Performance of Cellular Bucket Brigades with Hand‐Off Times

A cellular bucket brigade is a way to coordinate workers along an aisle with work content on both sides. Each worker in a cellular bucket brigade works on one side of the aisle when he proceeds in one direction, and he works on the other side when he proceeds in the reverse direction. Although the cellular bucket brigade eliminates the unproductive walk‐back, it requires more hand‐offs to assemble a product than a traditional (serial) bucket brigade. These hand‐offs may waste significant production capacity as each of them requires an exchange of work, which can be complicated and time‐consuming in practice. This motivates us to investigate the impact of hand‐off times on the cellular bucket brigade's performance. We identify sufficient conditions to ensure no workers are idle in the long run and for the system to self‐balance in a model with hand‐off times. Our results suggest that even with significant hand‐off times, the cellular bucket brigade can remain substantially (about 50%) more productive than the traditional bucket brigade especially if the team size is small and the workers’ work velocities are close to their walk velocity.     

Cellular Bucket Brigades on U‐Lines with Discrete Work Stations

It is challenging to maximize and maintain productivity of a U‐line with discrete stations under the impact of variability. This is because maximizing productivity requires assigning workers to suitable tasks and maintaining productivity requires sufficient flexibility in task assignment to absorb the impact of variability. To achieve this goal, we propose an operating protocol to coordinate workers on the U‐line. Under the protocol the system can be configured such that its productivity is maximized. Workers are allowed to dynamically share work so that the system can effectively absorb the impact of variability. Analysis based on a deterministic model shows that the system always converges to a fixed point or a period‐2 orbit. We identify a sufficient condition for the system to converge to the fixed point. Increasing the number of stations improves productivity only under certain circumstances. The improvement is most significant when the number of stations in each stage increases from one to two, but further dividing the U‐line into more stations has diminishing return. Simulations based on random work velocities suggest that our approach significantly outperforms an optimized, static work allocation policy if variability in velocity is large.     

Redundant configuration of automated flow lines based on “Industry 4.0”-technologies

Over the past decades, robots have been heavily used for flow lines to increase productivity and product quality and to relieve workers of repetitive and dangerous tasks. However, despite continuous improvement of robots, the occurrence of failures remains a significant challenge in the operation of automated flow lines. Due to the connection of the stations in a flow line via a material handling system, failures at one station can quickly lead to throughput losses due to blocking and starving of upstream and downstream stations, respectively. To some extent, these throughput losses can be reduced by installing buffers between the stations. However, the installation of buffers requires considerable investments and scarce factory space. Therefore, the minimization of the total number of buffers is one of the primary objectives in flow line planning. Due to the advances of manufacturing technologies that form the foundation of “Industry 4.0”, new solutions to reduce throughput losses caused by equipment failures open up. One solution is a redundant configuration, in which downstream stations automatically take over the operations of failed stations in the event of failure. The throughput loss in these situations mainly depends on the level of redundancy designed into the system. Based on existing methods for the design of automated flow lines, we present two line balancing formulations for the configuration of automated flow lines under consideration of redundancies. The first formulation aims at maximizing the lines’ level of redundancy. The second formulation aims at a balanced allocation of redundancies along the line. To evaluate the presented formulations, we compare the performance with an existing line balancing approach for automated lines. With respect to this approach, improvements of the throughput rate between 3 % and 7 % are achieved.     

Integration of disciplines for applied scheduling: a workshop report

The purposes of this paper are, first, to introduce several concepts and definitions related to Theory of Constraints design and management of unbalanced lines and, second, to illustrate the concepts of productive and protective capacity and inventory in a constrained line. Drum-buffer-rope is the Theory-of-Constraints based scheduling mechanism used to manage throughput at constraint work stations and flow at non-constraint work stations. A small simulation model is given to illustrate the importance of protective capacity and protective inventory at non-constraint stations. The line consists of several stations with the centre station being the constraint station. The capacity of (and inventory at) non-constraint stations is varied during the simulation. Line output increases as inventory at non-constraint stations increases. This result is contrary to traditional teaching about line design which says that line output is a function solely of the capacity of the slowest station.     

Impact of Storage Assignment Decisions on a Bucket Brigade Order Picking Line

Bucket brigade order picking is a method for retrieving orders from a storage rack where workers follow a fixed sequence and dynamically adjust to variability in work content along the rack. The method is simple and has been shown to provide superior performance in many applications. In this article, we analyze how the location in which products are stored in the rack affects throughput. We identify conditions where storage decisions have a large impact on throughput (e.g., a 20% increase in productivity) and conditions where the impact is minimal. Conditions associated with high impact are high variation in worker skill, high variation in SKU volume, and a moderate level of walking‐to‐picking work content per pick list.     

