Can I spot weld aluminium?

Yes, it’s always been possible, but with new technology it’s even easier. Aluminium has a low electrical resistance, so you need a lot of current to heat it up. This used to mean a huge transformer and a sub-station outside the back door. Now, with Medium Frequency transformers, driven by an Inverter, a small transformer can deliver a very high current. It’s still a good idea to pre-treat the material to remove the oxide layer, as this will make the welds much more consistent.

Does the force at the tips matter? Surely the current is the most important thing?

Certainly if the force is not right for the material, it’s normally possible still to get a good weld. But for example, if it’s too low, you will have to reduce the current and increase the weld times to get this result, so you’re losing production efficiency. The force has to match the material thickness for the ideal results. See the PW website for guide settings.

The cooling pipe inside my electrode tips has been lost. Does this matter?

The pipe ensures that a jet of cooling water is applied to the inside face of the tip. If there’s no pipe, there may be no flow anywhere near the “business” end of the electrode. When a weld takes place, the static water inside the face will be vaporised and steam is not a good coolant! Always check the pipe when replacing tips.

Why are my spot welds failing?

95% of the time it will be down to the diameter of electrode tip in contact with the material being welded. A new standard tip has a spot diameter of 5mm, which gives 19mm² of contact area . If the tip is not dressed and the contact diameter is allowed to increase to 7mm, visually not a big change, the contact area has doubled to 38mm², so you’ll have only half the heating effect.