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Projection Welding


 

Projection welding has fewer variables that affect the resistance welding process as compared to spot welding. The most important variables of this assembly technique are the quality of the projections and the response of the cylinder as the projection collapses during the welding time.



Lawrence Alexander & Co.

Quality of Projections

If the cross section of metal in the projection is fractured, the heat build up will form more rapidly in the stretched material then at the workpiece interface area. This will result in the projection collapsing before fusion takes place. When the projection is totally collapsed, further growth of a weld nugget will be impossible since the large surface of the copper electrodes will diffuse current density when the electrodes make full contact to the workpiece.

Response of Cylinder Follow Through

When the projection is collapsing, it is imperative that the electrode force be maintained otherwise massive expulsion will occur. This expulsion is none other than the projection material that needs to be fused to the workpiece. The cylinder is responsible for follow through.

Benefits of Projection Welding Techniques

Projection welding is very easy to maintain if the fundamentals are taken into consideration in the first place. Steel wire shopping carts, wire racks, and other crosswire products are all projection welding. Nuts and bolts are often assemble to other metal parts by projection welding. If you want to produce a part with very little heat surface marks on one side of the panel, then processing a projection on the alternate part and using large electrodes contoured to the finished part would facilitate the goal.

Good cylinder response that follows through the collapse of the projections on this weld nut produces very little expulsion and assures good weld quality

Photo: Centerline (Windsor) Ltd.

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