6 Little-Known Factors That Could Affect Your Choice of Grinding Jars for Planetary ball mill

//6 Little-Known Factors That Could Affect Your Choice of Grinding Jars for Planetary ball mill

6 Little-Known Factors That Could Affect Your Choice of Grinding Jars for Planetary ball mill

18th,July.2019


The Planetary ball mills are the most popular mills used in fine grinding of soft to hard, tough, brittle and moist materials. The grinding media have considerably high energy, because grinding stock and balls come off the inner wall of the grinding jars and the effective centrifugal force reaches up to 20 times gravitational acceleration. We may get an idea about the work principle of the planetary ball mill as below figure showing:

work-principle-of-planetary-ball-mill

As we can see, In addition to the instrument settings, the grinding jars and media is also of crucial importance for a successful grinding process in planetary ball mills. How should we to choose the right jars and balls ?

1, For the classic planetary ball mill, 4 grinding jars or bowls should be selected at least with corresponding number of grinding balls. The number of grinding balls depends on the jar volume used.

Planetary ball mill

2,  Grinding jars material should be the same as the grinding balls.

tungsten carbide grinding jars
high precious grinding balls

Click here for more detailed information about tungsten carbide grinding jars&balls

Grinding Jars and balls for planetary ball mill

3, Generally speaking, the grinding balls should be approximately 3 times larger than the largest sample particle to be ground.

4, Each grinding jar should be filled with 1/3 grinding balls, 1/3 materials to be ground, and the remaining 1/3 space served for the free movement of balls. The normal sizes of grinding jars is ranging from 25ml to 500ml. The below table provides details about usable volumes, maximum feed sizes and correct filling of the jars with grinding balls for dry milling.

Volume of grinding jarSample AmountMax Feed Particle Size
25ml<10ml<1mm
50ml5-20ml<3mm
80ml10-35ml<4mm
125ml15-50ml<4mm
250ml25-120ml<6mm
500ml75-220ml<10mm

Volume of Grinding jarD 5MMD10MMD15MMD20MMD30MMD40MM
25ml100pcs8pcs
50ml200pcs10pcs7pcs3pcs
80ml250pcs25pcs10pcs5pcs
125ml500pcs30pcs18pcs7pcs
250ml1200pcs50pcs45pcs15pcs6pcs
500ml2000pcs100pcs70pcs25pcs8pcs4pcs

5, The heavier and larger grinding jars and grinding balls with high density, the higher the impact energy, which can shorten the grinding time. For pulverizing soft samples, materials with low to medium density should be used, whereas for hard samples, it is better to use high-density materials.

6, To achieve the best grinding results, the selection of grinding jars material mainly depends on the ground sample materials. First and foremost is that the material of grinding jars and balls must harder than the sample materials. Otherwise the jars & balls will be grounded actually by the samples during the grinding process, therefore, the sample materials will be contaminated.

 

MaterialHardnessHardness(Mohs)Density(g/cm3)Wear ResistancePossible ContaminationApplication
Tungsten carbideHRA 90914-14.8 g/cm3highWC(extreme small amount)used for grinding very hard, brittle sample materials
Zirconium oxide1250 HV8.5 6.05 g/cm3highZrO2,Y2O3(extreme small amount) suitable for pulverizing medium-hard to hard and fibrous samples. It is typically used for heavy-metal-free grinding processes but also for ultrafine milling
Stainless steel ≤ 245 HB5.5-6.3 7.7 g/cm3mediumFe,Crused for pulverizing medium-hard to hard and brittle samples
Agate6.5-7 2.65 g/cm3LowSiO2a highly pure natural material suitable for pulverizing soft to medium-hard or fibrous samples. Due to its low-density agate is suitable for gentle grinding processes with low energy input
Sintered aluminum oxide1750HV8-8.53.9 g/cm3mediumAl₂O₃a ceramic material suitable for grinding soft to medium-hard or fibrous samples. It is mainly used for heavy-metal-free grinding processes.

By |2019-07-19T03:45:55+00:00July 18th, 2019|Blog|0 Comments

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