Lincoln Electric SVM103-A service manual Welding Circuit, Arc

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B-11

OPERATION

FIGURE B.3 – WELDING CIRCUIT CONNECTIONS

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2	5	8
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1.POWER SOURCE

2.ELECTRODE CABLE

3.ELECTRODE HOLDER

4.ELECTRODE

5.OUTPUT TERMINALS

6.WORK

7.WORK CLAMP

8.WORK CABLE

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THE WELDING CIRCUIT

When everything is connected properly, the current from the power source causes the electrode to melt and bond the metal being welded. Figure B.3. shows the components of the basic welding circuit. The cir- cuit starts at the electrode cable connection and ends at the work cable connection. Current flows from the POWER-ARC 4000 through the electrode cable, the electrode holder, the electrode, and across the arc.

On the work side of the arc, current flows through the work to the work clamp, the work cable, and back to the machine. The circuit must be complete for current to flow. That means the work clamp must be tightly connected to clean base metal. You should remove any paint or rust as necessary to get a good connec- tion. Also, you need to connect the work clamp as close as possible to the area you want to weld. Avoid letting the welding circuit pass through hinges, bear- ings, electronic components or similar devices that can be damaged by high current.

THE ARC

The electric arc is made between the work and the tip of the electrode. You make a gap for the arc in the welding circuit by holding the electrode tip 1/16 to 1/8 inch (1.6 to 3.2 mm) away from the work. You must establish the arc and hold it as you move the arc along the joint you’re welding. The arc melts both the elec- trode and the base metal of the work as you move.

Figure B.4. shows what’s happening in the welding arc. The arc itself is the electric current flowing between the tip of the electrode and the work. Its temperature is about 6000°F (3316°C). The arc is very bright and cannot be looked at with the naked eye without risk of painful and perhaps permanent injury. A very dark lens specifically designed for arc welding must be used with the handshield or headshield when- ever viewing the arc.

The arc melts the base metal and actually digs into it. The molten metal forms a pool or crater and tends to flow away from the arc. As it moves away, it cools and solidifies. Slag forms on the top of the weld and pro- tects it as it cools.

POWER-ARC 4000