Spot Welding Parameters Basic Calculation
= 0.241� w
.........................(1)
*Calculation for AC spot welding
where E : Energy (J)
P : Power (W)
tw : Weld time (sec)
= 0.241�2�
where I : Welding Current (A)
R : Panel Contact Resistance (Ω)
where Jv : Melting energy (J/mm3)
S : Surface contact (mm2)
L : Total plate thickness combination (mm)
.........................(3)
= JvSL
= Jv[π
.........................(2)
w
2
4
]L ........................(4)
where d : Required nugget diameter (mm)
Since
=4
min
for general spot point
= 5 min for important spot point
Where min : Min thickness of panel combinations
So, 0.241�2� = Jv[π
(4
min)2
4
= Jv[π4
min]]L
]L .......(5)
Combination eqn (2) & eqn (4)
.............(6)
Final equation;
�=
2
Jv[π4
min]]L
0.241�
2
2
=
..............(7) *Used for minimum nugget diameter requirement (general)
w
Jv[π ]L
4
0.241�
....................(8) *Used for specific required nugget diameter
w
Note :
Steel type
Low Carbon Steel
Aluminum
 Replace = 0.241�
w
w
to
= 250 min .............................(9) where w = Welding Force (kg) - target
*Go to Quadratic approximation for best data fitting (refer reference) – No 11
= 10
hold
*
w
Melting Energy
Contact Resistance
9.7
J/mm3
100
μΩ
3
2.9
J/mm
75
μΩ
= 0.37� w for MFDC / DC spot welding calculation
.............................(10)
min
=3~5 � �
squeeze
....................
where
where
w
hold
= Weld time (cycle) – 50 hz
= Hold time (cycle) – 50 hz
-
Pneumatic Gun : Min 17 cycle – Min time require for applied force to stable at 80%
-
Servo Gun (robot) : 0 cycles – Using integrated robot function (robot will send
signal once applied force is stable to welding
controller)
Servo Gun : 4 cycle – Min time require for applied force to stable
References
1. Spot Welding Process Sequence
2. Relationship between welding force & resistance
w
R=
So,
= �w�
��
A=
�
��
.............(1)
........(2)
�
where
Fw : Weld Force
Pw : Weld Pressure
A : Contact Area
where
R : Resistance, Ω
ρ : Resistivity , Ω/mm
........(3)
L : Total plate thickness combination (mm)
A : Contact Area, mm2
Combine eq (1) & (3)............
w=
�w��
�
........................(4)
w
α 1 � .... Force ↑ Resistance ↓
3. Relationship between welding force & welding current
�p = �� = �2�
.................................................(5)
where
Pp : Weld Power
Combine eq (4) & (5)............
w=
�w���2
�p
............................(6)
w
α �2 .... Force ↑ Current ↑
*Lobe curve sample from Lobe Curve Generator – Welding Force vs Weld Current
4. Welding Condition Graph (Base on formulas)
Using derived formulas as above, the new plot (yellow & blue colours) are published against original
welding chart to confirm the accuracy of the formulas. Also, the Lobe Curve estimator was
programmed to view weldability region as following sample;
5. Lobe Curve Generator (from equations) – Weld Time vs Weld Current
*Improved Lobe Curve Generator
6. AC vs DC Spot Welding Comparison
7. Lobe Curve Sample (Experimental Data)
Graph 3
Weld Current versus Weld Time Graph
14000
weld_current_total vs. weld_time_total
fit 1
13000
weld_current_total_NF vs. weld_time_total_NF
fit 2
Spatter Region
12000
weld_current_total_SP vs. weld_time_total_SP
Weld Current (A)
fit 3
11000
10000
9000
Applicable Region
8000
Small Nugget Region
No Fusion Region
7000
Required Nugget Diameter : 5.5mm
6000
6
8
10
12
14
Weld Time (cycle)
16
18
20
Graph
Part Combination
Nugget Diameter (Standard)
Welding Pressure
3
SPCC (1.2) x SPCD-SD (1.4)
x SPRC 40 (2.0)
5.5mm
250kgf
8. Welding Stepper Program Sample
UNDERBODY ROBOT UB053 / 054 (WELDING PARAMETER SETTING)
IS
WAS
CURRENT
(kA)
11.3
STEPPER 0
STEPPER 1
STEPPER 2
STEPPER 3
STEPPER 4
STEPPER 5
STEPPER 6
STEPPER 7
STEPPER 8
STEPPER 9
9.5
9.7
9.9
10.1
10.3
10.5
10.7
10.9
11.1
11.3
WTM
7
3
3
3
4
4
5
5
5
6
6
WELD COUNT
1~420
1~420
421~840
841~1260
1261~1680
1681~2100
2101~2520
2521~2940
2941~3360
3361~3780
3781~4200
WELD TIME
(cycle)
13
13
PRESSURE
(kgf)
250
250
Welding Current Setting versus Welding Current Actual
11300
11100
10900
Welding Current (A)
10700
10500
10300
10100
9900
9700
9500
Welding Current Setting
Welding Current (Actual)
0
420
840
1260
1680
2100
2520
Weld Count (no)
2940
3360
3780
4200
9. Stepper versus Typical Welding Comparison (Sample)
10. Weld Force Quadratic Approximation
11. Electrode Force Effect on Lobe Curve Range (Sample from experiments)
Electrode Pressure Effect on Applicable Region (Between Standard Nugget & Spatter Region)
Press_160_current_std vs. Press_160_weld_time_std
fit 1
Press_160_current_spatter vs. Press_160_weld_time_spatter
fit 2
Press_200_current_std vs. Press_200_weld_time_std
fit 3
Press_200_current_spatter vs. Press_200_weld_time_spatter
fit 4
11500
11000
10500
Spatter Region
10000
Weld Current (A)
9500
9000
160 kgf
8500
200 kgf
8000
7500
7000
Small Nugget Region
6500
6
8
10
12
14
Weld Time (cycle)
16
18
20
22
12. Shear Load versus Weld Nugget diameter
Shear Load Graph (Ordinary Weld)
8000
SPCE Shear vs. Nugget Diameter
fit [<390 MPa]
SPFC490 Shear vs. Nugget Diameter
fit [390MPa<TS<490MPa]
SPFC580 Shear vs. Nugget Diameter
fit [490MPa<TS<580MPa]
SPFC780 Shear vs. Nugget Diameter
fit [580MPa<TS<780MPa]
SPFC980 Shear vs. Nugget Diameter
fit [780MPa<TS<980MPa]
SPFC >980 Shear vs. Nugget Diameter
fit [TS>980]
7000
Shear Load, F [N]
6000
5000
4000
3000
2000
1000
2.5
2.7
2.9
3.1
3.3
Nugget Diameter, d [mm]
3.5
3.7
3.9
4.1
Shear Load Graph [Critical Weld]
11000
<390 MPa
fit [<390MPa]
390MPa < TS<490MPa
fit [390<TS<490]
490MPa<TS<580
fit [490<TS<580]
580<TS<780MPa
fit [580<TS<780
780<TS<980MPa
fit [780<TS<980]
TS>980
fit [TS>980]
10000
9000
Shear Load, F [N]
8000
7000
6000
5000
4000
3000
2000
3.4
3.6
3.8
4
4.2
Nugget Diameter, d [mm]
4.4
4.6
4.8
5
13. Temperature Distribution During Spot Welding
14. Dynamic Resistance Measurement (IJAME)
15. Welding Heat Distribution (SAE)