Spot welding parameters basic calculation.pdf

Spot Welding Parameters Basic Calculation 𝐸 = 0.241𝑃𝑡w .........................(1) *Calculation for AC spot welding

= 0.241𝐼2𝑅𝑡w

= JvSL

= Jv[π

.........................(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)

𝑑2 ]L 4

where E : Energy (J) P : Power (W) tw : Weld time (sec)

........................(4)

where d : Required nugget diameter (mm) Since 𝑑 = 4 𝑡min for general spot point = 5 𝑡min for important spot point Where 𝑡min : Min thickness of panel combinations

So, 0.241𝐼2𝑅𝑡 = Jv[π

(4 𝑡 min)2 4

]L .......(5)

Combination eqn (2) & eqn (4)

= Jv[π4𝑡min]]L .............(6) Final equation;

𝐼=

2

Jv[π4𝑡 min]]L 0.241𝑅𝑡 w 𝑑2 4

2

=

Jv[π ]L 0.241𝑅𝑡 w

..............(7) *Used for minimum nugget diameter requirement (general)

....................(8) *Used for specific required nugget diameter

Note : Steel type Melting Energy Contact Resistance Low Carbon Steel 9.7 J/mm3 100 μΩ 3 Aluminum 2.9 J/mm 75 μΩ  Replace 𝐸 = 0.241𝑃𝑡w to 𝐸 = 0.37𝑃𝑡w for MFDC / DC spot welding calculation 𝐹w = 250𝑡min .............................(9) where 𝐹w = Welding Force (kg) - target *Go to Quadratic approximation for best data fitting (refer reference) – No 11 𝑡w = 10𝑡min

.............................(10)

where 𝑡w = Weld time (cycle) – 50 hz

𝑡hold = 3 ~ 5 𝑐𝑦𝑐𝑙𝑒𝑠.................... where 𝑡hold = Hold time (cycle) – 50 hz

*𝑡squeeze

-

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

𝐹w = 𝑃w𝐴

R= So,

𝜌𝐿 A=

.............(1)

........(2)

𝐴 𝜌𝐿

𝑅

where

Fw : Weld Force Pw : Weld Pressure A : Contact Area

where

R : Resistance, Ω

........(3)

ρ : Resistivity , Ω/mm L : Total plate thickness combination (mm) A : Contact Area, mm2

Combine eq (1) & (3)............

𝐹w =

𝑃w𝜌𝐿

𝑅

........................(4) 𝐹w

α 1 𝑅 .... Force ↑ Resistance ↓

3. Relationship between welding force & welding current

𝑃p = 𝑉𝐼 = 𝐼2𝑅

.................................................(5)

where

Pp : Weld Power

Combine eq (4) & (5)............

𝐹w =

𝑃w𝜌𝐿𝐼2

𝑃p

............................(6)

𝐹w α 𝐼2 .... 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 [