Jordi Olivella

Work organisation practices for lean production

Purpose – The purpose of this paper is to obtain and to expose work organisation practices common to the factories that successfully follow lean production (LP) principles.Design/methodology/approach – Analysis of the literature and interviews with experts.Findings – An analysis of the literature reveals clear connections between work organisation practices and LP. However, general reports on LP barely deal with work organisation. A set of work organisation objectives for LP was established for the authors and interviewed experts and analysed by reviewing the literature. Similarities are found between the different sources in terms of defining a set of policies and practices covering all the aspects of work organisation. It is shown that there are indeed work organisation practices characteristic of LP.Originality/value – This paper is believed to be the first complete analysis of work organisation practices for LP.

Selecting and adapting weekly work schedules with working time accounts : A case of a retail clothing chain

A case of selection and adaptation of weekly work schedules is presented. Weekly work schedules in two franchises of an important retail clothing chain have to be established. Working time accounts are used: each week, an employee can owe the company a certain number of hours or vice versa. Nevertheless, over a certain threshold, the hours have to be paid for by the company and the account balance returns to zero. A minimum and desired level of capacity of employees is contemplated. Hierarchically, the planned capacity must attempt to reach the minimum level; then it must fit a desired level as much as possible. At present, the task of allocation and the final adjustment of schedules is done manually, which is difficult, ineffective and often inaccurate. The procedure proposed is divided into two phases. Firstly, a work schedule, selected from a list, is assigned to each worker; a mixed linear program, followed by a local optimization process, is used. In the second phase, the work schedules are modified according to predefined rules: if there is a surplus of capacity, work schedules are reduced, and if there is a shortage, work schedules are extended. The company considers the results to be satisfactory.

A detailed workforce planning model including non-linear dependence of capacity on the size of the staff and cash management

This paper introduces an original planning model which integrates production, human resources and cash management decisions, taking into account the consequences that decisions in one area may have on other areas and allowing all these areas to be coordinated. The most relevant characteristics of the planning problem are: (1) production capacity is a non-linear function of the size of the staff; (2) firing costs may depend on the worker who is fired; (3) working time is managed under a working time account (WTA) scheme, so positive balances must be paid to workers who leave the company; (4) there is a learning period for hired workers; and (5) cash management is included. A mixed integer linear program is designed to solve the problem. Despite the size and complexity of the model, it can be solved in a reasonable time. A numerical example, the main results of a computational experiment and a sensibility analysis illustrate the performance and benefits of the model.

Task assignment considering cross-training goals and due dates

When a worker performs a task at which he is not fully experienced, he is increasing his future performance in doing this task. Thus, task assignment can consider objectives regarding task accomplishment and objectives regarding cross-training. The contribution of this paper lies in presenting and modelling the assignment of a set of tasks to a set of workers considering cross-training goals and that some of the tasks have to be completed at given due dates. The influence of the experience of one task on the performance on other tasks is taken into account. The model allows (1) testing the feasibility of a given combination of cross-training goals and due dates; (2) obtaining the task assignment that maximises the total work done – considering the tasks that have a due date and the tasks that do not; and (3) calculating the change on the total quantity of work performed because of the establishment of cross-training goals or due dates. A computational experiment is carried out by using MILP optimisation software.

A manufacturing and remanufacturing aggregate planning model considering a non-linear supply function of recovered products

Abstract: This article addresses the joint aggregate planning of a system for manufacturing new units and remanufacturing used units to obtain items that are indistinguishable from the original product. A variety of used conditions are taken into account. A forecast of the number of items at the end of their useful life in each period is assumed to be available and the proportion of items that are returned is a non-linear function of the price paid for them. The case deals with products such as copiers, printers and scanners, and with containers that require a complex refilling process. A mathematical program is obtained whose constraints and objective function have non-linear terms that are linearised by means of piecewise functions. The solution of several instances is addressed and one example is examined in detail.

Production planning under a working time accounts scheme

Working time accounts (WTAs) provide flexibility to a company to adjust the capacity to the demand by planning, for each period and each worker, an appropriate number of working hours. Under this scheme, every worker has a balance that can be positive (the company owes hours to the worker), zero or negative (the worker owes hours to the company). Credit (or debit) hours are compensated by working less (or more) hours than the reference value in the subsequent periods. This scheme is especially useful for companies dealing with demand fluctuations, because WTA balances can take any value, provided that these belong to a given bounded interval. Other conditions that affect the number and distribution of working hours may be established either in law or in the WTA agreement. This paper proposes a new mathematical model for planning production, inventory levels, working time and temporary closures in a manufacturing company operating under a standard WTA scheme. The results of the computational study show that the model is an appropriate tool not only for planning but also for helping in the bargaining process (different WTA scheme configurations could be evaluated with the model).

Capacity planning with working time accounts in services

This paper presents, formalizes and classifies working time accounts (WTAs), a means of achieving flexible production capacity through the flexible organization of working time. We propose linear programming models to plan working time, using WTA, at companies in the service industry. A computational experiment shows that the models can be solved for any capacity planning problems of reasonable size.

Calibrating cross-training to meet demand mix variation and employee absence

We address the problem of determining the cross-training that a work team needs in order to cope with demand mix variation and absences. We consider the case in which all workers can be trained on all tasks, the workforce is a resource that determines the capacity and a complete forecasting of demand is not available. The demand mix variation that the organization wants to be able to cope with is fixed by establishing a maximum time to devote to each product. We contend that this approach is straightforward, has managerial practicality and can be applied to a broad range of practical scenarios. It is required that the demand mix variation be met, even if there are a certain level of absences. To numerically solve the mathematical problem, a constraint-based selection procedure is developed, which we term CODEMI. We provide illustrated examples demonstrating solution quality for the approximation, and we report on an illustrative set of computational cases.

An entropy-based measurement of working time flexibility

Working time flexibility is of major concern to companies, and must be established by reaching arrangements with workers. Comparing flexibility arrangements is far from easy. Measures of flexibility that assume a probability distribution of future demand are not really measuring flexibility, but rather risk. We define a space of states made up of possible working hours over several periods, and apply three measures of flexibility to it: the proportion of feasible states, the average cost and a new entropy-based measure of flexibility (EMF). The EMF is based on Shannons entropy. We propose the use of three measures simultaneously for comparing the flexibility provided by a working time arrangement. Two examples are given: one that assesses the flexibility generated by using time accounts and overtime in a working time accounts (WTAs) modality, and one that compares the WTAs and hiring and firing (H&F) modalities.

Organizational Practices Lean Enterprises Adopt to Focus on Value Streams

The purpose of this article is to investigate which practices lean enterprises adopt to focus on value streams. A case study of three plants: Delphi Diesel Systems, Sogefi Filtration, and a company within the furniture industry is presented. The three plants have successfully performed a lean transformation with significant performance improvements, respectively, to Delphi Diesel Systems, Sogefi Filtration, and a company within the furniture industry. The organizational practices under analysis are (1) the establishment of organizational units based on value streams, (2) the use of a performance measurement system based on value streams, and (3) the adoption of a formal meeting system. These organizational practices were found in all three of the studied plants and have been implemented in all of their organizational units; even concrete implementation detail differs between plants. This research provides a contribution in the fields of organizational practices and the transition to lean enterprise by establishing the relation between real practices and the focus on value stream lean principle. As insight for managers, the adoption of appropriate organizational units, indicators, and meetings appears to be a useful practice to support the focus on value streams.