Resistance Spot Welding: Process Comparison


Resistance spot welding is a particularly popular welding process in the automotive industry, as an economical method for joining aluminum sheets, for example. Users have two process variants available to them: namely, conventional spot welding guns or a system with a continuous process tape. Here, you will find out about the benefits of each of the two solutions and which applications they are best suited for.

Conventional spot welding

Conventional resistance spot welding is often used to join steel plates, but also aluminum sheets in body and vehicle construction. Aluminum has a lower resistance than steel, which means higher forces and greater amperages are required to join the materials. The spot welding process enables a high level of productivity and requires no filler metal. With certain limitations, even materials that are otherwise poorly suited for welding can be joined.

Welding is usually carried out using a gun with a servo drive, different versions of which are available. Guns with C and X geometry can be used, for example, to weld different components, depending on their accessibility. There is also the option of including a welding gun adjustment—this function helps when fine-tuning the gun before the actual welding process and prevents the sheets from deforming due to inaccuracies. This task can either be performed by robots with the gun mounted on them, or by the welding controller.

This resistance spot welding process is suitable for a wide range of tasks, including in the automotive industry, but also for tasks like welding small and ultra-small parts made from various metals and metal combinations in the electronics industry and electronics manufacturing. Conventional spot welding systems can universally be connected to different types of robot and are suitable for any production line thanks to their high level of automation.

Resistance spot welding with continuous process tape


Spot welding with a process tape is a unique welding process that is perfectly suited to joining steel and aluminum, as well as thin sheets and multiple sheets. Welding guns with X and C geometry are also used here, but with a continuous process tape situated between the gun’s electrodes and the component to be welded. This transfers the welding current and protects the electrodes’ contact surfaces against contamination. The tape is in constant motion, which results in a continuous welding process with consistently high quality, as the system provides a new contact surface for every welding spot. The resulting welding spots are spatter-free and there is no need to re-mill the electrodes, saving time and effort. Users can weld up to 7000 spots without interruption with a process tape—this ensures shorter cycle times particularly for workpieces with a high number of welding spots.

The service life of the electrodes is also significantly increased as they are protected by the process tape. Also, no alloying of the surface coatings or base materials on the electrode is required. The welding process is also highly efficient as additional heat is conducted into the workpiece owing to the high electrical resistance of the tape. This means up to 50 percent less energy is required depending on the application. As well as aluminum joints, this spot welding process can also be used to join titanium, magnesium, stainless steel, coated steel plates and high-strength steels.

Advantages of Both Welding Processes at a Glance

Conventional spot welding system without process tape:

  • High level of productivity thanks to shorter cycle times
  • Extremely economical joining process
  • Easy to automate
  • Easy to repair and maintain

Resistance spot welding with continuous process tape:

  • Extremely high productivity thanks to reduced milling times
  • Consistent welding quality
  • Electrodes protected against contamination
  • No tip dressing required
  • Less reworking thanks to high surface quality
  • Lower energy requirement for aluminum applications
  • Accurate and rapid balancing function due to integrated control

Two Systems—Countless Possible Applications

The resistance spot welding processes are used in various industries such as the automotive industry, rail vehicle construction, the aerospace industry and white goods manufacturing. Their specific strengths make them suitable for a range of applications. The following comparison will show you what the welding process is well suited and less well suited to:

Conventional spot welding system without process tape:

➕ Mass production with high cycle rates
➕ Fully automated production lines
➕ Components with a low number of spot welds
➕ Difficult-to-access areas
➕ High-strength steel applications

➖ Large components with a high number of welding spots
➖ Joining various materials and sheet metal thicknesses
➖ Steel and stainless steel combinations with extremely high quality requirements
➖ Micro welding

Resistance spot welding with continuous process tape

➕ Joining challenging sheet joints made from steel, aluminum, and other materials
➕ Difficult material combinations, dissimilar material joints, and uneven sheet metal thicknesses
➕ Components with a high number of welding spots
➕ Joining of thin sheets and multiple sheets Series production with high quality requirements

➖ Simple material combinations without high quality requirements
➖ Difficult-to-access areas
➖ Mass production with several welding systems in a production line
➖ Point diameter over 8.5 millimeters
➖ Micro welding
➖ Small gap applications

Want to know more about resistance spot welding systems? Here, you will find all the information on our conventional spot welding system DeltaCon and on DeltaSpot, the unique spot welding with continuous process tape.