Question

Describe spot welding and projection welding with neat sketches.

Answer 1

Could you clarify if you're looking for a detailed explanation of the processes, their applications, or both?

Answer 2

Spot welding and projection welding are two types of resistance welding processes used for joining metals. Here’s a brief overview of each process:

### Spot Welding

**Description:**
Spot welding is a process where two or more metal sheets are joined by applying heat and pressure at specific points. The heat is generated by electrical resistance at the contact points of the metals.

**Process:**
1. **Electrodes:** Two copper electrodes are used to apply pressure and conduct the electric current.
2. **Heat Generation:** An electric current passes through the electrodes, creating heat due to the resistance of the metals being joined.
3. **Weld Formation:** The heat causes the metal at the contact points to melt and form a weld nugget as the electrodes apply pressure.

**Applications:**
- Automotive manufacturing for joining body panels.
- Electronics for joining components.

**Sketch:**
```
  _________________________
 |                         |
 |       Metal Sheet 1     |
 |_________________________|
 |      (Electrode 1)      |
 |         _______         |
 |        |       |        |
 |        |  Weld |        |
 |        |       |        |
 |        |_______|        |
 |      (Electrode 2)      |
 |_________________________|
 |       Metal Sheet 2     |
 |_________________________|
```

### Projection Welding

**Description:**
Projection welding is a variation of resistance welding where projections (raised areas) on one of the metal surfaces are used to localize the heat and weld at specific points.

**Process:**
1. **Projections:** One of the metal parts has projections or dimples that are used to concentrate the welding current.
2. **Electrodes:** Electrodes apply pressure and current through the projections.
3. **Heat Generation:** The projections concentrate the heat at specific locations, causing localized melting and welding.

**Applications:**
- Joining components in automotive and electronics industries.
- Manufacturing parts with multiple welds in one operation.

**Sketch:**
```
  _________________________
 |                         |
 |       Metal Sheet 1     |
 |_________________________|
 |    / \  / \  / \       |
 |   |Projections|       |
 |   \_/  \_/  \_/      |
 |    \  /  \  /  \     |
 |     |___|___|__|     |
 |     (Electrodes)      |
 |_________________________|
 |       Metal Sheet 2     |
 |_________________________|
```

These sketches are simplified to illustrate the basic concepts. In practice, the setups can be more complex depending on the specific application and equipment used.