Mass finishing refers to the finishing method on several parts simultaneously. Finishing involves the deburing, polishing, smoothing, cleaning and separating of parts. The finishing practice is carried out in a tumbling or vibratory machine, with finishing media, finishing compounds and the parts to be mass finished thrown in collectively.
Depending upon the nature of the parts that necessitate
mass finishing, the finishing machine, finishing media and
finishing compounds should be preferred. In tumbling machines, parts can be tumbled with or without media. These machines are well matched for aggressive cutting and producing glossy polishes; they are good for working on edges and rounded corners. Vibratory machines are right for shaking parts and media at a high rate of speed; they are safe for use on delicate parts and these machines provide very smooth finishes even in parts with holes and deep recesses. Natural media like
corn cob media and
walnut shell media are used when a soft abrasive effect is necessary. For heavier abrasive needs, man made media like plastic and ceramic media can be used.
When general deburring has to be done,
ceramic media is very useful. Hard ceramic media are used for light deburring and polishing. Softer ceramic media that have more abrasive ingredients are used when faster cutting is needed. If delicate parts are subjected to mass finishing, plastic media can be used to give very smooth finishes without much shine. Because plastic media are much lighter compared to ceramic media, they do not damage fragile parts. It is important to use the right amount of media for the quantity of parts being finished so that the parts remain safe. Finishing compounds are used to improve the efficiency of the finishing media being used and to advance finishing cycle times. Compounds could be alkaline or acidic; they are very successful in de-greasing and de-scaling and they also help in increasing cutting speeds.
Vibratory finishing machines are used in mass finishing of parts. They comprise of tubs called finishing or processing tubs that are vibrated at high speeds. The parts to be finished are put into the tub along with finishing media and when the tub vibrates, the parts and media graze against each other. This abrasive action produces the deburring of parts. The cutting action that happens in a vibratory system is defined and thorough. Compounds especially suited for vibratory systems can be used to offer better performance.
The
vibratory finishing machines run at high speeds and very short strokes. So, they are powerful; yet, because of the short strokes, they do not place any undue stress on the parts. They can therefore be carefully used on large parts like wing spans and landing struts. The vibratory finishing machines simply dislodge material from holes and recesses in parts like bores and can work very delicate parts without causing any harm. The vibratory machines can be automated very easily – a full automation can be completed for a finishing process that is sequential in nature. It can also be used as part of a large batch finishing process.
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