An Overview of Capacitive Discharge Spot Welder

Posted on Jan 21, 2021

Capacitive discharge welding relies on the mechanism of metal sensitivity to heat and fuse metals. A strong current is initially passed through the workpiece, and the energy is dissipated due to the metal resistance in heat form which heats up and fuses weld materials.

What Is a Capacitive Discharge Spot Welder?

A capacitive discharge spot welder also called the capacitive resistance of capacitor discharge spot welder, is a resistance welding solution that has many advantages. It performs a resistance/projection welding technique commonly known as capacitor discharge resistance welding in which the welding energy is provided by releasing the energy stored in a large capacitor bank.

This type of resistance welding is particularly ideal for repeatable mass production of parts in the automotive, appliance, electrical industries, and more. It is also ideal for projection, press-fit, and annular ring projections up to a diameter of 4.5 inches. Capacitive discharge spot welding is often preferred because low marking weld can be obtained due to the small HAZ and dissimilar metals that are otherwise difficult to weld successfully using conventional resistance welding.

Capacitor-Discharge Spot Welding Explained

Capacitive discharge welding relies on the mechanism of metal sensitivity to heat and fuse metals. A strong current is initially passed through the workpiece, and the energy is dissipated due to the metal resistance in heat form which heats up and fuses weld materials. 

Unlike conventional spot welding which consists of three stages, capacitive discharge welding is made up of two phases. The welder first must withstand the material contact and bulk resistance of the material. On a micro-scale surface profile, material surfaces can only contact in a limited number of locations. Within the first few milliseconds of weld formation, this high resistance, the microscopic metal bridge allows other bridges to come into contact, heat up, and fuse. When all of the bridges have been fused, the contact resistance is equal to 0. The final stage of weld formation then revolves around the bulk resistance of the metal.

The Advantages of Capacitive Discharge Spot Welder

Capacitive discharge spot welding solution provides a great many benefits, most notable of which is its ability to handle repeatable productions in large volume and is in fact one of the most cost-effective fine-spot resistance welding solutions on the market. Let’s take a look below for its other benefits in detail:

Short Welding Times

Since the capacitive discharge spot welding process utilizes stored energy instead of using direct demand on incoming power for the conventional processes, the weld times are generally shorter – typically in 10 milliseconds or less.

Small Heat-affected Zone

This type of welding technique ensures the HAZ (if any) is minimized and makes sure that any changes in the metallurgy of the workpiece remain as small as possible.

Welding Capacity

By welding capacity, we mean the range of metals that you can weld using capacitive discharge spot welding. As a matter of fact, its nature of quick energy release makes it ideal for welding highly conductive metals such as copper.

Concentrated Welds

The resulting short weld times as we described above ascertains that the energy needed to spot weld remains concentrated in the weld zone. Furthermore, because the energy delivered during the capacitive discharge spot welding process is concentrated for such a short time (even at high levels), the electrode is less prone to wear compared to conventional welding processes. In fact, it is said that the electrode can last four to ten times as long.

Power Saving

Since the high electrical energy required is not directly harnessed from the power distribution network but large capacitors, you typically don’t need to upgrade the power service to your building. The bank of capacitors will store energy and recharge between welds.

Energy Utilization

This type of spot welding is capable of repeatable energy release not subjected to line voltage fluctuations. It is also capable of exceptionally fine energy adjustment.

Hazards and Precautions

This may seem obsolete for some but we cannot stress enough how important it is to know what kind of safety risks a welder can pose and what precautionary measures you can take to protect yourself or others from potential hazards. Some of the most notable hazards in relation to the use of any welder include burns, electric shock, fumes and gases, and even fire explosions. Burns usually occur when the operator is not mindful of hot parts on the equipment when it’s operating; shock accidents are usually related to the inappropriate placement of the power circuit; fire explosions are generally attributed to sparks flying off of the arc into other combustible equipment, fluids, etc.; and fumes and gases are often the results of inadequate ventilation in the work area. 

Thankfully, here are a few things you can do to keep these potential hazards to the minimum:

a.) Always put your safety glasses on when working with a welder of any kind. This includes your weld heads as well.

b.) Refrain from touching weld spots immediately after the welds have been created as they will be very hot. Also, avoid making contact with any part of your equipment that is hot during the operation.

c.) Be sure to not pinch fingers in moving weld head parts or between weld electrodes.

d.) Keep your personal accessories to the minimum. This means removing watches, jewelry, or anything that is susceptible to sparks and electricity. All welds should be performed at low voltage to ensure the safety of the operators.


Although capacitive discharge welding has been available for many years in the manufacturing of vehicle parts assemblies (e.g., transmission components and airbags), the welding technology is still not widely adopted in other sectors of automotive manufacturing and other industrial sectors. But we believe that it is only a matter of time that people start to notice the benefits associated with the welding process.

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