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Process of Manufacture

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  • Process of Manufacture

    اضغط على الصورة لعرض أكبر.   الإسم:	image_2091.jpg  مشاهدات:	3  الحجم:	116.3 كيلوبايت  الهوية:	224326
    Improvement in the process of manufacture is perhaps the salient point, and possible improvements deserving special consideration include (1) mechanizing manual operations, (2) utilizing more efficient facilities on mechanical operations, (3) operating mechanical facilities more efficiently, and (4) when changing an operation, considering the possible effects on subsequent operations. There are almost always many ways to produce a given design, and better production methods are continually being developed. By systematically questioning and investigating the manufacturing process, more effective methods will be developed.

    Setup and tools

    have such a dominant influence on economics that consideration must include quantity to be produced, chance for repeat business, amount of labor involved, delivery requirements of the customer, and capital needed to develop the setup and provide the tools. Specifically, consideration should be given to reducing the setup time by better planning in production control, designing tooling for the fullcapacity utilization of the production facility, and introducing more efficient tooling such as quick-acting clamps and multiple part orientations.

    Good working conditions are an integral part of an optimum process as they improve the safety record, reduce absenteeism and tardiness, raise employee morale, improve public relations, and increase production.

    Consideration should include

    (1) improved lighting; (2) controlled temperature; (3) adequate ventilation; (4) sound control; (5) promotion of orderliness, cleanliness, and good housekeeping; (6) arrangement for immediate disposal of irritating and harmful dusts, fumes, gases, and fogs; (7) provision of guards at nip points and points of power transmission; (8) installation of personnel-protection equipment; and (9) sponsorship and enforcement of a well-formulated first aid and safety program.

    Materials Handling The handling of materials is an essential part of each operation and frequently consumes the major share of the time. Materials handling adds nothing but cost to the product and increased throughput time. It should accordingly be reduced. When analyzing the flow process chart, keep in mind that the best-handled part is the least manually handled part. Whether distances of moves are large or small, points to be considered for reduction of time and energy spent in handling materials are

    (1) reduction of time spent in picking up material, (2) maximum use of mechanical handling equipment, (3) better use of existing handling facilities, (4) greater care in the handling of materials.

    Plant Layout Good process design requires good plant layout. This involves development of the workplace so that the location of the equipment introduces low throughput time and maximum economy during the manufacturing process. In general, plant layouts represent one or a combination of (1) product, or straight-line, layouts, and (2) process, or functional, arrangements. In the straight-line layout, machinery is located so the flow from one operation to the next is minimized for any product class. To avoid temporary storages between facilities and excess in-processing inventories there needs to be a balance in the number of facilities of each type. Process, or functional, layout is the grouping of similar facilities, e.g., all turret lathes in one section, department, or building.

    The principal advantage of product grouping is lower materials-handling costs since distances moved are minimized. The major disadvantages are:

    1. Since a broad variety of occupations are represented in a small area, employee discontent can readily be fostered.
    2. Unlike facilities grouped together result in operator training becoming more difficult since no experienced operator on a given facility may be located in the immediate area to train new employees.
    3. The problem of finding competent supervisors is increased due to the variety of facilities and jobs to be supervised.
    4. Greater initial investment is required because of duplicate service lines such as air, water, gas, oil, and power lines.
    5. The arrangement of facilities tends to give a casual observer the thought that disorder prevails. Thus it is more difficult to promote good housekeeping.

    In general, the disadvantages of product grouping are more than offset by the advantage of low handling cost and lower throughput time.

    Process, or functional, layout gives an appearance of neatness and orderliness and, consequently, tends to promote good housekeeping; new workers can be trained more readily, and it is easier to obtain experienced supervision since the requirements of supervising like facilities are not so arduous. The obvious disadvantages of process grouping are the possibilities of long moves and of backtracking on jobs that require a series of operations on diversified facilities.

    In planning the process, important points to be considered are:

    (1) For straight-line mass production, material laid aside should be in position for the next operation. (2) For diversified production, the layout should permit short moves and deliveries and the material should be convenient to the operator. (3) For multiple-machine operations, equipment should be grouped around the operator. (4) For efficient stacking, storage areas should be arranged to minimize searching and rehandling. (5) For better worker efficiency, service centers should be located close to production areas. (6) Throughput time is always a major consideration. Scheduling should be well-planned so in-process inventory is kept to minimum levels yet is high enough so that production facilities are not shut down because of lack of material and throughput time is controlled.

    Principles of Motion Economy The last of the primary approaches to process design is the analysis of the flow chart for the incorporation of basic principles of motion economy.

    When studying work performed at any work station, the engineer should ask:

    (1) Are both hands working at the same time and in opposite, symmetrical directions? (2) Is each hand going through as few motions as possible? (3) Is the workplace arranged so that long reaches are avoided? (4) Are both hands being used effectively, with neither being used as a holding device? In the event that ‘‘no’’ is the answer to any of these questions, then the work station should be altered to incorporate improvements related to motion economy

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