Manufacturing System Design Issues Accounting Essay

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The layout of the manufacturing plant has a close relationship with the output of products, mode of production and the products' changes. Production systems often is organized into job-shop production mode, blunt shop production mode and fixed production model, etc. Accordingly, manufacturing layout form is divided into the process, layout, product layout, fixed position layout [2].

The layout problem in manufacturing workshop is a very important and long-standing problem in industrial engineering research and practice. Long-term since, manufacturing layout has been regarded one of the most important and the most difficult design problems in the manufacturing industry, it requires to incorporate processing equipment, material handling equipment, passageway and any other manufacturing resources up reasonably and placed them in a limited space, which can be regarded as the process of organizational process. The production of automotive exhaust pipes is a kind of typical line operation process, so the choice of manufacturing layout will greatly depend whether the job shop can efficient run production.

Association of American modern layout puts forward four kinds of layout strategy [11]:

Distributed layout: It requires large fleet type unit be decomposed into smaller subunits. And distribute them throughout the workshop. In a highly dynamic environments, repeat configuration unit, this can help the units be visited from different positions of the workshop, thus improve logistics.

Modular layout: It means the machines which the working procedure subset in different process routes needs have to be grouped and arranged in a classic layout configuration, making transportation cost minimum. This kind of layout needs a hypothesis as in the short term, the product demand already known and stable.

(3) Reconfigurable layout: This is actually a multi-stage layout problem, obtained logistics fee at each production stage and reconstruction cost to decide the workshop layout for realizing cost minimum. This layout's realization depends on resource can be handling deft and easy to decorate.

(4) Agile layout: It is breaking classic layout design, operated with performance as a design indexes, and study out any type of layout. The method based on simulation and application of simulation optimization strategy.

This report is main discuss functional applicant in manufacturing and cellular manufacturing.

The functional manufacturing layout of the company have served the company for many years, and made a good performance. The company's automotive exhaust pipes manufacturing process includes loading material, baking and burning, unloading, separate water and oil, cooling, shot blast, brush, spraying, sintering, inspection and packing, eleven main steps.

Functional layout is a kind of traditional layout which uses traditional job shop procedures, like part family scheduling rules, under a variety of shop operating conditions. Functional layout is used in manufacturing, warehousing planning, building layout and many other aspects. Functional manufacturing layout used in job shop is deciding the layout of the production facilities by their functions through the production. In the production line, facilities with similar functions will be placed near each other. Another focus of functional manufacturing layout is the cohesion level of production or handling process. Facilities with high cohesion level will be placed near each other. The factories use the functional layout in manufacturing needs to install all equipments with one particular type in one area as different types of equipments in different areas [10].So in this condition, workers can be easily trained as they always use particular equipments and working in particular area and they can be easily managed.

The functional layout has been determined under the criterion of materials handling cost minimization [9]. The reduce of handling cost can be one important purpose of functional layout .As the facilities be placed with the principle of "put together when them have a similar function" or "put together when they have a similar handling method", workers can do the same kind of handling for different components and parts at the same time or at one time. As the workers always work with similar facilities, the efficiency of the production will rise with the growth of workers' experience; different types of facilities installed in different areas, they can be easily controlled and taken production performance evaluation.

As there are eleven procedures in the automotive exhaust pipes manufacturing, workers in the same job shop will work with different conditions, some process conditions are even contrary(like baking and burning, cooling). In order to avoid working procedure mutual interference, the conditions of the operation of procedures should be considered. The functional manufacturing layout can solve this problem perfect; when the job shop take the functional manufacturing layout, the performance of workers (or teams) can be easily effectively evaluated; when the equipments installed by their types and applications, if new equipments need to be installed, they are simple to be classified and placed.

