Use the spot welding electrode tip diameter formula calculator an essential factor that affects the quality of the pinch weld. The diameter of the electrode tip should be chosen based on the thickness of the material being welded plus the welding current, and the type of electrode being used to maximize weld quality.
TLDR: Spot Welding Electrode Tip Diameter Calculator
Factors to Consider When Choosing Electrode Tip Diameters
The resistance spot welding process is used in a vast array of industries. To maximize efficiency it relies heavily on the optimum size electrode tip. Use the calculator above to improve the performance of spot welded components.
Spot Weld Tip Size Too Large
As electrode tip diameter increases for a particular material thickness, If all other optimal welding parameters are set perfectly a few things happen. Because the contact area has increased the contact area where the welding current passes through the two layers of material, less heat is generated.
If you increase the weld time on the two layers of steel the visual weld nugget size does increase. The actual weld integrity is not necessarily stronger. Due to the lowering of the concentrated heated area, the liquified metal is not fluid enough for two layers of steel to form a strong bond,
This is known as the fusion zone. In turn, the surrounding area is subjected to more heat transfer through thermal conductivity.
A larger diameter in conjunction with a weld time increase can also reduce the duty cycle on the machine.
When the weld cycle has finished, the larger electrode diameter made from a copper alloy acts as a heat sink. This cools the weld quicker. With the use of modern carbon steel, a balance during resistance spot welding and correct cooling cycle time is required.
Resistance Spot Welding Electrode Tip Size Too Small
So now you are thinking..”I’m going to make the spot weld tip size way smaller.”
This also has negative effects on the spot weld quality. For example, I have a sheet thickness of 20 gauge / 0.0375 thou or 0.9mm. So the overall spot welding thickness is 0.75 thou or 2mm. I decide to reduce the copper electrode to 1/8th or 3mm.
The reduced point of contact with the steel during resistance spot welding will increase the concentration of the current flow to a smaller area. With the increase in welding current, the spot welding quality is reduced in two ways.
The nugget diameter is reduced. The weld nugget diameter is dictated by the electrode surface contact area. Resulting in the fusion zone size, reducing the joint strength.
The weld pool will become very unstable, with an increase of current on nugget diameter a term called expulsion happens. Once the two layers of steel become too hot with the combination of the electrode exerting pressure on the material, the liquid steel is forced out of the fusion zone. Commonly welding sparks.
In some cases, upon visual inspection, the nugget quality looks adequate. Internally the molten steel is ejected between the two layers of steel. Reducing its performance characteristics.
With the electrode tip surface area reduced it also leads to the deformation of the two layers. It creates an excessively concave surface. To minimize this increase in electrode tip size.
Maximize Your Performance Of Resistance Spot Welding
When doing multiple welds the electrode tip diameter increases from the repeated weld cycles. This affects the nugget size and you guessed it a reduced spot weld quality.
The effects of welding current and heat energy even if using the optimum welding parameters, you will notice a variation of nugget diameter. This is due to the increase in electrode tip contact area from repeated cycles.
This happens in both robotic automated machines and the automotive sector of collision repair or vehicle restoration using conventional resistance pinch welding by hand.
This is electrode tip deformation. For any given size of the tip, there is an acceptable maximum nugget diameter. A good rule of thumb is 3-5% of the electrode tip surface.
Spot Weld Tip Dressing
The electrode material is mainly a copper alloy so dressing the electrode tip for smaller machines is as easy as using a file to remove the tip deformation. Be sure to maintain the same geometry as the original. The drawback of this method may lead to a misalignment of the tongs from the incorrect filing of the electrode surface contact area.
In a situation where automation is used in the resistance spot welding process to maximize the performance of resistance spot welding. I suggest a Pneumatic tip dresser to ensure repeatable results, set in the optimal welding parameters to maximize the mechanical performance of the spot welding tip.
They are handheld tool that has the cutting tool shaped exactly to the required shape. When the contact surface area of the tip has deformed the dressing tool will simply be placed over the electrode and the cutting tool works like a pencil sharpener to repair and extend the life of the tip.
Choosing the correct diameter of the electrode tip is crucial for the quality of the weld nugget. The diameter of the electrode tip should be based on the thickness of the material being welded, the welding current, and the type of electrode being used.
If the diameter is too large, the contact area where the welding current passes through the two layers of material increases, resulting in less heat generated and a weaker bond. If the diameter is too small, the concentration of the current flow to a smaller area can reduce the nugget diameter, reduce the joint strength, and cause the weld pool to become unstable.
To maximize the performance of resistance spot welding, electrode tip dressing using a file or a Pneumatic tip dresser is recommended to ensure repeatable results in the optimal welding parameters and extend the life of the tip.