u形生產(chǎn)線的分析與優(yōu)化外文翻譯

1、ANALYSIS AND OPTIMIZATION OF A U-SHAPED PRODUCTION LINE Katsuhisa Ohno Koichi NakadeNagoya Institute of Technology(Received August 21, 1995; Revised January 16, 1996) Abstract In the just-in-time context, parts are o

2、ften processed by a single-unit production and conveyance system (called “zkko-nagash? in Japanese) without conveyors. The U-shaped layout, in which each multifunction worker takes charge of several machines, has been i

3、ntroduced as an implementation of this concept. Presently the layout is gaining an increasing popularity due to the low running cost .In this paper, first we deal with the U-shaped production line with a single multi-fu

4、nction worker. We derive his waiting time and a cycle time of the line when processing times of items, operation times, and his walking times between machines are constants. Then we deal with a U-shaped production line

5、with multiple workers. We derive the overall cycle time of this line, and consider an optimal worker allocation problem that minimizes the overall cycle time when the number of workers is given. In particular, it is show

6、n that the U-shaped layout is superior to the linear layout for lines with one or two workers. We also discuss the case where those processing, operation and walking times are stochastic.1. IntroductionIn a conveyor sys

7、tem for mass production as in the Ford system, each station processesjust one item in one cycle time, where the cycle time is the time-interval between two successive outputs. The sums of necessary operation and processi

8、ng times are intended to be equal among the stations, the items are processed synchronously among the stations, and there exist no items between adjacent stations.In the just-in-time (JIT) production system, the above c

9、oncept, which is called a singleunit production and conveyance (“ikko-nagashi,“ in Japanese), is applied to a production line without conveyors which manufactures different kinds of relatively small parts (Monden [3], p

10、.107). To achieve this at a low production cost, a U-shaped layout is used with multifunction workers. The U-shaped production line with three workers and ten machines is shown in Figure 1. When the entrance and exit of

11、 items are near as shown in Figure 1, we call this layout a U-shaped layout, and if the same worker handles both machines at the entrance and exit in the U-shaped layout then we call this layout a U-shaped production l

12、ine.The multifunction worker takes charge of multiple machines, and visits each of the mounce in one cycle. When he arrives at one of these machines, he waits for the end of processing of the preceding item if it is no

13、t completed, and then operates the items and walks to the next machine. The operation consists of detaching the processed item from the machine, putting it on a chute to roll in front of the next machine, attaching the

14、 new item to the machine, and switching it on. The cycle time of the worker is the time-interval between his consecutive arrivals at his first machine, and consists of the waiting times for the end of processing, operat

15、ion times and walking times between machines.In the JIT production system, two kinds of Kanbans, that is, a production ordering and a withdrawal Kanbans are used as tools to control production and withdrawal We can furt

16、her reduce an overall cycle time by admitting what Toyota calls mutual relief movement ([3], p.114). This means that a worker who has finished his own operations in one cycle helps another adjacent worker. This, however,

17、 is not taken into account in this paper, because the problem becomes more complicated. If multiple kinds of items are processed in this line, the processing times and operation times are not constant. In addition, the o

18、peration and walking times of the worker may fluctuate because of his weariness and learning effect. In Section 4, we deal with the case where the processes of operation, walking and processing times are stochastic. In

19、particular, we discuss the case where the sequences of random variables in these processes are independent and identically distributed and there is a bottleneck machine such that the sum of processing and operation times

20、 of this machine is larger than that of any other machine with probability one. It can be shown that the worker waits for the completion of processing at the bottleneck machine in all cycles. 2. Cycle and Waiting Times

21、of a Multi-Function WorkerIn this section we consider the U-shaped production line with a single multi-function worker, which is shown in Figure 2. The worker handles machines 1 through K. The facility has enough raw ma

22、terial in front of machine 1. The material is processed at machines 1,2,. . . , K, sequentially, and departs from the system as a finished product. Let K = {l,. . . , K}.When the worker arrives at machine k∈K, if the pr

23、ocessing of the preceding item is completed, then he removes it from machine k, sends it to machine k + 1, attaches the present item to machine k and switches it on. After the operation at machine k, he walks to machin

24、e k + 1. If the preceding item is still in process at his arrival, then he waits for the end of the processing before the operation.It is assumed as an initial condition that at time 0, there is one item on each machin