Dry Tumbling with Corn Cob Grit

Stamped, cut, machined and otherwise processed parts often contain cutting oils and lubricants and need to be cleaned. These parts also have burrs and sharp edges that may need to removed.

The steel parts pictured on the left are dirty and have light burrs that need to be removed. A typical process would simply demand a mass finishing, tumbling process with a Ceramic Media to degrease the parts and remove the burrs in a wet process. The challenge with these parts is the shape - long, flat parts. In a wet process these parts will stick together to form 'sandwiches' and will not be cleaned and will resist deburring.

The solution is to dry tumble the parts with Corn Cob Grit. The Corn Cob Grit media will remove and absorb the soils (note clean, brighter parts on right). In a barrel tumbler, with a high ratio of parts to media, the part-on-part tumbling action will remove the burrs. The Corn Cob Grit can be separated from the parts efficiently with a simple wire mesh screen. The dry tumbling process also eliminates the need to dry the parts so they are immediately ready for any further processing.

Smooth Aluminum Finish

Aluminum is a relatively soft metal that is easily nicked, scratched and damaged by handling - both during the part manufacturing process and after. Restoring aluminum to a uniform and smooth surface finish can be accomplished with mass finishing.



The aluminum part on the left clearly shows the scratches and damage due to heavy handling. The part on the right is the result of a simple mass finishing process to create a uniform, matte surface finish. The part (aluminum cylinders) were vibratory tumbled in a wet process with a general purpose (KM) Ceramic Media and cleaning/lubricating compound for 2 hours.

Ceramic Media is typically used with harder metals such as steel; however, in this case, there was no need to further polish the part. If a higher polish is required, a lighter cutting Plastic or Synthetic Media can be used in a (potentially) longer cycle time. This step would be followed with a polishing step.

Polishing Acrylic Plastic

Acrylic Parts

Acrylic plastic parts often need to be polished to create a high clarity. When machined, the acrylic takes on an opaque surface finish. The specifications will often require a clear, polished surface finish. While large parts with simple geometry can be polished by hand, smaller parts or more complex shapes cannot be processed by hand.

The above part (before on left, after on right) was tumbled in a barrel tumbling system for 48 hours. Using a Hardwood Peg Media with Microlyte Polishing Cream in a dry process producing a significant improvement in clarity after 48 hours. A dry process can produce a very fine polish and high clarity but can often require long cycle times.

10 Blasting Bullets

10 quick abrasive blasting tips:

• Nozzle size determines the air requirement (CFM), not the pot size.
• Pressure systems are more efficient than siphon or gravity fed blasters.
• More air is always better.
• DRY AIR: Use a moisture separator on the blaster and cooler on the compressor.
• Ceramic nozzles are inexpensive but carbide nozzles last much longer.
• It's rare to blast above 110 PSI - typical is 80-90 PSI.
• Ear plugs are helpful, especially if you are near the compressor.
• Avoid using a longer blast hose than is necessary. A longer air hose is preferred.
• Proper protection is important, especially an air supply helmet in a closed or contained area.
• DO NOT blast with silica sand. There are plenty of 'healthier' alternatives that might even work better.
• Bonus Tip: Expect a loss of 5 PSI per 50 feet of air and blast hose.

Silverware Burnishing Basics - Part 2

The purpose of silverware burnishing is to both physically and chemically clean and smooth the fine surface 'grains' of the metal. This is accomplished through the use of a barrel tumbler and the appropriate tumbling media and compound.

Stainless steel burnishing balls (media) are used to force the metal to 'flow' and fill the scratches on the surface. As the entire load is rotated in the barrel, the media lifts up the back side of the the barrel and cascades towards the front. As the parts are carried with the media in the sliding area, the weight of the burnishing balls impact with the surface of the silverware. This contact forces the metal to fill the low spots and even out the high spots.

In combination with the physical polishing, the water and burnishing compound help to remove the tarnish (silver sulfide) and keep the process lubricated. Using the proper compound (and changing the solution regularly) will limit damage to the silverware in process and keep re-deposition to a minimum.

The combination of chemical cleaning and microscopic, physical manipulation leads to a bright and polished surface finish.