Frequently Asked Questions About Planetary Ball Mill

1. Can planetary ball mill grind particles to the size smaller than 0.1 micron?

Yes, the size of particle can be smaller than 0.1um. We have customers using our planetary ball mills grinding particles to submicrons.

2. How to tell the size distribution of the particles?

The particle size distribution will be in microns. You can use a Beckman Coulter Light Scattering instrument to determine the particle size distribution. If you use Scanning Electron Microscope, you will be able to see the very small primary particle size less than 0.1um.

3. Will particles tend to agglomerate when they gets to 1um range? How to prevent agglomeration?

Yes, when the particle size gets to 1um range, the particles tend to agglomerate. One way to reduce the agglomeration is to use surfactants or polymer like PVA during ball milling.

4. For processing gypsum, a very soft material, what kind of jars and balls do you recommend?

We will recommend stainless steel jars and balls for processing gypsum.

5. What is the maximum filling level of the jar?

The filling level of the jar is very important for successful grinding. Generally a jar filling should not exceed 60% of the jar volume. The remaining 40% volume is necessary for the free movement of balls.

6. What size and how many balls would you recommend for the ND4L? Also what is the smallest particle size the ND4L can mill down to?

Our ball mills always come with a free standard set of balls, including 1000 Ø6mm balls, 200 Ø10mm balls, and 3 Ø20mm balls for EACH 1000ml jar. They do the basic job of filling each jar to about 1/2 of its volume. Sometimes, customers want to try different combinations of grind media and we recommend, as other manufacturers like Retsch and Fritsch would, 1500 Ø6mm balls, 200 Ø10mm balls, 90 Ø15mm balls, 35 Ø20mm balls, 10 Ø30mm balls, and 4 Ø40mm balls for each jar.

The smallest particle size our ND4L model can mill down to is 0.1µm. However, the final fineness varies greatly with different materials. The actual grinding result depends on mill speed, ball size, material, and grinding time. You will be able to find the best combination after a couple of tries.

7. How to choose the right jar material?

The general rule is the jar must be harder than the material being milled. Most times stainless steel is sufficient, if the material can react with metal, then agate is good. Otherwise, zirconia is common.

8. Is it necessary to use zirconia jars with zirconia beads?

It depends on why you are using zirconia beads as the grinding media. If the purpose is to avoid metal contamination, you should use zirconia, alumina, or agate jars. If the purpose is to use the hardness of zirconia to break up materials, stainless steel jars are fine. Although zirconia is much harder than stainless steel, these beads won't damage the jars.