Metal Finishing Guide Book


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Page 48 of 843

Finishing Lathe The finishing lathe is a device located in relation to the positioning mechanism. It allows a buff wheel to contact one of more surfaces of the workpiece at predetermined locations. Fixturing The workpiece fixture or tooling is used to position a part during the buffing cycle. Buffing machines can incorporate single or multiple fixtures. Fixtures can also be designed to automatically reorient a workpiece during the buffing cycle. Buffing fixtures are unique to each part being processed, although some may be adapted to an assortment of similarly shaped parts. The design of fixtures is extremely important. Unless a part can be fixtured properly at a reasonable cost, the economical utilization of finishing equipment cannot be justified. TYPES OF BUFFING MACHINES Fig. 11. Flap buff. Buffing machines fall within three broad categories: manual, semiautomatic, and fully automated. Manual Machines Manual buffing machines are used in low-volume applications and applications involving the buffing of extremely complex workpieces. Manual machines, when used in conjunction with the proper buff wheel and buffing compound, can be manipulated. Semiautomatic Machines Semiautomatic buffing machines are used in lower volume applications where a single finishing operation is performed on a variety of parts. Initial investment and fixturing and operating costs are low. Semiautomatic finishing machines can be used with a single- or double-end lathe. One operator can be employed to load, unload, and operate equipment. Semiautomatic machines hold the workpiece and present it to the buff wheel. A timed cycle controls dwell and retraction. Only one fixture is required for each machine for each type of part finished. Because the machine supports the part, operator fatigue is minimized. Various types of rotation also can be performed, depending on the type of semiautomatic machine selected. Production of semiautomatic buffing machines depends on part configuration and the degree of finishing required. By using a double-end jack with two semiautomatics, an operator can load one machine while the other is finishing a part. This can double production without increasing labor costs. Fully Automatic Machines Fully automatic machines are used in high-volume applications and where multiple surfaces of a workpiece must be finished. The two most common types of automatic buffing machines are rotary automatic and straight-line machines. 45

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