Resistance Welding
Welding has a variety of applications, like this battery tab weld
What is resistance welding?
Resistance Welding is a process for joining metallic parts together in a reliable, consistant process. A controlled amount of electrical energy is released into the the parts to be welded creating enough heat to melt the metals where they meet to form a small weld nugget or spot. This technique can also be called spot welding.
How Resistance Welding Works
Resistance Welding relies on the resistance of the space between the two metals to be joined. This may seem counter-intuitive at first, but the resistance between the two materials is much higher than the resistance of the individual metals themselves. The heat required to fuse the two metals together is a result of current passing across the interface of the two materials. The specific amount of heat generated is mainly due to the resistance at the interface, the amount of current that flows through the interface, and the amount of time that the process occurs in. All micro resistance power supplies control the weld energy by controlling the amount of current that flows through the interface in a given amount of time.Power Supplies for micro resistance spot welding
There are four major varieties of micro resistance welders on the market today. Each technology has specific advantages and are suitable for different applications.
Power Supplies can be open-loop or closed-loop. Open loop power supplies have no feedback method to control the output. Instead they rely on outputing a set amount of energy into the parts. When parts are consistant, this method of welding provides the most cost effective results. Closed loop power supplies monitor the weld site conditions and control the output to adapt to the changing conditions. Small part geometries, difficult materials, or inconsistent parts all benefit from closed loop feedback type power supplies.
In addition to the control type, each power supply can either be a stored energy system, where all the energy for a given weld pulse is stored prior to delivery, or a direct energy type power supply where the energy required for the weld comes directly from the input power.
The four (4) types of power supply technology are:
- AC type welders - Direct Energy and Open Loop for high duty cycles and long duration welding.
- Capacitive Discharge - Stored Energy and Open Loop for consistant output and highly conductive parts.
- Inverter - Direct Energy and Closed Loop for high energy output with weld monitoring and pulse shaping
- Linear DC - Stored Energy and Closed Loop feedback for applications requiring consistant low end control.