Miglioramento del design di un attuatore a pignone e cremagliera utilizzando una metodologia multidisciplinare basata sul Design-to-Value integrato con FEA e valorizzazione del lavoro di squadra: analisi critica dei vantaggi ottenuti e dei benefici delle problematiche affrontate.

The work presented in the thesis investigates the benefits of introducing a new original multidisciplinary methodology that integrates in a global homogeneous process the benefits of the state of the art of product development techniques, mechanical finite element analysis and collaborative teamwork strategies. For exposing this interdisciplinary and Holistic new Product Development approach, a case study is presented, focusing on a re-design project of a pneumatic rack and pinion actuator for valve actuation, first time designed in 1984, investigating the potential of joint application of the Design to Value (DtoV) process, coupled with design techniques utilizing FEA simulations, and giving high priority to teamwork during the execution of the project. The rack & pinion actuator is a mature product, having nevertheless a constant demand from the valve automation market. The final objective of this study is to show how it is possible to optimize its design, obtaining compliance with the requirements of the last versions of main international product standards, increasing weight efficiency and performances, while maintaining high safety and reliability, and at the same time to also simplify the design, with a reduction of components construction complexity and a simplification of assembling procedures, according to the growing demand for a lean production. The methodology applied for the actuator design improvement is based on the instruments and procedures foreseen by the DtV process, coupled with design techniques based on FEA, called “Design by Analysis”, that are going to re-place, or integrate, the verifications of “Design by Formulas”, used in the occasion of the first design. Focusing on this new design strategy, originally not available, and orienting the design choices for maximizing the product value according to the findings of DtV process, it is possible to obtain important benefits and introduce a totally renewed and more efficient actuator. The high importance of the “secret ingredient” represented by giving high priority to teamwork during all the activities will be also presented. In fact, the principle that guided all the activities during the execution of the studied Design Enhancement Project was valorizing the power of teamwork, focusing the team on Safety and Reliability. In a First step of the application of the methodology, the procedures and tools foreseen by the “Design-to-Value” process for fostering improvement ideas generation are applied. Investigations were carried out involving all the company functions interacting with the product, and every single part and feature of the actuator was the subject of in-depth study, by means of techniques developed in the context of the theory of “Product Design and Development”, like “teardown analysis” and “function analysis”. After completing the classification of the contents constituting its most important sources of value, by integrating the investigations by means of other useful techniques like “House of Quality”, the subsequent step has been to outline the input for detailed design phase, by choosing the best value increase proposals and officializing them in “Design Change Proposals”, elaborated for the purpose of obtaining efficient construction solutions. The design change proposals have been the driver of the second phase of the project, dedicated to the detailed design activities aimed to the re-design of the actuator. The peculiarity of this project has been to combine the “classical” approach for structural verifications based on formulas, and then called "Design by Formulas", with advanced FEA simulations, called "Design by Analysis", aiming to stress, deformation, and topology optimization, obtaining a much higher level of accuracy confirmed by experimental validation phase. Furthermore, the conformity of the actuator parts finalized to containing pressure has been verified with respect to an international standard for pressure vessels (EN13445-3), as required by the main actuator product standards (EN15714, ISO12490, API 6DX). Finally, a two-step experimental validation is foreseen, for confirming the results of the calculations and simulations, based on a preliminary test plan to be performed on a "mockup" prototype, followed by a series of in-depth tests to be performed on a complete detailed prototype, only after the main positive confirmations have been achieved thanks to “mockup”. Experimental tests have the purpose to validate the safety of the parts under pressure as well as confirming the good reliability and fatigue life of the parts subjected to mechanical loads, as required for the obtainment of certification for use up to SIL 3 Safety Instrumented Systems (SIS), in accordance with EN61508 (SIL = Safety Integrity Level). This new value-oriented design strategy, implemented with a sort of “secret ingredient” given by collaborative teamwork, allowed to obtain tangible benefits and introduce a totally renewed more efficient actuator. Preliminary results obtained thanks to the project show that the approach based on the described multimethodology, makes it possible to optimize the design of the actuator, maintaining safety, reliability, and increasing performances. In particular, for the studied prototype, the achieved weight reduction is -8% and economic efficiency increase, expressed in $/Nm, is expected to be +22%.