The workflow under functional manufacturing layout production system in the company's job shop is as flow:

Loading materials is the first step, so the loading place should in the front of the conveyer and near the raw materials repertory, so workers can easily load the materials; Baking and burning is done through dry burning machine, which will send out a lot of heat, so these dry burning machines should be installed far away from the cooling machines to avoid premature cooling and they should placed as near the loading place as possible; unloading machines are just near the dry burning machines; water and oil separators also need a high working temperature(usually it is almost 80℃), so they also should be pay attention for the distance from the coolers; After separating water and oil there should be a certain distance of conveyer between the materials come into coolers; shot blasting machines are installed between coolers and brushing machines; bushing machines and spraying machines should placed nearby, as their functions are similar and have a really high cohesion level in production; sintering machines as they have a similar working condition with dry burning machines, so they should placed near each other; inspection and packing should done in the same place, at the end of the conveyer, as they are the last step of the production of automotive exhaust pipes. In order to finish all these steps under functional manufacturing layout, the conveyor belt should not be linear but be u-shaped or tortuous.

As to manage the workflow in functional manufacturing layout production system effectively, these facilities and worker should be divided into functional groups. These eleven production steps can be divided into five groups: loading material, baking and burning, unloading, separate water and oil, cooling will be composed the first group; shot blast will be the second group; bush and spraying compose the third group; sintering is the fourth group; inspection and packing will be composed the last group. This kind of grouping's main consideration is the cohesion level of production process and production environmental factor (like temperature). After grouping, a superintendent should be chosen from workers in each group to take charge of facilities and productions.

The inventory under the functional manufacturing system is always small. As under functional layout, the equipments have similar function are installed together, which provides a lot of flexibility [14], it doesn't requires huge amount of inventory to cope with the volatile market demand, especially some key components' inventory; the workers in each functional group take the charge of the raw materials they need, they decide the inventory and the outbound quantity of each time; the information system of inventory will take each functional group as a unit to hold the inventory information and give the orders to the suppliers; When the market demand produced fluctuations, the inventory maybe only needs a little change as the functional group can effective cope with fluctuations.

Cellular manufacturing is an important part of Lean Production. Lean Production (LP) is a kind of efficient enterprise management mode, which involves concept, organization, process, environment, management methods and management goal. [7]

Lean production is derived from Toyota Production System. During the 1990s, America did a lot of research and practice of lean manufacturing. Besides auto industry, more American business such as Boeing, Lockheed Martin, HP and many other big companies started to take lean production into use. In this process, the Japanese provided the basic thinking and method, with excellent practice proved lean production powerful vitality; American scholars' studies, the American enterprises, and even the U.S. government's researches and practice proved lean thought is scientific and effective for modern production and sublimate it into a kind of manufacturing philosophy, lean production grown from experience into theory, a new production method which gets a formally birth.

Lean Thinking (LT) refers to apply a variety of modern management techniques and methods, take the customer demand as the basis, so as to make full use of man as a fundamental, in order to realize effective distribution and rational use of enterprise's resources and get the goal of maximum for enterprises strive for economic benefits. Its core is creating as much value as possible with the least investments. [8]

Competitive forces in both domestic and global markets are challenging batch processing firms to become more efficient and, at the same time, to become more flexible (De Meyer et 1989) [5]. Cellular manufacturing is a layout organization that has been used to meet this challenge. Cellular manufacturing system is based on the group technology, which is the key for setup reduction.

Mitrofanov founded the group technology in 1959, it is a method to identify and explore similarities between a group of target characteristic and its application fields including classification and coding, the processing plan, components ethnic group and machine manufacturing unit design, grouping technology layout and grouping plan etc.

Cellular Manufacturing is using the group technology organization machine unit to process a group of components. Flexible manufacturing, computer-integrated manufacturing, just-in-time production are common examples of automation units. [13]

Cellular Manufacturing mainly includes: (1) cell formation by grouping parts into part families and machines into cells (components coding), (2) layout of the cells within the shop floor (i.e. (manufacturing cell constructing) [20] (3) the cell layout. Besides, it also needs reasonable work plan for short-term production, the flow control and efficient organization structure plan and arrangement. [12]

In the traditional functional production mode, machining parts need to be transmitted in the whole workshop, making the material traffic volume increased; Due to the diversity of production, causing equipment adjust time increased; Because of the huge number of varieties and resource sharing, causing difficulties increased in production plan; Meanwhile, operation of priority is difficult to control, production supervisor hold a large stock of spare parts to ensure workshop working normally and effectively. Cellular Manufacturing system put individual parts manufacturing in one unit of production, thus material control and operation plans have become much more simple; In Cellular Manufacturing system, operating worker have to be comprehensive trained, which makes even only one worker can complete the whole operation process of production from start to finish; In addition, the similarity product production reduced equipment adjust time, thus reduced the entire product production cycle.