Flexible Servers in Understaffed Tandem Lines

We study the dynamic assignment of cross‐trained servers to stations in understaffed lines with finite buffers. Our objective is to maximize the production rate. We identify optimal server assignment policies for systems with three stations, two servers, different flexibility structures, and either deterministic service times and arbitrary buffers or exponential service times and small buffers. We use these policies to develop server assignment heuristics for Markovian systems with larger buffer sizes that appear to yield near‐optimal throughput. In the deterministic setting, we prove that the best possible production rate with full server flexibility and infinite buffers can be attained with partial flexibility and zero buffers, and we identify the critical skills required to achieve this goal. We then present numerical results showing that these critical skills, employed with an effective server assignment policy, also yield near‐optimal throughput in the Markovian setting, even for small buffer sizes. Thus, our results suggest that partial flexibility is sufficient for near‐optimal performance, and that flexibility structures that are effective for deterministic and infinite‐buffered systems are also likely to perform well for finite‐buffered stochastic systems.     

Residential Location,Work Location,and Labor Market Outcomes of Immigrants in Israel

We develop and estimate a comprehensive dynamic programming (DP) model for the joint decisions of residential location, employment location, occupational choices, and labor market outcomes. We use data on immigrants from the former Soviet Union (FSU). We provide an extensive empirical evaluation of policies that have been designed to affect the residential and employment location decisions of the migrant population. The results shed new, and important, light on several issues regarding this group of immigrants. We find large regional differences in wages for the white‐collar workers, but only little differences for the blue‐collar workers. A careful examination of a number of policy measures indicate that a direct subsidy, in the form of a lump‐sum transfer, is most effective in achieving the government stated goal of inducing people to reside in the northern region of the Galilee and southern region of the Negev. Other policies, such as rental and wage subsidies, can also be quite effective, but these are more difficult to administer.     

Impact of Absenteeism on Assembly Line Quality and Throughput

Assembly lines function best when every worker is present. When a worker is absent, management must scramble to quickly find a replacement. Usually, the replacement will not be as proficient as the absent worker. This can reduce quality and throughput. We present two assembly line work‐systems models (one for lines with Andon and one for lines without Andon) that show one mechanism whereby absenteeism could impact quality and throughput. We exercise these models to provide insights into absenteeism's impact on quality and throughput. While the paper is written in the concrete terms of automotive assembly, the concepts and results apply to manual assembly lines in general.     

Criteria for evaluating qualitative studies

Many countries are becoming increasingly reliant upon an aging workforce. Yet, much literature positions older workers as ‘last resort’ employees, held in low esteem by employers whose preference for youth extends into decision-making about workplace engagement and support. As part of a broader study on maintaining the competence of older workers, we investigated the extent to which a group of employees in Australia aged 45 or more perceived they were discriminated against because of their age, including access to training, promotion opportunities and job security. Against expectations arising from the literature, informants reported little in the way of explicit age-related bias in their employment, opportunities for advancement and further development. Although the informants have particular characteristics and featured paraprofessional and professional workers, the contrast is noteworthy between what is reported in the literature and often premised on surveys, and our data were based on interviews. The findings indicate a need to be wary of making easy generalizations about the extent to which older workers per se are discriminated against in the workplace, while at the same time acknowledging that such discrimination exists, and perhaps for particular kinds of workers. In addition, we found a range of nuanced responses that suggest there are tensions between discriminations policies and practice that are a challenge for human resource development professionals.     

Night work and symptoms of anxiety and depression among nurses: A longitudinal study

Over the last few decades, night work has been found to be associated with negative somatic consequences; however, there is less knowledge about its impact on mental health. In a sample of 633 Norwegian nurses, we investigated by means of latent growth curve modelling whether different work schedules predicted differences in baseline values of anxiety and depressive symptoms, and trajectories of these over a two-year span. All participants completed the Hospital Anxiety and Depression Scale as part of a larger survey conducted during the winters of 2009, 2010 and 2011. The results revealed that night workers and nurses who changed from day work to night work during the study period did not differ from day workers either in terms of baseline symptoms of anxiety or depression, or in terms of trajectories of these symptoms. However, nurses who changed from night work to day work reported a significant decrease in symptoms of both anxiety and depression over time compared to day workers. Furthermore, supporting previous work, languidity was related to higher anxiety and depression and hardiness to lower levels of those symptoms. Possible mechanisms underlying the results are discussed.     

