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POLCA is an important card-based control system for low volume, high variety production contexts. A job can only be produced at an upstream station if it has acquired a POLCA card that has returned from its downstream station. A common assumption in the POLCA literature is that cards are allocated to jobs as soon as they return to the upstream station. This dissects the queue in front of a station into jobs that have a card (and can be produced) and those that do not have a card (and cannot be produced). This artificially and prematurely constrains the dispatching decision, i.e. the decision concerning which job to produce next at a station. In response, this paper proposes integrating the card-allocation and dispatching decisions such that the allocation of POLCA cards to jobs is postponed until the dispatching decision is made. Simulation results demonstrate that this integrated approach does not improve performance under simple ERD dispatching, as is commonly applied in the POLCA literature. But when a more powerful rule is applied, percentage tardy and mean tardiness performance improve by more than 75% and 50%, respectively, for an integrated decision. Most importantly, results suggest that in production environments like the one considered in this study, the integrated approach dispenses with the use of POLCA altogether if a suitable priority rule is used.

In this study, we consider a real-life Line Balancing Problem (LBP) at a metalworking company. Based on the concerns of the company’s managers, the number of workstations is considered as the main performance criteria for line balancing, while line efficiency and smoothness are considered as the second and the third performance criteria. Two alternative line configurations, i.e., the straight line and the U-shaped line, are considered in the study as a company request. The Grouping Evolution Strategy (GES) algorithm, as one of the novel and powerful method in the literature, is used at a first step, assuming deterministic task times. At a second step, discrete event simulation is used to analyse the impact of stochastic’ times on the dynamic behaviour of the two line configurations in terms of throughput time and throughput rate. Results of this study are expected to contribute to both research and practice in the context of line balancing.

Material Flow Control (MFC) mechanisms control the movement of jobs through a set of stationery capacity resources on the shop floor. Although the objective of MFC is item-centric, i.e. to control the flow of individual jobs, most existing MFC mechanisms are resource-centric, i.e. focus on managing the capacity resources. While this was justified by technical constraints on real-time information feedback, advances in technology allow for new designs. In particular, smart products are cognizant of their local context and can communicate with one another through the Internet of Things, thereby enabling self-organized control of individual jobs. Despite this potential most application of smart products and the Internet of Things, including multi-agent systems for scheduling and holonic control, continue to focus on hierarchical, centralized data and control structures. In response, this study develops a simple item-centric MFC mechanism and uses simulation to proof the feasibility of self-organized control.

The market globalization and worldwide competition has raised the level of demand in the industrial sector. Due to this aggressive competitiveness, some management strategies and tools needed to start to be applied in the industry. For example, maintenance has become increasingly important in the production planning and strategy of some companies. This work focuses on the implementation of a strategic maintenance plan, applied in an industrial context, namely in a company of Clutches and Hydraulic Controls. The Total Productive Maintenance (TPM) methodology application was worked on and implemented at two sections, CNC Lathes and CNC Machining Centers, to focus on eliminating losses due to inefficiencies. In this way, the main problems detected in relation to the cells were eliminated. New autonomous maintenance procedures (AM) and preventive maintenance plans with well-defined schedule were also developed. The results obtained were very positive: there was a decrease of 23% in breakdowns in CNC lathes sector and 38% in CNC machining centers sector. In global terms, there was an increase in the availability of the machines and the Overall Equipment Effectiveness (OEE) of approximately 5%. The implementation procedure and the compromise adopted by the whole company staff and management was the secret to success.

