Dug Hee Moon

A case study of the body shop design in an automotive factory using 3D simulation

There are five major shops in an automotive factory, namely, press shop, body shop, power train shop, paint shop, and trim shop (general assembly shop). When an automotive factory develops a new car model, new production lines should be constructed at the same time, and the body shop especially needs to be entirely rebuilt whenever a new car model is developed. The body shop is a typical example of the flow shop (or transfer line). Many parts are assembled together in the body shop by various welding operations. Therefore, the cycle time of each robot and the buffer size between two sub-lines should be determined in the design phase of the body shop. This paper explains a case study of a body shop design using 3D simulation in a Korean automotive factory. 3D simulation is useful in verifying if the factory design would meet the production quantity target. It also helps in understanding the structure of the factory. QUEST®, IGRIP®, and Factory-CAD® are used for the 3D simulation model.

Determination of optimal production rates on a single facility with dependent mold lifespan

Abstract In this paper, we consider a situation where several dedicated items are produced on a single facility and production rates can be controlled within maximum and minimum limits. Thus, this problem is a modification of the economic lot scheduling problem (ELSP). We also take into account two different manufacturing costs that are functions of the production rate: (1) operating cost of the facility, and (2) mold cost. Operating cost is modeled as a linearly increasing function of the ratio between demand rate and production rate. Mold cost is modeled as an exponentially decreasing function. A mathematical model is developed and a heuristic iterative solution procedure is suggested. The objective of this problem is to minimize annual production-related cost in a model whose decision variables are common production cycle time and production rate for each product.

A Simulation Study for Implementing Color Rescheduling Storage in an Automotive Factory

This article outlines a simulation study relating to the design and the implementation of color rescheduling storage (CRS) in an automotive factory. In a painting shop, the colors of vehicles are changed frequently according to the assembly schedule. When the color of a vehicle is changed, the cleaning process of the painting gun is necessary, which generates a cost. The major objective of CRS is to reduce the changeover cost in the painting process by grouping vehicles with the same color. In this article, a case study of CRS in an automotive factory is presented. The procedure for designing CRS is explained, and the storage/retrieval algorithms are suggested. The proposed system is verified using simulation models, and comparisons among alternatives are examined to determine the best design. The authors also investigate the effect of color distribution on the system performance measures.

A Dynamic Algorithm for the Control of Automotive Painted Body Storage

This article introduces a simulation study relating to the dynamic operating algorithm for the painted body storage (PBS) in an automotive factory. The manufacturing process in the trim shop of an automotive factory is a typical example of the mixed-model assembly production. In the paint shop, which comes before the trim shop, same-colored bodies are grouped together to reduce the changeover cost. Therefore, the PBS is located between the paint shop and the trim shop to allow for the rescheduling of the input sequence of cars to the assembly line. In this article, a case study on PBS in an automotive factory is presented. The storage/retrieval algorithms are suggested, and the proposed system is verified using simulation models. A sensitivity analysis for operating factors is also carried out.

A simulation study integrated with analytic hierarchy process (AHP) in an automotive manufacturing system

A variety of circumstances, such as developing a new product, changing the design of an existing product, changing the production volume, or changing the product mix, can drive the need for a manufacturing system redesign. Simulation technology has been widely used for evaluating manufacturing system design alternatives. Various performance measures including throughput, utilization of resources, lead-time, and work in process are obtained from simulation studies. However, the dimensions of performance measures are different, and it requires that the trade-offs between them should be considered. In addition, personal preferences in the selection of performance measures vary from person to person. Thus, the multi-criteria decision-making (MCDM) system is required to complement the simulation technology. This paper presents a case study that integrates a simulation study with analytic hierarchy process (AHP), applied to the design of a transmission case line in a Korean automotive factory. The simulation model is developed with QUEST®. Four performance measures (criteria) and seven design alternatives are considered utilizing AHP.

Approximations of retrial queue with limited number of retrials

We consider the retrial queues in which the number of retrials of each customer is limited by a finite number, say m. If a customer fails to enter the service facility at the mth retrial, then the customer leaves the system forever without service. Approximation formulae for the distributions of queue length process, waiting time and the number of retrials made by a customer during his waiting time are derived by the approach in Fredericks and Reisner [10]. Some monotonicity properties are also presented.

An operator load-balancing problem in a semi-automatic parallel machine shop

This paper deals with a load-balancing problem among several operators in a semi-automatic parallel machine shop in which two types of machine are operated. The objective is to assign jobs to the proper machines and allocate machines to operators in order to minimize the unbalance of the workloads among operators under the constraints of available machine- and operator-time. There are two types of parallel machines and jobs are classified into the two types. However, operator can handle machines of both types.Although, this situation can be formulated with non-linear integer programming, it is difficult to solve this program. Therefore, a hierarchical heuristic solution procedure is suggested and the performance of the algorithm is evaluated with various data.

Approximation of M/M/c retrial queue with PH-retrial times

We consider the M/M/c retrial queues with PH-retrial times. Approximation formulae for the distribution of the number of customers in service facility and the mean number of customers in orbit are presented. Some numerical results are presented.

A simulation study for dynamic scheduling in a hybrid assembly/job shop considering the JIT context

This paper is a report of a simulation study that investigates a dynamic approach to scheduling jobs in a hybrid assembly/job shop, with special application to welding shop operations. Both JIT arrival and JIT delivery are considered. Various dispatching rules with different utilization are tested for the following performance measures; mean flow time, percentage of tardy jobs, mean tardiness, sum of mean tardiness and mean earliness. The results indicate that the SPT rule is the best for the mean flow time. The MSLACK rule, that we suggest in this paper, is the best for mean tardiness, the sum of mean tardiness and mean earliness. However, it is not clear which rule is the best for the percentage of tardy jobs. We also investigate the effect of changing the release time on the performance measure.

Effects of Failure Distribution Considering Various Types of Layout Structure in Automotive Engine Shops

Manufacturing system design poses many challenges for new factory construction. Factories producing the same product may nevertheless have different layouts. The machining line of the engine shop in an automotive factory is a typical flow line, but the layout concept of the line varies among factories. In this paper, a simulation study on the design concept of the manufacturing system for automotive engines is discussed. For comparison, three types of real engine block lines in different factories are analyzed, and three structures of parallel lines are extracted. The effects of failure distribution on the performance measures of three types of parallel line structures are investigated, and some insights are offered regarding the layout concept.