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An analysis on operation
This can be due to a lack of knowledge about cost and thought that it is necessary to specify closer tolerances and specifications than are actual needed to have the manufacturing departments produce to the actual required tolerances range. Methods analysts should be well versed in the details of cost and should be fully aware of what unnecessary close tolerance and/or rejects can do to the selling price. If designers are being needlessly tight in establishing tolerances and specifications, management should embark on a training program clearly presenting the economies of specifications. Also, consideration should be given to the extra cost of products because of scrap and/or rejects. Today, there is only one way that a company can be competitive: all part in every product must be produced to the precise dimensions given on the drawings. Developing quality products in a manner that actually reduces costs is a major tenet of the approach to quality instituted by Taguchi(1986). This approach involves combining engineering and statistical methods to achieve improvement in cost and quality by optimizing product design and manufacturing methods. One manufacture’s drawings called for a 0.0005-inch tolerance on a shoulder ring for a DC motor shaft. The original specification called for a 1.8105to 1.8110-inch tolerance on the inside diameter. This close tolerance was deemed necessary because the shoulder ring was shrunk onto the motor shaft. Investigation revealed that a 0.003-inch tolerance was adequate for the shrink fit. The drawing was immediately changed to specify a 1.809 to 1.812-inch inside diameter. This change meant that a reaming operation was eliminated because someone questioned the absolute necessity of a close tolerance. Analysts must also be alert for too liberal, as well as too restrictive, specifications. Closing up a tolerance often facilitates an assembly operation or some other subsequent step. This may be economically sound, even though it may increase the time required to perform a preassembly operation. In this connection, analysts should recognize that the overall tolerance is equal to the square root of the sum of the square of the individual tolerances comprising the overall tolerance. Analysts should also take into consideration the ideal inspection procedure. Inspection is a verification of quality, quality, dimensions, and performance. Such inspections can usually be performed by a variety of techniques: spot inspection, lot-by-lot inspection, or 100 percent inspection. Spot inspection is a periodic check to assure that established standards are being realized. For example, a nonprecision blanking and piercing operation set up on a punch press should have a spot inspection to assure the maintenance of size and the absence of burrs. As the die begins to wear or as deficiencies in the material being worked being to show up, the spot inspection would catch the trouble in time to make the necessary changes, without generating an appreciable number of rejects. Lot-by-lot inspection is a sampling procedure in which a sample is examined to determine the quality of the production run or lot. The size of the sample depends on the allowable percentage of defective unity and the size of the production lot being checked. A 100 percent inspection involves inspecting every unit of production and rejecting the defective units. However, experience has shown that this type of inspection does not assure a perfect product. The monotony of screening tends to create fatigue, thus lowering operator attention. The inspector may pass some defective parts, or reject good parts. Because a perfect product is not assured under 100 percent inspection, acceptable quality may be realized by the considerably more economical methods of lot-by-lot or spot inspection. For example, in one shop, a certain automatic polishing operation had a normal rejection quality of 1 percent. Subjecting each lot of polished goods to 100 percent inspection would have been quite expensive. Management therefore decided, at an appreciable saving, to consider 1 percent the allowable percentage defective, even though this quality of defective material would go through to plating and finishing, only to be thrown out in the final inspection before shipment. By investigating tolerances and specification and taking action when desirable, the company can reduce the costs of inspection, minimize scrap, diaminish repair costs, and keep quality high. 4 MATERIAL One of the first questions an engineer considers when designing a new product is,” what material shall be used?” Since choosing the correct material may be difficult because of the great variety available, it is often more practical to incorporate a better and more economical material into an existing design. Methods analysts should consider the following possibilities for the direct and indirect materials utilized in a process: 1.	Finding a less expensive material. 2.	Finding materials that are easier to process. 3.	Using materials more economically. 4.	Using salvage materials. 5.	Using supplies and tools more economically. 6.	Standardizing materials 7.	Finding the best vendor from the standpoint of price and vendor stocking. FINDING A LESS EXPENSIVE MATERIAL Industry is continually developing new processes for producing and refining materials. Monthly publications summarize the approximate cost per pound of steel sheets, bars, and plates, and the cost of cast iron, cast steel, cast aluminum, cast bronze, thermoplastic and thermosetting resins, and other basic materials. These costs can be used as anchor points from which to judge the application of new materials. A material that was not competitive in price yesterday may be very competitive today. One company used Micarta spacer bars between the windings of transformer coils. Separating the windings permitted the circulation of air between the windings. An investigation revealed that glass tubing could be substituted for the Micarta bars at a considerable savings. The glass tubing was less expensive, and it met service requirements better because the glass could withstand higher temperature. Furthermore, the hollow tubing permitted more air circulation than did the solid Micarta bars. Another company also used a less expensive material that still met service requirements in the production of distribution transformers. Originally ,a porcelain plate separated and held the wire leads coming out of the transformers. The company found that a fullerboard plate stood up just as well in service, yet was considerably less expensive. Methods analysts should remember that items such as valves, relays, air cylinders, transformers pipe fittings, beatings, couplings, chains, hinges, hardware, and motors can usually be purchased at less cost than they can be manufactured. FINDING A MATERIAL THAT IS EASIER TO PROCESS Some materials are usually more readily processed than others. Referring to bandbook data on the physical properties usually helps analysts discern which material will react most favorably to the processes to which it must be subjected in its conversion from raw material to finished product. For example, machinability varies inversely with hardness, and hardness usually varies directly with strength. Today the most versatile material is reinforced composites. Resin transfer molding can produce more complex parts