Optimisation of burn-in time considering the hidden loss of quality deviations in the manufacturing process

The burn-in test time is an important parameter of the complex batch processing machine scheduling problem. The omission of the loss of quality deviations in manufacturing generates a non-comprehensive and imperfect result in the optimisation of burn-in time, which hinders the identification of proactive and economical optimisation strategies to prevent infant failure in manufacturing. To solve this problem, this study visualises and quantifies for the first time the hidden loss caused by quality deviations in manufacturing and uses it as a newly added constraint to optimise the burn-in time. Firstly, a quality loss model composed of visible yield loss and warranty costs related to measurable but undetectable reliability vulnerabilities is defined. Secondly, the loss effects of growing defects are measured during the burn-in test, and the optimal burn-in time expressed by the proposed quality loss model is traded off between the additional burn-in cost and the decreased quality loss for an acceptable low infant failure rate. Finally, the effectiveness of the proposed optimisation approach is demonstrated using actual data from a control board with a high infant failure rate. Results show that the proposed method can systematically combine the fundamental loss of quality deviations in the optimisation of burn-in time, which supplements the commonly used optimality criteria, with the upstream loss of quality deviations in the form of manufacturing defects.     

Implications of form postponement to manufacturing: a case study

Postponement is an approach that helps to deliver more responsive supply chains. Form postponement involves the delay of final manufacturing until a customer order is received and is commonly regarded as an approach to mass customization. However, while much is written in the literature about the benefits and strategic impact of form postponement, little is still known about its application. This paper addresses how form postponement was applied in terms of its operational implications within a manufacturing facility through a retrospective study that tracked implementation of form postponement in a manufacturer of specialist high-voltage cabling equipment, called here ‘ElectriCo’. The operational measures for products selected for form postponement were compared with those for products that continued to be made under make-to-order and make-to-stock regimes. Propositions were tested that addressed the operational implications of form postponement within the manufacturing facility, the impact of form postponement on selected performance metrics, and the demand profile for which form postponement was the preferred regime. Multiple data collection methods were used whereby documentary, archival and database evidence were used to measure operational characteristics across a broad front. The findings show that form postponement improved responsiveness but did not necessarily improve delivery reliability. The extent to which the order lead time can be reduced is dependent not only on the responsiveness of the postponed process, but also crucially on the responsiveness of the planning system. It was found that the problem of adapting the manufacturing planning and production scheduling systems at ElectriCo had been underestimated. This and other problems subsequently undermined the form postponement application and led to its eventual abandonment. The authors are undertaking further research of form postponement applications in different production contexts to provide further evidence for its operational implications.     

Parallel machine scheduling with preference of machines

This paper considers a scheduling problem in the manufacturing of anodic electro-etching aluminium foil. To reduce cost and increase efficiency, the manufacturer of aluminium foil usually designs the equipment for electro-etching of aluminium foil into specialised equipment that is dedicated to produce high voltage or medium voltage aluminium foil based on the range the aluminium foil can bear. Nevertheless, high voltage equipment can be used to produce medium voltage aluminium foil with longer processing time, and vice versa. The problem is to schedule jobs on the high and medium voltage equipment, each having several pieces in parallel, with setup times to minimise to the total completion time. In this paper, we propose a three-stage heuristic for this problem and computationally evaluate the performance of the heuristic in comparison to a heuristic for unrelated parallel machines and a branch-and-bound algorithm.     

Freeform fabrication of functional aluminium prototypes using powder metallurgy

Freeform fabrication methods allow the direct formation of parts built layer by layer, under the control of a CAD drawing. Most of these methods form parts in thermoplastic or thermoset polymers, but there would be many applications for freeform fabrication of fully functional metal or ceramic parts. We describe here the freeforming of sinterable aluminium alloys. In addition, the building approach allows different materials to be positioned within a monolithic part for an optimal combination of properties. This is illustrated here with the formation of an aluminium gear with a metal-matrix composite wear surface.     

