1,721,202 research outputs found
Setup time reduction: SMED-balancing integrated model for manufacturing systems with automated transfer
No full textThe importance of short setup times is increasing in every type of industry. It has been known how to address this problem for about 20 years. The SMED method, originally developed by the Japanese industrial engineer Shigeo Shingo for reducing the time to exchange dies, gives a really straightforward approach to improve existing setups. On the other hand, in the case of complex manufacturing systems the simple application of the SMED methodology is not enough. Manufacturing systems composed of different working machines with automated transfer facilities are a good example. Technological constraints, task precedence constraints, and synchronization between different setup tasks are just some of the influencing factors that make an improved SMED desirable. The present paper, starting from an industrial case, aims to provide a heuristics methodology that integrates the traditional SMED with the workload balancing problem that is typical of assembly systems, in order to address the setup reduction problem in the case of complex manufacturing systems. An industrial case is reported to validate the proposed model and to demonstrate its practical implications
Service spare parts versus production parts: A centralised or decentralised warehouse?
No full textThe management of service spare parts has been a challenging
problem for decades. Considering the case in which components are used for
both production and spare parts, there are two basic strategies in inventory
management: 1) warehouse centralisation, in which production parts and spare
parts are stored together in the same warehouse; 2) warehouse decentralisation,
in which production parts and spare parts are stored in two different
warehouses. Each of these two strategies presents benefits and drawbacks. In
the real industrial environment it is possible to find both these strategies. On the
other hand, the definition of the warehouse centralisation/decentralisation
strategy seems to be related more to following some rules of thumb
than to following a structured decision-making process. The aim of this paper is
first to define a set of influencing factors driving the decision. Secondly,
starting from wide experimental data derived from Italian companies, it
provides a rapid and easy heuristic procedure for practitioners based on a
decision tree approach to the correct definition of the service spare parts
warehouse centralisation/decentralisation strategy
The impact of production mix variations and models varieties on the parts-feeding policy selection in a JIT assembly system
No full textOne of the significant challenges in operating a mix-model assembly system is the feeding of parts to the productive units. In order to avoid production loss, assembly systems require uninterrupted availability of components to feed workstations. On the other hand, the feeding of assembly components has to be performed in a way that minimises the related costs. In the past, the feeding system most widely used was so-called 'line storage' in which the components were stored along the assembly stations in large quantities and were periodically refilled by the central warehouse. Following just-in-time principles, nowadays, assembly system feeding is undertaken by supermarkets, as in decentralised storage areas close to the assembly lines. From such kinds of warehousing, a growing number of manufacturers are adopting two other feeding strategies: the kanban system, which continuously refills the assembly stations through the pull kanban system, or the kitting system, in which kits of components are prepared and delivered following the product through the assembly stations. This paper aims to quantitatively analyse and compare these two recent feeding strategies, considering the production mix variation and the assembled models variety influence. Moreover, kanban-kitting feeding policy and the related optimization issues are considered as hybrid. The findings from an industrial case study and a simulation analysis are also reported. Finally, a decision-making tool that defines a series of 'convenience areas' for the different feeding policies is provide
L'assemblaggio nella moderna produzione industriale
Full text linkThis work deal with the assembly system, focusing on the critical aspects of the modern production, characterized by different models produced, quik responde to the market and flexibility.
The aim is to map and to improve the methods and the models regarding the layout of the assembly system, the task time calculation and its variability in case of multi models productions, the effects of these variations and the ergonomics aspects that influence the balancing problem and the sequencing problem for the modern assembly lin
Energy saving in operations management through variable-speed drive technology: environmental versus economic convenience
No full textCO2 emissions are mainly due to electricity generation. The
percentage of electrical energy used within industry rises up to 70% in
industrialised countries and electrical motors use the greatest part. Due to the
high degree of flexibility required in production systems, the classical on-off
control system causes large energy losses due to mismatches between the
output power of fixed-speed motors and the mechanical power demands of the
electromechanical system. Variable-speed drive (VSD) systems, developed
through the inverter-fed alternating current technology, are identified as the
motor system technology with the most significant energy-saving potential. The
purpose of this paper is to analyse and compare both the economic and the
environmental benefits related to the potential retrofitting of existing
production systems managed using the traditional on-off control according to
different variable typologies: the flexibility requirement variables, the
production system variables and the variables related to the specific country
considered. As a result, the paper identifies the relation between the two
economic and environmental objectives according to the analysed variables.
Two company cases are reported in order to demonstrate both the economic
and the environmental benefits of applying the VSD technology to existing
production systems
Editorial Parts Feeding system for Assembly:macro and micro logistics
No full textAssembly is the last phase in the process of production and involves hundreds and even thousands of different parts. Even the
omission of a single part is enough to make the product defective. Therefore, an inventory is made for each part type. Acquiring,
handling and managing a multitude of inventories is a significant burden with significant cost, both ofwhich are much higher in cases
where multiple productversions are assembled on the same assembly line.
