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Media Selection

MEDIA GUIDELINES FOR VIBRATORY DEBURRING/POLISHING EQUIPMENT
MEDIA SELECTION | MEDIA GRADES | APPLICATIONS | SHAPES 
LIQUID CHEMICAL COMPOUNDS 

SELECTION

All material removal processes are called "cut down operations" and use abrasive media, water, and chemical compounds. Material removal is accomplished by the media grinding against the work piece, modifying its surface and removing excess burrs or non-parent material. In this process, the media itself also breaks down. Therefore, it too must be checked periodically for its size so it does not get stuck in the pieces to be worked.

Material removal processes using this media are called wet processes because they need liquid to lubricate and remove debris. Abrasive deburring media can consist of preformed shapes, random irregular irregular shapes and different sizes of aluminum oxide, silicon carbide, sands, etc. However, because irregular sizes tend to get stuck in parts, most deburring media in use is a man made preform shape. These shapes consist of a matrix of abrasive grit and a bonding agent of either ceramic or plastic compounds. The speed and surface finish of the finished part depends on the size of the abrasive grit and the bonding compound that holds the shape together. The faster the bond breaks down and exposes new abrasive the faster the material removal process, Ceramic abrasive media is primarily used to deburr ferrous matal parts and plastic media is used to deburr non-ferrous parts.


Burnishing medias are not considered abrasive, but achieve some surface and edge modification through a rolling or lapping type action combined with heavy density and weight Any material removal is accomplished by flexing and/or metal fatigue. Primarily, burnishing medias are used to brighten the work piece as a secondary type operation or step. Care should be taken where close tolerances and/or distortion may be a problem. Also, this media may work harden and stress relieve the finished worked pieces.

Organic medias can be used to deburr as well as polish materials. If you have any concerns or problems whatsoever about chemicals, pollution, the environment, or EPA, then this is the way to go. Unlike previously mentioned medias which all use water and a safe liquid chemical compound, organic media is normally run dry and requires no special precautions for disposal of spent materials. On the other hand, because of their specific gravity/weight, they also require the greatest amount of processing time. Then again, they also achieve the best polish finish of any media in use today with vibratory equipment.

All finished parts/materials, have an existing outside appearance and/or measurable surface variation known as RMS (Root Mean Square) which is measured by a profilometer. The lower the number, the finer the finish. Typically, most common mill bar and sheet stock measure around 35 RMS, but castings usually exceed that number. Material hardness can produce variations in processing times and finishes; therefore, in the following application information there are references to a range of expected RMS finishes and approximate time cycles.

The standard approach to deburring and/or surface finishes, is to get rid of these excess variations in the fastest, easiest, and most effective way possible. With reference to media only, this means you want to select the largest coarsest media and matrix that will not bend or distort your parts, but will also be capable of reaching all the areas that have to worked. That also means that the fastest way to accomplish the smoothest finish is to use steps, rather than to start out with the finest media possible.

For more information, please refer to our step processing kits. These are the basic parameters for media selection. Detailed information as follows:

GRADES

For ease and simplicity, Nova Finishing Systems, Inc, has preselected three categories of cut down media in both ceramic and plastic compositions. These self explanatory terms state the general characteristics of the media and internal grain sizes.

Burnishing medias come in two basic compositions of steel and porcelain. The latter being the finest grade of ceramic media. There are no grade classifications by grain sizes but their differences are determined by their physical size and specific gravity or weight. Organics are also classified by size and specific gravity, but can be combined with additive compounds that do have grades; therefore, characteristics are similar to both grain size and specific gravity.*

* The estimated times and finishes shown are based upon step processing rather than a one step operation. That means that to achieve the stated results shown in medium and fine, you must start with the results of the previous coarse or medium operation.

APPLICATIONS

Ceramic Media -- Series 30000

Recommended for heavy deburring or material removal on castings, machined ferrous metals, stainless steel, and flexible synthetics. Comes in three grades: 

Coarse

A fast cut silicon carbide or equal matrix media that leaves a galvanized matted appearance in 10 to 20 minutes and a 26-32 RMS.

Medium

An aluminum oxide matrix media that leaves a smoother finish, still matted appearance, in 15 to 30 minutes and a 22-29 RMS.

Fine

An aluminum oxide matrix media that leaves a dull luster in 30 to 60 minutes and a 16 to 24 RMS.

