Semi-finished Items Research Articles

Sustainable Green Economy for a Supply Chain with Remanufacturing by Both the Supplier and Manufacturer in a Varying Market

Background: In a typical multiechelon supply chain, the supplier makes semifinished items, from which the manufacturer produces finished products to eventually get sold at retailers. However, the majority of existing supply chain models consider the remanufacturing of defective products by solely one organization, despite the fact that both the supplier and manufacturer can produce defective products. This study considers the remanufacturing of defective products with fresh materials and additional expenses by both the supplier and manufacturer. Contrary to well-established articles that hold major partners to be accountable for reducing carbon emissions under a carbon cap-and-trade policy, the proposed model presumes an initial green technological investment by each chain partner. Methods: This study represents a varying market with fuzzy cost components that are then defuzzified with λ-integral method. This study determines the critical values of three discrete and four other continuous decision variables that globally maximize the profitability of the proposed model. Results: Slower production with a longer cycle boosts profitability in a developing market. To increase profit, a case study on the oil and natural gas business suggested to reduce the production of defective items and cutting emission through green investments. Conclusions: Managers can sustainably boost profit via careful production, modern machinery, and slightly longer cycles.

Fresh Light on the Mass Production of Stone Adzes and Chisels in the Southern Bonaigarh, Odisha

Fresh investigation carried out in the southern part of Bonaigarh subdivision of Sundargarh district, Odisha, brought to light some very significant dimensions of lithic celt production sites located in the village Sulabhdih and its surrounding region. Not only valley floors and foothills, but slope and top of hills were also utilized for mass production of semi-finished celts, particularly chisels and adzes. Our study suggests that mass production of these craft specialized semi-finished items were probably intended for not only local use at settlement areas where these were further modified into finished products, but these were presumably transported to different regions of highland Odisha and also beyond through trade and/or exchange network. Although no datable material could be recovered during our limited section scrapping, keeping in view available dates from within Odisha, Jharkhand and Karnataka, these sites are tentatively dated to the beginning of second millennium BCE. The present paper intends to bring out some new aspects of celt production in the southern part of Bonaigarh subdivision, hitherto unknown in Odisha and other parts of the sub-continent.

Optimal order release dates for two-level assembly systems with stochastic lead times at each level

In this paper, we examine an optimisation problem for component replenishment in two-level assembly systems under stochastic lead times. The Assembly-to-Order principle is applied. The demand for a finished product and its planned due date are known. The capacity of the assembly system at each level is considered infinite. At each level, the assembly process starts when all the required components or semi-finished items are available. At the second level, the components are ordered from external suppliers and order release dates are decision variables of the problem. A backlogging cost is incurred if the finished product demand is satisfied after the planned due date. If the finished product, a given component or a semi-finished product is available before the corresponding assembly date, an inventory holding cost is considered. Genetic algorithms (GA) reinforced with different techniques are developed to find order release dates that minimise the total expected cost. A Branch and Bound method is also developed to assess the effectiveness of the hybrid GA. Regardless of the number of components and the variability of the costs related to the finished product, the experimental results indicate that the proposed GA are highly efficient.

Joint effects of variable carbon emission cost and multi-delay-in-payments under single-setup-multiple-delivery policy in a global sustainable supply chain

Abstract In today's global market, supply chain players have to cooperate mutually for extra benefits, long lasting paybacks, and to control carbon emission for a clean environment. This study develops the three-echelon sustainable supply chain model in the context of multi-level trade credit and single-setup-multiple-delivery policy for mutual coordination in financial support and reducing carbon emissions. These joint effects will benefit the firms for interim financing as well as minimize carbon emission for a clean environment. This model quantifies the effects of the environmental regulations and trade credit period under the single-setup-multiple-delivery policy. The supplier produces semi-finished items and transports it to the manufacturer, the manufacturer transform these semi-finished items into final products. These finished products finally transported to multi-retailer. The shipments are permitted to proceed from the particular lot during production instead after completing the entire lot This strategy save the environment by minimizing carbon emission. Additionally, a multi-level trade credit policy is considered in this model for short-term investment. An algebraic approach is used to derive a closed form optimal result for the designed model. This non-derivative method provides the effective solution algorithm. The main contribution of this study is to minimize the sustainable supply chain cost of the system by jointly considering the multi-level delay-in-payment, variable carbon emission cost, and variable transportation cost under the single-setup-multi-delivery policy. The study presents an optimal solution for the individual scenario and also derived a comparison between them with a numerical example. The findings directed that implementation of multi-level trade credit under single setup-multiple-delivery improves the economic and environmental performance of three-echelon supply chain. Sensitivity analysis of the developed study is also illustrated to prove the real practice.

