Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture

A Product-Service System (PSS) is an integrated combination of products and services. This Western concept embraces a service-led competitive strategy, environmental sustainability, and the basis to differentiate from competitors who simply offer lower priced products. This paper aims to report the state-of-the-art of PSS research by presenting a clinical review of literature currently available on this topic. The literature is classified and the major outcomes of each study are addressed and analysed. On this basis, this paper defines the PSS concept, reports on its origin and features, gives examples of applications along with potential benefits and barriers to adoption, summarizes available tools and methodologies, and identifies future research challenges.

Optimizing the energy efficiency of processes has become a priority in the manufacturing sector; driven by soaring energy costs and the environmental impact caused by high energy consumption levels. The energy consumed by a machine tool performing a turning process consists of not only the energy required by the tool tip for material removal but also the energy used for auxiliary functions. Traditionally, the energy required for the cutting process is estimated based on cutting force prediction equations. However, this estimation is limited to the energy consumption of the tool tip. Thus, the aim of this paper is to develop a reliable method to predict the total energy consumption of a selected machine tool performing a turning operation. In order to compare the energy consumption under different cutting conditions, the specific energy consumption is defined as a functional unit: the energy consumed to remove 1 cm³ of material. An empirical model is obtained based on power measurements under various cutting conditions, and it is able to provide a reliable prediction of energy consumption for given process parameters. Additional investigations are conducted in order to understand and explain each coefficient in the energy consumption model.

Various kinds of layer manufacturing process are available, such as stereo lithography (SL), fused deposition modelling (FDM), Poly-jet, selective laser sintering (SLS), three-dimensional printing (3DP), laminated object manufacturing (LOM), etc. The object of the current study is the quantifications and comparisons of the processes' characteristics using representative apparatus and various materials. Through the tests, mechanical properties, such as tensile and compressive strengths, hardness, impact strength, and heat resistance, and surface roughness, geometric and dimensional accuracy, manufacturing speed, and material costs were compared for each process and machine. It was verified that the SL process is advantageous in hardness, accuracy, and surface roughness and the Poly-jet process in tensile strength at room temperature. The SLS process was advantageous in compressive strength and manufacturing speed, the 3DP process in speed and material costs, and the LOM process in heat resistance. The FDM and LOM processes were superior in impact strength in the scanning direction, but the change of building direction significantly reduced the tensile and impact strengths.

This study presents a thorough literature review on the powder-bed laser additive manufacturing processes such as selective laser melting of Inconel 718 parts. This article first introduces the general aspects of powder-bed laser additive manufacturing and then discusses the unique characteristics and advantages of selective laser melting. The bulk of this study includes extensive discussions of microstructures and mechanical properties, together with the application ranges of Inconel 718 parts fabricated by selective laser melting.

Understanding and estimating the energy consumed by machining are essential tasks as the energy consumption during machining is responsible for a substantial part of the environmental burden in manufacturing industry. Facing the problem, the present paper aims to analyse the correlation between numerical control (NC) codes and energy-consuming components of machine tools, and to propose a practical method for estimating the energy consumption of NC machining. Each energy-consuming component is respectively estimated by considering its power characteristics and the parameters extracted from the NC codes, and then the procedure estimating energy consumption is developed by accounting for the total energy consumption of the components via the NC program. The developed method is verified by comparing the estimated energy consumption with the actual measurement results of machining two test workpieces on two different machine tools, an NC milling machine and an NC lathe, and is also applied to evaluate the energy consumption of two different NC programs on the NC milling machine. The results obtained show that the method is efficient and practical, and can help process planning designers make robust decisions in choosing an effective energy-efficient NC program.

Among the various forms of material damage, delamination due to drilling is one of the major concerns in machining a composite laminate. The thrust force has been cited as the primary cause of the delamination. The analysis for multidirectional composite laminates is based on linear elastic fracture mechanics (LEFM), classical bending plate theory and the mechanics of composites. This paper presents a general closed-form mechanical model for predicting the critical thrust force at which delamination is initiated at different ply locations. Good correlation is observed between the model and the experimental results.

