A methodology for assessing the feasibility of producing components by flow forming

This paper describes a methodology for assessing the applicability of the flow forming process for the manufacture of specific components. The process starts by filtering potential candidates for flow forming from a component collection and then carries out a detailed assessment of quantitative, technological and economic feasibility before determining a viable process plan. The process described uses analytical relationships and criteria drawn from the literature. For example, qualitative feasibility is evaluated using analytical relationships for ultimate strength prediction. Similarly technological validation is done estimating forming process forces and defects rate which are evaluated against threshold values. A process time model is used to develop a hybrid cost model in order to evaluate economic feasibility. Using these calculated values production feasibilities are established by comparison with reported reduction ratios and process parameters. The paper concluded with a brief summary of the results of applying the process to an industrial case study

A methodology for near net shape process feasibility assessment

Manufacturing engineers are frequently asked to select the best process for creating components but often the judgement is qualitative rather than quantitative. This paper presents a methodology (DCFA – Differential Cost and Feasibility Analysis) for assessing the technological and economic feasibility of using Near Net Shape (NNS) processes for the manufacturing of specific components. The methodology examines changes in raw material usage and finish processes (e.g. machining processes) that would result from adaption of a new manufacturing process. To illustrate the method, a case study that assesses the feasibility of using centrifugal casting for the production of valve cages is detailed. The case study concludes that the application of this process to the current manufacturing lines could result in significant cost reductions (particularly in machining time and reduction of scrappage). The feasibility methodology is generic and can potentially be used to investigate the application of a broad range of NNS processes in general manufacturing applications. Further, the developed cost models also allow the economic impact of a new process to be assessed, even at the early stages of product design

Concurrent optimization of process parameters and product design variables for near net shape manufacturing processes

This paper presents a new systematic approach to the optimization of both design and manufacturing variables across a multi-step production process. The approach assumes a generic manufacturing process in which an initial Near Net Shape (NNS) process is followed by a limited number of finishing operations. In this context the optimisation problem becomes a multi-variable problem in which the aim is to optimize by minimizing cost (or time) and improving technological performances (e.g. turning force). To enable such computation a methodology, named Conditional Design Optimization (CoDeO) is proposed which allows the modelling and simultaneous optimization of process parameters and product design (geometric variables), using single or multi-criteria optimization strategies. After investigation of CoDeO’s requirements, evolutionary algorithms, in particular Genetic Algorithms, are identified as the most suitable for overall NNS manufacturing chain optimization The CoDeO methodology is tested using an industrial case study that details a process chain composed of casting and machining processes. For the specific case study presented the optimized process resulted in cost savings of 22% (corresponding to equivalent machining time savings) and a 10% component weight reduction

Process selection methodology for near net shape manufacturing

This paper presents a new selection methodology that for the first time supports the identification of Near Net Shape (NNS) processes. The methodology, known as "Product, Geometry, Manufacturing and Materials Matching" (ProGeMa3), is composed of four steps, which aim to minimize raw material usage and machining by adopting a NNS approach. A key component of the methodology is the Process Selection Matrix (ProSMa) that associates a component’s shape and production volume with its material requirements to reduce the number of candidate NNS processes. A final selection is then made from this shortlist by using fuzzy logic and considering other constraints and functional requirements. The ProGeMa3 selection process is illustrated by its application to an industrial component that resulted in changes to the processes used for its commercial manufacture. The ProGeMa3 and ProSMa presented in this paper aspires to be current and comprehensive for solid metallic components produced by casting, forging and additive technologies. However, ProSMa is also accessible as an open source resource available for other researcher to extend and adapt

A review of flow forming processes and mechanisms

After years of purely academic interest and niche applications, today the flow forming process is increasing demand in aerospace, automotive and defense industries. This review surveys academic paper of last fifty years, in order to evaluate the current state-of-the-art for academic and practitioner. Theoretical and experimental approaches are collected and compared by evaluating their prediction models. As a result, several knowledge gaps are identified, for example stress and strain tensors evolutions are not determined for workpiece, due to high computational cost and uncertainty about the correct finite elements approach to adopt. Similarly although, the final microstructure is often evaluated for specific cases, study of its evolution during plastic deformation has not been reported. Residual stress and final material proprieties, such as corrosion behavior, have been not studied numerically or experimentally. Tool path impact and alternative geometries are not deeply explored. Particular attention is given to process experimental optimization and characterization through Design of Experiment, which is still limited to a few papers and sometimes not well developed. The results of this review will help define a research agenda for future developments

An exact Coulomb cutoff technique for supercell calculations

We present a new reciprocal space analytical method to cutoff the long range interactions in supercell calculations for systems that are infinite and periodic in 1 or 2 dimensions, extending previous works for finite systems. The proposed cutoffs are functions in Fourier space, that are used as a multiplicative factor to screen the bare Coulomb interaction. The functions are analytic everywhere but in a sub-domain of the Fourier space that depends on the periodic dimensionality. We show that the divergences that lead to the non-analytical behaviour can be exactly cancelled when both the ionic and the Hartree potential are properly screened. This technique is exact, fast, and very easy to implement in already existing supercell codes. To illustrate the performance of the new scheme, we apply it to the case of the Coulomb interaction in systems with reduced periodicity (as one-dimensional chains and layers). For those test cases we address the impact of the cutoff in different relevant quantities for ground and excited state properties, namely: the convergence of the ground state properties, the static polarisability of the system, the quasiparticle corrections in the GW scheme and in the binding energy of the excitonic states in the Bethe-Salpeter equation. The results are very promising.Comment: Submitted to Physical Review B on Dec 23rd 200

Systematic process selection for cold forging

This paper presents a hybrid model for determining feasible cold forging methods for individual components that is extendable to other manufacturing areas. An initial screening of candidate processes could potentially be followed by a systematic comparison of their capabilities through fuzzy sets and the product’s functional requirements. A comparative complexity evaluation between the component and a Near Net Shape (NNS) approximation formed product allows evaluation of the further effort necessary to produce the final component. The model supports the possibility of redesign by means of an iterative procedure in order to assess different cold forging processes with different designs. After presentation of the methodology the paper end with a case study application that ranks feasible combinations of process for a given design. This illustrates both the strengths and limitations of the proposed approach