Measuring long-term performance of a manufacturing firm using the Analytic Network Process (ANP) approach

This paper provides a multicriteria performance measurement model to measure a manufacturing firm's performance in terms of areas of success, which can be defined as critical areas in generating revenues and controlling costs in the operations of a manufacturing firm. In developing the performance measurement model, the Analytic Network Process (ANP) approach is used. The ANP approach, which is the general form of the Analytic Hierarchy Process (AHP) methodology, is recommended when independence among different elements of a system assumption is violated. In a manufacturing system, the system's attributes are interrelated. Furthermore, the relative importance of these attributes with respect to each other and their contribution to the overall performance are affected by the competitive strategies applied by the manufacturing firms. The performance evaluation model developed here incorporates the competitive strategies and interdependence between the system attributes in its hierarchical structure and achieves a more realistic and accurate representation of the firm's long-term performance.     

A Biaxial Fatigue Specimen for Uniaxial Loading

Abstract: The aim of this paper is to present a novel un‐notched fatigue test specimen in which a biaxial stress state is achieved using a uniaxial loading condition. This allows the problem of multi‐axial fatigue to be studied using relatively common one‐axis servo‐hydraulic testing machines. In addition the specimen presented here is very compact and can be made using a small volume of material (100 × 40 × 4.5 mm). For this specimen, the degree of biaxiality, defined by the parameter is equal to approximately 0.45. The specimen geometry was optimised using the Dang Van multi‐axial fatigue criterion. In addition to use as a fatigue specimen, it has been demonstrated that the biaxial specimen presented here is also suitable for biaxial tensile tests, to determine the rupture strength of a material in a biaxial stress state. Two different materials have been investigated: The first was wrought aluminium 2024‐O in the form of 5 mm sheets. The second was a cast aluminium‐silicon alloy AlSi7Cu0.5Mg0.3, commonly used in automotive and aeronautical applications. The fatigue strengths were determined at 2 × 10⁶ cycles and at various R‐ratios using a staircase procedure. For the aluminium 2024, it is shown that the biaxial stress state increases the maximum permissible first principal stress when compared to the uniaxial condition. However, in terms of the cast aluminium alloy, it has been demonstrated that this type of fatigue specimen is not suitable for materials containing casting defects, in particular micro‐shrinkage pores, because the volume of material, in which the stress state is biaxial, is not large enough.     

A review of wire arc additive manufacturing and advances in wire arc additive manufacturing of aluminium

Although wire arc additive manufacturing (WAAM) has proven its capability of fulfilling demands of production of medium-to-large-scale components for automotive and allied sectors made up of aluminium, at present, WAAM cannot be applied as a fully fledged manufacturing process because of practical challenges such as under-matched mechanical properties, the presence of large residual stresses and mandatory post-deposition operation for the formed component. This paper is a review of WAAM technology including a brief of WAAM history, status, advantages and constraints of the WAAM field. A focus is provided including the efforts directed towards the reduction of porosity, tensile properties, microstructural investigations and other valuable advancements in the field of WAAM of aluminium.

This review was submitted as part of the 2018 Materials Literature Review Prize of the Institute of Materials, Minerals and Mining run by the Editorial Board of MST. Sponsorship of the prize by TWI Ltd is gratefully acknowledged.     

A novel engineering method based on the critical plane concept to estimate the lifetime of weldments subjected to variable amplitude multiaxial fatigue loading