A method is described for calculating the chip flow direction in terms of the tool cutting edge geometry and the cutting conditions, namely feed and depth of cut. By defining an equivalent cutting edge based on the chip flow direction it is then shown how cutting forces can be predicted given the work material's flow stress and thermal properties. A comparison between experimental results obtained from bar turning tests and predicted values for a wide range of tool geometries and cutting conditions shows good agreement.

Micro-electrodischarge machining (EDM) can produce microhole and other complex three-dimensional features on a wide range of conductive engineering materials such as titanium super alloy, inconel, etc. The micromachining of titanium super alloy (Ti—6Al—4V) is in very high demand because of its various applications in aerospace, automotive, biomedical, and electronics industries, owing to its good strength-to-weight ratio and excellent corrosion-resistant properties. The present research study deals with the response surface methodology (RSM) and artificial neural network (ANN) with back-propagation-algorithm-based mathematical modelling. Furthermore, optimization of the machining characteristics of micro-EDM during the microhole machining operation on Ti—6Al—4V has been carried out. The matrix experiments have been designed based on rotatable central composite design. Peak-current (Ip), pulse-on time (Ton), and dielectric flushing pressure have been considered as process parameters during the microhole machining operation and these parameters were utilized for developing the ANN predicting model. The performance measures for optimization were material removal rate (MRR), tool wear rate (TWR), and overcut (OC). The ANN model was developed using a back-propagation neural network algorithm, which was trained with response values obtained from the experimental results. The Levenberg—Marquardt training algorithm has been used for a multilayer feed-forward network. The developed model was validated using data obtained by conducting a set of test experiments. The optimal combination of process parametric settings obtained are pulse-on-time of 14.2093 μs, peak current of 0.8363 A, and flushing pressure of 0.10 kg/cm² for achieving the desired MRR, TWR, and OC. The output of RSM optimal data was validated through experimentation and the ANN predicted model. A close agreement was observed among the actual experimental, RSM, and ANN predictive results.

Porous metals, typically produced through powder metallurgy, represent a class of relatively new materials with wide industrial applications, lately extending into the microscale domain. Although produced in near-net shapes, most components fabricated from these materials still require some form of secondary machining. Despite the progress made in the field, relatively little is known either on the inherent cutting mechanism or on the behaviour of these materials under micromachining conditions. The present study reviews the main cutting theories proposed in macroscale machining, along with one of the primary parameters used to describe its machinability performances, namely cutting forces. Then, the feasibility of macroscale concepts is discussed in the context of micromachining technology that is characterized by comparable tool and pore sizes. The microslot cutting experiment performed in a porous titanium sample outlined the relative interplay between the magnitude of the cutting force and porosity of the material. Based on this, it was concluded that the impact of structural porosity on cutting forces experienced during micromachining is significant and therefore further in-depth investigations will be required.

It is well recognized that the cutter run-out appearing in the milling process will cause an uneven redistribution of the instantaneous uncut chip thickness through the cutter flutes and thereby will generate an irregular distribution of the cutting forces in different tooth periods. This work aims to develop a new approach able to identify the cutter radial run-out and cutting-force coefficients in the flat end milling. It is shown that the total cutting forces can be considered as the sum of a nominal component that is independent of the run-out plus a perturbation component induced by the run-out. Mathematical formulations of both components are developed, accounting for the cutting geometry and the radial run-out parameters. Firstly, to calibrate the cutting-force coefficients, a generic procedure is proposed using the instantaneous value of the nominal component instead of the average value. Secondly, considering the fact that the perturbation component of the cutting force depends non-linearly upon the run-out parameters, the identification of run-out parameters is carried out by solving the linearized equation. In the identification procedure, some key techniques such as the calculation of the immersion boundary at any cutting instant and the reasonable selection of the depth of cut are discussed in detail. Finally, based on simulation and experimental results, the validity of the identification approach is demonstrated.