Factors When Selecting Tumbling Media

Vibratory finishing and deburring machines require the addition of abrasive media to deburr and polish parts. Selecting the correct media is critical to a successful deburring and finishing process. Media keep parts separate, provide the abrasion to conduct the deburring or finishing process, and can get into the curves and holes in oddly shaped parts. Consider these factors when selecting tumbling media.

Match Materials

The primary consideration will be the materials that make up both the parts and the media. Most finishing processes are for metal parts, but metals come in varying hardness densities, and the desired appearance of the surface after finishing may range from flat and dull to brilliantly shiny.

Tumbling media may be:

• Ceramic – Generally used for hard metals or heavy plastic, ceramic media provide good deburring via peening threads, offering more aggressive abrasion for tough parts.
• Plastic – Plastic media is essentially the opposite of ceramic: it is used for soft metals like copper, brass, or aluminum. The result is a flat, smooth finish.
• Porcelain – Remember the “p” in porcelain, because porcelain is for polishing. It doesn’t deburr, but it does provide a smooth look.
• Steel – Steel media can deburr, polish, and shine metal, plastic, or even ceramic parts.
• Natural media – Nutshells and corncobs are two types of natural media that can deburr and clean.

Shape and Size

The shape of the deburring material is another important factor in selecting tumbling media. Ceramic, plastic, porcelain, and steel media come in a variety of shapes; triangular, cylindrical, and ball shapes are common. These, in turn, come in various sizes. The concern is that the tumbling media reach all surfaces of the part without becoming lodged in holes or recesses. The size is important because the material shrinks through the abrasive deburring action. Choose a shape that will contact all surfaces of the part undergoing deburring or polishing, in a size that can pass through holes without getting stuck as the object shrinks during the process.

Wet or Dry Process

Although some deburring and finishing processes are conducted dry, others use an additive compound to clean and polish parts and to protect them from corrosion and rust. Wet processes can also suspend the deburred material and the amount of abrasive that rubs off the media in the compound until the user empties the metal vibratory tumbler bowl and prepares it for the next batch of parts.