To sum up, the main advantages of Cellular Manufacturing system includes:

(1)Reduce total production time

(2) Reduce the inventory of work -process production

(3) Improve the quality of components or the products

(4) Reduce customer order response time

(5) Reduce the time of transmission of materials in job shop

The advantage of Cellular Manufacturing system is obvious, but at the same time, it also brought some defects. On the one hand, Cellular Manufacturing system bring a great of limitation to the production line of flexible, so static product combination and the weight result from trying to hold the balance between units lead to increased production cycle; On the other hand, once the production which used to be produced changed, existing unit structure will fail. Although there are many assumptions assume products demand in a relatively long period is fixed, but in fact in the dynamic environment of market economy, the product update quickly.

As long as the product demand became diversity day by day, in machinery manufacturing system, diversified, small batch production is becoming more and more important and holds a big proportion. As such system has a greater flexibility, but its production efficiency is low and is difficult for management. In order to improve the production efficiency of production system, people put forward several of new mode of modern manufacturing, such as Lean Production Lean Production System, autonomous manufacturing island, Cellular Manufacturing System, etc. These systems have the structure characteristic of distribution, by using system production technology, remarkably raised the diversified, sheet small batch production flexibility and efficiency.

Because of the application scope of Cellular Manufacturing System is different, it also has different classification, from logistics perspective, it can be divided into four categories:

(1) Virtual group cell: it means processing the similar components by group, but make the design by functional arrangement, just take the machine group corresponding to parts families as a logical unit, by using this dynamic production management structure, production flexibility can be improved. This virtual unit faults is logistics route doesn't shortened, management is more complex, but the management problem will be easily solved as the computer management techniques improves.

(2)Quasi group cell :it refers to the comparatively extensive cell organization, which includes two types: (1) when some factory product type always have to be transformed or market supply and marketing situation is difficult to estimated, the cell can be design a little bigger, components family similarity level can be lower. On one hand, we can save design time, reduce design difficulty level; On the other hand made it more possible to be adapted to the development in the future, (2) open cell. Some parts can be flowing from unit to unit, or allow some machine be shared by some units. This can achieve balance machine load, solve some of the difficulties in constructing cell and as far as possible obtain benefits created by group processing

(3)Closed group cell: this is a kind of typical group cell. All machines a category of components need are concentrated in one working place and finish the machining from blank to finished products.

(4) Pipelined group cell: this is also a kind of closed group cell, it requires the product components in processing have a consistent flow direction, but it does not require the strict production tempo.

Cellular Manufacturing System differentiates by automatic level includes the following five categories:

(1) General machine (including CNC machine): can not only be formed by single machine which can complete a single process, but also can group with some other machine as a component process cell.

(2) Processing center: it is a numerical control machine which can automatically change the machine tool and work piece, can perform multiple processes, and can complete almost all of the processing for many parts by a fixture. In the parts families selected by machine features, often needs to be divided into parts of tooling clan, so as to improve production efficiency.

(3) Flexible manufacturing cell (FMC): on the basis of machining center adds automatic loading and unloading work pieces storage function, which can realize library for a long time without humanization work.

(4) Flexible production line (FML): can be regarded as a highly automatic pipelined group cell form, used for large-scale components production or on the components of the occasion that similarity between them is high.

(5) Flexible manufacturing systems (FMS); it is composed by multiple numerical control processing machine or machining center equipped with automatic consisting. It can adjust and control information flow and logistics by materials handling system and storage system, the whole cell system is highly automatic, flexibility, so it can adapt to the kind of the bigger components processing. Required adjust time is very short, but the whole system needs huge investment. FMS can be regarded as a group cell of automation form.

Cellular manufacturing requires similar parts be classified into part families and dissimilar machines are assigned into machine cells in order to exploit the cost-effectiveness of mass production and flexibility of job shop manufacturing. As cellular manufacturing can realize reduction in setup time[17], reduction in throughput time, reduction in work-in-process inventories, reduction in material handling costs, better quality and production control, incrementing flexibility etc.[6] With the corresponding cellular layout effectively simplifies the workflow, making the material transport maintained in a small range [3].

