2. Spot weldability Lesson Objectives When you finish this lesson you will understand: Concept of Spot Weldability Electrode arrangements Learning Activities 1.View Slides; 2.Read Notes, 3.Listen to lecture 4.Do on-line workbook Keywords: Current Level, Current Range, Lobe Curve, Electrode Life, Peel Test, Nugget Size, Button Size, Interfacial Failure, Shunting Effect, Multiple Direct Electrodes, Series Electrodes, Electrode Tooling

3. Process Characteristics as a Measure of Weldability Current Level Current Range & Weldability Lobe Process Deterioration –Characterization of the loss in weld size at constant welding conditions –Characterization of the variation in process requirements for maintaining welds of an adequate quality Peel Test Used As Measure

5. Button Size as a Measure of Weld Quality Button Diameter

6. Modes of Failure in Spot Welds Full Button Irregular Button Interfacial Failure

11. Process Characteristics as a Measure of Weldability Current Level Current Range & Weldability Lobe Process Deterioration –Characterization of the loss in weld size at constant welding conditions –Characterization of the variation in process requirements for maintaining welds of an adequate quality Peel Test Used As Measure

12. Nugget Diameter vs. Weld Current Expulsion Small Nuggets Acceptable Nuggets Minimum Nugget Diameter Weld Current Nugget Diameter Nominal Current

14. Process Characteristics as a Measure of Weldability Current Level Current Range & Weldability Lobe Process Deterioration –Characterization of the loss in weld size at constant welding conditions –Characterization of the variation in process requirements for maintaining welds of an adequate quality Peel Test Used As Measure

15. Current Range & Weldability Lobe Expulsion Acceptable Nuggets Small Nuggets Minimum Nugget Diameter Weld Current Expulsion Level Time A Smaller “Brittle” Nuggets Acceptable Nuggets Lobe Curve Nugget Diameter Weld Time Time A

19. Process Characteristics as a Measure of Weldability Current Level Current Range & Weldability Lobe Process Deterioration –Characterization of the loss in weld size at constant welding conditions –Characterization of the variation in process requirements for maintaining welds of an adequate quality Peel Test Used As Measure

20. Process Deterioration Minimum Acceptable Diameter Number of Welds Weld Diameter

21. Shunting Effect AB IBIB IAIA I total = I A + I B I A R A = I B R B I B /I total = 1 - R B /(R A + R B ) [Reference: Resistance Welding Manual, p.1-7, RWMA]

22. Multiple Direct Electrodes Series Electrode

23. Tooling for Multiple Welding Stud and Jam Nuts Equalizing Bar Split and Clamped to Electrode Flexible Conductors Slip-Fit Lower Electrode Welding Pressure Adjustment Screw Compression Spring Flexible Conductors Slip-Fit Workpiece (a)(b) [Reference: Resistance Welding Manual, p.17-8, RWMA]