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CD-Welding Details
Capacitor Discharge Welding Process
Here we present the possible variations of Schlemmer CD-welding, as well as the technical and economic advantages.
CD-Welding or
Capacitor Discharge Welding Process
The CD-welding process belongs to the short-time processes. The process is characterized by high welding currents and higher electrode forces. It is therefore mainly suitable for projection welding.
In CD-welding, the energy required for welding is switched from a previously charged capacitor bank via a switch (thyristor) to a welding transformer. By means of the sudden discharge of the energy stored in the capacitors, the current in the secondary circuit increases very quickly. With the help of the electrical resistance in the welding projection, the material heats up to the welding temperature within a few milliseconds.
Due to the rapid temperature increase, the weld zone heats up, joins the materials, and cools down before the surrounding areas can heat up.
Possible Capacitor Discharge (CD) Welding Processes
CD-Welding
Areas of application
The extremely short weld time and high welding current enable a flawless connection of metals with high electrical and thermal conductivity.
A unique feature of Schlemmer’s capacitor discharge welding is the ability to weld steels with a high carbon content, a process we developed and invented in 1990. In addition to the second welding impulse, the specific welding projection geometry for carbon welding is also an invention from our company.
Below are some typical material pairings:
- Copper-Aluminum/Copper/Brass/Stainless Steel/Silver
- Steel-Silver/Steel/Brass
- Copper-Nickel/Steel
- Tantalum-Nickel
- Nickel-Platinum
Areas of application in pictures
CD-Welding
Advantages
Capacitor Discharge Welding (CD-welding) offers the following advantages:
- Precision welding without distortion: The process is highly controlled, preventing material warping.
- Accurate reproducibility: You get consistent results every time.
- Precisely controlled welding energy: The regulated capacitor charging ensures accurate energy delivery.
- Extremely short welding time and high welding currents: This allows for rapid and efficient welds.
- Millisecond welding: Minimal discoloration or thermal stress on the surrounding area.
- High-volume production: Consistent quality is maintained for mass-produced items.
- Economical and energy-efficient: The process uses less power.
- Relief on power grids: The welding is powered by a capacitor bank, not the main grid.
- Welding of different materials: It can join dissimilar metals.
- Welding of coated materials: The process works even with pre-coated surfaces.
- Welding of sheets with different thicknesses: It can join materials of varying gauges.
- Consistent weld quality: The output is reliable and uniform.
- High reproducibility: The process is easily repeatable with the same results.
CD-Welding and
Cost-Effectiveness
Resistance welding, and specifically capacitor discharge welding (CD-welding), are very economical processes. The weld joint is created without the need for filler material or other consumables, and the required geometry of the components can be achieved using simple forming processes.
The energy for CD-welding is drawn from pre-charged capacitors. Charging takes place during typical idle times, such as during the cylinder stroke or while loading and unloading parts. Since very little heat is transferred to the surrounding material or the electrodes during CD-welding, essentially only the energy needed to heat the projection geometry is supplied.
This is also why water cooling is not typically necessary for CD-welding; it’s only required for a very fast cycle rate. The welding energy has a minimal impact on the power connection requirements, which makes it possible to weld long seams or large diameters.
