Vibratory finishing: Tips for a successful technique

When it comes to finishing techniques, there are a lot of benefits to using a vibratory finishing process over barrel finishing. Not only can a vibratory finishing process finish a variety of parts, regardless of how fragile or large it is, that a barrel tumbler is incapable of finishing, but it also creates smoother surfaces and can abrade inside deep cavities or tubular parts. In addition, vibratory machines are easier to load and unload, will abrade or polish in less time, keep parts cleaner and maintain a better colour. They are also more easily automated or semi-automated, can process more parts than a barrel tumbler of the same size, can recirculate water and compound, cause less media wear in proportion to the amount of work performed, and permit fast inspection of parts. 

Indeed, vibratory finishing is a wise choice when it comes to finishing technique; however, there are a variety of factors that play a role in the success of the process.

• Media: It is recommended to use the largest possible media for fast abrasive action and best circulation of parts. To avoid issues of lodging, separation and parts damage, avoid using small stones (⅜ inches or less) at speeds lower than 1,600 RPM. Lower speeds will separate parts from media. It is also important to know that plastic media abrades faster when a minimum amount of water is employed and produces a better finish as the quantity of water is increased.
• Compound: Plastic media usually requires only a cleaning compound, while ceramic media requires occasional runs with abrasive compound to remove glaze. When using a heavy abrasive compound, do not recirculate water.
• Water: Use the minimum amount of water possible to achieve the best cutting action. If two different types of metals are being processed in the same tub, a heavy flow of water will prevent contamination. Small media generally will hold large amounts of water after it has been running for some time, reducing circulation. Abrasive action increases as water use decreases; however, surface finishes become worse. Large amounts of water are generally necessary for polishing.
• Frequency and amplitude: Fast speeds and small amplitudes produce the best surface finishes and should be used for polishing operations or internal deburring. Increasing the amplitude of the vibrator improves circulation of the parts and creates a more abrasive action to speed the cutting rate.
• Load size: Vibratory finishing systems work best when they are 75 to 90 per cent full. 
• Speed: The usual frequency is 1,700 vibrations per second. Once the speed drops much below this, the parts can sink to the bottom.

Vibratory finishing is one of the services offered by Vibra Finish, a Mississauga, Ont.-based company with more than 40 years of experience in manufacturing machinery and production finishing. Contact Vibra Finish to learn more. 

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