cyc)

Weld

Curre

nt(kA)

Electrode

Force(kN)

11 13 7.5 1.96 111 13 7.5 1.96 212 13 7.5 1.96 313 13 7.5 1.96

12 13 7.5 1.96 112 13 7.5 1.96 213 13 7.5 1.96 314 15 8.0 2.94

13 13 7.5 1.96 113 13 7.5 1.96 214 13 7.5 1.96 323 17 7.5 1.96

14 13 7.5 1.96 114 13 7.5 1.96 222 15 7.5 1.96 324 17 8.0 2.94

22 15 7.5 1.96 121 13 7.5 1.96 223 17 7.5 1.96 333 17 8.0 2.94

23 15 7.5 1.96 122 15 7.5 1.96 224 17 7.5 1.96 334 17 8.0 2.94

24 15 7.5 1.96 123 15 7.5 1.96 232 17 7.5 1.96 343 17 8.0 2.94

33 17 7.5 1.96 124 17 7.5 1.96 233 17 7.5 1.96 344 17 8.0 2.94

34 17 7.5 1.96 131 13 7.5 1.96 234 17 8.0 2.94 414 15 8.0 2.94

44 17 8.0 1.96 132 15 7.5 1.96 242 17 7.5 1.96 424 17 8.0 2.94

133 17 7.5 1.96 243 17 8.0 2.94 434 17 8.5 2.94

134 17 7.5 1.96 244 21 8.0 2.94 444 21 8.5 2.94

141 13 7.5 1.96

142 15 7.5 1.96

143 17 7.5 1.96

144 21 8.0 2.94

Only General sheet is applied.


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(A-class )

Max 'd' MIN 'D WELD

TIME

TIP

PRESSU

CURRENT NUGGET

DIA

SHEAR

STRENGTH

mm mm mm mm mm cycle Kgf Amprs mm Kgf

0.4 3.2 10 8 10 5 115 5200 4 180

0.5 4.8 10 9 11 6 135 6000 4.3 240

0.6 4.8 10 10 11 7 150 6600 4.7 300

0.8 4.8 10 12 11 8 190 7800 5.3 440

1 6.4 13 18 12 10 225 8800 5.8 610

1.2 6.4 13 20 14 12 270 9800 6.2 7801.6 6.4 13 27 16 16 360 11500 6.9 1060

1.8 8 16 31 17 18 410 12500 7.4 1300

2 8 16 35 18 20 470 13300 7.9 1450

2.3 8 16 40 20 24 580 15000 8.6 1850

3.2 8 16 50 22 32 820 17400 10.3 3100

* The welding Speed is high

* The dispersion of welding strength is small

*Welding machine of high capacity is required*Welding is done for particular stength

BEST CONDITION (A - CLASS )SHEET

THICKNESS

TIP DIA PITCH

MIN

LAP

MIN

D

d lap


46/96

Max

'd'

