Modeling of process-induced geometrical deviation in broaching for fir-tree slots

Broaching is a key technology for the manufacturing of fir-tree slots. Due to the high-temperature-resistant materials used, a high mechanical load is applied to the workpiece during machining. Because of the filigree workpiece structure, the high mechanical load leads to a geometrical deviation of the machined webs which are formed by two consecutive fir-tree slots on the rotor circumference. Therefore, a methodology was developed to predict the resulting geometrical workpiece deviation. It was shown and validated in analogy experiments that the minimum achievable deviation is a function of the web geometry independent of the number of calibration cutters.