Q: What are a few checks used to confirm weld quality in a solid material handling or parts washing basket?
It's virtually impossible to visually confirm that a resistance weld meets your strength requirements, so there's no substitute for destroying a welded part from time to time to confirm weld strength. However, that can get expensive. As an alternative, there are several types of resistance-welding monitors that can confirm that the proper amount of welding amps are being passed through the part being welded. Some of these monitors are portable and battery-operated. Others operate on 110 V and are designed to be installed on a machine. Some models include printers and the ability to output weld data to a network for evaluation or permanent storage. Secondary welding amperage is just one of the three most important variables of the resistance welding process -- along with pressure (forging force) and weld time -- so these monitors are not foolproof.
Q: Since proper dressing of electrode tips leads to better quality welds of wire baskets, what are some techniques that confirm consistency in electrode dressing?
Frequent "dressing" or re-machining of your electrodes or flat copper bar stock material is critical to making quality welds. Cleaning (dressing) of all electrodes on a regular schedule is recommended -- and well before the electrodes get in bad shape.
Q: Does welding in a materials-handling basket environment differ from other types of welding due to the precise and small tolerances involved?
The "secret" to successful resistance welding is to identify and closely control all the variables. There can be as many as a dozen variables at play during the process, so this can be quite a challenge. In making a material-handling basket, the most critical thing is to make sure you have good part fit-up. Some people incorrectly consider the welder to be a metal-forming tool. It is not. If your parts do not consistently fit together correctly, the pressure needed to overcome the variable "spring back" robs the process of forging force.
Q: Are there unique challenges to consider when welding stainless steel?
On the contrary, stainless steel is the easiest material to resistance weld. Due to its high resistance to current flow, heat at the weld joint is generated easier and quicker than mild steel. One thing to remember: stainless steel requires more forging force, due to its hardness.
Q: What are the benefits of pulse welding in building a material-handling basket?
Resistance welding with multiple impulses can be a good method of welding thick material. Also, it can allow you to "fool mother nature" if your welder is marginally too small for the application. Most resistance welding of wire products can be done with a single impulse, however, providing that the machine can produce the needed welding amps and pressure (force).
Acknowledgments
This white paper was produced with assistance from Tom Snow, CEO of T.J. Snow Resistance Welding Machinery & Supplies in Chattanooga, TN.