Material flow control mechanisms determine: (i) whether an order should be released onto the shop floor; and (ii) whether a station should be authorized to produce. Well‐known approaches include Kanban, Drum‐Buffer‐Rope (DBR), Constant Work‐in‐Process (ConWIP), Paired‐cell Overlapping Loops of Cards with Authorization (POLCA), Workload Control (WLC), and Control of Balance by Card Based Navigation (COBACABANA). The literature typically treats these approaches as competing, meaning studies argue for the superiority of one over another. However, a closer look reveals that existing mechanisms either focus on order release (ConWIP, DBR, WLC, and COBACABANA) or on production authorization (Kanban and POLCA). This study therefore calls for a paradigm shift and argues that the different mechanisms may play complementary rather than competing roles. Using simulation, we assess the performance of COBACABANA and POLCA in a high‐variety make‐to‐order shop, a type of shop arguably in most need of material flow control given the importance of throughput times and delivery time adherence. Results demonstrate that COBACABANA outperforms POLCA, but the simultaneous adoption of both control mechanisms outperforms the use of either one in isolation. More specifically, adding POLCA production authorization to COBACABANA order release enables the superfluous direct load to be further reduced, resulting in shop floor throughput time reductions of between 15% and 26% while further reducing the percentage tardy and mean tardiness by up to 14%. Compared to no material flow control, the new combined mechanism realizes a reduction of almost 50% in the percentage tardy and more than 30% in mean tardiness.

Maintenance has assumed an increasing importance in the reorganization of the industrial sector. However, there are several companies where a maintenance strategic plan needs to be implemented. This work was developed in an industrial context, in a company of Clutches and Hydraulic Controls. The focus was the implementation of a strategic plan for maintenance. The methodology chosen was Total Productive Maintenance (TPM) and the cells chosen for implementation were CNC Lathes and CNC Machining Centers. The TPM uses some maintenance activities, whose come from preventive maintenance (PM), and focuses on eliminating efficiency losses. The main problems of the cell equipment were analyzed and eliminated. Through the analysis of maintenance manuals and internal know-how, autonomous maintenance (AM) procedures and preventive maintenance plans have been created to be executed following a given timeframe. At the end of the study, the results were clearly positive due to the corrective and preventive maintenance. There was a decrease in breakdowns due to failure by 23% for CNC lathes and by 38% for CNC machining centers, which resulted in an evident increase in machine availability and OEE (Overall Equipment Effectiveness) improved by 5%.

This project was carried out at a company in the electric mobility sector, which manufactures chargers for electric vehicles, specifically in the wiring section. The main objective of the developed work was to improve the production processes in order to enhance responsiveness to the growing demand. After analyzing the processes in the section, the objectives were outlined to enable the improvement of some practices in the production department, such as the ones related to the organization of the raw material supermarket, as well as the calculation of the wiring consumption by chargers, and the implementation of a production control system. After the improvement actions were implemented, it was possible to observe a 14,9% reduction in the changeover process of the cable cutting process; weekly wiring consumptions were estimated, and procedures were defined to generate orders of raw material and supply to the workstation, which led to the elimination of stock shortages. In addition, worker autonomy increased and production downtime was reduced.

The management of end-of-life vehicles (ELVs) is a key element for global sustainability. In this context, vehicles dismantling companies need to improve their production processes in order to achieve not only cost-effective, but also sustainable systems. Major challenges for these companies result from the enormous variety of components to be disassembled and stored, and from uncertainty at the ELVs’ supply and at the components demand. In this paper, a study for the improvement of the processes associated with the locating and identification of stored components in the warehouse of a Portuguese ELVs dismantling company was developed, observing the company’s current processes and the potential opportunities for improvement. From here, propositions were made to update the warehouse management system (WMS), warehouse layout, components location/ identification and its codification. This study is potentially useful for the case-study company as well as other businesses from the same sector.

This paper presents an intelligent system capable of dispensing pills after the programming of the daily doses by the user. This system has been studied and designed for elderly people and their caregiver. In order to add value to the product, the equipment has an improved recharge system and user interface. Thus, it uses trays, and each one of them takes a different type of medication, taking advantage of an easy-to-use touch screen for the programming of the doses, a buzzer for sound signaling and employing a weight sensor to detect the presence of the collection cup. Alongside that, the equipment has a communication system to warn the caregiver if the patient hasn’t taken their pills, if it is necessary to reload the trays or even if the patient forgot to put back the cup.