advantageously from the standpoint of quality and production rate than most other metal and plastic forming procedures. Thus, by specifying a plastic made of reinforcing carbon fibers and epoxy, the analyst can substitute a composite for a metal part, at both a quality and a cost advantage. USING MATERIAL MORE ECONOMICALLY The possibility of using material more economically is a fertile field for analysts. If the ratio of scrap material to that actually going into the product is high, then greater utilization should be examined. For example, if the material put into a plastic compression mold is preweighed, it may be possible to use only the exact amount require to fill the cavity; excessive flash can also be eliminated. In another example, the production of stampings from sheet metal, if the skeleton seems to contain an undue amount of scrap material, the analyst would consider going to the next higher standard width of material and utilizing a multiple die. If a multiple die is used, the cuts should be carefully arranged to assure maximum utilization of material. Many world-class manufacturers are finding it not only desirable, but absolutely necessary, to take weight out of existing designs. For example, the average 1997 automobile must lost about 1200 pounds to meet an 80-mile-per-gallon fuel efficiency rating for the next generation of automobiles. This goal will require functional designers and methods analysts to reengineer many automobile components. For example, we can expect to see the cladding of stainless steel to high-strength aluminum to replace chrome-plated steel bumpers, as well as a much greater use of plastics and structural composites to replace ferrous components. Similar weight reduction is taking place on many other well-known products, such as washing machines, video cameras, VCRs, suitcases, and TV sets. Today, powder coating is a proven technology that is replacing many other methods of metal finishing. Coating powders are finely divided particles of organic polymers (acrylic, epoxy, polyester, or blends) that usually contain pigments, fillers, and additives. Powder coating is the application of a suitable formulation to a substrate, which are then fused into a continuous film by the application of heat, forming a protective and decorative finish. In view of current environmental regulations affecting traditional metal finishing operations, such as electroplating and wet painting, powder coating offers a safer and cleaner environment. The methodology can also provide a durable, attractive, cost-effective finish foe metal surface used in many commercial products, such as wire shelving, control boxes, trailer hitches, water meters, handrails, boat racks, office partitions, and snow shovels. USING SALVAGE MATERIAL Materials can often be salvaged, rather than sold as scrap. Byproducts from an unworked portion or scrap section can sometimes offer possibilities for saving. For example, one manufacturer of stainless steel cooling cabinets had 4-to-8-inch-wide sections left as cuttings on the shear. An analysis identified electric light switchplate covers as a possible byproduct. Another manufacturer, after salvaging the steel insert from defective bonded rubber ringer rolls, was able to utilize the hollow, cylindrical rubber rolls as bumpers for protecting moored motorboats and sailboats. If it is not possible to develop a byproduct, then scrap materials should be separated to obtain top prices. Separate bins should be provided for tool steel, steel, brass, copper, and aluminum. Chip-haulers and floor sweepers should specifically be instructed to keep the scrap segregated. For electric light bulbs, for example, the brass socket would be stored in one area, and after the glass bulb is broken and disposed of, the tungsten filament is removed and stored separately for greatest residual value. Many companies save wooden boxes from incoming shipments, and then saw the boards to standard lengths for use in making smaller boxes for outgoing shipments. This practice is usually economical, and it is now being followed by many large industries, as well as by service maintenance centers. There are also a few interesting examples from the food industry. A manufacturer of tofu processes the beans, centrifuges out the edible protein material, and leaves behind tons of waster fiber. Rather than paying to haul it away to a landfill, the manufacturer gives it away to local farmers for hog feed, as long as they come and pick it up. Similarly, meatpackers utilize everything from a cow: hiders, bones, even blood, all except the ”moo”. USING SUPPLIES AND TOOLS FULLY Management should encourage full use of all shop supplies. One manufacturer of dairy equipment introduced the policy that no new welding rod was to be distributed to workers without the return of old tips under 2 inches long. The cost of welding rods was reduced immediately by more than 15 percent. Brazing or welding is usually the most economical way to repair expensive cutting tools, such as broaches, special from tools, and milling cutters. If it has been company practice to discard broken tools of this nature, the analyst should investigate the potential saving of a tool salvage program. Analysts can also find a use for the unknown portions of grinding wheels, emery disks, and so forth. Also, items such as gloves and rags should not be discarded simply because they are soiled. Storing dirty items and then laundering them is less expensive than replacing them. Methods analysts can make a real contribution to a company by simply minimizing waste, which today claims about one-fifth of our material. STANDARDIZING MATERIAL Methods analysts should always be alert to the possibility of standardizing materials. They must minimize the sizes, shapes, grades, and so on of each material utilized in the production and assembly processes. The typical economies resulting from reductions in the sizes and grades of the materials employed include the following. Purchase orders are used for larger amounts, which are almost always less expensive per unit. Inventories are smaller, since less material must be maintained as a reserve. Fewer entries need to be made in storage records. Fewer invoices need to be paid. Fewer spaces are needed to house materials in the storeroom. Sampling inspection reduces the total number of parts inspected. Fewer price questions and purchase orders are needed. The standardization of materials, like other methods improvement techniques, is a continuing process. It requires the continual cooperation of the design, production planning, and purchasing departments. FINDING THE BEST VENDOR For the vast majority of materials, supplies and parts, numerous suppliers will quote different prices, quality levels, delivery times, and willingness to hold inventories. It is usually the responsibility of the purchasing department to locate the most favorable supplier. However, the best supplier last year may not be the best one now. The methods analyst should encourage the purchasing department to rebid the highest-cost materials, supplies, and parts to obtain better prices and superior quality and to increase vendor stocking, where the vendors agree to hold inventories for their customers. It is not unusual for methods analysts to achieve a 10 percent reduction in the cost of materials and a 15 percent reduction in inventories by regularly pursuing this approach through their purchasing departments.