Spot Weld - Pres
-
Upload
avinashbatra1 -
Category
Documents
-
view
228 -
download
2
Transcript of Spot Weld - Pres
-
8/3/2019 Spot Weld - Pres
1/96
-
8/3/2019 Spot Weld - Pres
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
-
8/3/2019 Spot Weld - Pres
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.
-
8/3/2019 Spot Weld - Pres
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
-
8/3/2019 Spot Weld - Pres
5/96
TYPES OF RESISTANCE
WELDING
1. SPOT WELDING
2. PROJECTION WELDING
3. FLASH WELDING
4. SEAM WELDING
5. BUTT WELDING
-
8/3/2019 Spot Weld - Pres
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.
-
8/3/2019 Spot Weld - Pres
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.
-
8/3/2019 Spot Weld - Pres
8/96
MAJOR ELEMENTS OF SPOT WELDING
* WELD CURRENT
* WELD TIME
* PRESSURE
* RESISTANCE
* ELECTRODE SHAPE (CURRENT DENSITY)
-
8/3/2019 Spot Weld - Pres
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 )
-
8/3/2019 Spot Weld - Pres
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
-
8/3/2019 Spot Weld - Pres
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
-
8/3/2019 Spot Weld - Pres
12/96
WELDT
IMECO
NTROL
FOR
SPOTWELDINGT
IM
E
CURRENT
SQEEZE
UP SLOPE
WELD
DN SLOPE
HOLD
OFF
-
8/3/2019 Spot Weld - Pres
13/96
TIMER CONTROLLER
-
8/3/2019 Spot Weld - Pres
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
-
8/3/2019 Spot Weld - Pres
15/96
How to check current?
Weld checker
Toroidal coil
-
8/3/2019 Spot Weld - Pres
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
-
8/3/2019 Spot Weld - Pres
17/96
Change in Current Density
-
8/3/2019 Spot Weld - Pres
18/96
-
8/3/2019 Spot Weld - Pres
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.
-
8/3/2019 Spot Weld - Pres
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.
-
8/3/2019 Spot Weld - Pres
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
-
8/3/2019 Spot Weld - Pres
22/96
How to check pressure?
Pressure gauge
Electrode
-
8/3/2019 Spot Weld - Pres
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
-
8/3/2019 Spot Weld - Pres
24/96
Contact Resistance
-
8/3/2019 Spot Weld - Pres
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
-
8/3/2019 Spot Weld - Pres
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 )
-
8/3/2019 Spot Weld - Pres
27/96
Temperature gradient
-
8/3/2019 Spot Weld - Pres
28/96
Temperature gradient
-
8/3/2019 Spot Weld - Pres
29/96
Change in Contact Resistance during Welding
-
8/3/2019 Spot Weld - Pres
30/96
Heat Zone
-
8/3/2019 Spot Weld - Pres
31/96
PSW WELDING SYSTEM
Welding gun Transformer Controller ELCB
ELCB
-
8/3/2019 Spot Weld - Pres
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
-
8/3/2019 Spot Weld - Pres
33/96
PSW (X TYPE GUN)
-
8/3/2019 Spot Weld - Pres
34/96
-
8/3/2019 Spot Weld - Pres
35/96
Gun Body
-
8/3/2019 Spot Weld - Pres
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
-
8/3/2019 Spot Weld - Pres
37/96
-
8/3/2019 Spot Weld - Pres
38/96
Electrode cooling
-
8/3/2019 Spot Weld - Pres
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!
-
8/3/2019 Spot Weld - Pres
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
-
8/3/2019 Spot Weld - Pres
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
-
8/3/2019 Spot Weld - Pres
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
Dia 16 tip 49 spots/min or less 35 spots/min or less
Dia 13 tip 19 spots/min or less 13 spots/min or less
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).
-
8/3/2019 Spot Weld - Pres
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
-
8/3/2019 Spot Weld - Pres
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.
-
8/3/2019 Spot Weld - Pres
45/96
REFERENCE FOR MS SPOT WELDING
(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
-
8/3/2019 Spot Weld - Pres
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
REFERENCE FOR MS SPOT WELDING
( B & C Class )
-
8/3/2019 Spot Weld - Pres
47/96
Welding parameters board
-
8/3/2019 Spot Weld - Pres
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
-
8/3/2019 Spot Weld - Pres
49/96
How to do the dressing of electrode?
