Machining of small-lot large parts (i.e. planet carriers) for windmill gear boxes in the wind power sector at Gamesa.

Machining of small-lot large parts (i.e. planet carriers) for windmill gear boxes in the wind power sector at Gamesa.
Context: The continuously increasing demand for energy is leading to the manufacturing of eolic towers that are able to produce more power. These towers demand larger components and require new and lighter materials for easier assembly. The machining of components such as the planet carrier is critical, since very small product features have to be machined at very tight tolerance requirements (normally tenth of microns on dimensional and geometrical features) on very large parts (outer diameters up to 2500 mm, weight up to 7000 kg). Situation before MuProD: - The production system is composed of two parallel machining centres dedicated to roughing and finishing operations. The process sequence entails two machining phases (different positioning). - The causes of defects are related to the input casted material, part deformation due to fixturing, tool wear, vibrations, etc. - In order to achieve highly demanding manufacturing goals, the company makes use of a hybrid inspection procedure. The first part of the lot is extensively measured at the CMM for compensating possible machine deteriorations by machining parameter adjustment. Then, the lot production is started. For each processed feature, extensive in-process part verification is carried out to avoid the generation of any possible type of defect. Indeed, due to the high value of casting parts, part scrapping is not a considered option. However, these continuous machining, measuring and adjustment loops interfere with the cycle time and the productivity of the plant. -The part clamping, positioning and adjustment during set-ups between the two machining phases is highly time consuming and strongly affects the quality of the process. MuProD solution: - Design, development and testing of an innovative adaptive fixturing system, explicitly designed for supporting precise positioning of large parts. The adaptive fixture allows reducing the fixturing and positioning time of a 70%, also eliminating the effect of the operator errors on the positioning process. - Selection and implementation of a laser scanner for in-line part quality verification, as complementary to the CMM off-line inspection, for predicting quality deviations earlier in the process chain. - Development of a methodology and a software platform for the optimal selection of the machining parameters, depending on the specific machine conditions, based on mechanistic cutting models. - Design, selection and implementation of a contact sensor for in-process automatic part quality verification, substituting the previous manual in-machine quality verification procedure. - Design, development and installation of the Information Sharing Platform (ISP) for making the whole set of data retrieved from the new sensors and actuators available at shop floor level into a knowledge based platform for enabling further analysis and knowledge retrieve.
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