Projection Welding

Questions and Answers

One cannot calculate the welding parameters (squeeze, weld, hold – force & amperage). A very similar question was recently answered for 4MM wire.

CAN THE BUTT END OF A 4MM (0.156”) MILD STEEL WIRE BE PROJECTION WELDED AT 90 DEGRESS TO A PIECE OF 4MM (0.156”) MILD STEEL WIRE?

 Cross Wire Welding

The process is very doable but the parameters are likely not published. They cannot be calculated. One will need to either consult the literature for similar operational data or do trial and error.

Another article in this blog describes the steps one must follow to do the trial and error:

“HOW DO YOU DEVELOP A PROJECTION WELDING PROCESS?”

This outlines the processes to develop a schedule and the important factors to consider in setting up the equipment:

FORCE APPLICATION AND FOLLOW-UP

ALIGNMENT

PROJECTION SHAPE, SIZE & CONSISTENCY

ELECTRODE MATERIAL AND CONFIGURATION

A “T” weld is not a cross wire weld. It is a projection weld similar to an elongated projection weld. The most important factor will be the cut off of the wire end. Secondly, fixturing it to maintain its perpendicularity as force is applied. Good tooling and maintenance can make this work and many good welds will be produced.

Reference: AWS C1.1 Recommended Practices for Resistance Welding
                  AWS J1.3 Specification for Materials Used In Resistance Welding Electrodes and Tooling
                  AWS J1.2 Guide to Installation and Maintenance of Resistance Welding Machines

Burrs in projection welding be it Capacitive Discharge, AC or MFDC resistance welding are caused by several factors. One is the inability to contain the molten weld nugget as it is forms. Another is the weld interface may have been overheated. A very important factor is that the full force must be maintained on the projections as they collapse. Pressure/force is a factor in each of these considerations. To reduce the burrs and weld flash/expulsion that creates this condition one must look at the basics of force application.

Material at 0.250” (6.4 mm) is generally beyond the limits for resistance spot welding. This question did not define the shape of this bar (round or square). The possibility of using a resistance welding process is viable on this bar with either shape if projection welding is used.

This question should be further elaborated to include how close should the fixture bottom support be to the outside of the nut wall?  Secondly which is preferred a ball end shaped rod or a threaded bold for even consistent force application.

  Projection Weld Parts

ASSORTED WELD NUTS

This is a question in two parts – Fixturing the assembly to be evaluated, and the push off tooling used to apply force directly against the actual weld nut.

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