Overwelding
Overwelding is a common error which increases the chance of distortion.. Sometimes it is caused by simple ignorance and other times it is a combination of people and factors. Typically the engineer calls for a 3/8 fillet five inches long. The detail draftsman rounds it up to say six inches. . . after all a six inch bead was called for for all the other parts of the job. The fabricator in the shop assembles the unit and marks out the welds for the welder. He wants to make sure that the marks are at least six inches apart and in his haste some of the marks are seven inches apart. The welder, seeing that he must use stitch welds goes one half inch past the marks left by the fitter.
Now the weldment is completed. The welds are certainly strong enough however the item has been overwelded by 3/5 or sixty percent. If there was potential a distortion problem it will now rear its ugly head. Now is the time everyone will try to point fingers. It is of no use because the deed is done. Care in following instructions would have prevented the problem before it occurred.
An example is the welding done on a small aluminum tool tote. The material that it was made of was 3mm thick aluminum The bottom and sides were one piece formed into a "U" with end pieces welded on. The welds were all corner joints done from the outside to form a nice radius. The owner had not time to run fillets on the inside of the box.
He expressed the intention of doing those inside welds when he had time so that the box would be much stronger. It was pointed out to him that the only likely place of weakness was at the top edge of the corner joint and a one inch long bead on the inside at the top would be more than adequate. If he welded the complete inside corner he would be the owner of a twisted and buckled tool tote that would not be any stronger.
The example is shown below. For most cases an open corner joint will produce more than enough strength when it is welded from one side only. If there is a serious strength concern then stitch the inside at critical points only.
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