Electode
Dressing
-
8/3/2019 Spot Weld - Pres
50/96
ALIGNMENT OF TIPS
BEST SPOTTIP ALIGNMENT
OK
100 %
Matching90 %
Matching
< 90 %
Matching
NOT OKACCEPTABLE
-
8/3/2019 Spot Weld - Pres
51/96
GUN ALIGNMENT FOR UNDLATION
NOT OKNOT OK
OK
-
8/3/2019 Spot Weld - Pres
52/96
Electrode Pushing
-
8/3/2019 Spot Weld - Pres
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
-
8/3/2019 Spot Weld - Pres
54/96
Verifying Weld spot
300Kg
-
8/3/2019 Spot Weld - Pres
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.
-
8/3/2019 Spot Weld - Pres
56/96
Weld defects
-
8/3/2019 Spot Weld - Pres
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
-
8/3/2019 Spot Weld - Pres
58/96
Causes Electrode tip diameter
Weld force Weld time
Surface condition
Cooling
Current shunting Impedance / resistance
Input power
Work piece
S i f
-
8/3/2019 Spot Weld - Pres
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
BALANCING AND COMP BALANCING
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
-
8/3/2019 Spot Weld - Pres
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
BALANCING AND COMP BALANCING
GUN POSITIONNGOPERATER EDUCATION FOR GUN
BALANCING AND COMP BALANCING
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
-
8/3/2019 Spot Weld - Pres
61/96
Error caused by work pieces.
-
8/3/2019 Spot Weld - Pres
62/96
Error caused by work pieces 2
S tt
-
8/3/2019 Spot Weld - Pres
63/96
Spatters
Generally spatters are caused by an incorrect adjustment!
With correct adjusted welding parameters und electrodeswell lined up no spatters will occur!
-
8/3/2019 Spot Weld - Pres
64/96
Calculation of the time needed to weld a spot -1
-
8/3/2019 Spot Weld - Pres
65/96
Calculation of the time needed to weld a spot -2
-
8/3/2019 Spot Weld - Pres
66/96
Calculation of the time needed to weld a spot -3
-
8/3/2019 Spot Weld - Pres
67/96
COATED SHEETS PRESENTATION
-
8/3/2019 Spot Weld - Pres
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!
-
8/3/2019 Spot Weld - Pres
69/96
zinc splatters
Due to possible zinc splatters galvanizedsheets need a correct adjusted welding
current
-
8/3/2019 Spot Weld - Pres
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
-
8/3/2019 Spot Weld - Pres
71/96
PROJECTION WELDING
-
8/3/2019 Spot Weld - Pres
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.
-
8/3/2019 Spot Weld - Pres
73/96
PROJECTION NUT WELDING
UPPER ELECTRODE
PIN
LOWER ELECTRODE
SPRING
OKNG
NUGGET
PIN
Reference for projection nut welding
-
8/3/2019 Spot Weld - Pres
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
-
8/3/2019 Spot Weld - Pres
75/96
PROJECTION STUD WELDING
LOWER ELECTRODE
AFTERBEFORE
UPPER ELECTRODE
WORK PC.
FUSION
WATER
CIRCULATION
Reference for projection Stud welding
-
8/3/2019 Spot Weld - Pres
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 )
-
8/3/2019 Spot Weld - Pres
77/96
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
-
8/3/2019 Spot Weld - Pres
78/96
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
-
8/3/2019 Spot Weld - Pres
79/96
THANKS
extra files ahead
EXTRA lid
-
8/3/2019 Spot Weld - Pres
80/96
EXTRA slides
-
8/3/2019 Spot Weld - Pres
81/96
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
-
8/3/2019 Spot Weld - Pres
82/96
El t d T & Si
-
8/3/2019 Spot Weld - Pres
83/96
Electrode Type & Size
W ldi i t
-
8/3/2019 Spot Weld - Pres
84/96
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
-
8/3/2019 Spot Weld - Pres
85/96
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:
-
8/3/2019 Spot Weld - Pres
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
-
8/3/2019 Spot Weld - Pres
87/96
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
-
8/3/2019 Spot Weld - Pres
88/96
Weld defects
E l i t ld i t f
-
8/3/2019 Spot Weld - Pres
89/96
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
-
8/3/2019 Spot Weld - Pres
90/96
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
-
8/3/2019 Spot Weld - Pres
91/96
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
-
8/3/2019 Spot Weld - Pres
92/96
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
-
8/3/2019 Spot Weld - Pres
93/96
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
-
8/3/2019 Spot Weld - Pres
94/96
Cracks in weld nuggets
Hold time too short
Weld force too low
Dirty, scaly material
Di l d ld t
-
8/3/2019 Spot Weld - Pres
95/96
Displaced weld nugget
Electrode misaligned
Poor heat balance
Poor fit-up
W ld h ldi
-
8/3/2019 Spot Weld - Pres
96/96
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.