Fig. 1 — Poor fitup of similar tubes. The material used is mild steel, 0.06- in. wall thickness, with 0.16- in. outside radius. MARCH 2016 / WELDING JOURNAL 45 working with tube and profiles. When purchasing raw material, the material consistency of the tube is often quite poor, which leads to repercussions further down the manufacturing line. Whenever it is possible to use sheet metal, which is typically of a higher quality than tube, there is often a benefit. The Importance of Radius Measurement, Dimensions Also, consider the interior and exterior radius of the tube. It is common for the material chemistry and thickness to vary throughout. This is not only problematic to the manufacturing process, but any opening created between inconsistent tubes can ultimately mean failure when trying to create aesthetic, crisp seams. This is especially problematic when welding parts together. In furniture manufacturing, where the final parts are highly visible, poor results are highly detrimental to the end user. Simply put, nobody will pay top dollar for an office chair that is not aesthetically constructed. There is also a high cost associated with nontypical tube diameters. Finding a supplier for tube stock with standard dimensions might be easy, but when trying to find an atypical tube dimension, either because the print requires it or a slightly different size tube will provide for a better fitup of the parts, the price suddenly goes up, sometimes dramatically. In that same vein, there are myriad benefits to being able to self-determine the diameter of a simple square or rectangular-shaped tube. These include greater freedom and creativity in part designs, especially considering what is now possible with engineering software. Laser Welding Highlights This freedom and flexibility in part design often stems from what is possible, technically, in manufacturing. As technologies evolve, new opportunities arise. Laser welding is one such technology that has greatly impacted manufacturing. In the automotive world, it might mean lighter cars with better fuel efficiency. In furniture manufacturing, it could mean more interesting or aesthetically pleasing designs at a lower cost. In this article, we consider an application where small design changes combined with laser welding enhances the end product while reducing the cost of fabrication. Application: Join Together Two Tubes of the Same Dimension As Fig. 1 shows, there is an opening created when fabricators try to join two similar tubes together (in this example, the tubes are mild steel, 0.06- in. wall thickness, with 0.16- in. outside radius). This is too large for successful laser welding, and as a result, it’s difficult to achieve a consistent weld without using filler metal. This is not ideal, however, as the performance of a laser-welded joint will diminish and the consistent, finish-free result that laser welding is known for will be severely affected. Crafting Tube Profiles from Sheet Metal Although the use of filler metal is the simplest answer, there are other alternatives. Consider using tube profiles made from cut and bent sheet metal instead. The benefits of making tube profiles from sheet metal are numerous assuming the solution fits the application. This would not be as feasible, for example, if the application required high volumes of long, simple tubing, because it would be very difficult to achieve a consistent fitup throughout the length of the tube. When it is possible to create the tube profiles from sheet metal, however, there are many advantages to doing so. In addition to the consistency and quality of the material, as discussed previously, fabricators are also able to achieve a better weld by eliminating
Welding Journal | March 2016
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