This paper summarizes an attempt at proposing a new engineering method suitable for estimating the fatigue lifetime of steel‐ and aluminium‐welded connections subjected to variable amplitude multiaxial fatigue loading. In particular, the proposed approach is based on the use of the so‐called Modified Wöhler Curve Method (MWCM), i.e. a bi‐parametrical critical plane approach, whose accuracy has been checked so far solely in addressing the constant amplitude multiaxial fatigue problem. In order to extend the use of our criterion to variable amplitude situations, the critical plane is suggested here as being determined by taking full advantage of the maximum variance concept, that is, such a plane is assumed to be the one containing the direction along which the variance of the resolved shear stress reaches its maximum value. The main advantage of such a strategy is that the cycle counting can directly be performed by considering the shear stress resolved along the maximum variance direction: by so doing, the problem is greatly simplified, allowing those well‐established cycle counting methods specifically devised to address the uniaxial variable amplitude problem to be extended to those situations involving multiaxial fatigue loading. The validity of the proposed methodology was checked by using two different datasets taken from the literature and generated by testing both steel and aluminium tube‐to‐plate welded connections subjected to in‐phase and 90° out‐of‐phase variable amplitude bending and torsion. This new fatigue life assessment technique was seen to be highly accurate allowing the estimates to fall within the calibration scatter bands not only when the constants in the governing equations were calculated by using the experimental uniaxial and torsional fully reversed fatigue curves, but also when they were determined by using the reference curves supplied, for the investigated geometry, by the available standard codes. These results seem to strongly support the idea that, thanks to its peculiar features, our method can be considered as an effective engineering approach capable of performing multiaxial fatigue assessment under variable amplitude loading which fully complies with the recommendations of the available standard codes.     

A priority scheduling approach for flexible job shops with multiple process plans

This paper considers the job shop scheduling problem with alternative operations and machines, called the flexible job shop scheduling problem. As an extension of previous studies, operation and routing flexibilities are considered at the same time in the form of multiple process plans, i.e. each job can be processed through alternative operations, each of which can be processed on alternative machines. The main decisions are: (a) selecting operation/machine pair; and (b) sequencing the jobs assigned to each machine. Since the problem is highly complicated, we suggest a practical priority scheduling approach in which the two decisions are done at the same time using a combination of operation/machine selection and job sequencing rules. The performance measures used are minimising makespan, total flow time, mean tardiness, the number of tardy jobs, and the maximum tardiness. To compare the performances of various rule combinations, simulation experiments were done on the data for hybrid systems with an advanced reconfigurable manufacturing system and a conventional legacy system, and the results are reported.     

Suppliers’ green performance evaluation using fuzzy extended ELECTRE approach

In the present context of the globalized market, sustainable manufacturing has become a major concern for all organizations. The sustainable manufacturing system includes economic, environmental, and social sustainabilities. Green manufacturing enhances the environmental sustainability but, it also affects the economic and social sustainabilities. The compulsion to follow the environmental rules and regulation in any business activity has increased the awareness for the use of green products, recyclable materials for packaging, reduction of carbon emission, etc. Due to the involvement of extra costs in green manufacturing, some ignorance in the implementation of green practices may be observed. To ensure sustainable systems, selection of suppliers based on green performance measures is very important. This study evaluates the suppliers’ performances based on Green Practices as follows: environmental management and pollution control, cost, quality, and flexibility using the fuzzy-extended Elimination and Choice Expressing Reality approach. This approach helps the managers to incorporate the linguistic decision of the decision makers and convert it into quantitative scale. This method is used to eliminate and outrank the poor performers. As poor performers are outranked, this approach helps to select the most suitable green suppliers as per organization’s requirement.     

Selective laser melting raw material commoditization: impact on comparative competitiveness of additive manufacturing

The paper analyses the impact of cheaper metal powder supplies on the comparative competitiveness of additive manufacturing (AM). By utilising two case studies, we compare the economic impact of an innovative titanium extraction method on Selective Laser Melting (SLM) and conventional methods of machining and casting. A switch-over analysis identifies the production quantities above which conventional manufacturing is more cost competitive than additive manufacturing. This analysis is performed for current raw material as well as cheaper raw material supply. The results illustrate the improved comparative competitiveness of SLM as the titanium supply is commoditised and more readily available in powder form. The responsiveness of the supply chain is improved as the switch-over point between SLM and conventional methods increases. Moreover, as the raw material supply chain for titanium is transformed through the use of this novel extraction method, the manufacturing supply chain is simplified.     

