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Tuesday, January 22, 2019 .....4:20:25 PM

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1. What are the three most important variables for resistance spotwelding?
1. Force, Current, and Pressure.
2. Pressure, Current, and Heat.
3. Time, Force, and Heat.
4. Pressure, Time, and Heat.

2. How is the heat generated during a spotweld?
1. The force compresses the material, causing heat.
2. The resistance converts current to heat.
3. The current causes heat.
4. The resistance causes heat.

3. How does resistance change with a change in tip force?
1. It doesn't
2. It increases as tip force increases
3. It decreases as tip force decreases
4. It decreases as tip force increases

4. How does the heat change as tips "mushroom"? HINT: "Heat" is energy, not temperature.
1. Heat goes down as tips get larger.
2. Heat goes up because resistance goes up with larger tips.
3. Heat is the same, but spread over a larger area, so temperature is lower.
4. Heat goes up because pressure goes down as tips get larger, with the same weld force.

5. In a typical welding application, about how much current change will result from the greater contact area of the tips as they "mushroom"? Consider the stepper to be OFF.?
1. Current would double.
2. Current would be half.
3. Current would increase less than 5%.
4. Current would drop about 50%

6. If your welder gives excessive expulsion, but turning the heat down results in cold welds, what is wrong?
1. Pressure is too low.
2. Current is erratic, fix the control.
3. Force is too high.
4. Cool time is too short.

7. What is the purpose of squeeze time?
1. To allow the part to pull together.
2. To allow the first cycle of current to stabilize.
3. To insure full pressure before the current is applied.
4. To time the gun cycle for spot spacing on a manually operated hand gun.

8. What is the purpose of hold time?
1. To allow the coating to flow back over the weld.
2. To reduce the shunt current effect.
3. To pull the heat out into the water cooled tips.
4. To allow the nugget to solidify.

9. What are the two most important functions of pressure?
1. Contain the nugget, and make the part fit.
2. Set the work resistance and contain the nugget.
3. Solidify the weld and forge the parts.
4. Minimize the mushrooming & enhance tip alignment.

10. What is a weld lobe?
1. The material that expels between the two sheets.
2. The indentation left after a weld.
3. An area added to a part to allow an extra spotweld.
4. The material's weldability, expressed as a chart.

11. What happens when a weld is placed closer than 2" from a previous weld?
1. Nothing happens.
2. A shunt current always causes the weld to reheat.
3. Current is diverted, from the new weld that is forming.
4. The weld is better, because the pressure is higher between the sheets.

12. What is happening in figure A, and how does it affect the weld? HINT: trace the current path(s?) TipDwg
1. The tips are too close to the edge.
2. The tips are too large for the small flange.
3. The tips are positioned wrong, and will cause a shunt path, giving a cold weld.
4. The tips are positioned properly and a good weld can be made.

13. What effect does "more metal in the throat of the gun" have on the current flow?
1. It increases it because of better conductivity.
2. It has no effect on the current to the weld, and doesn't need automatic current compensation
3. Inductance goes up, so current tries to go down, automatic current compensation is helpful here.
4. It causes a larger shunt path, giving a cold weld.

14. What happens when you use "skate straps" on the secondary cables?
1. The inductance decreases.
2. The current increases.
3. The efficiency of the welder goes up.
4. All of the above.

15. What is expulsion?
1. Throwing a welding consultant out of the plant.
2. Metal thrown out of the nugget.
3. Deformation due to heat and pressure and extrusion from under the tips.
4. Burned surface coating.

16. What does expulsion cause?
1. Thinner cross section at the weld.
2. Hazard to personnel.
3. Slag build-up on the gun.
4. All of the above.

17. What does slag on the gun cause?
1. Greater protection to abrasion of the electrodes.
2. Better cooling of the tips.
3. Intermittent current paths.
4. Lower inductance.

18. What causes expulsion?
1. Too much tip pressure during welding.
2. Too much current and too much pressure.
3. Excessive inductance in the throat of the gun.
4. The inability of the force to contain the molten nugget.

19. What are steppers PROPERLY used for?
1. To compensate for tip wear.
2. To increase current when the copper gets hot during production.
3. To boost heat when the expulsion gets greatest.
4. To lower heat as the tips mushroom, as this causes lower effective pressure at the same tip force.

20. What option is best to use UNTIL WE FIX a variable fitup problem?
1. Higher pressure, because it will pull the part together.
2. Longer weld time, to allow the material to heat, soften, and be pulled together.
3. Impulse to allow the dynamic resistance change to regulate the heat automatically.
4. Upslope, to heat the surface just enough to pull the part together.

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