Assembly Line Balancing with Resource Dependent Task Times*

Paced assembly lines are widely used in repetitive manufacturing applications. Most previous research on the design of paced lines has assumed that each task along the line can be performed by only one worker (or a fixed number of workers). In many cases, however, task duration times may be reduced by increasing the number of workers or changing the equipment assigned to work stations. Thus, the problem becomes one of assigning resource alternatives (e.g., workers and/or equipment) and tasks to work stations to minimize total cost for a desired production rate. For this problem, we present three procedures. The first formulates the problem as a shortest path problem and guarantees optimality. The second and third are heuristic adaptations of the shortest path procedure that are capable of solving large problems. The procedures are compared in terms of solution quality and computation time on a set of 128 randomly generated problems for which optimal solutions could be found. Our simulation results indicate that the choice of procedure depends on problem complexity and resource costs.     

Atypical Employment Relations and Government Policy in Europe

Abstract. This paper analyses government policy towards the two major forms of atypical work in Europe: part-time employment and temporary work. It is submitted that the policies implemented promote the volume of marginal part-time employment and temporary work. The policies aiming at more temporary jobs did not result in additional employment; they merely resulted in a redistribution of unemployment and a shift in the recruitment patterns in the direction of subsidised temporary jobs. Too much emphasis on numerical flexibility is not without danger. Countries run the risk that employers will not pay sufficient attention to the source of their long-term flexibility, manpower training. I t is argued that regular part-time work is an alternative for uncertain temporary jobs, Its potential expansion is considerable. Some recommendations are put forward to promote regular part-time jobs and improve the position of flexible part-time workers and temporary workers.     

Sleep disturbances in shift-workers: A marker for maladaptation syndrome

Abstract

This study aims to examine whether the relationship between overtime and well-being is influenced by the voluntary vs. involuntary (i.e., compulsory) nature of overtime work and by the presence or absence of rewards for overtime. We also explored the prevalence of these types of overtime and how they were related to work and personal characteristics. A survey was conducted among a representative sample of Dutch full-time employees (N=1612). AN(C)OVA was used to compare rewarded and unrewarded, voluntary and involuntary overtime workers on personal and work characteristics, fatigue, and work satisfaction. Most overtime workers were rewarded (62%). About half of the sample (n=814) could be classified as either voluntary or involuntary overtime workers, or as having “mixed reasons” to work overtime. Voluntary and unrewarded overtime workers had a relatively high income and favourable job characteristics. Involuntary overtime work was associated with relatively high fatigue and low satisfaction, especially for involuntary overtime workers without rewards who can be considered a burnout risk group. Voluntary overtime workers were non-fatigued and satisfied, even without rewards. It can be concluded that control over overtime and rewards for overtime are important for well-being. Moderate overtime work may not be a problem if it is done voluntarily. Moreover, the negative effects of compulsory overtime work may be partly offset by fair compensation for the extra work.     

Work–family conflict and crossover in volunteer emergency service workers

Abstract

A growing literature indicates that organizational and work demands place pressure on the partners and families of volunteer workers as it does on paid workers. This study evaluated a conceptual model integrating work–family conflict and stress crossover theoretical frameworks, to investigate the mechanisms by which emergency service volunteer work, specifically, predicts outcomes for the partners of volunteers. Matched data from 102 couples in which one partner was an Australian emergency services volunteer – firefighter, ambulance officer or emergency rescue volunteer – were analysed using structural equation modelling analyses. Findings suggested that one mechanism by which inter-role conflict related to partner adjustment was through elevated withdrawn marital behaviour and decreased intimacy reported by the couple, which indirectly affected partners’ distress. This finding regarding withdrawn behaviour appears to be novel and may also be applicable to paid workers. Alternative mechanisms involving role overload and angry marital behaviour were not supported. These findings extend limited research which has adapted organizational theory to understand processes affecting volunteer workers, and advance conceptual accounts of the mechanisms through which the partners and families of workers are impacted by inter-role conflict.     