Peculiar Features of Thermal Aging and Degradation of Rapidly Quenched Stainless Steels under High-Temperature Exposures

This article presents the results of comparative studies of mechanical properties and microstructure of nuclear fuel tubes and semifinished stainless steel items fabricated by consolidation of rapidly quenched powders and by conventional technology after high-temperature exposures at 600 and 700°C. Tensile tests of nuclear fuel tube ring specimens of stainless austenitic steel of grade AISI 316 and ferritic–martensitic steel are performed at room temperature. The microstructure and distribution of carbon and boron are analyzed by metallography and autoradiography in nuclear fuel tubes and semifinished items. Rapidly quenched powders of the considered steels are obtained by the plasma rotating electrode process. Positive influence of consolidation of rapidly quenched powders on mechanical properties after high-temperature aging is confirmed. The correlation between homogeneous distribution of carbon and boron and mechanical properties of the considered steel is determined. The effects of thermal aging and degradation of the considered steels are determined at 600°C and 700°C, respectively.

The influence of ruthenium on structure, corrosion and mechanical properties, and fatigue characteristics of titanium α-alloys in corrosive environment

This article discusses test results of corrosion mechanical properties and fatigue properties of deformed semifinished items (forgings and pipes) made of titanium alloys PT-7M and PT-7M with addition of ruthenium. The main mechanical properties of titanium alloys, the structure, and the ruthenium distribution in the structure are determined. Results of static three-point bending tests of specimens with crack are discussed for determination of corrosion mechanical strength and cyclic fatigue strength of forgings and pipes of these alloys in a corrosive medium.

On Reliability of Stainless Maraging Steel

The investigation results on the problem of the reliability of high-strength low-carbon maraging steel products have been generalized. The influence of a method for remelting on the reliability behavior is shown and the ways for the reliability behavior improvement are suggested. The study of the reasons for decreasing KCU during heat treatment shows that in addition to the precipitation of phases causing brittleness at cooling, chromium zones at heating, and formation of chemical and structure inhomogeneity in the two-phase region, the main reason is the remelting method with the parameters which predetermine the variation in grain size in the structure, a small number of interstitial elements (IE), retained austenite in the structure, and lower level of KCU of the steel prepared by VAR both after quenching and after TST. Shows influence of the quenching temperature on the amount of retained austenite and level of impact strength (KCU), of the time of aging on the work of the crack development (KCV) at the temperature of maximal development of brittleness in steel 08Cr15Ni5Cu2Ti and on the position of brittleness transition temperature prepared by ESR and VAR. After cooling down to the liquid nitrogen temperature, the VAR-steel is less liable to brittle fracture after maximal strengthening aging and more reliable after 1.5h-aging (KCV is twice as much as that in ESR-steel despite the low KCU level). The science-based regimes are developed for stamped semi-finished items from steel 08Cr15Ni5Cu2Ti allowing guaranteeing the proper quality and reliability of functioning of the items made from them.

A VSM and VSA methodology for performance assessment of complex product manufacturing processes: an industrial case study

This manuscript describes a Value Stream Mapping (VSM) based generic methodology that enables the visualisation, performance assessment (PA) and waste reduction (WR) in a Complex Products' Manufacturing Process (CPMP). The VSM, along with Kanban, enables modelling and implementing an order-driven or pull manufacturing process (MP) together with just-in-time material (or semi-finished items) arrivals. The methodology also incorporates a number arrays-based approach that enables a comprehensive Value Stream Analysis (VSA) when the value stream map (VS-Map) becomes significantly large and complex. A case study has been performed in collaboration with a saw-blade sharpening machines' manufacturing firm to illustrate the use of the suggested VSM-based generic methodology and number arrays in VSA for PA of CPMPs. The calculated lead-time of the case study complex product (CP) is almost 323 days. All cycle times are smaller than takt time (TT) (i.e. 600 min).

