تويت
Total quality control implies the involvement of all members of an organization who can affect the quality of the output—a product or service. Its goal is to provide defect-free products 100 percent of the time, thus completely meeting the needs of the customer.
ISO 9000 is a quality assurance management system that is rapidly becoming the world standard for quality. The ISO 9000 series standards are a set of four individual, but related, international standards on quality management and quality assurance with one set of application guidelines. The system incorporates a comprehensive review process covering how companies design, produce, install, inspect, package, and market products. As a series of technical standards, ISO 9000 provides a three-way balance between internal audits, corrective action, and corporate management participation leading to the successful implementation of sound quality procedures.
The series of technical standards include four divisions:
· ISO 9001 This is the broadest standard covering procedures from purchasing to service of the sold product.
· ISO 9002 This is targeted toward standards related to processes and the assignment of subcontractors.
· ISO 9003 These technical standards apply to final inspection and test.
· ISO 9004 These standards apply to quality management systems.
Control Of Materials
Control of materials is critical to the smooth functioning of a plant. Raw materials and purchased parts must be on hand in the required quantities and at the time needed if production schedules are to be met. Unless management is speculating on raw materials, inventories should be at the lowest practicable level in order to minimize the capital invested and to reduce losses due to obsolescence, design changes, and deterioration. However, some minimum stock is essential if production is not to be delayed by lack of materials. The quantity for ordering replenishment stocks is determined by such factors as the lead time needed by the supplier, the reliability of the sources of supply in meeting promised delivery dates, the value of the materials, the cost of storage, and the risks of obsolescence or deterioration.
In many instances, plant management has the choice of manufacturing the components used in its product or procuring them from outside suppliers. Where suppliers specialize in certain components, they may be able to reach high-volume operations and produce more economically than can the individual users. Procurement from outside suppliers simplifies the manufacturing problem within a plant and permits management to concentrate on the phases where it has critical know-how. Extreme quality specifications may preclude the use of outside suppliers. Likewise, if components are in short supply, the user may be forced to manufacture the units to ensure an adequate supply.
The control of raw materials and component parts may involve considerable clerical detail and many critical decisions. Systems and formulas will routinize this function, and the computer has been able to eliminate all of the arithmetic and clerical activities in those plants that make use of its capability.
Shrinkage throughout the manufacturing process may be a significant factor in materials control, scheduling, and dispatching. Spoilage rates at various stages in the process require that excess quantities of raw materials and component parts be started into the process in order to produce the quantity of finished product desired. If the original order has not allowed for spoilage, supplementary orders will be necessary; these are usually on a rush basis and may seriously disrupt the plant schedule.
Production control seeks optimum lot sizes with minimum total cost and adequate inventory. Figure 17.1.4 shows the time pattern, under an ideal situation, for active inventory. With assumed fixed cost per unit of output (except for starting and storage costs) and with zero minimum inventory, the optimum lot size Q is given by √ah/B, where B 5 factor when storage space is reserved for maximum inventory 5 0.5[1 2 (d/r)](2s 1 ip); h 5 starting cost per lot (planning and setup); a 5 annual demand; s 5 annual cost of storage per unit of product; i 5 required yield on working capital; p 5 unit cost of production; d 5 daily demand; and r 5 daily rate of production during production period
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