CD Resistance Welding

The Advantages of Capacitive Discharge Spot Welders

Capacitive discharge spot welders (CD spot welders) have many advantages over other welding technologies:

  • Quick energy release for welding highly conductive metals such as copper
  • Available in 200, 400, 600, 1000, & 1100 ws Models
  • Small heat affected weld zones
  • Repeatable energy release independent of line voltage fluctuations
  • Capable of extremely fine energy adjustment

Capacitive Discharge spot welders are one of the most cost-effective welding solutions for fine-spot resistance welding. Whether you are manufacturing battery packs or microscopic assemblies, Sunstone Capacitive Discharge spot welders are the most affordable, precision fine-spot resistance welders on the market.

Understanding CD Resistance Welding

How does CD Resistance Welding Work?

Capacitive Discharge resistance welding or CD Resistance welding uses capacitors to store energy for quick release. A capacitor, like a battery, store energy for release. Unlike a battery, a capacitor has the ability to release energy at a much higher rate.

CD Resistance welding uses the microscopic gap between two parts to create heat in a very localized area. At the microscopic level, every metal has peaks and valleys ( See Picture to the Right). As two metals are placed surface to surface, peaks will touch other peaks. Depending on the force that is applied to these pieces, more or less surface contact will occur. As electricity passes through these peaks it causes heat to build up, and melt the peaks. This is the basic understanding of how a resistance weld is accomplished.

Pressure is Important

Pressure Plays a huge role in  CD resistance welding. As described above, the greater the pressure the more surface contact will be generated. Therefore, the great the weld pressure, the colder the weld will be. This is opposite of what many might think. Because there is more surface area, the resistance is lower, therefore it will create less heat.

In CD Resistance welding, repeatable results are one of the most important factors. To trust that when you complete a weld, it will not ruin your project or part, but complete the desired result. When done incorrectly Capacitive Discharge welding has the ability to blow up, or pop. This is due to not enough contact between the weld parts, and an electrical arc is created.

In order to get consistent results using Capacitive Discharge welding, both energy and power must be held constant. This is why the use of a pressure regulated handpiece, or weld head is recommended. These will provide consistent and repeatable welds.

What is Needed in a CD Welding System?

Each of the CD Resistance welding systems come standard with a power cord (international converter included) and will a foot switch for weld actuation. Check out our CD Products Page CD200DP, CD400DP, CD600DP, CD1000DP.

Outside of the power supply, you will need a method to deliver the power to your workpiece. This can be accomplished in two different ways.

Weld Head:

The most popular method of delivering energy to a weld site is a weld head. Weld heads come in a variety of different operation types, including Pneumatic, servo, and manual actuation. Weld heads differ is pressure settings depending on your application. For more information on different weld head options check out our weld heads page.

Hand Attachments:

Hand Attachments give you the flexibility to hold the weld tips in hand and have ultimate control. Handpiece options vary from simple weld probes to more sophisticated pressure actuated handpieces. Depending on your application, and access to your pieces, Sunstone has the perfect handpiece for you. Handpieces are grouped into three simple groups.

  • Single Probe – One Probe & A Grounding Pieces
  • Dual Probe- Two probes to accomplish a parallel weld.
  • Tweezer – Two opposing electrodes with the ability to apply force between them.

See our Hand Attachments page to find the perfect Handpiece.

Metal under microscope
Resistance welding close up
Orion Power Cord
parallel weld heads

What is Parallel welding?

There are several different configurations to accomplish a resistance weld. Parallel welding is using two electrodes right next to one another in parallel. Both electrodes are on the same side of the weld, pressing down on the weld joint.  one electrode is positive and the other is Negative. The energy flows down into the workpiece through the one electrode and up the other to complete the weld. See the simple Graphic below for a visual representation. Parallel welding is used in battery pack welding. In battery welding a welding current cannot be passed through the cell, therefore a parallel configuration is required. In most applications, an opposed configuration will generate a better weld and require less energy. This type of weld will create two spots, where each electrode touched.

Resistance Welding Configurations

What is Opposed Welding?

Opposed welding is when the two electrodes are opposed to one another and pressing toward each other. This is like a tweezer. One electrode is on the bottom of the joint, and another is on the top. Pressure is applied from both sides, pinching the weld site. See the above graphic for a visual representation. Opposed welding is preferred to parallel and can accomplish better weld results. If you have access to both sides of your weld and can apply force to the joint, and opposed configuration is best. This configuration will create one spot on each side of the piece, where the electrodes came in contact with the piece.

What is a Step Weld?

A step weld is similar to a parallel weld in that there are two electrodes on the same side. The difference is one electrode is on the joint and the other is only on one single layer. This focuses the energy on one side of the electrode rather than on both. This configuration allows for a more powerful weld than a parallel weld, but not as powerful as an opposed. This configuration will result in one spot being created.