A VSM and VSA methodology for performance assessment of complex product manufacturing processes: an industrial case study

This manuscript describes a Value Stream Mapping (VSM) based generic methodology that enables the visualisation, performance assessment (PA) and waste reduction (WR) in a Complex Products' Manufacturing Process (CPMP). The VSM, along with Kanban, enables modelling and implementing an order-driven or pull manufacturing process (MP) together with just-in-time material (or semi-finished items) arrivals. The methodology also incorporates a number arrays-based approach that enables a comprehensive Value Stream Analysis (VSA) when the value stream map (VS-Map) becomes significantly large and complex. A case study has been performed in collaboration with a saw-blade sharpening machines' manufacturing firm to illustrate the use of the suggested VSM-based generic methodology and number arrays in VSA for PA of CPMPs. The calculated lead-time of the case study complex product (CP) is almost 323 days. All cycle times are smaller than takt time (TT) (i.e. 600 min).

Middle Palaeolithic technical behaviour: Material import-export and Levallois production at the SU 13 of Oscurusciuto rock shelter, Southern Italy

The Oscurusciuto rock shelter, located in southern Italy (Puglia), has yielded a long Middle Palaeolithic stratigraphy rich in lithic assemblages, fireplaces and faunal remains, attesting Neanderthal occupation during the MIS 3. This paper is focused on the stratigraphic unit 13, consisting of a sandy compact deposit mixed with pyroclastic sediment above a thick level of tephra-US 14, identified as Mt. Epomeo green tuff (dated Ar/Ar ~ 55 ka).Level 13 represents the first stable human occupation after the deposition of tephra. Our goal was to examine the lithic assemblage of this stratigraphic unit by means of an interdisciplinary approach (technology, RMU, refitting program) in order to identify the economic behaviour and technical strategies of Neanderthals occupying the stratigraphic unit 13 of Oscurusciuto.The technical strategies applied indicate fragmentation of the reduction processes, as well as probable events of importation and exportation of objects. The lithic material were introduced at different stages of manufacturing. Pieces were introduced in the form of rough objects (pebbles), as well as semi-finished items, and as finished tools. This fragmentation of the chaîne opératoire also demonstrate the palimpsest nature of the level which is made up of different events happening one after another.The main concept of debitage was Levallois, generally realized on local jasper and siliceous limestone pebbles or cortical flakes. Jasper and siliceous limestone flakes, backed flakes and convergent flakes were the technological objectives of the debitage. A marginal volumetric debitage aimed at producing bladelets was also attested.

Development of alternative technology of dual forming of profiled workpiece obtained by buckling

A possibility of application of longitudinal bending (buckling) as an economical way of profiling workpieces, ensuring replacement of pinching impressions and edgers was shown for manufacturing of eye-bolt forgings. For realization of this method of impression-free profiling of blanks, a process of twin forging of eye-bolt forgings was designed as well as the arrangement of the forging facilities. The peculiarity of this process is that the cut-off blank is upset, it loses its stability and thus obtained profiled semi-finished product is turned over on its side and eventually it is put inside the impression for simultaneous forging of two forgings from one blank. It was found that profiled semi-finished items acquired the desired shape at the degree of blank’s upsetting equal to 39 %, the central angle between the twin eye-bolts forgings being 54° and it had been taken into account for the dies’ design. Experimental forming of eye-bolts forgings according to the proposed and conventional processes on physical lead models of blanks, which helped to find out that the proposed technical solution, can ensure metal saving at 21.7 % level. Comparison of these two methods revealed improved technical and economic indices of the new process; particularly the coefficient of metal consumption at cutting was raised by 1.4 %, the quotient of output of quality forgings by 21.1 % and coefficient of application of forgings metal along the consumption rate by 27.9 %.

