3 Parts and Pieces
Pre-Made or Custom Made
Welded fabrications are made from pre-cut and pre-formed parts or parts cut and formed by hand.
Advantages of pre-formed parts include lower costs, a higher speed of fabrication, a higher accuracy of measurements, and less waste produced.
Custom-fabricating parts makes certain types of work easier, such as creating originals or prototypes, performing repairs, or other custom jobs. However, most cutting processes remove metal and leave a small gap or space, also known as kerf space. Take this into consideration when choosing where to cut.
Materials
Weldments may be constructed from a combination of shapes, sizes, and metals. Common metals include carbon steel, aluminum, stainless steel, and titanium.
Metal stock comes in a variety of shapes including plates; sheets; flat, square, and round bars; angles; c-channels; i-beams and flange beams; square and round tubing; and pipes.
Laying Out Parts
Parts for fabrication may require lines to be laid out and points to be marked for various operations. Methods of marking include soapstone, metal markers, chalk lines, metal scribes, and a center punch.
Factors affecting the layout process include the materials involved, the shapes of parts, and allowable tolerances.
Layout Tools
Unimaginable amounts of special tools have been developed for laying out parts. There are a few that you will interact with more than others. Tools of note include: tape measures, square, protractors, rulers, calipers, bevel gauges, angle meters, and lazer tools.
Nesting
Nesting shapes is a way of laying out parts so that the least amount of scrap is produced. Odd-shaped and unusual-sized parts often produce the largest amount of scrap. The parts must all fit together in the most optimal way for the sheet or plate. This process may be completed by computer or manually.
Tolerance
The overall tolerance is the amount the final assembly can vary from the layout drawing. Remember that the finished weldment must be within overall tolerance. The engineer has developed the blueprint to allow for margin of error on the smaller parts without jeopardizing the final assembly.
The part’s tolerance is the amount a part can be bigger or smaller than it should, and still be acceptable. This allows the parts to fit into the larger assembly without having to re-cut or grind them.
