8 facility layout
Toshiba: producer of the first notebook computer
Tokyo shibaura denki (Tokyo shibaura Electric Co. Ltd. ) was formed in 1939 by a merger of two highly innovative Japanese companies: shibaura seisaku-sho (shibaura Engineering Works ),which manufactured transformers, electrical motors, hydroelectric generators, and X-ray tubes, and Tokyo electric Company, which produced lightbulbs, radio receivers, and cathode-ray tubes. The company was soon after know as “Toshiba,” which became its official name in 1978. Toshiba became the first company in Japan to make fluorescent lamp (1940), radar (1942), broadcasting equipment (1952), and digital computer (1954) Toshiba also became the first on the world to produce the powerful 1-megabit DRAM chip and the first laptop computer, the T3100, both in 1985
Toshiba has built its strength in the notebook PC market by beating its competitors to the market with aggressively priced, technologically innovative products. Competition in the notebook PC market is fierce, and Toshiba can retain its position as a market leader only by relentlessly improving its manufacturing processes and lowering its costs.
Dell computer is a formidable competitor and seeks to minimize its costs by assembling to order and selling directly to customers. Toshiba has some significant advantages over Dell that stem largely form huge investments in technologies, such as thin-film transistor (TFT) color displays, hard disk drives, lithium-ion batteries, and DVD drivers. In addition, by forming partnerships and joint ventures with other industry giants, Toshiba can share the risk of developing expensive new technologies.
Put yourself in the position of the Toshihiro Nakamura, the production supervisor at Toshiba’s Ome works plant. Production of Toshiba’s latest subnotebook computer is scheduled to begin in only 10 days. As he wends his way through a maze of desks, heading to the factory floor, he wonders if it is really feasible to get the line designed in time.
Read the details related to designing the new assembly line in the case at the end of this chapter titled “Designing a Manufacturing Process.”
Layout decisions entail determining the placement of departments, work groups within the departments, workstations, machines, and stock-holding points within a production facility.
the objective is to arrange these elements in the way that ensures a smooth work flow (in a factory) or a particular traffic pattern (in a service organization). In general, the inputs to the layout decision are as follows:
1. Specification of the objectives and corresponding criteria to be used to evaluate the design. The amount of space required and the distance that must be traveled between elements in the layout are common basic criteria.
2. Estimates of product or service demand on the system.
3. Processing requirement in terms of number of operations and amount of flow between the elements in the layout.
4. Space requirements for the elements in the layout.
5. Space availability within the facility itself or, if this is a new facility, possible building configurations.
In our treatment of layout, we examine how layouts are developed under various formats (or work-flow structures). Our emphasis is on quantitative techniques, but we also show exing and service facilities are covered in this chapter
Analyzing the four most common layout formats
the formats by which departments are arranged in a facility are defined by the general pattern of work flow; there are three basic types (workcenter, assembly line, and project layout) and one hybrid type (manufacturing cell).
A workcenter (also called a job-shop or function layout) is format in which similar equipment to function are grouped together, such as all lathes in one area and all stamping machines in another. A part being worked on then travels. According to the established sequence of operations, form area to area, where the proper machines are located for each operation. This type of layout is typical in hospitals, for example, where areas are dedicated to particular types of medical care, such as maternity wards and intensive care units.
An assembly line (also called a flow-shop layout) is one which equipment or work processes are arranged according to the progressive steps by which the product is made. The path for each part is, in effect. A straight line. Assembly lines for shoes, chemical plants, and car washes are all product layouts.
A manufacturing cell groups dissimilar machines to work on products that have similar shapes and processing requirements. A manufacturing cell is similar to a workcenter in that cells are designed to perform a specific set of processes, and it is similar to an assembly line in that the cells are dedicated to a limited range of products. (group technology refers to the parts classification and coding system used to specify machine types that go into a cell.)
In a project layout, the product (by virtue of its bulk or weight) remains at one location. Manufacturing equipment is moved to the product rather than vice versa. Construction sites and movie lots are examples of this format.
Many Manufacturing facilities present a combination of two layout types. For example, a given production area may be organized as a workcenter, while another area may be an assembly line, It is also common to find an entire plant arranged according to product flow-for example, a part fabrication area followed by subassembly area, with a final assembly area at the end of process. Different types of layouts may be used in each area, with workcenters used in fabrication, manufacturing cells in subassembly, and an assembly line used in final assembly.
Workcenters (Job Shops)
the most common approach to developing a workcenter layout is to arrange workcenters consisting of like processes in a way that optimizes their relative placement. For example, the Workcenters in a low-volume toy factory might consist of the shipping and receiving workcenters, the plastic molding and stamping workcenters, the metal forming workcenters, the sewing workcenters, and then sent to assembly workcenters where thay are put together. In many installation, optimal placement often means placing workcenters with large amounts of interdepartment traffic adjacent to one another.
Example 8.1: Workcenter layout Design
Suppose that we want to arrange the eight workcenters of a toy factory to minimize the interdepartmental material handling cost. Initially, let us make the simplifying assumption that all workcenters have the same amount of space (say, 40 feet by 40 feet) and that the building is 80 feet wide and 160 feet long (and thus compatible with the workcenters dimensions) the first things we would want to know are the nature of the flow between workcenters and how the material is transported. If the company has another factory that makes similar products, information about flow patterns might be abstracted form the records. On the other hand, if this is a new-product line, such information would have to come from routing sheets or from estimates by knowledgeable personal such as process or industrial engineering. Of cause, orders over the projected life of the proposed layout.
Let us assume that this information is available. We find that all material is transported in a standard-size crate by forklift truck, one crate to a truck (which constitutes one “load”). Now suppose that transportation costs are $1 extra for each workcenters in between. The expected loads between workcenters for first year of operation are tabulated in exhibit 8.1 ; available plant
8.2 building Dimensions and Workcenters
space is depicted in exhibit 8.2. Note that, in our example, diagonal moves are permitted
solution
Given this information, our first step is to illustrate the interworkcenters flow by a madel, such as Exhibit 8.3. this provider the basic layout pattern, which we will try to improve.
The second step is to determine the cost of this layout by multiplying the material handling cost by the number of loads moved between each pair of workcenters. Exhibit 8.4. present this information, which is derived as follows: The annual material handling cost between Workcenters 1 and 2 is $175 ($1*175 moves), $60 between Workcenter 1 and 7 ($3*20 moves), 240 between diagonal Workcenters 2 and 3 ($3*80), and so forth. (The “distances” are taken from Ehibit 8.2. or 8.3, not Exhibit 8.4.)
the third step is a seach for workcenter location changes that will reduce costs. On the basis of the graph and the cost matrix, it seems desirable to place Workcenters 1 and 6 closer together to reduce their high move-distance cost. However, this requires shifing several other workcenters, thereby affecting their move-distance costs and the total cost of the second solution. Exhibit 8.5.shows the revised layout resulting from relocating Workcenter 6 and an adjacent workcenter. (Workcenter 4 is arbitrarily selected for this purpose.) The revised cost matrix for the exchange, showing the cost changes, is given in exhibit 8.6. Note the total cost is $262 greater than in the initial solution. Clearly, boubling the distance between Workcenters 6 and 7 accounted for the major part of the cost increase. This points out the fact that, even in a small problem, it is rarely easy to decide the correct “obvious move” on the basis of casual inspection.
thur far, we have shown only one exchange among a large number of potential exchanges; in fact, for an eight-workcenter problem, there are 8! (or 40,320) possible arrangements. Therefore, the procedure we have employed would have only a remote possibility of achieving an optimal combination in a reasonable number of tries. Nor does our problem stop here.