What kind of media do I need?
When choosing media you will need to choose the type, size & shape and the level of abrasiveness. Below are some basics to begin with.
We are happy to help you find the right media for your job. This is our specialty. C & M has experienced people to talk with you. We also offer free test runs on your parts in our laboratory to ensure you are using the best media for your application.
- Ceramic is most common used for steel and stainless steel.
- Plastic is used for aluminum and soft metals.
Size & Shape:
The size and shape will be determined by the size of any holes or slots in your parts. You will want to pick a media that will get into the smallest places of your parts but not get lodged. Media lodging is the main thing you want to avoid regardless of the material you are doing. There is something called the 70% rule. Meaning when selecting media, it should be at least 70% the size of any hole or slot. That way two pieces cannot get side by side and get stuck in the part. Also the media can be used for a substantial time before lodging becomes a problem.
Level of Abrasivness:
This is determined largely by the hardness of the material, the amount of deburring and the type of finish you want on your product. We have extensive description the formulations on our tumbling media page.
If you are deburring aluminum such as 6061alloy, plastic media in the VF-X formulation is the most common media used for this. Some aluminum alloys such as 7075 or 2024 are hard enough that they can be de-burred in ceramic media also.
If you are deburring steel or stainless, ceramic media in the VF-SF formulation is the most common media used.
Plastic parts can also be de-burred in our machines using ceramic media. Plastics have high abrasion resistance, so you need to be aggressive to get good burr removal. Plastic parts will have a matte finished when done. A second step in porcelain media to bring the plastic part back up to a polished surface.
For polishing steel, stainless, aluminum and plastic parts, porcelain media is the most common media used. Any shape of porcelain can be used. One of the most common polish media used is a 3/16-3/8 angle cut cylinder. The theory is that a cylinder has more surface contact with the part than other shapes. If you are polishing aluminum, you need to use balls. The porcelain media is very hard and if you use other shapes like cylinders or triangles the edge of the media will nick the part. The most common ball used is 4, 5 or 6 mm porcelain. To polish brass, dry media such as walnut shells or corncob with rouge coating is the most common. Dry media is not usually used on other materials because the run times will be too long. Plain cob will sometimes be used to dry parts. Most often polishing will require two steps, the first step, called the “cut down” will remove machining marks and imperfections in the part. This will be done with gray ceramic media for steel or green plastic for aluminum. Then there will be a media change, to porcelain for the second step. A special compound will be used for the polishing step.
See more on media selection here.