With the introduction of PMI MBD, the 3D CAD model with all of the relevant information, prepared by the mechanical designer, is the only characterization of the workpiece that the subsequent CAM and CAI steps can make use of. The creation and printing of drawings is dispensed with. In these further steps, we will start to see progressively greater levels of automation. It is essential that the communication between these systems aligns with each other. CAM and CAI software must be able to read the CAD information. This requires the information to be semantically stored on the CAD model. A widely used file format for this is STEP 242. Complete and correct workpiece With the introduction of PMI MBD, it is more imperative than ever that the designer specifies their workpiece “completely and correctly“ according to valid, up-to-date standards. For geometric specifications, these standards are defined in the ISO Geometric Product Specifications (GPS) matrix and in the American ASME standards. Geometrical Dimensioning and Tolerancing constitutes part of the geometric product specification and form a symbolic language that the CAM and CAI software are capable of reading. These ISO GPS standards have been subject to frequent changes in recent years. The reason for this is that the standards are not always unambiguous. We also see changes due to the steps ISO is taking to apply the independence principle in a consistent manner. Lastly, the move is being made to base standards on rules rather than examples. In that respect, the end is not yet in sight. Complicating factor A designer then needs to be proficient in the use of this geometrical dimensioning and tolerancing language. Its use is not merely a matter of knowing the symbols, but also having the skill to use them. In this context, the frequent changes in the standards act as a complicating factor. Given the fact that the CAD, CAM, CAI software is based on these ISO standards, it is necessary that designers are aware of the updated standards. Mikrocentrum offers, among other things, Dutch and English Geometrical Dimensioning and Tolerancing training for designers at HBO (University of Applied Sciences) and TU (University of Technology) levels. As an introduction, attention is paid to being able to interpret the geometric tolerance symbol. Nevertheless, the task of the designer is to be able to define and outline the workpiece requirements. The focus of the training is therefore on developing the skills to unambiguously define such requirements. “All requirements that are not semantically standardized on the model necessitate intervention.” 11
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