Plastic Media - Series 40000

Recommend for general purpose deburring and material removal on non-ferrous castings, brass, copper, aluminum, zinc, as well as gold and silver. Comes in three grades:

Coarse

A fast cut, coarse zircon or silicon carbide fill matrix media that leaves a matted appearance in 15 to 20 minutes and a 24-29 RMS.

Medium

An aluminum oxide fill matrix media that leaves a smoother finish and a dull luster in 30-60 minutes and a 18-26 RMS.

Fine

An aluminum oxide fill matrix media that leaves a good luster in 60- 180 minutes and a 10-20 RMS.

Burnishing Media - Series 50000

Recommended as a secondary step type process, after ceramic or plastic. Media achieves a bright shiny finish on all materials. Chemical compounds greatly effect brightness of finish. This media is not regulated or classified as grades but is affected by weight, density, and/or size. The longer the time cycle, the brighter the parts.

Porcelain

Lightest of burnishing media. Normally used on lighter more fragile parts. Also, it will not contaminate nonferrous materials. Produces a 16 to 22 RMS in 60 to 360 minutes after cut down cycles.

Carbon Steel

Works 2-3 times faster than porcelain. Precautions are necessary for storage and may contaminate nonferrous parts. Leaves bright appearance or 18 to 24 RMS in 30 to 60 minutes.

Stainless Steel

Works the same as carbon steel, but does not require any special storage. Leaves bright appearance or 18 to 24 RMS in 30 to 60 minutes.

Organic Media - Series 60000

This is dry processing media. Recommended for both deburring and polishing of all materials. Especially effective on small, delicate and detailed parts. Time cycles are extremely long, maybe days; however, mirror finish and RMS are better than any process other than finished by hand. For time cycles and finish, see "Shapes."

NOTE: Wood media is normally used in a 2 part system in a ratio of 5 parts of A to 1 part B, but can be used separately. Add a handful or one cup of new part B material per batch of parts. Part C additive can be used to replace and/or speed up part B.

Wood Shapes (Part A)

Lightest specific gravity/weight of organics. Shapes provide bulk and pressure for compounds to do their work faster.

Wood Compound (Part B)

This is a saw dust mix that behaves similar to water. It penetrates and carries fiber and compound to work pieces.

Corn Cob

Heavier, denser, and more granular than wood. Less likely to get stuck in small places, but will not achieve better results. Works faster initially than wood.

Walnut Shell

Heaviest specific gravity of organics. Similar to corn cob, but works faster up to a point, but not as fine a finish.

Additives (Part C)

Liquid additive compounds that can be used with wood shapes to replace sawdust where lodging is a problem. Can also be used with Part B sawdust, corncob, or walnut shell to enhance and/or speed up operations.

SHAPES

Again, for ease and simplicity, Nova Finishing Systems, Inc., has pre-selected a number of shapes to offer. Description and recommended applications are as follows: 

Ceramic

Triangles: Recommended for external or outer surface features, outside edges, and edges of holes.

Tri-star: Recommended for all of the above, but deeper penetration.

Cylinder, angle cut 22 degrees: Recommended for inner burrs and/or passing through holes and deeper hole penetration than items above.

Cylinder, angle cut 60 degrees: Recommended for deepest penetration of holes and cavities.

Wedge, V-cut: General purpose media. The most unstable and most aggressive for all surfaces.

Plastic(s)

Tetrahedrons/Tetraforms: Recommended for outer surfaces, edges, and recesses.

Cones/Coniforms: Recommended for flat areas and slightly smoother surfaces.

Wedge, V-cut: General purpose media. The most unstable and most aggressive for all surfaces.

Burnishing

Spheres-Porcelain (micro-brite balls): Recommended for uniformity and surface contact or outside features.

Spheres-XM sintered aluminum bauxite - same as above.

Balls-CS & SS: Recommended for uniformity and surface contact and/or outside features.

Ballcones-CS & SS: Recommended for parts having internal sharp angles or recesses.

Cones-CS & SS: Recommended for sharper angles and/or configurations than above.

Diagonals-CS & SS: Greater surface contact than cones and works comers and recesses well.

Ovalballs-CS & SS: Greatest amount of surface contact. Recommended for large flat areas.

Pins-CS & SS: Smallest size of uniform burnishing media available. Best penetration of recesses and comers.

Tailings-CS: Similar to pins but smaller more random shape and unfinished. Extremely good on detail; however, may get stuck in small areas.

NOTE - CS = Carbon steel media. SS = Stainless steel media 

Organics (Part A)

Cubes-Wood: Recommended for general purpose applications. Uniformity of size helps prevent lodging.