In today's market, the intense competition drives producers to cater to different market segments by offering a larger variety of
products. This growth in product variety is broad, but applies slronglyto the assembled products. Changes in demand, volume and
product mix, as well as the appearance of new product models and components, require a proper, flexible assembly system.
Therefore, successful assembly systems design and management must deliver efficient, flexible systems that can deal with product
variety and changes in product volume and mix. A crucial part of such a system is the part supply and part feeding.
With an increasing productvariely, thousands of different parts need to be delivered just-in-time (JIT) to a multitude of assembly
stations. Some of the issues which have to be addressed are: high number of parts managed, mixed-model production, variety of
Darts' sha~esan d sizes, limited sDace at assemblv stations and mani~ulationo f a wide varietv of ~ a r t t v ~deusri ng the assemblv.
Forming efficient part-supply and'part-feeding mechanisms presents an important challenge kced by today's assembly systems.
These are crucial factors in making an assembly business sustainable and competitive
Absenteeism/Turnover Analysis in Mixed-Model Assembly Lines.
No full textMixed model line produces several product models, and requires from a substitute worker more learning than single-model lines. Assembly lines typically employ hundreds of workers and absenteeism and turnover are encountered daily. Absenteeism and turnover in any station along the line require replacing the absent worker by a new one with a learning curve. The new replacement worker has slower learning process due to the less repetitive work. Still, the learning pattern and effectiveness of the substitute worker depends on the similarity of product models launched. This research analyzes the impact of absenteeism and turnover in assembly lines of mixed model. It shows that model sequencing policy has very significant effect on the line's throughput as it affects bottleneck stations. A small case stud
The Combined Effect of Multiple Models Sequencing and Absenteeism/Turnover on the Throughput of Assembly Lines
No full textThe Assembly lines typically employ dozens and sometime hundreds of workers. So absenteeism and turnover are encountered daily in these lines. This research analyzes the impact of absenteeism and turnover in assembly and production lines of mixed model mass production. It shows that model sequencing policy has very significant effect on the line's throughput. Replacing an experienced absent worker by a new one in a station results in a learning curve of the new worker. The new worker starts slowly and has a good chance of becoming a bottle-neck and dictating the pace for all the line. In that case, the throughput at the end of the line mirrors the new worker learning curve. In mixed model assembly lines the work in some stations varies according to the arriving model. A new replacement worker at such a station has slower learning process due to the less repetitive work. Still, there are typically many work elements that are common to all the models; there may be work elements that are only missing in one model, etc. We show how to compute the station's learning curve in such cases. A small case study shows that sustitute workers generate smaller throughput on mixed model lines than on a single model line
Energy saving in case of intermittent production by retrofitting service plants systems through inverter technology: a feasibility study
Full text linkMany production machines have high energy consumption due to the large number of electrical motors used to rotate equipment, such as tools, fans and pumps. Moreover, in different industrial sectors production is not continuous but intermittent, where working times alternate with idle times. During idle times continuous switch off is not always possible due to technical limitations, and if it is possible, it can cause higher energy consumption due to peak current at the start-up of the electrical motors. The purpose of this paper is to introduce the possibility of managing intermittent production using inverter technology. The inverter provides power control by managing the frequency and voltage of the power supplied to the alternating current motors. The study analyses the potential energy consumption reduction as a function of the production parameters (number of daily stops, average working time, etc.) and develops a feasibility analysis, its related investment cost and its potential energy consumption reduction. As a result, the proposed feasibility study defines the set of production parameters and the types of equipment for which this technology is suitable, bringing rapid investment payback. The proposed feasibility analysis is validated by an industrial case study related to a tannery spray plan
AGVs and AMRs in materials handling: integration challenges in the design of the loading/unloading points
No full textIn modern manufacturing environments, the integration of production and logistics systems is increasingly critical but remains insufficiently explored, particularly at the operational interface where material handling crosses with machine servicing. Existing literature has mostly focussed on Automated Guided Vehicles (AGVs) and Autonomous Mobile Robots (AMRs) from a routing, scheduling, or performance optimisation point of view, without addressing how different levels of automation at the production-machine interface affect overall system cost. This study tries to fill this gap by analyzing the integration challenges, specifically the decision between manual, semi-automated, and fully automated loading and unloading strategies. A novel mathematical cost model is proposed, together with numerical simulations, and validated through a case study in an injection molding company. The model quantifies and compares scenarios in terms of total annual cost per machine, incorporating investment, operational, maintenance, and quality-related costs. Results show that semi-automated solutions combined with AMRs can offer significant cost advantages in medium-productivity settings, while full automation becomes economically viable only at high throughput levels. These insights provide guidelines for industries to customise automation strategies based on operational parameters and open new paths for future research on adaptive, cost-optimised production-logistics integration
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