A simulation analysis of the impact of production lot size and its interaction with operator competence on manufacturing system performance

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Abstract

In the process of production planning, planners have to define the production quantity to be loaded to the production line (commonly referred as “lot size”). The decision is mainly based on the primary concerns of avoiding late completion of contracts and minimizing costs. To provide more insights to the decision, this research aims to explore the impact of lot size and its interaction with operator competence on manufacturing system performance using simulation technique. During the simulation process, two inadequacies which hinder the representativeness of the simulation analysis are identified in the existing literature. They concern the inadequacy in simulating realistic operator learning curves and incompetent approach of simulation experimental analysis. A simulation model is proposed to refine these inadequacies before it is applied to explore the mentioned research issue. The simulation results confirm the significant effect of lot size and its interaction effect with operator competence on all performance measures.

Introduction

In the process of production planning, one of the functions is to define the production quantity to be loaded to the production line. In the current manufacturing world which stresses short lead time and Quick Response supply, planners usually split the customer order into lots of different sizes before loading them to the production lines in order to enhance flexibility and responsiveness. The decision is very important as production quantity has been convincingly recognized as an influential factor affecting the operator performance curves [1], [23], [29]. However, the decision regarding the production quantity to be loaded is made mainly based on the primary concerns of avoiding late completion of contracts and minimizing costs [9]; minimal concern has been placed on the impact of the defined production quantity and its interaction with operator performance curves on the manufacturing system performance. In the related literature, researchers also neglect the close relationship between the production quantity and operator performance curves. They mostly emphasize on the modeling of different extensions in attempt to imitate a realistic manufacturing situation and generate line loading plan with minimum costs for different situations [3], [5]. To provide more insights to the production planning process, this paper aims to explore the impact of the production quantity to be loaded to the production line and its interaction with operator competence levels on the manufacturing system performance in terms of average work-in-progress (WIP) level, flow time, machine and operator utilization rates.

A simulation-based factorial design is proposed in the research. The experimental design is carried out by simulating a manufacturing system using the ProModel package and output is analyzed using the SPSS statistical package. In the simulation process, two inadequacies are identified in the existing simulation literature which would affect the investigation on the above issue. They concern the failure in simulating realistic operator learning curves [6], [12], [16], [18], [28] and the incompetent approach of simulation experimental analysis [16], [28]. Therefore, this research also aims to propose a practical simulation modeling approach by refining these inadequacies to aid accurate assessment of the manufacturing system performance.

The remainder of the paper is organized as follows. Section 2 is the background and motivation for the research. In Section 3, we will explain the proposed simulation modeling approach; the experimental factors considered and present an analysis of the experimental output including the main effect and interactions between factors. Finally, a conclusion is drawn in Section 4.

Section snippets

Background and motivation

In common practices when planners split the customer order into lots of different sizes, they decide mainly based on two primary concerns: to avoid late completion of contracts and to minimize costs [11]. Little emphasis has been placed on how the decision regarding lot sizes affects manufacturing system performance on operative level in terms of WIP level, flow time, machine and operator utilization rates. In academic prospective, researchers tend to focus on factors such as batch size,

Framework of the proposed simulation model

A new simulation model is proposed to fill the above inadequacies before it is used for the mentioned research issue regarding the quantity loaded to the production line. The proposed simulation model consists of three phases (Fig. 1).

In Phase 1, real production data collected from the factory is used to configure a specific manufacturing system. The data covers operator sequences, the Standard Allowed Minutes (SAM) of each operation and operator competence records. Based on the data,

Conclusion

This paper attempts to draw the attention to the impact of quantity loaded to a production line on the manufacturing system performance in the hope of improving the production loading process. A simulation-based factorial design is conducted for the study. During the simulation process, two inadequacies regarding simulation of operator learning curves and simulation experimental analysis are identified in the existing literature which hinders accurate analysis. The application of a

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