Manual operations in manufacturing companies are still a common practice. This often results in high costs, high cycle times and therefore in lower productivity, particularly for companies operating in western countries. This is why many manufacturing companies relocated their production facilities in low age countries. This study was developed at a leading Portuguese material construction manufacturing company. The objective was to improve the packaging and labeling processes, that were identified as main bottlenecks in the factory. Lean was used to streamline these processes before being automated. This allowed for annual savings of 12432 €, with human operators being reallocated to other departments where they are more useful. Furthermore, cycle times were reduced by 42,9%, non-value-added activities were minimized, and operations with potentially high ergonomic risks were eliminated. In addition, a reduction of 84,3% in lithographed packaging was achieved, with a cost reduction of around 36 000 €/year, which is expected to continue in the forthcoming years.

Manufacturing companies need to be effective in meeting customers’ delivery requirements. Due to customers’ expectations of shrinking delivery times, manufacturing lead times need to be short. This can be achieved through efficient Production Activity Control (PAC) methods. Currently PAC methods rely mostly on centralized decision-making and, seeming not to be adequate to deal with the increasing complexity and dynamics of manufacturing. Autonomous Production Control (APC) methods are a promising alternative to current methods, due to their rapid and flexible reaction to disturbances of the production systems’ operation. APC methods transfer the power of decision-making from a central unit to distributed logistic objects, such as machines, jobs and material handling devices. In this study, three APC methods, namely Pheromones (PHE), QLE (Queue Length Estimator) and a refined version of QLE (RQLE), are compared and analysed via simulation. The study was accomplished for two shop configurations, namely a flexible flow shop and a general flexible flow shop. Simulation results show a superior performance of RQLE in both configurations. Results also show that a new dispatching rule here proposed, the SPT-RTT rule, performs better than others with which it was compared. The study may have important implications for industrial practice and future research in PAC., This work has been supported by FCT – Fundação para a Ciência e Tecnologia within the R&D Units Project Scope: UIDB/00319/2020.INCT-EN - Instituto Nacional de Ciência e Tecnologia para Excitotoxicidade e Neuroproteção(UIDB/00319/2020)

The simplicity of Constant Work-In-Process (ConWIP) makes it one of the most widely adopted card-based production control solutions. Its simplicity, however, also limits the opportunities that are available to improve the concept. There are arguably only two major search directions: (i) to alter the meaning of cards away from controlling jobs; and (ii) to adopt alternative, more sophisticated backlog sequencing rules. In this study, we outline a simple, practical load-based ConWIP system that changes the meaning of cards. Rather than controlling the number of jobs, cards are associated with a certain amount of workload. Simulation results demonstrate the positive performance impact of limiting the total shop load. The Workload Control literature advocates the use of a corrected load measure as it better represents the direct load queuing at a station; but this worsens performance when compared to a shop load measure in the context of ConWIP.

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POLCA (Paired-cell Overlapping Loops of Cards with Authorization) is a production control system specifically designed for low-volume, high-mix and custom-engineered products. It is a visual control system that manages the flow of jobs though the shop floor by making use of overlapping loops of cards between pairs of successive manufacturing cells. These overlapping loops of cards realize a decentralized decision-making structure for job release. This means that jobs do not await release in a centralized pre-shop pool. Rather jobs are immediately forwarded to a gateway manufacturing cells at their shop arrival, where they wait in release lists for available POLCA cards. However, the Workload Control literature has shown that using a centralized pre-shop pool provides important benefits. Therefore, this paper investigates the impact of centralized job release on POLCA performance. Using simulation, we demonstrate that centralized job release outperforms decentralised release if the right card acquisition rule for job release is used. This has important implications for both research and practice calling for more research on POLCA systems.