Diamonds-Wood: Normally heavier because of size and therefore seems to work faster than cubes and pegs.

Pegs-Wood: Recommended for penetration and/or internal recesses.

Organics (Part B)

Wood-6A compound: Recommended for deburring delicate parts. Leaves a satin finish on all materials or 22-32 RMS in 2 to 6 hours. After cut down cycles, figure 2-4 RMS/hour with maybe 10-12 RMS for best possible finish.

Wood-6D&E compound: Recommended for almost buffed appearance. Possible 4-12 RMS in 24 to 96 hours.

Corn Cob-6F: Untreated, used mainly for drying parts. Maybe a 24 RMS improved surface possible in 6 to 24 hours.

Corn Cob-6G: Treated with polish and capable of a 2-6 RMS improvement in 6 to 24 hours. Best possible RMS around 8.

Walnut Shell-6H: Untreated, used mostly as a blast abrasive, but can slightly deburr and/or dry parts. Maybe a 2-6 RMS improvement possible in 6 to 24 hours.

Walnut Shell-61: Treated with polish and capable of a 2-12 RMS improvement in 6 to 24 hours. Best possible RMS around 6.

Organics (Part C)

61A abrasive: Paste additive that helps bind abrasives to wood shapes or compound. Fastest coarsest grade available.

61B abrasive: Same as above but leaves a finer appearance on work piece.

62A polish: Paste additive that helps improve RMS and/or appearance of work piece.

62B polish: Paste additive that helps produce finest finish on work piece.

63 liquid polish: Liquid additive similar to 62 B but blends faster and easier.

LIQUID CHEMICAL COMPOUNDS

Nearly all mechanical deburring systems use a combination of media and a cutting type fluid. The media's grinding action against the part removes most excess materials and modifies the surface variations. The fluid can react chemically to the materials in question: however, their primary function is to keep the abrasive medias free of oils, metals, and synthetics.

Most chemical compounds are formulated and controlled by the pH of the liquid. The pH is a unit of measure or scale to determine if a product is acid or alkaline. Water registers 6.7 or neutral on the scale. Acidity increases as the scale decreases; whereas, alkalinity increases as the scale increases. Therefore, a 1 or 2 pH acid or an 11 or 12 pH alkaline caustic are strong solutions that would etch most metals.

Deburring or burnishing compounds are normally alkaline; however, some people prefer slightly acidic products for non-ferrous materials. Also, most people prefer products that contain a rust inhibitor. This is especially important on ferrous materials or when using carbon steel medias. Inhibitors are also favored on non-ferrous parts to maintain luster and limited protection against oxidation.

When using compounds check the label. Current laws have changed and some products may not be suitable for disposal or use. Also check dilution rate. Too much compound may cause over foaming which will slow down and/or buffer the action of the media. Some newer products will not foam at all; therefore, read instructions. Lastly, to get the cleanest parts possible it is recommended that a good flow of product pass through the machine and drain to an outside exit.

Again, for ease and simplicity Nova Finishing Systems, Inc., has preselected a-limited number of products and packaging for you to choose. They are as follows:

L100: A super concentrated deburring and burnishing compound for non-ferrous materials. Dilute 640:1 pH of 4.2

L200: A super concentrated deburring compound with rust inhibitor for ferrous materials. Dilute 640:1 pH of 10.5

Proprietary and Specialty Items:

Nova Finishing Systems, Inc., specializes in producing mirror finished processes using vibratory mills. To accomplish this task, we are constantly doing research and development with media and compounds. The following are considered proprietary or specialty items:

Liquid Chemical Cleaner

Product L6 - This chemical is primarily used to clean and wash parts; however, it is excellent for use deburring plastic materials. Material has a USDA A I rating and exceeds DOD 2000 Mil Spec. Formulated for ferrous, non-ferrous, and neutral.

Product L8 - This is a liquid additive used to treat very small porcelain and/or certain ceramic media so that it can be used for dry processing with porcelain or XM materials.

Dry Organics

Product 56A - This is a mix of dry organic abrasive materials and special ceramic media. Relatively lightweight but heavier than organics alone and therefore, works faster. Use for deburring.

Product 56D & E - This is specialty blend of dry organics and special ceramic media. Produces mirror finishes in a shorter time period than organics alone.

Product L63 - This is heavy viscous aluminum oxide additive used to rejuvenate dry organic polishing media. It can also be used with fine plastic media with outstanding results.


 




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