Tolerance design approach to meet Zero defect requirements on aerospace components

Sammanfattning: In manufacturing, variation is and will always be present. To control and define variationtolerances are of paramount importance. To maintain profitability and continuously obtainnew product development and manufacturing contracts, GKN must strive towards zerodefect (ZD)-manufacturing to further improve their product quality and reduce the nonconformance quantities. With capability targets of Cpk = 1.33, possibly increased toCpk = 2.0 in a foreseeable future, the number of faulty products allowed is remarkablylow, and further reaching towards the goal for ZD.The question that this thesis treats is ”how can GKN improve their work with tolerancesto further support the company vision of ZD?”. This is done in three steps. Firstly, aninterview study that displays shortcomings within the design process. Enlightening thelack of capability knowledge and differences between today’s way of work and the AS13100aerospace standard which is to be implemented. The interview study exposed an imperfecttolerancing process with knowledge gaps and relatively low priority. Secondly, with anindustry benchmark highlighting SKFs extensive capability knowledge and Husqvarnas’extensive geometry assurance work. And thirdly, a pilot case study comparing two GASproducts using geometry assurance and tolerance design to display a methodology ofimproving the design to suit the manufacturing processes without compromising qualityor evidence.The study showed that with the original design and tolerances, this product would benearly impossible to manufacture as the distance between the surfaces defining a weldinggap is allowed to fluctuate with, at its maximum, ±1.14 mm, where the desired weldinggap is 0.1 mm. Regardless, the product is continuously produced, but in an alternate waythan initially intended. Conclusively, the design departments at GAS do not possess asufficient tolerancing process. Contributors are the absence of time, knowledge, distinctprocesses, and concurrent work. Major improvements could be made by widening theinternal knowledge regarding their process capability while also utilizing tools for variationanalysis in design. Additionally, take interest in the manufacturing processes, historicalresults, and the people responsible.