But since the cells are designed for a specific group of parts family, which will greatly reduce the workshop of flexible. So when the cellular layout be designed, there is one hypothesis, the product demand can be forecasted and it is stable [4].

If the company takes the cellular manufacture system into use, the work flow of the production of automotive exhaust pipes need some change and the production units also need to be reconstructed.

First of all, the components needed in the eleven production steps should be coded and the code information will be saved in the information system, this can make the production more systematic. Then the manufacturing cell should be constructed. For automobile exhaust pipes production, there should be three kinds of manufacturing cell: (1) basic manufacturing cell, processing cell and assembly and inspection cell. Basic manufacturing cell has five sub cells; they are responsible for the manufacturing of four kinds of basic components of automotive exhaust pipes: exhaust tubes former vent-pipe posterior vent-pipe, exhaust tail pipe and related spare components (like silencer). Dry burning machines, water and oil separators, shot blasting and cooling machines will be installed in this manufacturing cell.

Processing cell responsible for separate water and oil, brush, spraying and sintering of the components, the processing link have not finished by basic manufacturing cell , this kind of cell will get brushing machines spraying machines ; assembly and inspection cell will done the assembly work and inspection work, after that a complete automobile exhaust pipes come out.

The core problem that manufacturing cells layout should take into account is how to occupy as little space as possible, while reducing the handling time between the work piece. In contrast, the space allocation of straight line-shaped conveyors make the space which even without action also become workspace, it is a waste of the limited space. Linear structure with equipment and transmission equipments as the main line also needs a manipulator activity area and channels on either side of the liner conveyors, these areas are separated and barely able to be public. So the layout of these manufacturing cells should be along the u-shaped conveyors; each manufacturing cell should have a superintendent to manage the production and these still need several technicians to maintain equipments and inspect equipments; the whole job shop will be controlled and managed through the computer system, in order to keep the manufacturing quality.

As cellular manufacturing need more accurate prediction of market demand and need some inventory for the components of machines (machine wear very quickly when they always manufacture day by day), so the inventory is always kept at a high level. But the powerful computer information system can help workers manage the inventory, which is connected with each manufacturing cell.

From the discussion above shows, functional layout system and cellular manufacturing both have its advantages and disadvantages. To summarize and complement, they are showed in the table1 and table 2:

Functional Layout

Cellular Manufacturing





(1)worker can be easily trained and managed

(2) has great deal of flexibility

(3)saving handling time

(4)save working space

(5) Suitable for mass customization

(1)Hard to meet the changeable market demand

(2)hard to track down work-in-progress(WIP)

(3)hard to correct manufacturing mistake[15]

(4)high inventory cost

(1)can wonderful combined with time-based manufacturing[16]

(2)can adapt to the multi-species small batch demand

(3)saving set up time

(4)effectively simplifies the workflow

(5)short queue time[18]

(1)high level inventory

(2)easy to cause the waste of space

(3) may need huge investment

Table 1 Table 2

Due to development of technology and diversification of customer requirement,period of product life-span become shorter and shorter and production development tends to be small quantity and excessive variety. As cellular manufacturing still have some limitations and disadvantages, the company choose is as the new manufacturing system is the better way. Because the manufacturing environment depends which is the better one. Cellular Manufacturing (CM) is an approach that can be used to enhance both flexibility and efficiency in today's most production environment. [19]

Today's market demand for cars is very changeable, automobile companies always take out range of automobiles and different cars need different kinds of automotive exhaust pipes, so the production system have to fulfill the changeable market; Just in Time (JIT) production is an important requirement for modern manufacture, by use information techniques cellular manufacturing can better fulfill JIT than functional[16].

What's more, some limitations of cellular manufacturing system can be broken by modern management: high level of inventory can be solved by VMI ( Vendor Managed Inventory), which can great reduce the inventory stress of the company; the development of the engineering technology have a certain degree of reduction on investment costs also.

As a result, in the long run, Cellular manufacturing is a better choice.

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