Production environments are becoming more complex and dynamics. This is influenced by external factors related with products' characteristics and costumers' requirements and internal factors related with processing times variability, machine failures, setup times, between others. To face this increasing complexity and dynamics, it is crucial to have effective production control methods, considering Interoperability Enablers for Cyber-Physical Systems. However, production control methods most in used today, are focused on centralised decision-making and planning, and considered inadequate to deal with the increasing dynamics of these systems. Autonomous Production Control (APC) may be an adequate alternative to face this complexity, allowing flexible and rapid reaction to possible disturbances that may occur in the production system. However, as APC is the relatively new concept, there are no existing surveys. Therefore, we review and discuss the literature on APC methods to bring more attention to this promising topic of research, highlighting future research directions., This work was supported by the Fundação para a Ciência e a Tecnologia [UID/CEC/00319/2019].

Lot splitting is an important approach for shops that compete on short delivery times. Similarly, such shops can benefit from load-limiting order release mechanisms that balance workloads and regulate throughput times. Yet few studies have examined the combined effect of lot splitting and load-limiting order release. We use simulation to assess the combined effect of lot splitting and P aired-cell O verlapping L oops of C ards with A uthorization (POLCA), an important load-limiting order release mechanism in the context of time-based competition. The experimental design includes different lot sizes, lot transfer policies, and POLCA quanta, i.e. the limit on the size of jobs represented by a single POLCA card. Lot splitting improves performance if lots can proceed independently as this ensures the quick replenishment of queues at downstream stations. However, we find that enforcing the synchronization of all lots that make up a job at every routing step leads to a deterioration in performance. This extends previous research, which appears to have overemphasized the positive effects of lot splitting. Meanwhile, although POLCA cards were originally used to represent lots, we demonstrate that using cards to represent a certain amount of workload can improve percentage tardy performance. This may also have resonance with other card-based solutions, including kanban.

Paper aims POLCA is a production control system that forwards to gateway manufacturing cells jobs that arrive to a manufacturing system. However, Workload Control literature shows benefits from using a centralized release pre-shop pool. Thus, the paper aims at investigating the performance impact of incorporating centralized job release into POLCA, in high-variety make-to-order production. Originality This has not been investigated before. Research method Simulation was used for experimentation. Main findings In the case of the general flow shop, a manufacturing system configuration aligned with many real-world production systems, the investigation shows that adding centralized job release to the POLCA system, together with job release based on job workload, leads to a markedly improvement of job delivery performance. Implications for theory and practice The results show theoretical and practical relevance of applying central job release to POLCA system, in high-variety production, due to its markedly positive impact on delivery performance.

© Springer-Verlag GmbH Germany, part of Springer Nature 2020, Background: Depression is common in patients after acute coronary syndromes (ACS) and with stable coronary artery disease (CAD) and has been associated with increased mortality and morbidity. However, it is unclear whether selective serotonin receptor inhibitors (SSRIs) reduce mortality or cardiac events in patients with CAD and depression. Objective: We conducted a systematic review and meta-analysis to assess the efects of SSRIs on cardiovascular events in depressed CAD patients. Methods: The CENTRAL, MEDLINE, and PsycINFO databases were searched (April 2020) for randomized controlled trials (RCTs) and extended follow-up analyses of RCTs that compared SSRIs with placebo or no intervention in patients with CAD and depression. The primary outcomes were all-cause mortality, cardiovascular mortality, and myocardial infarction incidence. The results were calculated through random-efect meta-analyses and reported in terms of risk ratio (RR) with 95% confdence intervals (CI). Results: We retrieved 8 RCTs (2 of which with extended follow-up analyses), comprising a total of 1148 patients. 7 studies only included post-ACS patients. SSRIs were associated with a signifcantly lower risk of myocardial infarction in patients with CAD and depression (RR 0.54, 95% CI 0.34–0.86), and in post-ACS patients with depression (RR 0.56, 95% CI 0.35–0.90). We found no statistically signifcant diference in all-cause mortality, cardiovascular mortality, hospitalizations, angina, congestive heart failure, or stroke incidence. Conclusion: The use of SSRIs in post-ACS patients with depression was associated with a 44% relative risk reduction of myocardial infarction. No diference in mortality was found. Given that the quality of the evidence was low, further research is warranted.

