Media For Vibratory Finishing Machines
Selecting the suitable media for your application
The process to achieve the required surface finish involves using the correct machinery but the media and compound are of equal importance and the following factors should be considered when selecting these.
The media transmits the energy generated by the equipment to the parts being processed and are capable of heavy burr removal, edge radiusing to smooth and bright surfaces. A variety of different media types are available: Ceramic, Plastic, Agro, Pre-Treated and Stainless Steel.
Ceramic Media is recommended for removing burrs, edge radiusing, burnishing and quickly removing polishing lines on components made from harder materials. Faster cut Medias are designed to be softer, to continuously expose fresh cutting surfaces. Polishing Medias are harder but contain no abrasives and are used for burnishing. In general, the slower the cut, the harder the media.
Plastic Media is lightweight and is manufactured out of soft bonding agents, which allow it to remove burrs without rolling the burr onto the part. This media is suitable for obtaining a very smooth surface finish or a bright or matte finish on components made from softer materials.
Agro Media is used for surface brightening or final finish refinement while Pre-treated Media is for achieving a high lustre or mirror finish. Stainless Steel Media is used for burnishing, cleaning, improving compressive strength and light deburring.
When choosing the shape of the media it is important to consider the geometry of the part to prevent it lodging in the component and to ensure the finish is consistent.
Flat sided media, such as triangles, tri-stars, wedges and the end side of cones, can generate longer surface contact time on edges for deburring and radiusing.
Round shaped media, such as balls, cylinders and cones generate a single point contact, concentrating energy in one small point, and producing more work in that area.
For components which have corners, holes and slots both Tri-Star media and wedge media are recommended, to minimise the possibility of media lodging in the component.
For surface improvement of hard to reach areas, an ellipse or cylinder shape can be considered.
The component finish can also depend on the size of media chosen. Larger media will generate higher energy and will cut, and finish, faster but will suffer from higher wear rate. Larger media is also recommended for processing larger parts.
Smaller media can hold more water and compound and reduce part-on-part damage. Smaller media also has a gentler impact on the component, resulting in longer processing times but better finishes and less media wear.
Media size should be a different size to the components to enable complete separation at the end of the finishing process. If the media is larger than the components, an inverse separation system can be used. For ferrous components, magnetic separation is also available.
To avoid damaging the component, it is important to consider the part material and the hardness of the media. Ceramics are harder than plastic and may cause damage to components made from soft materials.