No abstract

Open-die forging is a manufacturing process commonly used for realising simple shaped components with high mechanical performances and limited capability in terms of production volume. To date, an analytical model for estimating the costs of components manufactured with this technology is still an open issue. The paper aims to define an analytical model for cost estimation of axisymmetric components manufactured by open-die forging technology. The model is grounded on the analysis of geometrical features available at the design stage providing a detailed cost breakdown in relation to all the process phases and the raw material. The model allows predicting product cost, linking geometrical features and cost items, to carry out design-to-cost actions oriented to the reduction of manufacturing cost. The model is mainly conceived for design engineers, cost engineers and buyers, respectively, for improving the product design, the manufacturing process and the supply chain. Cost model and related schemas for collecting equations and data are presented, including the approach for sizing the raw material and a set of rules for modelling the related cost. Finally, analytic equations for modelling the cost of the whole forging process (i.e. billet cutting, heating, pre-smoothing, smoothing, upsetting, max-shoulder cogging, necking and shoulders cogging) are reported. The cost model has been tested on eight cylindrical parts such as discs and shafts with different shapes, dimensions and materials. Two forge masters have been involved in the testing phase. The absolute average deviation between the actual and estimated costs is approximately 4% for raw material and 21% for the process. The absolute average deviation on the total cost (raw material and manufacturing process) is approximately 5%.

Design of new architectures and systems is a fundamental task in each design stage of complex products such as gas turbines and requires everyday more and more an immediate focus on cost. Due to high variability of worldwide conditions (pandemics, international scenarios, raw material costs fluctuations), it is exceedingly difficult to provide to design engineers a reliable estimation of final commercial cost of each component, while it would be a fundamental enabler to guarantee high competitivity to new products. Based on that, the aim of this paper is to analyze Technical Cost that can be addressed directly with design choices, and which shall be formally distinguished by other types of cost definitions (economical, commercial…). A case study of a rotor wheel is presented to demonstrate the value of the proposed approach in the development of Technical Cost models from raw material to final machining. The aim is to design production processes based on its Technical Cost, guiding engineering choices at each stage of program definition, from conceptual to detailed. With this method, the engineering department can control and guide Technical Costs, being the owner of all design choices and can support procurement in the overall effort of economic and commercial cost optimization.