What a Spot welding machine is and how it works
The basic mechanism through which a spot welding machine operates is with a pair of copper alloy electrode clamps.
These clamps are used to clamp the two sheets of metal to be joined together, placed side by side.
A powerful current is then fired through the electrodes, strong enough to melt the metal at the point where the electrodes are bracketing it.
Advantages of Spot Welding:
- In this type of welding the base metal does not undergo to large heat affected area.
- This type of welding is a easy process.
- Spot welding has a high production rate.
- Spot welding can be applied to different metals to join.
- Spot welding is a low-cost process.
The molten metal from both pieces of metal mixes together, then cools and hardens into a single metal continuum, effectively fusing the two pieces together at the points where the spot welding has been carried out.
Spot welding is most effective with thin pieces of metal, where the current passes directly between the upper and lower parts of the electrode.
The thicker the pieces of metal, the more of the electricity disperses sideways into the metal rather than traveling through it to complete the circuit.
Thus, greater and greater amounts of electrical power are needed to spot weld thicker pieces of metal.
The practical limit on the thickness of metal that can be fused in this way is 1.25” for steel plate, with other types of metal have thinner limits.
Beyond these limits, spot welding is ineffective or impossible.
The best thickness of metal for spot welding is very thin – from between half a millimeter to 3 millimeters.
The time during which the metal is exposed to the electrical current must be carefully controlled if the spot welding is to produce good, solid results.
Depending on the thickness and the type of metal, anywhere from 0.01 to 0.63 seconds of current may be necessary.
Too little or too much can crack the metal, so precise adjustment is usually necessary for anything beyond hit-or-miss results to be attained.
Voltage used is very low – generally no more than 10 volts for the thickest piece of aluminum, and considerably less than that for other kinds of metals.
High amperage is needed for the process, however, with 90,000 to 100,000 amperes being needed to fuse aluminum.