MIN

'D

WELD

TIME

TIP

PRESS

URE

CURRE

NT

NUGGE

T DIA

SHEAR

STREN

GTH

WELD

TIME

TIP

PRESS

URE

CURRE

NT

NUGGE

T DIA

SHEAR

STREN

GTH

mm mm mm mm mm cycle Kgf Amprs mm Kgf cycle Kgf Amprs mm Kgf

0.4 3.2 10 8 10 8 75 4500 3.6 160 20 40 3500 3.3 125

0.5 4.8 10 9 11 10 90 5000 4 210 24 45 4000 3.6 175

0.6 4.8 10 10 11 12 100 5500 4.3 280 26 50 4500 4 225

0.8 4.8 10 12 11 15 125 6500 4.8 400 30 60 5000 4.6 355

1 6.4 13 18 12 20 150 7200 5.4 540 36 75 5600 5.3 530

1.2 6.4 13 20 14 23 175 7800 5.8 680 40 85 6100 5.5 650

1.6 6.4 13 27 16 30 240 9100 6.7 1000 50 115 7000 6.3 925

1.8 8 16 31 17 32 275 9500 7.2 1200 55 130 7500 6.6 110

2 8 16 35 18 36 300 10300 7.6 1370 58 150 8000 7.1 1305

2.3 8 16 40 20 44 370 11300 8.4 1770 65 180 8600 7.9 1685

3.2 8 16 50 22 60 500 12900 9.9 2850 78 260 10000 9.4 2665

*Welding speed is medium * The welding speedis low

*The dispersion of welding strength is averag *The dispersion of welding strength is large

*Welding machine of small capacity is suffici

*Welding is done for strength *Welding strength is not a criteria

C- CLASSB - CLASSSHEETTHICKN

ESS

TIP DIA PITCHMIN

LAPMIN


( B & C Class )


47/96

Welding parameters board


48/96

ELECTRODE TIP

WATER

TEFLON TUBE

6 mm

2~3 mm

0.5 mm

TIP DIA BE CHECKED AFTER DRESSING WITH GO / NOGO GAUGE

ELECTRODE

GO NOGO

6~8 mm < 8mm

GAUGE FOR TIP DIA

USED NEW

WEAR LINE


49/96

How to do the dressing of electrode?

Electode

Dressing


50/96

ALIGNMENT OF TIPS

BEST SPOTTIP ALIGNMENT

OK

100 %

Matching90 %

Matching

< 90 %

Matching

NOT OKACCEPTABLE


51/96

GUN ALIGNMENT FOR UNDLATION

NOT OKNOT OK

OK


52/96

Electrode Pushing


53/96

TESTING METHOD AND

ACCEPTANCE CRITERIA

SL.

NOTYPE OF TEST METHOD OF CHECKING FREQUENCY

NON-DESTRUCTIVE TEST VISUAL CHECK FOR ALL SPOTS

I. NO CRACK

ii NO PIN HOLE

iii NO UNDULATION

b. CHIESEL TEST

DRIVE CHIESEL IN B/W

TWO PLATES BY HAMMER

TILL YOU HEAR METALLIC

SOUND

EVERY ONE

HOUR

2 DESTRCUCTIVE TEST BY CHIESEL

a. SHEAR TEST

DRIVE CHIESEL IN B/W

TWO PLATES BY HAMMER

TILLNUGGET IS FOUND

ONCE IN 2

Hrs on

( Test Pc )

B. TENSILE SHEAR TEST BY UTM

STANDARD TEST SHEETS

ARE TESTED IN UTMFOR

SHEAR STRENGTH

ONCE INA

MONTHS

a. APPEARANCE TEST1


54/96

Verifying Weld spot

300Kg


55/96

Size of the welded spot The size of the nugget depends on the thickness of the

sheets as well as on the size of the electrode tips. To avoid unwanted deformations on the outer surface of

car panels, the concerning electrode should have a large

contacting area.


56/96

Weld defects


57/96

Spot Weld defectso Expulsion

o Surface fusion

o Excessive indentation

o Blow hole

o Crack in nugget

o Insufficient nugget

o Too much fusion

o Deformed nugget


58/96

Causes Electrode tip diameter

Weld force Weld time

Surface condition

Cooling

Current shunting Impedance / resistance

Input power

Work piece

S i f


59/96

Spot welding defectsSl no. DEFECTS CAUSES COUNTERMEASURES

DIRTY AND SCALY MATERIAL

POOR FIT UP OF PARTS

TIP MATCHING NG TIP DRESSING TO BE DONE EVERY ONEHOUR

SQUEEZE TIME TOO LESS ENSURE THE CORRECT SQ TIME

WELD CURRENT VERY HIGHT

ENSURE THE CURRENT SETTING OK

(CURRENT TO BE CHECKED WITH

CALIBERATED WELD CHECKER )

