Yang Woo Shin

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.

APPROXIMATION OF PH/PH/c RETRIAL QUEUE WITH PH-RETRIAL TIME

We consider the PH/PH/c retrial queues with PH-retrial time. Approximation formulae for the distribution of the number of customers in service facility, sojourn time distribution and the mean number of customers in orbit are presented. We provide an approximation for GI/G/c retrial queue with general retrial time by approximating the general distribution with phase type distribution. Some numerical results are presented.

A Simulation Based Study on Increasing Production Capacity in a Crankshaft Line Considering Limited Budget and Space

In this paper, we discussed a problem for improving the throughput of a crankshaft manufacturing line in an automotive factory in which the budget for purchasing new machines and installing additional buffers is limited. We also considered the constraint of available space for both of machine and buffer. Although this problem seems like a kind of buffer allocation problem, it is different from buffer allocation problem because additional machines are also considered. Thus, it is not easy to calculate the throughput by mathematical model, and therefore simulation model was developed using ARENA® for estimating throughput. To determine the investment plan, a modified Arrow Assignment Rule under some constraints was suggested and it was applied to the real case.

Impact of Service Interruptions and the Variability of Service Time in Queueing Systems: Numerical Investigations.

In this paper, we consider the queueing systems with finite buffer and service interruptions. The effects of service interruptions and the variability of service time to measure of departure process such as the asymptotic mean and variance of the number of departures are investigated numerically. We find numerically so called interruption paradox or failure paradox that the departure rate of the system with service interruptions under preemptive-repeat-different policy can be greater than that of the system with reliable server and it increases as the interruption rate increases for the case of large variability of service time. The results give an insight for the effects of the system and may be helpful to design and control the more complex systems.

Approximation of discrete time tandem queueing networks with unreliable servers and blocking

Abstract We consider the discrete time tandem queues with single unreliable server at each service station and a buffer of finite capacity between service stations. The blocking after service (BAS) mechanism and operation dependent failure (ODF) rule are adopted. The service time of each server is a constant unit time. A failure of each server occurs in a time slot with a fixed probability and the repair time distribution of each server is of discrete phase type. In this paper, we present an approximate analysis for the system based on the decomposition method and show that the approach can be applied to the variants of the system.

Variance of Departure Process in Two-Node Tandem Queue with Unreliable Servers and Blocking.

This paper provides an effective method for evaluating the second moments such as variance and covariance for the number of departures in two-node tandem queue with unreliable servers. The behavior of the system is described by a level dependent quasi-birth-and-death process and the departure process is modeled by a Markovian arrival process. Algorithms for the transient behavior, the variance and covariance structure for the output process and the time to the nth departure are developed. We show that the results can be applied to derive approximate formulae for the due-date performance and the distribution of the number of outputs in a time interval.

Variability of output in two-node tandem production line

The second order measures such as the variance and covariance of the output process in a production system are very useful to design and control the systems in a more effective way. This paper concerns to the two-station system with a buffer of finite capacity. An effective method for evaluating the second moments of the number of outputs and inter-departure times is provided and the effects of the system parameters such as the buffer capacity and the variabilities of the processing time, failure time and repair time to the variability of output processes is investigated. Some applications of the results are also discussed.

Comparison of the Two Layout Structures in Automotive Body Shops Considering Failure Distributions

There are many challenges in manufacturing system for new factory construction. Although factories produce same product, the layout of each factory may be different. The body shop in an automotive factory is a typical flow line with assembly, but the layout concept of the line varies among factories. In this paper, two types of layouts in the body shops of automotive factories, one for layered build and the other for modular build, are compared using simulation study. The simulation experiments indicate that the modular build layout is better than the layered build layout with respect to production rate. The effects of various failure distributions on the throughputs are also investigated, and some insights are suggested regarding the layout concept.