FROM A 2D DRAWING TO A 3D MODEL, WHAT DOES THAT IMPLY FOR ME AS A DESIGNER? By Hans van Kimmenade Lecturer Geometrical Dimensioning and Tolerancing A technical drawing specifies the requirements that a designer sets for a workpiece. These workpiece specifications are still commonly executed via 2D drawings. It took time to make the 2D drawings and they had to be printed. Also, the handling of an order was mostly done by hand and was often cumbersome. In the event of a change, all these steps have to repeated again and again. More often the specifications are incorrect or incomplete which in turn results in unnecessary extra effort in the manufacturing and measuring process. Incorrect specifications can lead to needless waste. If everything went right, the mechanical designer’s mistakes were usually taken care of by the skilled worker in the manufacturing process and questions may have cropped up during the measurement stage because only things that were correctly specified can actually be verified. Model Based Definition In recent years, we have seen that people are willing to make the step to paperless communication. This is not entirely new. In 1989, steps were already being taken in the direction of Model Based Definition. At that time, it was expected that the transition to being paperless could be made within two years. By 1991, we were supposed to be fully Model Based. Model Based Definition (MBD) is a way of not traditionally putting the workpiece specification on a drawing but in a 3D model instead. MBD can include things like dimensions, tolerances, geometric specifications, surface treatments, references and general 10 notes. When manufacturing information and information also become relevant for verification, then this is referred to as Product Manufacturing Information (PMI). “Why designers need to start paying more attention to ensuring that their workpieces are complete and correctly specified.”
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