On the Road to Improved Scheduling: Reducing the Effects of Variation in Duration

Lindhard, Søren Munch; Wandahl, Søren

doi:10.1061/9780784413135.012

Cited by 4 publications

(3 citation statements)

References 8 publications

(8 reference statements)

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“…According to Hudghes et al (2004) both negative and positive variation is creating chaos in the production system. While negative variation is creating delay (Howell and Ballard 1994) positive variation creates gaps in the production which most often result in unexploited capacity (Lindhard and Wandahl 2013;Yeo and Ning 2006). Thus, if the gaps of positive variation are exploited they could, in theory, counterbalance the effect of negative variation (Yeo and Ning 2006).…”

Section: Introductionmentioning

confidence: 99%

Understanding the Effect of Variation in a Production System

Lindhard

2014

J. Constr. Eng. Manage.

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Variation is a root cause to waste in a production system because it creates interruptions in the production system. Variation is dissipating through the production flow and reduces productivity; therefore, to minimize the effect variations need to be handled with great care. In this research study it is examined how task starting time and duration is affected by variation. By simulating a sequence of work tasks using a normal distribution it has been possible to analyze variations' effect on task starting time, task durations, crew waiting time, etc. Ten simulation circles were simulated and analyzed. The analysis revealed that variation itself does not create waste. Waste is only emerging between handoffs, thus increased activity duration decreases the effect of variation. Moreover, by comparing a linear sequence and a network of activities, the effect of variation was found to depend on the design of the sequence.

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Section: Introductionmentioning

confidence: 99%

Understanding the Effect of Variation in a Production System

Lindhard

2014

J. Constr. Eng. Manage.

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“…It is important to notice that the remaining constraints are expected to be removed before activity start, and could for instance be a late delivery of materials. Finally, the making ready process should seek towards optimal fulfillment of the preconditions to secure the best possible working conditions to improve the workflow and hinder negative variation which results in delay (Lindhard and Wandahl 2013b).…”

Section: Recommendations At the Look-ahead Levelmentioning

confidence: 99%

Looking for Improvement in the Last Planner System: Defining Selection Criteria

Lindhard

Wandahl

2013

Iccrem 2013

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Last Planner System has been critiqued for an inconsistent application of flows. Central for this critique was that the sequence of activities was determined based on only duration and interrelationships. In an attempt to improve the on-site scheduling processes, an in-depth analysis of selection criteria was carried out. Six flows are identified as relevant: workforce, material, and machinery which comprise the needed resources and safety, climate conditions, and space which affect the pace of the work. Because of the importance to progress in the workflow, and the on schedule completeness of activities, all six flows need to be systematically controlled. The output of the analysis is a list of recommendations of how to refine the schedules by including the six flows both in the Phase Scheduling, the Look-ahead, and the Commitment level.

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“…Negative as well as positive variation is undesirable in a production system (Hughes et al 2004). Negative variation is destructive to plans and schedules, because it introduces delay (Howell and Ballard 1994) while positive variation creates unexploited gaps in the production which result in unexploited capacity (Lindhard and Wandahl 2013b;Yeo and Ning 2006). Negative as well as positive variation is everyday life in on-site production (Wambeke et al 2011;Thomas et al 2002).…”

Section: Introductionmentioning

confidence: 99%

Handling and Reducing Variation in On-Site Production

Lindhard¹

2014

Iccrem 2014

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Variation is undesirable in a production system because it complicates production management. Variation caused by completing activities too early (positive variation) or too late (negative variation) is studied through a questionnaire survey where focus was on how to reduce or handle this variation. It was found that the top initiatives to handle variation were: mutual core values, collaboration, process transparency, control of interdependencies and schedule robustness while the top initiatives to reduce variation were: collaboration, output quality, buffering, standardization, and multi skilled craftsmen. The results are compared and discussed according to the construction control principles Last Planner System (LPS). LPS is found to focus on removing negative variation to improve the efficiency of the planning system. Therefore, LPS has only minor focus on the actual process, on communication and collaboration on-site, on how the process is managed by the construction managers in relation to mutual core values, leadership and motivation, and on the quality of the production output..

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On the Road to Improved Scheduling: Reducing the Effects of Variation in Duration

Cited by 4 publications

References 8 publications

Understanding the Effect of Variation in a Production System

Understanding the Effect of Variation in a Production System

Looking for Improvement in the Last Planner System: Defining Selection Criteria

Handling and Reducing Variation in On-Site Production

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