مشکل برش و کنترل موجودی در صنعت ساخت از اجناس از جنس استنلس استیل

Circular pieces are often cut from stainless steel roll to make common commodities such as pots and cups. The related factories are often make-to-order ones. The stock rolls usually have the same width. Each working order requires pieces of the same size. Pieces of different sizes cannot appear in the same cutting pattern because the orders do not arrive simultaneously. The approach proposed in this paper assumes that the original roll can be slit into a strip and a partial roll. The strip is used to fulfill the current order. The partial roll will be used to fulfill future orders and cannot be slit further. The approach determines several standard widths for the partial rolls and uses a greedy procedure to select the roll (either the original roll or a partial roll) to fulfill the current order. The computational results indicate that the approach is efficient in improving material utilization.

Stainless steel rolls are often cut into circular pieces to make household commodities such as water jugs, buckets, pails, pots, cups, and basins. Typically, a factory producing such products may consume several thousand tons of stainless steel rolls in a year. Because stainless steel is much more expensive than ordinary steel, it is important to take good cutting-and-inventory policies to improve material utilization. The problem discussed comes from a factory that produces pots, cups, and kettles. The factory consumes about 10 000 tons of stainless steel rolls in a year. The rolls must be cut into circular pieces to make the products. A customer order may include one or more products. Each product is made from circular pieces of the same type (same diameter and thickness). For production management convenience, each working order includes only pieces of the same type. To shorten the throughput time in the cutting shop, a working order is processed immediately after receiving it. Pieces of different types usually cannot appear in the same cutting pattern because the orders do not arrive at the same time. The factory orders rolls each month, and it takes about two months for the ordered rolls to arrive. The rolls in inventory usually have the same width that is 1090 mm in January 2005. Before 2005, the cutting process consisted of two stages. At the first stage, guillotine shears cut the roll into equal-size segments. The segment width was equal to the roll width, and the length was not longer than 1.5 m. At the second stage, stamping presses punched out the pieces from the segments. This process had led to poor material utilization and high labor cost. Several automated cutting lines have been set up in the cutting shop since 2005. Each line consists of a numerical controlled stamping press and the feeding devices. Once a roll is set up on the cutting line, it will be cut into pieces continuously without being segmented. It is necessary to implement good cutting-and-inventory policies so that the new lines operate with high level of material utilization. This new type of cutting lines is gaining wider acceptance in industry because it is more efficient in improving material utilization and productivity. The contents of the paper are arranged as follows: Section 2 introduces two cutting-and-inventory policies and reviews the literature briefly. The first policy referred to as simple slitting is summarized from the practice of the factory, and the second is the proposed policy referred to as planned slitting. Section 3 describes the procedure for performing the simple slitting. Section 4 presents the approach to perform the planned slitting. Section 5 presents the computational results. Section 6 terminates the paper with conclusions.

The proposed policy has been described in detail. It has the following advantages: (1) saving material when compared with the common practice of simple slitting; (2) short throughput time for the working orders in the cutting shop, because each working order can be processed immediately after receiving it; and (3) simple to perform because the cutting process has the same complexity as that of the simple slitting, i.e. at most two times of slitting are necessary to fulfill a working order. The specialized tests in Section 5.2 indicate that the saving is not sensitive to the values of the parameters, and using planned slitting can improve material utilization level under the reasonable ranges of all parameters. When the number of working orders is too small, the approach may become non-applicable because the number of main types may be very small or even zero. This makes it difficult to determine the widths of the standard partial rolls. Future research work may include the following: (1) use more practical instances to further test and improve the approach; (2) try to construct an exact approach for solving the problem.