Process Considerations

Engineers must not only consider design and material requirements, but also should take the actual welding process into account. Part positioning and welding procedures affect weld quality. Designers must compensate for distortions induced by welding. And once the parts are welded, they must be inspected. The quality of welds is ultimately the designer's responsibility. Use jigs, fixtures, and positioners: Jigs and fixtures hold parts in correct alignment for welding. Fabrication shops may have suitable ones available, but when designers and manufacturing engineers have to specify new ones, this cost must be included in the cost of welding. Motorized positioning equipment can turn massive components to position them for welding. If such equipment is available, workers must mount the components on the equipment and make sure that it is properly aligned before welding. The time this takes must be compared to the welding time involved. If mounting time equals or exceeds the welding time saved, it is better to choose a welding process that will operate in the position the structure is already in. Welding position is important. Thoughtful designers can arrange to have most welding done flat, so processes such as submerged-arc welding can be used. Flat-position welding is easier for welders, yields better quality, and improves production rates. Other positions limit the processes that can be used. The lack of access also makes inspection more difficult, and both quality and productivity are likely to suffer. Ideal welding procedures are those that produce acceptable-quality welds at the lowest overall cost. The procedures should be tailored to the application and should spell out exactly what welds are to be made and how they are to be made. Procedure variables include the welding process, conditions, and operation details; joint details; filler metal and shielding gas (if any), and safety. Different procedures produce different