1 The Importance of Force and Displacement Resistance Welding Training Marty Mewborne Product Engineer

2 Resistance Welding Diagram: EQUIPMENT PROCESS MATERIALS WELDING SUCCESS MATERIAL CONTROL OPTIMIZED SETTINGS & MONITORING Part Positioning, Electrode Maintenance, etc. Composition, Plating, Hardness, Geometry, etc. Power Supply, Weld Head, Electrodes, etc. EQUIPMENT SELECTION

3 Weld Heat = I 2 Rt – Thermal Loss Weld Current Note: Thermal Loss is the heat sinking into the parts, electrodes and tooling. where: I = weld current, amperes R = resistance of work pieces, ohms t = duration of current, seconds Weld Heat Formula

4 How Electrode Force Affects Contact Resistance: High Force Reduces Contact Resistance Low Force Causes High Contact Resistance

5 Poor Weld Force Control Results in: o Weld splash o Excessive part deformation o Wide variations in weld strength o Inconsistent weld heat o Reduced electrode life

6 Weld Study: Application:.032” Diameter Nichrome Wire; 90° Cross Wire Weld Pull Strength vs. Current for 14, 16, 18, & 20 lbs Electrode Force:

7 Pull Strength vs. Displacement: Application:.032” Diameter Nichrome Wire; 90° Cross Wire Weld: Pull Strength of 60 lbs or Greater is Highlighted Displacement of.009” -.012” is Highlighted

8 Weld Head Actions: o Approach o Impact o Squeeze o Fire o Follow-up o Hold

9 Force Control Methods: o Manual è Foot Pedal o Pneumatic è Direct Air è Coil Spring è Proportional Pressure Control è EZ-AIR o Cam Driven o Electronic è Servo Motor è Electro Magnetic

10 Electrode Force vs. Time for Force Fired Weld Head: Electrode Force Time Final Force Firing Force Weld Current 150 msec Squeeze Time Hold Time

11 Electrode Force vs. Time for Two Different Operators: Electrode Force Time Firing Force Final Forces Weld Current

12 Solenoid No. 2 Air Cylinder Fixed 78 psi Regulator Exhaust 85 to 130 psi Shop Air Solenoid No. 1 Solenoid No. 3 EZ-AIR Overforce Protection:

13 Electrode Force vs. Time Before and After EZ-AIR:

14 Proportional Pressure Control: Force can be controlled and programmed using a Proportional Valve:

15 Force Monitoring: Force can be monitored using a Load Cell:

16 Displacement Monitoring:  Sensor Options: LVDT (Linear Variable Differential Transformer) Linear Encoder  Uses: Part Detection Measure Weld Collapse Weld To Displacement

17 Weld to Displacement: Measure Initial Part Thickness Measure Final Thickness Cut Off Current at Displacement Limit

18 Built-in or External Monitoring:  HF27 (Built-In)  MG3 (External)

19 Resistance Welding Diagram: EQUIPMENT PROCESS MATERIALS WELDING SUCCESS MATERIAL CONTROL OPTIMIZED SETTINGS & MONITORING Part Positioning, Electrode Maintenance, etc. Composition, Plating, Hardness, Geometry, etc. Power Supply, Weld Head, Electrodes, etc. EQUIPMENT SELECTION