Psychological and physiological stress responses during repetitive work at an assembly line

The association between psychological and physiological stress responses was examined in 20 male workers at an assembly line. Each worker was studied during a 2 h period on two consecutive days in their normal job and, in order to obtain physiological baseline values, during a corresponding paid 2 h period off the job on the third day. Self-reports of work demands, mood, etc., measurements of catecholamine and cortisol excretion and of systolic and diastolic blood pressure and heart rate were obtained at the end of each of the three 2 h periods. Work induced a significant elevation in almost all psychological and physiological measurements. Levels were consistently lower in workers reporting a 'good' workday compared to those reporting a 'normal' or a 'bad' day. Correlations between self-reports and physiological values showed that catecholamine and cortisol responses, respectively, tended to be associated selectively with different psychological conditions, catecholamine values being associated with feelings of time pressure and pressure by demands, cortisol values with irritation, tenseness and tiredness. The results show that perceived stress at an assembly line is consistently reflected in cardiovascular and neuroendocrine functions of the workers.     

Alternative uses of temporary work and new forms of work organisation

The purpose of this study is to investigate the relationship between the use of temporary workers and the adoption of new forms of work organisation (NFWO) in production. This study aims to understand to what extent these two forms of human resources flexibility are synergic or mutually exclusive. In order to answer this main goal, we discuss different levels of temporary workers adoption in relation to different levels of use of NFWO, the level of integration of temporary workers within the overall production organisation and the joint and synergistic use of NFWO and temporary work. Evidence drawn from seven case studies in manufacturing plants in northern Italy is provided. Results highlight that, according to the characteristics of the production process, temporary workers and NFWO are not mutually exclusive, that temporary workers can be integrated with other workers in the shop floor, and that NFWO can also be adopted for temporary workers. In addition, NFWO has been proven to be a key enabler to integrate temporary workers within the organisation, thus showing an important synergistic effect between the two human resource flexibility practices.     

Optimizing the number of stations in assembly lines under learning for limited production

This paper considers finding the optimal number of stations for an assembly line producing a limited quantity of a new product under learning conditions. This type of production characterizes heavy products (such as airplanes and communication systems) and science-based industries (e.g. laser cutting devices and special equipment for hospitals). These products are manufactured in assembly line fashion in small batches of a few hundred. Since the products are assumed to be totally new to the workers, the learning phenomenon is significant (i.e. task times decrease from cycle to cycle as experience is gained). Therefore, standard balancing methods are no longer applicable. Determining the number of stations has a large effect on the production rate while the actual assignment of tasks to stations helps to fine tune the cycle time. Thus, the number of stations can be regarded as a strategic decision variable . This paper discusses two ways for determining the optimal number of stations, namely as a cost minimization problem and as a profit maximization problem.     

Leader-Member Exchange across two hierarchical levels of leadership: concurrent influences on work characteristics and employee psychological health

Leader-Member Exchange (LMX) theory suggests that the quality of the leader–employee relationship is linked to employee psychological health. Leaders who reside at different hierarchical levels have unique roles and spheres of influence and potentially affect employees' work experiences in different ways. Nevertheless, research on the impact of leadership on employee psychological health has largely viewed leaders as a homogeneous group. Expanding on LMX theory, we argue that (1) LMX sourced at the levels of the line manager (LM) and senior management (SM) team will be differentially linked to employee psychological health (assessed as worn-out) and that (2) these relationships will be mediated by perceived work characteristics (reward and recognition, workload management, quality of relationships with colleagues and physical environment). Structural equation modelling on data from 337 manual workers partially supported the hypotheses. Perceptions of the physical environment mediated the relationship between LMX at the LM level and employee psychological health, whereas perceptions of workload management mediated the relationship between LMX at the SM level and psychological health. These findings corroborate arguments that leaders are not a uniform group and as such the effects of LMX on employees will depend on leadership hierarchy. Implications for expanding leadership theory are discussed.     

Out of mind,out of sight? Leading distributed workers to ensure health and safety

ABSTRACT

Current frameworks of leadership are based on face-to-face interaction. A growing number of workers work away from their main location of work; this makes it challenging for leaders to ensure the health and safety of distributed workers. In the present study, we explore the relationship between line managers’ health and safety leadership and distributed workers’ health and safety behaviours. We also explore the organisational procedures and practices that may enhance the impact of health and safety leadership. We included a broad range of distributed workers (in analyses, minimum N?=?626) from 11 organisations. We found that health-and-safety-specific leadership was positively related to distributed workers’ self-rated health, safety compliance and safety proactivity. These relationships were augmented by distributed workers’ sense of being included in the workplace. Knowledge sharing among colleagues was associated with safety compliance when health-and-safety-specific leadership was low. Our results indicate that one way of addressing the challenges of distributed working may be through line managers putting health and safety on the agenda.