Metal Finishing Guide Book

2013

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close to the tank, 10 to 15 psig tank pressure may be sufficient, while 6 to 8 guns could require 40 to 45 psig tank pressure. A drum pumping system is inserted into a steel drum. The pump then transfers the compound through a fluid line or manifold that feeds the guns. Depending on the size of the system, the drum pump is operated at 10 to 40 psig air pressure. The spray gun is usually mounted in back of the buffing wheel so it will not interfere with the operator and is at a distance from the buffing wheel face so that complete coverage of the face of the buff is obtained with proper regulation of the spray gun. An opening in the dust collecting hood allows the compound to be sprayed from this position. Where buffing machines are totally enclosed, there are no hoods to interfere with the placement of the guns. The spray guns are actuated by air, which is released, in the case of manually operated lathes, by a foot valve that allows the buffer to keep both hands on the part being buffed. With automatic machines, solenoids allow the flow of air to operate the guns. The solenoids are connected to an electric timer where an on-time and an off-time can be set depending on the frequency of the compound needed on the buff face. A buffing head is a series of buffing wheels put together producing a buff face. This buff face can vary in length depending on contact time needed to do a certain job function. To adequately apply buffing compound to the wheel face, spray gun movers or multiple gun set-ups are usually employed. This allows the liquid compound to be applied across the entire buff wheel face. Spray guns will generally produce a fan of 10 to 12 inches per gun. In manual operations, the main advantage of the spray composition method is to save the operator time. He or she does not have to stop buffing to apply the cake of conventional solid composition. The operator can remain buffing and apply the liquid compound by the use of a foot peddle, hence less motion is used in applying the compound thus increasing productivity. In the case of automatic machines, the spray equipment replaces mechanical application. Shutdown time for regulation of mechanical applicators in most cases amounts to more than 25% of the theoretical maximum production time. This is almost entirely eliminated. The advantages of liquid spray buffing for both automatic and manual buffing procedures are as follows: 1. Optimum quantity of composition is readily controlled on the buff surface, the composition being supplied regularly rather than haphazardly. With buffing bars, an excess of composition is present when the first piece is buffed and an insufficient amount is present for the last piece of work before another application of the bar. If this were not true, the operator would handle the bar of composition more often than the work. Using the spray method, the desired amount of composition is present for each piece buffed. 2. With a deficiency of composition of buffing compound present, the buffing cloth is worn excessively. Spray compositions, eliminating this deficiency of coating, also eliminate this cause of unnecessary buff wear. 3. Solid buffing dirt is packed into the crevices of the work when an excess of buffing composition is present. The serious cleaning problem presented by this dirt is well known. As there need be no excess of composition using the spray method with properly formulated compositions, cleaning after buffing is greatly simplified. 4. Significant savings can be realized in compound consumption, because all the liquid composition brought to the lathe can be used. There are no nubbins left over. 28

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