Multi-stage multi-objective production planning using linguistic and numeric data-a fuzzy integer programming model

This paper introduces a methodology to solve a multi-stage production planning problem having multiple objectives, which are conflicting, non-commensurable and fuzzy in nature. The production process consists of multiple stages having one or more machines in each stage. Every processing stage produces work-in-process, semi-finished items as an output, which becomes an input to the subsequent stage either fully or partially depending on the cycle times of the machines. Events of machine breakdowns and imbalances in input–output relations in one or more stages may affect both work-in-process (WIP) and final production targets. Our paper provides a methodology based on fuzzy logic to maintain the desired balanced input–output relation at each stage and the targeted production output at the final stage. This is done by procurement of work-in-process inventory (WIP) and installation of new machines at appropriate stages. The objectives or goals expressed in linguistic terms are represented as fuzzy sets. The Induced Ordered Weighted Averaging (IOWA) operator is used to aggregate the objectives as per their priorities and finally to formulate the production process as a Mixed Integer Programming (MIP) problem. The solution to MIP shows the degrees of achievements of the production process objectives. The methodology is illustrated with a real life application of crankshaft productions in an automobile industry.

Recrystallization behavior of boron-modified commercial-purity titanium during hot deformation

A comparative investigation of the recrystallization behavior of as-cast commercial-purity (CP) titanium VT1-0 with addition of 0.2 wt % boron and of unalloyed CP titanium in the hot-rolled and as-cast states has been performed. The introduction of boron leads to the formation of uniformly distributed short filaments and particles of titanium monoboride (TiB), which stimulates a substantial refinement of the cast structure. The recrystallization behavior of the alloys was studied after deformation by compression at T = 900-600°C using the EBSD analysis. It has been established that the kinetics of the recrystallization of the as-cast VT1-0-0.2B alloy is substantially accelerated compared with that of the unalloyed VT1-0 alloy due to the presence of borides. The recrystallization behavior of the VT1-0 alloy with the initial hot-rolled structure and of the VT1-0-0.2B alloy with the as-cast structure proved to be approximately similar. Based on the investigations performed, recommendations have been made that should facilitate (and reduce the cost of) the production of fine-grained and ultrafine-grained semi-finished items of CP titanium.

Effect of radial-shear rolling on structure of aluminum alloy D16 (Al-4.4Cu-1.6Mg)

The modes of radial-shear rolling (RSR) of hot-pressed rods of aluminum alloy D16 providing for production of high-quality long-length semifinished items are experimentally studied. Investigations of the microstructure of alloy D16 reveal that the rolling modes provide its homogeneous refinement. The average distance between high-angle grain boundaries in longitudinal cross section decreases from 10 to 6.5 μm, whereas the average size of subgrains in the surface layer and central part amounts to 0.9 μm.

A Queueing-Game Model for Making Decisions About Order Penetration Point in Supply Chain in Competitive Environment

This study is dedicated to Order Penetration Point (OPP) strategic decision making which is the boundary between Make-To-Order (MTO) and Make-To-Stock (MTS) policies. This paper considers two competing supply chains in which a manufacturer produces semi-finished items on a MTS basis for a retailer that will customize the items on a MTO basis. The two-echelon supply chain offers multi-product to a market comprised of homogenous customers who have different preferences and willingness to pay. The retailer wishes to determine the optimal OPP, the optimal semi-finished goods buffer size, and the price of the products. Moreover, the authors consider both integrated scenario (shared capacity model) and competition scenario (Stackelberg queueing-game model) in this paper. A matrix geometric method is utilized to evaluate various performance measures for this system and then, optimal solutions are obtained by enumeration techniques. The suggested queueing approach is based on a new perspective between the operation and marketing functions which captures the interactions between several factors including inventory level, price, OPP, and delivery lead time. Finally, parameter sensitivity analyses are carried out and the effect of demand on the profit function, the effect of prices ratio on completion rates ratio and buffer sizes ratio and the variations of profit function for different prices, completion percents, and buffer sizes are examined in both scenarios.

