Overview

The term Media Blasting applies to any process where an abrasive is propelled at high pressure against the surface to be treated. This is most commonly achieved with the use of compressed air but can also be done with a Pressure Washer which uses a pump to pressurize water or in the case of peening and de-burring operations the media can be “thrown” by a spinning wheel.

Media blasting is an effective means of cleaning, de-rusting, peening, de-burring, or etching metal, plastic, wood, resin, and glass. Perhaps the best known process is sand- blasting which is commonly used to clean and de-rust metal or to etch and engrave glass or stone. (Nowadays sand is rarely used as an abrasive because of the hazard of silicosis.)

There is a variety of media that can be used; Glass beads, Crushed Glass, Aluminum Oxide, Silicon Carbide, Steel Shot, Stainless Steel Shot, Steel Grit, Garnet, Coal Slag (Black Beauty), Corn Cobs, Walnut Shells, dry ice, and Soda to name some of the most common. All blast media wears out, some, such as aluminum oxide, silicon carbide, and steel shot are quite durable and may last as many as thirty cycles. Other media such as coal slag, soda and dry ice are strictly single-use abrasives. Everything else falls somewhere between these two extremes and in all cases the useful life of an abrasive depends heavily on a variety of factors such as air pressure, contamination, and surface being cleaned.

Unfortunately no single media works for everything and choices need to be made as it isn’t practical to stock quantities of all the different types of media available. Additionally, changing media in the blast cabinet is a time consuming process, some media choices have health concerns, and some media can be recycled many times while others are consumed in a single use.

Here at Makersmiths a survey of interested members found that our Media Blast cabinet will most often be used to clean and derust steel items prior to either welding, painting, or powder coating. For this reason the cabinet has been filled with Aluminum Oxide abrasive in a medium grit. Air pressure should be regulated to 50-90PSI which will allow the operator to adjust the aggressiveness of the media slightly. Lower air pressure should be used for sheet metal or other less robust items while 90PSI will yield faster rust removal on heavier items. PLEASE NOTE! All parts must be de-greased and dry before they can be placed in the media blast cabinet, failure to do so will result in the media sticking to the grease. Your part will not come out clean and the media will be contaminated!

To use the Media Blast Cabinet

1. Turn on air compressor (switch is in the wood shop).
2. Verify that all three filter bags on back of the media blast cabinet are empty. If not then empty them.  
3. Make certain that your parts have been degreased, are completely dry, and that important machined surfaces have been masked off. You may also wish to fill threaded holes with an old bolt or a silicone taper as used for powdercoating. 4. Check air pressure to the cabinet and adjust if necessary.
4. Check that the view port glass is clean so you can see what you’re doing.
5. Place your item inside the cabinet and verify that both doors are securely closed.
6. Turn on interior lights and vacuum system.
7. Place your arms in the gloves and step on the foot control air valve to start blasting.

NOTE! Please position your work and aim the gun so that media does not hit the view port.

HINT! Reduce air pressure and hold the gun further from the work when working with sheet metal or other less robust parts. This is especially important when your work piece is aluminum or other soft metal.

When you are finished

1. Wait for the dust to go away in the cabinet before opening the doors. Remove your part from the cabinet rotating it while it is still inside the cabinet to get all the loose media out of it so that you don’t spill media on the floor.
2. Turn off the interior light and vacuum.
3. Empty the filter bags into a trash can and take the filters outside to give them a good shake before reinstalling them.
4. Sweep up any media that is on the floor.
5. Using a slightly damp paper towel GENTLY wipe the dust off both sides of the view port glass.
6. A clear acetate film is glued to the inside of the view port window to protect the glass from being etched. This is a consumable item and must be replaced periodically to maintain a clear view. If this film is hazy enough to make it difficult to see into the cabinet please replace it.
7. Check to make certain no one else is using the air compressor and if not then turn it off.

DO

1. Make certain that the parts you wish to media blast are completely free of oil , grease, tar, and abrasive residue and that loose rust and/or paint flakes have been brushed off.
2. When you are done clean up the blast cabinet and the area around it before leaving.
3. Get permission and assistance from the shop steward before changing media in the blast cabinet. Make certain to allow yourself enough time to thoroughly clean the cabinet and replace the normal blast media before you leave.
4. Always position your part and the blast gun in such a way that the blast media will not hit the viewing window. The gun and your part should always be positioned so that neither the direct stream from the gun or the media bouncing off your part will impact the window.

DON’T

1. Put any media into the cabinet except 80 grit aluminum oxide. (see #3 above) 2. Attempt to blast an item that is too large to fit into the blast cabinet. Both doors must be securely closed before you can blast anything.
2. Leave the machine before you clean up after yourself.