30th International Conference on Flexible Automation and Intelligent Manufacturing (FAIM2021) 15-18 June 2021, Athens, Greece., POLCA (Paired-cell Overlapping Loops of Cards with Authorization) is a decision support system for material flow control under Quick Response Manufacturing. It operates in the context of low-volume, high-mix, and cellular manufacturing. While there is an increasing literature on POLCA performance, current studies usually assume full availability of components (or parts) at assembly stations, neglecting parts manufacturing and feeding. Therefore, this study uses simulation to assess POLCA performance in a two-stage production system, where at the first stage parts are manufactured and at the second, they are assembled into end-products. The study demonstrates that using POLCA to control both production stages, manufacturing and assembly, significantly outperforms the use of POLCA at the assembly stage only, leading to important reductions of the total throughput time of orders and on the percentage of tardy orders. Statistical analysis of our results was conducted using ANOVA., This work has been supported by FCT – Fundação para a Ciência e Tecnologia within the R&D Units Project Scope: UIDB/00319/2020

Literature on two-stage assembly systems typically assume that parts (subassemblies) require several sequential operations at the first production stage. However, parts can often be produced at a single station. This shifts the focus away from coordination to the provision of parts. The literature on parts feeding typically assumes the full availability of parts at stock points (e.g. warehouses or supermarkets), thereby neglecting the potential impact of capacity constraints at upstream stations. In response, this study assesses the performance of different parts feeding policies (kitting and line stocking). Simulation results show limited operational performance differences between kitting and line stocking in to-stock systems, with the main difference being where stock points are located. However, results also highlight the potential for producing subassemblies to-order if the constraint is how much (and not where) stock can be kept. This links together the literature on parts feeding with that on customer order decoupling points.

This paper addresses the problem of lot splitting in the context of workload control (WLC). Past studies on WLC assumed that jobs released to the shop floor proceed through the different stages of processing without being split. However, in practice, large jobs are often split into smaller transfer sublots so that they can move more quickly and independently through the production process and allow operations overlapping relating to the same job. This paper assesses the performance of different lot splitting policies for job release and dispatching strategies under lot splitting. A new dispatching rule was designed to specifically take advantage of lot splitting and operations overlapping in the context of WLC. Discrete-event simulation is used to assess system performance in relation to the ability to provide shorter delivery times and on time deliveries. Results highlight the importance of releasing the sublots of the same job together and demonstrate that combining an effective lot splitting policy with an appropriate dispatching rule can enhance the performance of production systems.

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Manufacturing industries are currently experiencing important changes towards digitization and autonomous production control, which is known as Industry 4.0. However, the profitability of some companies, namely Small and Medium Enterprises (SMEs), and of some industrial sectors does not allow for great investments, meaning that is necessary to undertake simple changes that potentially can lead to significant gains. This is the case for the metalwork company under study, where wastes related to the large parts movement and non-conformities detected before and after the parts delivered to the customers have been identified. The elimination of these wastes can contribute to a significant increase in the profitability of the company. The use and integration of several Lean tools made it possible to achieve this goal for this company. Amongst other improvements on productivity and waste reducing, a 59% reduction in the time required to move parts of up to 1000 kg, a reduction of 2.04% on the external non-conformities (i.e. on non-conformities detected outside the company) and 3.99% on the internal non-conformities, was achieved.

Autonomous production control (APC) aims at improving production systems performance through fast and flexible reaction to changes in dynamic production environments. APC shifts the power of decision from a central planning unit, towards single intelligent and distributed logistic objects that can cope with the rising complexity of today’s manufacturing systems. The purpose of this research is to analyse the current state of art on APC in discrete manufacturing industries, throughout a systematic literature review. The study’s objectives were to: (1) identify specialists in APC; and (2) identify theoretical developments and practical implementations. The reviewed was obtained by searching the Scopus database - a total of 49 papers have been analysed. The findings revealed that there is not much work carried out on APC until now, and that most of the contributions are theoretical. It is hoped that this literature review will contribute to enhance research in this science field.