the filler metal. There are two common ways to do so: 1) Change the dimensions of one or both tubes so that the flat edge of the horizontal tube meets just inside the radius of the vertical tube. This may work if the two tubes do not need to have the same dimensions. In many cases, however, that is not an option. 2) Create a radius in the horizontal tube to match the bent radius in the vertical tube. Achieving this is easy; design an assembly in the 3D engineering software and draw the radius to include a portion of the outside radius of the mated tube, while considering the wall thickness, as shown in Fig. 2. This provides the tightest possible fitup without relying on the tube profiling capability. It closes the opening tightly, which will allow the material to fuse properly during welding. Bending Basics Of course, with this sort of design, the cutting and welding processes are also important, but perhaps even more so, the bending process is essential. As we know with laser welding, the consistency of the joint is of the utmost importance, so a high-quality, accurate press brake and good, accurate tooling are required to properly execute this design. It is, therefore, necessary to use modern press brake tooling. With a traditional three-point air bending process, the newly designed radius that was added along the edge of the part would flare and distort during the bending process. This would create an opening that would disrupt the weld and eliminate the design’s usability. The die shown in Fig. 3 controls the distortion by supporting the part during the bending process, keeping the resulting geometry true to the design. The die also creates a bend radius, which exactly matches the radius of the punch used for bending. This allows for some creativity when determining the best fitup between both tubes, as a combination of radiuses might give the best results (e.g., smaller radius on the contoured tube, larger radius on the noncontoured tube). A combination of different bend radii were used in this example to find the best fit and achieve these results. In this case, an inside radius of 0.04 46 WELDING JOURNAL / MARCH 2016 Fig. 2 — Using 3D software to create a radius in the horizontal tube to match the bent radius in the vertical tube will create a better manufacturing fit. Fig. 3 — Modern press brake tooling is important for manufacturing parts with good fitup, as the appropriate tools control for distortion.
Welding Journal | March 2016
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