WELD TIME VERY HIGH

WELD PRESSURE LESS

ENSURE THE TIP PRESSURE RIGHTAFTER

CHECKING WITH CALIBERATED PRESSURE

GAUGE

GUN POSITIONNOT OKOPERATER EDUCATIONFOR GUN

BALANCING AND COMP BALANCING

HOLD TIME VERY LESS INCREASE THE HOLD TIME

TIP WORNOUT REPLACE THE TIP

HIGH CURRENT

ENSURE THE CURRENT SETTING

CORRECTLY (CHECK IT WITH CALIBERATED

WELDCHECKER )

DIRTY , SCALY AND RUSTED MATERIALCLEAN THE PARTS

TIP PRESSURE LESS

ENSURE THE TIP PRESSURE RIGHT AFTER

CHECKIN

G WI

TH CA

LI

BERA

TED PRESSUREGAUGE

GUN POSITIONNGOPERATER EDUCATIONFOR GUN


ELECTRODE ALIGHNMENT NG GUNARMS PLAY ,TO BE CORRECTED

SHEET OVERLAP LESS OPERATER EDUCATION

TIP PRESSURE HIGHENSURE THE TIP PRESSURE RIGHT AFTER

CHECKING WITH CALIBERATED PRESSURE

PARTS ARE NOT FITTED PROPERLY IN

THE FIXTURE CLAMPING OF PARTS TO BE DONE

UNDULATION3

SPOT BURR

(EXPUSION )

AND TIP

STICKY

1

PIN HOLE2

S ldi d f


60/96

Spot welding defectsSl no. DEFECTS CAUSES COUNTERMEASURES

WELD CURRENTVERY LOWENSURE THE CURRENT IS CORRECT

(CHECK WITH CALIBERATED WELD

WELD FORCE VERY LOWENSURE THE TIP PRESSURE IS CORRECT

(CHECK WITH CALIBERATED PRESSURE

WELD TIME VERY LOW ENSURE THE CORRECT WELD TIMEPOOR FIT UP OF PARTS IN THE

FIXTURE

EXCESS UNDULATIONOPERATER EDUCATION FOR GUN


GUN POSITIONNGOPERATER EDUCATION FOR GUN


TIP MATCHING NGTIP DRESSING TO BE DONE EVERY HOUR

AND ENSURE THE TIP MATCHING

DIRTY OR SCALY MATERIAL SHEET CLEAN THE SURFACE

SPOT ON ROOT RADIUS ENSURE PROPER GUN POSITION

ELECRODE FACE TOO LARGE /TIP

WORNOUT / DEFORMED

TIP TO BE REPLACED. INSIDE TEFLON TUBE

TO BE CHECKED

TIP RAW MATERIAL NG ENSURE STANDARD QUALITY OF TIPS.

WATER FLOW TO BE CHECKEDGUNARM TOUCHING/ ( SHORT CKTING

OF CURRENT )

GUNARMINSULATION / OBSTACKLE TO BE

RECTIFIED

SPOT PITCH LESS ( SPOT TOO CLOSE

)

PROPER PITCH TO BE MAINTAINED.

OPERATER EDUCATION

LOW LINE VOLTAGE

FOOL PROOFING TO BE DONE FOR LINE

VOLTAGE

SPOT FAILURE

( NO NUGGET OR

LITTLE NUGGET

- WELD NOT

HOLDING )

4


61/96

Error caused by work pieces.


62/96

Error caused by work pieces 2

S tt


63/96

Spatters

Generally spatters are caused by an incorrect adjustment!

With correct adjusted welding parameters und electrodeswell lined up no spatters will occur!


64/96

Calculation of the time needed to weld a spot -1


65/96



66/96



67/96

COATED SHEETS PRESENTATION


68/96

Galvanized steel sheets

Galvanized steel sheets require a higher welding current in

alliance of a higher electrode-force (approximately 10%)

than not coated steel sheets!


