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O P E R A T I O N A L D E S C R I P T I O N
INTRODUCTION
Resistance welding is a process where metals are joined by clamping the material between two
electrodes and then passing enough current through the material to heat and fuse it. Electrodes are used to
both clamp and to pass the current through the work. Since all metals have some resistance, current passing
through the material generates heat. However, since most metals are reasonably good conductors of current,
the currents used must be moderately held under force to provide a good mechanical fit, for good electrical
contact between the materials and electrodes, and to aid in the fusing process.
The area heated to the fusing level is referred to as the “nugget”. In a good weld, the nugget will
be pliable enough and for force level will be such that the material is joined with a minimum of distortion
while providing a good bond.
SPOT WELDING METHOD
Spot welding is one of the most widely methods of resistance welding. To perform this process,
the work is clamped between two copper electrodes. Shape of electrode face helps determine size and
shape of nugget. Typical uses is to join two over lapping sheets. Main consideration is joining strength.
MACHINE CLASSIFICATION
A FURTHER CLASSIFICATION CAN BE MADE OF RESISTANCE WELDING
EQUIPMENT. And that classification is SINGLE PHASE and THREE PHASE. Single phase, three phase
refers to the type of input power that must be supplied for your machine. However, each of these two
classes has characteristics that you should be aware of when applying your machine.
As the term applies, the single phase machine is only connected across one phase of the input line.
Since most resistance welders draw a reasonable amount of current, this may unbalance your input line
causing problems. However, this problem can be overcome if the remaining plant load is properly
distributed across the other two phases. In addition to the input problem, the secondary output of a single
phase is more sensitive to load changes than a three phase machine. Any change in the secondary load;
throat depth; resistance, etc., will cause a greater change in the output current that for a similar change with
a three phase machine.
Since the three phase machine is connected across all three input phases, it provides better input
power distribution than the single phase machine. Additionally, the three phase machine provides better
power control in the secondary circuit. This type of machine is primarily resistance sensitive and is not
affected as greatly by changes in the secondary as the single phase machine.
PRESS TYPE RESISTANCE WELDERS
The press type refers to how the electrode force is applied to the work. The press type machine has
advantages for certain shapes of work, as it is usually used for all purpose type applications. The press type