An integrated operations-marketing perspective for making decisions about order penetration point in multi-product supply chain: a queuing approach

This study is dedicated to strategic decision-making regarding order penetration point (OPP), which is the boundary between make-to-order (MTO) and make-to-stock (MTS) policies. This paper considers a supply chain in which a manufacturer produces semi-finished items on an MTS basis for a retailer that will customise the items based on MTO policy. This two-echelon supply chain offers different products to a market comprised of homogenous customers who have different preferences and willingness to pay. The retailer wishes to determine the optimal OPP, the optimal semi-finished goods buffer size, and the price of the products with assumption of price sensitive demand function. Moreover, we consider both shared and unshared capacity models in this paper. A matrix geometric method is utilised to evaluate various performance measures for this system, and then, optimal solutions are obtained by enumeration techniques. The suggested queuing approach is based on a new perspective between the operations and marketing functions which captures the interactions between several factors including inventory level, product pricing, OPP, and delivery lead time. Finally, parameter sensitivity analyses are carried out and the effect of demand on the profit function, the effect of prices ratio on completion rates ratio and buffer sizes ratio and the variations of profit function for different prices, completion percents, and buffer sizes are examined.

Learning effects and the phenomenon of moving bottlenecks in a two-stage production system

This paper studies the effects of learning and forgetting on a two-stage production system and the position of a potential bottleneck in the system. We start with developing a model for a two-stage serial production system where semi-finished items are fed by the first stage to the second stage, which, in turn, processes the items to their final state. The finished items are transferred either to a subsequent stage or to customers. The paper assumes that both stages of the production system considered are subject to learning and forgetting effects. Learning quickens the production rate as more experience is gained (i.e., when the number of repetitions increases), while forgetting has the opposite effect when production is intermittent (i.e., experience is lost over production breaks). The paper studies how different values of the learning and forgetting parameters influence the ratio of the production rates of both stages and the flow of material in the system. The results of the paper indicate that learning may cause a bottleneck to shift its position in a production system. This happens when an initially slower stage overtakes a previously faster stage over time due to a higher learning rate. The paper thus contributes to the literature on moving bottlenecks and provides practitioners with a model that helps predicting where bottlenecks may arise in the production system, and which enables the system to flexibly react to moving bottlenecks.

Make-to-stock policies for a multistage serial system under a make-to-order production environment

Production control policies for a make-to-order manufacturing system composed of several stages under uncertain demand are considered. Conducting order-specific operations at each stage can produce a variety of final products from the same raw material. The production quantity per period at a stage depends on the workload. To shorten lead times, it is permitted to start production at upstream stages without confirmed orders, hold semi-finished items within the system as make-to-stock, and then match orders to these items under the constraints of specifications and quantities. Eight make-to-stock policies are prepared by combining buffer selection rules, matching acceptance rules, and make-to-stock replenishment rules. Their performance is evaluated via computer simulation. In the case of relatively limited capacity, aggressively matching orders to make-to-stock items are preferable in terms of the average lateness of orders and the average inventory level of the make-to-stock items. A policy that loads carefully to avoid undesirable processing delay by calculating the workload and considers the planned order quantities explicitly obtain better results under increased production capacity.

Property variations in large AlSi7 alloy foam ingots

The actual foam density affects its mechanical energy absorption capabilities. Making structural elements starting from the cutting of semi-finished items may produce uneven results due to the lack of homogeneity in the foam. The subject of this work is the study of AlSi7 metallic foams, the focus being on the evaluation of the effective density distribution throughout large ingots. This is the first step required to establish a correlation between manufacturing process parameters and mechanical properties. The results highlighted that the void density increases from the centre toward the ingot outer wall and that specimens coming from different regions of the ingot have a very different mechanical behaviour. This is probably due to the difficulty in controlling temperature gradients and cooling rates throughout big mould cavities during the production process.

A queueing model of delayed product differentiation

We consider a production system in which a supplier produces semi-finished items on a make-to-stock basis for a manufacturer that will customize the items on a make-to-order basis. The proportion of total processing time undertaken by the supplier determines how suitable the semi-finished items will be to meet customer demand. The manufacturer wishes to determine the optimal point of differentiation (the proportion of processing completed by the supplier) and its optimal semi-finished goods buffer size. We use matrix geometric methods to evaluate various performance measures for this system, and then, with enumeration techniques, obtain optimal solutions. We find that delayed product differentiation is attractive when the manufacturer can balance the costs of customer order fulfillment delay with the costs associated with unsuitable items.