Weld splash

Weld splash (expulsion/spatter) happens when molten material comes out from the weld nugget. It causes cosmetic problems, defective welds, safety issues for workers, and maintenance problems in the production line. Weld splash is one of the most common issues in the welding industry.

Severe weld splash in the automotive production line running with robots

Why does weld splash happen?

There are many causes of splashes. The most common reason is the welding parameters, but any factors that produce too much heat can cause weld splash.

  • Welding parameters: too high weld current, too long weld time, or low weld force
  • Small electrode contact: small contact area, misalignment of electrodes
  • Surface conditions: dirt, oxide, or anything that leads to high resistance on the surface
  • Poor fit-up of parts: gap between sheets

To ensure good quality welds, the welding process parameters are often set close to a splash condition. It is because there are always some dynamic disturbs during the production such as electrode degradation which could reduce the weld nugget sizes. Therefore the parameters close to the splash limit can be a safe choice for a more stable welding production and consistent weld quality.

How to stop weld splash?

It is important to minimize the root causes.

Get process windows and choose optimal weld parameters

Finding optimal parameters is important to minimize splash in the production line. Too high current can generate excessive heat in a short time. Too low force can increase the contact resistance and generate more heat. If the force is not enough to hold the molten metal inside, it can also cause a weld splash. Finding good parameters is quite delicate work and that’s why most engineers are using the process window.

Process window (or weld lobe) shows the parameter ranges for acceptable weld size

You can get process window data from (a lot of) coupon tests or with guidance from experienced engineers. You can also get help from simulation to generate process windows or make weld planning. SORPAS® can save you time and resources in manual testing. According to customer feedback, the time for optimizing the parameter of a welding line is reduced from 5 days to 1 day. It’s not only the time saved, but also production stability improved.

Check electrode tip and alignment

Small contact areas mean high current density which will generate more heat and lead to splash. Check the electrode contact and use a proper electrode tip. Misaligned electrodes can be another reason for small contact areas or they squeeze out the molten metal due to position error. Make sure your electrodes are squared to parts to minimize expulsion.

Try to remove any gaps between parts

Alignment errors or stamping tolerance can sometimes cause gaps between parts to be welded. It is best to remove the problems before welding, but you can also adjust welding parameters to improve the weld quality. Increasing squeeze time can help to close the gap before welding current flows. Increasing force or using pre-pulse to make the sheets soft can be another way to close the gap. Here you can read our case study about how to find optimal parameters for welding with gaps.

Keep the clean surface condition for welding spots

The contact resistance at the weld interface is quite an influential parameter. Any contamination on the welding surface can dynamically increase the contact resistance and lead to weld splash.