Normal Wear and Unusual Breakage of Zirconia Beads

Normal wear and unusual breakage of zirconia beads are sometimes unavoidable.

To determine if the damage is within the normal wear and tear, one should first inspect the appearance of the media. After a period of use, zirconia beads will become smaller and have a smooth surface without sharp edges, which is considered normal wear. However, when zirconia beads show sharp edges, flakiness, or irregular shapes, it falls under the category of abnormal breakage.

The occurrence of bead breakage can be attributed to both the material quality of the beads and their compatibility with a specific type of grinding machine.

From a stress perspective, when the dispersing disc transmits force to the beads, if the liquid viscosity is high, for instance when cleaning the sand mill with solvents or water, the material's thrust might not be sufficient, and this could cause the beads to come into contact with the dispersing disc, leading to breakage. Hence, it is advisable to minimize the cleaning time as much as possible.

If a high-viscosity liquid is used for machine cleaning, the beads can also wear down other beads or the machine's contact components. To ensure a longer lifespan for zirconia beads and the sand mill, it is best to use resin for cleaning and maintain an adequate material viscosity during the production process.

Reasons for Zirconia Bead Breakage:

1. Incorrect installation of internal components in the sand mill: Loose dispersing discs, sharp edges on the dispersing disc, foreign objects inside the sand mill, loose valve internals, and similar issues can all potentially lead to the breakage of zirconia beads.

2. Wear or incorrect installation of contact components in the sand mill: The dynamic separator or sieve may be worn, the sieve may have tears, or it may be installed incorrectly. If this causes the grinding medium to pass through the separator and enter the feed pump, the pump may crush the beads before getting clogged or shutting down.

3. Back pressure: When the feed pump is turned off, the residual pressure inside the sand mill can press the beads into the pump. Therefore, when the pump is restarted, it can crush these beads. Check valves are not always reliable and may sometimes allow beads to pass before the valve closes.

4. Accumulation of zirconia beads: If zirconia beads accumulate at the bottom of the sand mill or if the working pump's speed is too high and concentrates zirconia beads near the outlet of the horizontal sand mill, it can lead to this situation. The solution is to start the sand mill in an on-off-on-off manner to loosen the accumulated zirconia beads.

5. Wear of the dispersing disc: This situation can be more difficult to determine. The worn edges of the dispersing disc can become uneven, and these areas, where the dispersing disc rotates at high linear speed, may create strong vortices.

In addition, for vertical milling machines, zirconia beads tend to accumulate near the lower edge of the dispersing disc due to their own weight. All of these factors combined can potentially cause zirconia bead breakage. Excessive wear of the dispersing disc is often caused by slow feed pump speeds and high-density zirconia beads. This problem can be solved by replacing heavily worn components and using beads from the same batch.

1. Mixing zirconia beads from different manufacturers: Products from different manufacturers may have different densities. Mixing beads from different manufacturers can increase wear between the beads. The solution is to avoid mixing zirconia beads from different manufacturers. If mixing is suspected, the only option is to discard them all.

2. Debris or small, worn beads: Often, debris or small worn beads can attach to the sieve, shaft, support, or other corners inside the machine. When new zirconia beads are added, these small objects can dislodge from their attachment points and mix with the new beads, creating the illusion of immediate breakage. In reality, what you see are some naturally worn beads from the past. If the problem is not significant, you can allow these small objects to naturally dislodge after some time. Otherwise, you will need to replace the old beads with new zirconia beads.