69/96

zinc splatters

Due to possible zinc splatters galvanizedsheets need a correct adjusted welding

current


70/96

Reference for Galvanized sheet Spot welding

mm MICRONES cycle Kgf Amprs Kgf

0.6 9000 250 7 300

0.8 10000 270 8 450

1 10000 300 9 600

1.2 12000 350 10 700

1.6 15000 450 12 1150

2 19000 600 15 15500.6 9000 250 7 330

0.8 10000 270 8 500

1 10500 300 9 650

1.2 11500 350 10 850

1.6 13500 450 12 1300

2 17000 600 15 1600

0.6 9000 250 7 330

0.8 10000 270 8 500

1 11000 330 9 650

1.2 12500 400 10 900

1.6 15000 450 12 1300

2 20000 650 15 1600

SHEAR

STRENGTH

WELD

CURRENT

TIP

PRESSURE

WELD

TIME

TYPE SHEET

THICKNESS

ONE SIDE

PLATING

THICKNESS

8 ~ 12

HOT DIP

PLATING10 ~ 15

ELECTROP

LATING2 ~ 3

ALLOY

PLATING


71/96

PROJECTION WELDING


72/96

PROJECTION WELDING

* PROJECTION WELDING IS A TYPE OF RESISTANCEWELDING.

* AS THE NAME IMPLIES IN THIS TYPE OF WELDING

ONLY THE PROJECTED PORTION IS MELTED ANDJOINED TO THE BASE METAL..

* HIGH CURRENT IN LESS TIME IS THE MAIN

FEATURE OF THIS WELDING.

* PROJECTION NUT AND PROJECTION STUD OF

STANDARD SPECIFICATION CAN BE WELDED.


73/96

PROJECTION NUT WELDING

UPPER ELECTRODE

PIN

LOWER ELECTRODE

SPRING

OKNG

NUGGET

PIN

Reference for projection nut welding


74/96

Reference for projection nut welding

mm mm cycle amp Kgf Kgf

M 5 / M 6 0.7 5 9000 225 250/350

0.8 5 10000 225 250/350

1.2 6 11000 225 250/350

M 8 0.7 6 9500 230 450

0.8 6 11000 230 450

1.2 6 13000 260 450

M 5 / M 6 0.7 5 9000 200 250/350

0.8 5 10000 240 250/350

1.2 5 10500 300 250/350

M 8 0.7 5 9500 220 450

0.8 5 10000 240 450

1.2 6 11000 270 450M 10 0.8 6 12000 300 600

1.2 6 13000 370 600

M 12 0.8 6 13000 300 800

1.2 6 14000 370 800

WELD TIME

PROJECTIONHEXAGONAL NUT

PROJECTION SQUARE NUT

NUT SIZE SHEET

THICKNESS

SHEAR

STRENGTH

WELD

CURRENT

TIP

PRESSURE


75/96

PROJECTION STUD WELDING

LOWER ELECTRODE

AFTERBEFORE

UPPER ELECTRODE

WORK PC.

FUSION

WATER

CIRCULATION

Reference for projection Stud welding


76/96

Reference for projection Stud welding

TWIST Kg-

cm

TENSILE

Kg

M82.6 9 11000 570 800

1900

1 9 9000 340 290420

M62.6 9 6500 210 400

1100

1 9 5800 190 180

320

M52.6 9 5500 180 200

800

1 9 4800 160 120

260

M42.6 9 5000 140 100

500

1 9 4000 90 60240

WELDING STRENGTHWELD TIMESCREW

SIZE

SHEET

THICKNESS

WELD

CURRENT

TIP PRESSURE

STUD WELDING (FLASH WELDING )


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STUD WELDING (FLASH WELDING )

LIFT PLUNGE

LIFTINGACTION

WELDING

CURRENT

HEATING

TEMPERATURE

STUD

BASE METAL

EXCITATION

OF COIL

LIFTED CONDITION

PILOT ARC

VOLTAGE PILOT ARC

WELDING

PULSE

PLUNGE

POINT

MELT CONDITION

Reference condition for Stud welding


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Reference condition for Stud welding

