Resistance Projection Welding with Direct Contact
A spot welding process where predefined projections localize current flow and heating, enabling multi-point connections in a single operation.
In projection welding with direct contact, the current flows specifically through the projections that you have previously made in the sheet. This heats only the spot at the projection, the material melts locally there, and the two parts weld together. The advantage: the heat stays nicely contained, you get a clean fusion zone and less distortion than with normal spot welding. Make sure the projections sit cleanly and evenly on the seam. If they don't lie properly or the contact is uneven, the joint will be nothing – then you'll have cold spots or the material deforms uncontrollably. Too much energy or a wrong distance can also give you hot cracks. In practice, that means: set the projections cleanly, align the electrodes well, and then choose the welding time and current so that the projection collapses completely, but the sheet around it doesn't glow through. If you have that under control, you'll get a tight, load-bearing joint without much rework.