陶瓷废料在建筑材料中的应用进展

随着社会经济及陶瓷行业的迅猛发展,建筑陶瓷废料日益增多,环境污染也日趋严重,因此陶瓷废料的再利用近年来成为人们关注的焦点。利用陶瓷废料生产建筑材料,既能使资源得到有效利用,又可以减少对环境的污染和破坏。综述了陶瓷废料的分类以及在建筑材料中的应用,重点讨论了利用陶瓷抛光废料制备建筑材料的最新制备工艺,最后展望了陶瓷废料的应用前景,并分析了在陶瓷废料的回收利用中亟待解决的问题。     

Concurrent optimal allocation of distributed manufacturing resources using extended Teaching-Learning-Based Optimization

The optimal allocation of distributed manufacturing resources is a challenging task for supply chain deployment in the current competitive and dynamic manufacturing environments, and is characterised by multiple objectives including time, cost, quality and risk that require simultaneous considerations. This paper presents an improved variant of the Teaching-Learning-Based Optimisation (TLBO) algorithm to concurrently evaluate, select and sequence the candidate distributed manufacturing resources allocated to subtasks comprising the supply chain, while dealing with the trade-offs among multiple objectives. Several algorithm-specific improvements are suggested to extend the standard form of TLBO algorithm, which is only well suited for the one-dimensional continuous numerical optimisation problem well, to solve the two-dimensional (i.e. both resource selection and resource sequencing) discrete combinatorial optimisation problem for concurrent allocation of distributed manufacturing resources through a focused trade-off within the constrained set of Pareto optimal solutions. The experimental simulation results showed that the proposed approach can obtain a better manufacturing resource allocation plan than the current standard meta-heuristic algorithms such as Genetic Algorithm, Particle Swarm Optimisation and Harmony Search. Moreover, a near optimal resource allocation plan can be obtained with linear algorithmic complexity as the problem scale increases greatly.     

Recent progress in continuous and semi-continuous processing of solid oral dosage forms: a review

Context: Continuous processing is an innovative production concept well known and successfully used in other industries for many years. The modern pharmaceutical industry is facing the challenge of transition from a traditional manufacturing approach based on batch-wise production to a continuous manufacturing model.

Objective: The aim of this article is to present technological progress in manufacturing based on continuous and semi-continuous processing of the solid oral dosage forms.

Methods: Single unit processes possessing an alternative processing pathway to batch-wise technology or, with some modification, an altered approach that may run continuously, and are thus able to seamlessly switch to continuous manufacturing are briefly presented. Furthermore, the concept of semi-continuous processing is discussed. Subsequently, more sophisticated production systems created by coupling single unit processes and comprising all the steps of production, from powder to final dosage form, were reviewed. Finally, attempts of end-to-end production approach, meaning the linking of continuous synthesis of API from intermediates with the production of final dosage form, are described.

Results: There are a growing number of scientific articles showing an increasing interest in changing the approach to the production of pharmaceuticals in recent years. Numerous scientific publications are a source of information on the progress of knowledge and achievements of continuous processing. These works often deal with issues of how to modify or replace the unit processes in order to enable seamlessly switching them into continuous processing. A growing number of research papers concentrate on integrated continuous manufacturing lines in which the production concept of “from powder to tablet” is realized. Four main domains are under investigation: influence of process parameters on intermediates or final dosage forms properties, implementation of process analytical tools, control-managing system responsible for keeping continuous materials flow through the whole manufacturing process and the development of new computational methods to assess or simulate these new manufacturing techniques. The attempt to connect the primary and secondary production steps proves that development of continuously operating lines is possible.

Conclusion: A mind-set change is needed to be able to face, and fully assess, the advantages and disadvantages of switching from batch to continuous mode production.     

