by Dave Davidson |http://about.me/dave.davidson | dryfinish@gmail.com | 509.230.6821

The honest answer is that in some cases and with some applications you might.  It’s unavoidable.  However, a great many parts are being hand-deburred currently because the conventional mass finishing method(s) being used in the shop are incapable of exerting sufficient abrasive media pressure against edges and surfaces to remove unwanted and undesirable projections, sharp edges and burrs.  In many cases, it is possible to minimize hand-deburring procedures by utilizing a higher energy method that makes use of centrifugal force to propel abrasive material and rub away at edges and surfaces with dramatically more strength.  This is especially true of smaller part geometries which limit access to features to larger abrasive preformed media.  In a centrifugal system, much smaller dimensioned abrasive media can also be utilized and still have sufficient abrasive power to meet edge and surface finish requirements.

Additionally, in many cases, depending on the depth of tooling marks, cutter paths, and step overs it is possible to blend in the irregular surfaces left behind by many machining operations. (There are limitations, these methods are not going to correct surfaces left behind by excessively coarse or rough machining.  Nor will it blend in surfaces left by abusive machining, or dull or worn tooling).

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BEFORE (upper) and AFTER (lower) example of clearing machining marks and step overs in titanium.  The parts shown above are titanium test coupon specimens that were surface machined with a fly-cutter operation,  Centrifugal Isotropic Finishing was used to deburr, edge-contour and smooth surfaces in a hands-free finishing operation.  Other mass finishing methods would typically require some degree of hand-grinding or sanding to prepare these surfaces prior to processing in a conventional barrel or vibratory finishing operation.
High speed centrifugal finishing in the lean context at MacKay Manufacturing, Spokane, WA
BEFORE (right) and AFTER (left) medical devices such as these are used within body cavities during surgical procedures.  Extremely smooth surfaces are required because of the medical application.  Centrifugal Isotropic Finishing is used in this application to automate the smoothing and blending of machine marks in a hands-free operation.  Prior to the introduction of centrifugal technologies, these parts required manual intervention to produce the smooth surfaces required.

Some burrs that are heavily rooted and be resistant to barrel and vibratory finishing technologies and require a method the delivers higher force loads on the media in order to remove the burr cleanly.  The above BEFORE (left) and AFTER (right) example is a good case in point. Prior to use of Centrifugal Isotropic Finishing hand deburring was required.

In some cases, rough surfaces left behind from precision investment castings or forgings can be smoothed and polished in an automated hands-free operation.  A multi-step centrifugal procedure was used on these parts to produce polished surfaces 

 

small titanium parts finishing
These titanium medical splints that were previously manually finished are now centrifugally finished in a hands-free operation.  The centrifugal high force pressure makes it possible for very small media to process part edge features effectively while producing lower microinch Ra finishes simultaneously.

 

Below is some process video footage demonstrations of high-speed centrifugal isotropic finishing.  These automated edge and surface finishing methods are capable of producing very refined low micro-inch surfaces that can improve functional part performance and service life.

Centrifugal barrel (isotropic) finishing

Centrifugal barrel finishing (CBF) is a high-energy finishing method, which has come into widespread acceptance in the last few decades . Although not nearly as universal in application as vibratory finishing, a long list of important CBF applications have been developed in the last few decades.

Similar in some respects to barrel finishing, in that a drum-type container is partially filled with media and set in motion to create a sliding action of the contents, CBF is different from other finishing methods in some significant ways. Among these are the high pressures developed in terms of media contact with parts, the unique sliding action induced by rotational and centrifugal forces, and accelerated abrading or finishing action. As is true with other high energy processes, because time cycles are much abbreviated, surface finishes can be developed in minutes, which might tie up conventional equipment for many hours.

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Centrifugal Barrel Finishing principles – high-intensity finishing is performed with barrels mounted on the periphery of a turret. The turret rotates providing the bulk of the centrifugal action, the barrels counter-rotate to provide the sliding abrasive action on parts.

The principle behind CBF is relatively straightforward. Opposing barrels or drums are positioned circumferentially on a turret. (Most systems have either two or four barrels mounted on the turret; some manufacturers favor a vertical and others a horizontal orientation for the turret.) As the turret rotates at high speed, the barrels are counter-rotated, creating very high G-forces or pressures, as well as considerable media sliding action within the drums. Pressures as high as 50 Gs have been claimed for some equipment. The more standard equipment types range in size from 1 ft3 (30 L) to 10 ft3, although much larger equipment has been built for some applications.

Media used in these types of processes tend to be a great deal smaller than the common sizes chosen for the barrel and vibratory processes. The smaller media, in such a high-pressure environment, are capable of performing much more work than would be the case in lower energy equipment. They also enhance access to all areas of the part and contribute to the ability of the equipment to develop very fine finishes. In addition to the ability to produce meaningful surface finish effects rapidly, and to produce fine finishes, CBF has the ability to impart compressive stress into critical parts that require extended metal fatigue resistance. Small and more delicate parts can also be processed with confidence, as the unique sliding action of the process seems to hold parts in position relative to each other, and there is generally little difficulty experienced with part impingement. Dry process media can be used in certain types of equipment and is used for light deburring, polishing, and producing very refined isotropic super-finishes.

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