M3

0.6-1.2 4.5 60-90 15-25

M4 0.6-1.2 5.5 70-100 15-25

M50.6-1.2 6.5 90-130 15-25

M60.6-1.2 7.5 130-170 18-30

M80.6-1.2 9.5 180-240 18-30

DIA OF STUD

TO BE

WELDED

STUD

SIZE

SHEET

THICKNESS

CHARGING

VOLTAGE

STRENGTH OF

SPRINGmm

REMARKS

SET STICK OUT TO 2 ~ 2.5 MM IN ALL CASE

SET LIFT 1 ~ 1.5 MM

SET CURRENTAND TIME FOR PILOT ARC MOST SUITED

A 5030

200 400M.S.

15

100

SPRING FORCE


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THANKS

extra files ahead

EXTRA lid


80/96

EXTRA slides


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Resistance welding

Resistance & Effect of Pressure

R1In welding it is

desirable to have

R1,R2,R4,R5 lowR3 high

R1&R5 Resistance between tip and sheet

R2 & R4 sheet individual resistance

R3 Surface contact resistance

R2

R3

R4

R5


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El t d T & Si


83/96

Electrode Type & Size

W ldi i t


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Welding processing-parameters Welding processing-parameters cannot be determined by theoretical

calculations. Only with test rows welding process parameters can beoptimized.

Start a test row with the lower theoretical welding process parameterand increase one of the parameters (for example the welding current)step by step.

The test rows should be focused to the most important object, as thereare quality, strength or process pace.

Research for the best welding spot can be done for example byverifying the grinding pattern.

Diameter of the welded connection


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Diameter of the welded connection Welding two sheets with different thickness or welding more than two sheets

the lens diameter doesnt correspond with the diameter of the mating area.

Decisive for the tightness of the welded spot is the mating area between thesheets.

The required minimum diameter can be calculated as shown in the example:


86/96

The secondary current depends directly from the secondary

voltage. Important to solve the welding job is the voltage

over the work piece.

U work piece = U total (U upper electrode arm + U lower electrode arm)

SPOT CHECKING METHOD


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SPOT CHECKING METHOD

WELD SPOTS

CHIESEL

NUGGET CHECKING METHOD

IF METAL SOUND ----- OK

NUGGET DIA

U T M

TENSILE STRENGTH CHECKING METHOD

SPOT SHOULD NOT FAIL

Weld defects


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Weld defects

E l i t ld i t f


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Expulsion at weld interface

Dirty , scaly material

Poor fit-up

squeeze time too short Weld force too low

Weld current too high

Weld time too high

S f l i l t d ti ki


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Surface expulsion, electrode sticking

Dirty , scaly material

Poor fit-up

squeeze time too short

Weld force too low

Weld current too high

Weld time too high

Tip dirty

El d M h i


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Electrode Mushrooming

weld time too long. Weld force too high

Weld current high

Insufficient cooling Electrode area too small

Electrode alloy too soft

E cessi e eld indentation


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Excessive weld indentation

weld time too long. Weld force too high

Weld current high

Insufficient cooling Electrode area too small

Poor fit-up

Littl ld t


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Little or no weld nugget

Weld time too short Weld force too high

Weld current too low

Electrode face too large

Poor heat balance

Welds too close together

Dirty or coated material

Low line voltage


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Cracks in weld nuggets

Hold time too short

Weld force too low

Dirty, scaly material

Di l d ld t


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Displaced weld nugget

Electrode misaligned

Poor heat balance

Poor fit-up

W ld h ldi


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Weld not holding

Weld force too high

Weld force too low

Poor fit-up of parts

Weld current too low

Weld time too short

Poor set up of tools.

Documents

Spot Weld - Pres