Controls & Transformers

Questions and Answers

Weld controls are incorporated into many automated systems. The weld control is required to take signals from and communicate back to the main system in all of them. Communication in the numerical control environment is normal and a given for weld controls. The weld control runs the actual welding operation but the rest of the automated machine operations are controlled by the central machined communications center. This center may also be a storage center for the weld parameters that will be downloaded from the weld control for each weld. The ability to exchange data both directions is limited by imagination only.

Adaptive controls monitor one or more weld conditions which can be directly traced to nugget quality. These controls monitor feedback within the first milliseconds of the weld initiation. Based on this instantaneous feedback the control makes adjustments to inputs and can change the weld parameters to correct the forming weld nugget. The goal is to produce a quality weld nugget each and every weld. The controls are in the marketplace and are being used.

During welding operations some high alloy materials become brittle in the area near the nugget due to the cooling rate. The parts in fact are quenched in this area and are brittle. Tempering will alleviate this quenched condition. This means bring the material back up to a modest tempering temperature and hold briefly and then cool slowly.

In some materials there is a tendency for voids to form in the weld nugget. Aluminum often has this problem. Forging the nugget in the plastic state is a desirable means of improving the nugget’s strength and acceptance.

In some instances it is advantageous to immediately repeat the same weld sequence on a spot weld. This is usually done in an attempt to grow the nugget larger or to permit a brief cooling of the part. Immediately at the end of the weld sequence one or two cycles of cool or current off are introduced with full force maintained then the original weld sequence is repeated.

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