Learning factories as a novel medium for practical training in the new ISO-GPS-system on the model of functional tolerancing of precision-manufactured workpieces

As the production engineer of the future operates in a global market environment, a common language for the exchange of technical product information is required. This need has been met with the introduction of the ISO-GPS-system for codifying geometric product specifications. While this standard has been applied in the area of quality assurance for a long time, its importance in the early stages of product design along the lines of functional tolerancing has so far not been recognised sufficiently. In order to address this shortcoming, a new laboratory concept has been developed in the “smartfactory@tugraz”, the learning factory of Graz University of Technology. In it the basics of functional tolerancing are taught within the context of manufacturing precision parts for a hydraulic function assembly. A spool-type pressure relief valve (PRV) is proposed as a suitable function assembly as its operating characteristics are primarily determined by the geometric specifications of the moving spool. Moreover, such hydraulic control valves can easily be modelled and the correlation between geometry and function intuitively understood. Students are provided with a series of machined spools with a targeted variance in their macro and micro geometry. These deviations from the nominal geometry of the spool are then determined using methods of manufacturing metrology. In addition, students conduct functional tests of the valve, which result in a characteristic curve for the respective spool. The valve characteristics determined are then compared with the measured geometrical product specifications and interpreted with regard to design and manufacturing aspects.