Developing trends in disc bralke technology for rail application

Abstract

Disc brake manufacturing for railway vehicles has become a popular fieldfor assessing the possibilities of MMC application during recent years. The substitution of conventional ferrous materials by light alloys allows for a significant reduction in the rotating masses in a vehicle bogie which leads to a decrease in energy consumption. The use of conventional aluminium casting alloys is not suitable to solve this. Castable MMC materials are a highly promising alternative. Under economic pressure MMC solutions are required to be not only mechanically superior but also cost effective, and due to the low ductility of these particle reinforced materials there is a needfor new concepts. Locally optimised discs consist of a ductile carrier (body) with wear resistant rubbing surfaces. This led to several prototype disc brakes being manufactured by various casting processes. This paper gives an overview of the state of the art and newly developed manufacturing routes and materials, metallic and non-metallic, for rail disc brake applications.     

Economic design of reliable networks

This paper describes a general approach to the optimal design of communications networks when considering both economics and reliability. The approach uses a genetic algorithm to identify the best topology of network arcs to collectively meet cost and network reliability considerations. This approach is distinct because it is highly flexible and can readily solve many versions of the network design problem, including formulations not previously seen in the literature that more closely reflect actual design scenarios. The method is shown to be effective, computationally efficient and flexible on a suite of diverse test problems.     

An Algorithm for the Manufacturing Equipment Selection Problem

This paper provides a unified framework in which product and process demands can be related to manufacturing system requirements. A nonlinear cost minimization model is developed that can be used by facility planners to guide the analyses underlying the equipment selection problem. The approach extends current work by accounting for machine flexibility. The objective is to determine how many of each machine type to purchase, as well as what fraction of the time each piece of equipment will be configured for a particular type of operation.

The resultant problem is solved with a depth-first branch and bound routine that employs a greedy set covering heuristic to find good feasible solutions. This permits early fathoming and greatly contributes to the efficiency of the algorithm. A small example is presented to highlight the computations. This is followed by a discussion of me results for a series of test problems designed to evaluate overall algorithmic performance. We show mat 16 process, 25 machine problems can be readily solved in less than 6 minutes on a microcomputer.     

Dip-coating of aluminium by lead

A study of the problems connected with the coating of aluminium by molten lead has been made. A theoretical approach shows that lead only wets the aluminium surface if the latter is completely free of oxide. Contact of liquid lead with a “clean” aluminium surface may be effected by using an intermediate layer of molten chlorides as a flux and this process has been studied using electrochemical methods. It has been shown that the flux (formed by a eutectic mixture of KCl and ZnCl₂) reacts with the aluminium to form a surface layer of various Al-Zn alloys as shown by electron probe microanalysis. After removal of all traces of chlorides, the resulting surface may be readily wetted by molten lead at the appropriate temperature.     

Divergent production scheduling with multi-process routes and common inventory

This research considers a scheduling problem in a divergent production system (DPS) where a single input item is converted into multiple output items. Therefore, the number of finished products is much larger than the number of input items. This paper addresses two important challenges in a real-life DPS problem faced by an aluminium manufacturing company. One challenge is that one product can be produced following different process routes that may have slightly different capabilities and capacities. The other is that the total inventory capacity is very limited in the company in the sense that a fixed number of inventory spaces are commonly shared by raw materials, WIP (work-in-process) items and finished products. This paper proposes a two-step approach to solving this problem. In the first step, an integer programming (IP) model is developed to plan the type and quantity of operations. In the second step, a particle swarm optimisation (PSO) is proposed to schedule the operations determined in the first step. The computational results based on actual production data have shown that the proposed two-step solution is appropriate and advantageous for the DPS scheduling problem in the company.     

Short-Range Image-Based Method for the Inspection of Strong Scatterers Using Microwaves

In this paper, a new inverse-scattering-based reconstruction method is presented. The aim of the approach is to "invert" wavefleld samples, which are collected by experimental tomographic systems working at radio frequencies and microwaves. Imaging systems operating in this band require the solution of a nonlinear and highly ill-posed inverse problem. The need to regularize the inverse problem is addressed here by considering an efficient inexact Newton method that is able to inspect strong scatterers. In this paper, the mathematical formulation of the approach is detailed and discussed. Moreover, the results of several numerical simulations concerning the reconstructions of dielectric structures in noisy environments and in several applicative scenarios are reported.