Frosting Glass

Frosting clear glass to create a totally different look or put some type of design on the glass is a very simple process. This clear glass was abrasive blasted with a White Aluminum Oxide Grit - 240 Mesh to produce a translucent finish.

The use of a resist or pattern with exposed areas will allow for only select areas of the glass to be etched leaving the rest clear.

Different grit sizes will produce smoother or rougher finishes and cut to different depths into the glass.

Investment Casting

Investment casting is process where parts are produced inside a mold (a.k.a., investment) which is then removed from the part to expose the molded piece. As the investment casting process typically requires high temperatures to liquefy and pour the metal alloy into the mold, discoloration of the final part is common. In addition, the investment material can often get stuck inside slots and grooves of the part. Both the discoloration and stuck investment can be seen in the part on the bottom of the picture.

The clean part seen in the top of the picture was a result of abrasive blasting. In this case, the hard metal alloy part was tumble blasted with White Aluminum Oxide for only a few minutes. The end result is a clean, uniform surface finish ready for the next steps in the part production process.

A good explanation of the investment casting process can be found on Wikipedia at http://en.wikipedia.org/wiki/Investment_casting.

Wood Parts Tumbling to Remove Flashing

Common practice to remove flashing and sand wooden parts is by hand. Sandpaper or sanding wheels can be used to effectively clean up parts one at a time. A more efficient process (especially for large quantities of parts) is to use barrel tumbling.

This picture shows a before (left) and after (right) of a walnut wood part with heavy flashing, excess material on the edges and a rough cut surface finish. This is probably an extreme example; however, a simple barrel tumbling process created the surface finish on the right.

This part was tumbled with Hardwood Media and a small amount of 120 Mesh White Aluminum Oxide overnight. The result is a smooth surface finish with rounded edges and no excess material.

Titanium Medical Screws

Titanium metal is used for medical and dental implants due to its strength, non-corrosive properties and bonding ability with soft tissue and bone. In order to encourage this bonding process and to give the tissue a good surface to adhere to, the metal needs to have an anchor profile. This very similar to preparing a surface for paint or coating. A rougher surface will provide more surface for bonding.

The titanium bone screws in the picture show a before and after blasting. These screws have a very smooth surface (before on left) after the machining process. Since the size of the screw is very small, it is difficult to blast the screws one at a time. A Tumble Blast system was used to create the lightly etched profile (blasted part on right) on the surface. The tumble blasting batch process allows for a large number of parts to be blasted at one time in a short period.

The surface finish shown was accomplished in about 10 minutes using 60 Mesh White Aluminum Oxide. This grade of media (99.5% pure aluminum oxide) was used to prevent contamination of the metal surface and provide a consistent and uniform finish from part to part.

Fired Clay Parts Tumbling

Common sense would state that using a barrel tumbler for fragile fired clay parts would be inadvisable. The aggressive tumbling action would damage or crush the parts. This logic might follow for brittle parts such as ceramic tile and the like.

In fact, tumbling all types of fragile and brittle parts can be accomplished quite successfully in a barrel tumbler. The part in the picture above is a molded and fired clay pendant that is only about 1/8" thick. The project required that the excess material on the edges be removed and that the edges are heavily rounded.

In this case, a wet process would have involved undesirable absorption of water into the pendant. A dry tumbling process was used to achieve the stated goals. The parts were tumbled with Hardwood Media and White Aluminum Oxide for less than 2 hours to achieve the edge rounding as seen in the part on the right. As long as the proper ratio of media to parts (about 4:1 in this case) is maintained, damage the parts will be insignificant and batches as large the barrel will allow can be done.

Scratch Resistant Coatings

Improving the life of a coating such as polyurethane, acrylic or epoxy can be achieved with the addition of a small amount of a abrasive such as Aluminum Oxide, White Aluminum Oxide or Silicon Carbide. These materials are significantly harder than the coating material and will increase the scratch resistance of the coating with minimal impact on the other properties of whatever coating you are using.

The specific type of abrasive will depend on a variety of job specific requirements including color, clarity and thickness. The size of the abrasive used is generally a very fine grade such as a 600 or 800 mesh but larger grit (~240 mesh) can be used in thicker coating. The addition rate is also very dependent on the coating you are using specifically related the solids content. Rates of 3 - 5% (about 1/2 pound per gallon) are common.

Wood Deflashing

Before

This saw-cut wood part (before) has sharp edges and flashing that need to be removed prior to staining and sealing the wood. The traditional process would involve hand sanding with progressively finer sand paper. Given the round shape of the part and the requirement to sand the interior areas, a sanding wheel process is not feasible.

After

This finished part (after) has been barrel tumbled for 8 hours with Hardwood Media and Aluminum Oxide Grit. Since the part has some 'closed', internal areas that need to be sanded, the Hardwood Media is ideal to get into those areas and provide a much larger surface area for surface finishing. The grit acts as the sanding medium to quickly and efficiently removes sharp edges and result in a smooth surface.

If a very smooth surface is required, a couple of steps with finer and finer Grit will perform similarly to hand sanding with finer grades of sandpaper - without the hand work required.

Non-Skid Flooring

Non-skid or anti-slip flooring is generally created by embedding an abrasive grit into a floor coating. The most versatile and durable grit is aluminum oxide since it is available in a wide variety of grit sizes and does not break down in high traffic areas. Broadcasting the grit onto a tacky floor coating (e.g., epoxy primer) followed by a top coat will 'lock' the grit in place.

These pictures show examples of using 36 grit white aluminum oxide on the left and 24 grit white aluminum oxide on the right. Notice the difference in media density used and the height of the 'peaks'. Given a fixed coating thickness, larger grit will provide more non-skid properties and a rougher surface. White aluminum oxide is used to minimize concerns about discoloration of the coating system.

Aluminum Oxide

Aluminum Oxide (a.k.a. aluminium oxide, alumina, aloxite, corundum) is generally sourced from bauxite ore. While bauxite is the primary ore for aluminum metal, Aluminum Oxide is extracted using the Bayer Process to remove unwanted impurities.

Aluminum Oxide is a very hard, versatile blasting media that can be used in a variety of applications for removing oxidation and scale off metals to etching stone and glass surfaces. The pure (>99%) White Aluminum Oxide is used when surface non-contamination is critical like when blast cleaning medical parts.

The hardness and large grit sizes available also make Aluminum Oxide an excellent choice for non-skid flooring. Aluminum Oxide is commonly used as an abrasive for sandpaper.

I'll bet you didn't know that precious stones like rubies and sapphires are simply Aluminum Oxide (corundum) crystals contaminated with other metals like chromium, titanium and iron.