PM 100 Planetary Ball Mill

• Reproducible results due to speed control
• Easy and safe clamping of grinding jars
• The Safety Slider prevents starting the machine without securely clamped jars
• Perfect stability on the lab bench thanks to FFCS technology
• Innovative counterweight and imbalance sensor for unsupervised operation
• Comfortable parameter setting via display and ergonomic 1-button operation
• Automatic grinding chamber ventilation
• 10 SOPs can be stored, programmable starting time
• Power failure backup ensures storage of remaining processing time

SETTINGS AND OPTIONS

• Dry and wet grinding possible
• Suitable for long-term trials, 99 h max.
• Interval operation allows for cooling breaks
• Direction reversal helps to minimize caking effects

COUNTERWEIGHT

Planetary mills with a single grinding station require a counterweight for balancing purposes. In the planetary ball mill PM 100 this counterweight can be adjusted on an inclined guide rail to compensate for the different heights of the centers of gravity of differently-sized grinding jars and thus avoid undesired oscillations of the machine.

SAFETY SLIDER

Operation of the RETSCH planetary ball mills is particularly safe. They feature a robust Safety Slider which ensures that the mill can only be started after the grinding jar has been securely fixed with a clamping device. The self-acting lock ensures that the jar is seated correctly and securely. This proven solid mechanical system is less failure-prone than electronic solutions – the user has full access to the sample at any time. When the electronic system fails, it is not possible to unlock the jars, for example.

Wet grinding is used to obtain particle sizes below 5 µm, as small particles tend to get charged on their surfaces and agglomerate, which makes further grinding in dry mode difficult. By adding a liquid or dispersant the particles can be kept separated.

To produce very fine particles of 100 nm or less (nano-scale grinding) by wet grinding, friction rather than impact is required. This is achieved by using a large number of small grinding balls which have a large surface and many friction points. The ideal filling level of the jar should consist of 60 % small grinding balls.

For more details on jar filling, wet grinding and sample recovery watch the video.

The graphic shows the result of grinding alumina (Al₂O₃) at 650 rpm in the PM 100. After 1 h of size reduction in water with 1 mm grinding balls, the mean value of the particle size distribution is 200 nm; after 4 h it is 100 nm. 

Grinding of alumina in water with 1 mm grinding balls (left) after 1 hour (blue) and after 4 hours (green)

In another trial, the material was first pulverized for 1 hour with 1 mm grinding balls and then for 3 hours with 0.1 mm grinding balls. In this case, an average size of 76 nm was achieved.

Grinding of alumina with 1 mm grinding balls (1 hour) and then with 0.1 mm balls (3 hours) in water

In a detailed study, Gobindlal et al. (2022) [10] investigated the mechanochemical destruction (MCD) of perfluorosulfonic acids (PFSAs), a subclass of persistent per- and polyfluoroalkyl substances (PFASs), using the PM 100.

• Milling Setup: 0.05 g of PFAS standards were mixed with 5 g of quartz sand in a 50 ml stainless steel jar with ten 10 mm stainless steel balls.
• Milling was performed at ambient temperature and pressure, without solvents or chemical additives. Samples were milled for up to 720 minutes, under relatively mild conditions, to assess degradation kinetics and establish the underlying degradation mechanisms.
• The PM 100 achieved 99.99% degradation of total PFSA content after 720 minutes. Individual compounds like PFOS, PFHpS, PFHxS, PFPeS, and PFBS showed rapid degradation, with PFBS reaching complete destruction by 180 minutes.

Activated clays are among the most promising supplementary cementitious materials (SCMs) because they are globally available, can be locally sourced, and enable significant clinker reduction. Traditionally, reactive clays are produced via clay calcination, but mechanochemical activation is an emerging activation technology that can provide a compelling alternative in certain applications. Mechanochemical activation of clay – particularly using ball mills such as the PM 100 or PM 300 – uses mechanical energy to alter the crystal structure, enable amorphization, and increase reactivity, making a wide range of local clay types usable as cement replacement materials. The PM 100 and PM 300 are ideally suited for this process at laboratory and pilot scale. Studies show that mechanically activated clays are finer, structurally modified, and more chemically reactive than calcined clays, especially those with a high mica content.

A key element of activation technology process control is the GrindControl system, which continuously measures temperature and pressure inside the grinding jar, helps prevent overheating, and provides important insights into mechanochemical reactions. The sensors are compatible with various jar sizes. During clay activation, temperature and pressure rise significantly, indicating gas release and mineral transformation; this monitoring is essential for controlling reactivity and ensuring consistent SCM product quality. The data can also support conclusions about clay composition – for example, materials with higher dolomite content generate higher pressures due to CO₂ release [1].

Reactivity of different clays after thermal and mechanical activation; GrindControl pressure increase reflects dolomite content

The grinding jar is arranged eccentrically on the sun wheel of the planetary ball mill. The direction of movement of the sun wheel is opposite to that of the grinding jars in the ratio 1:-2. The grinding balls in the jars are subjected to superimposed rotational movements, the so-called Coriolis forces. The difference in speeds between balls and jars produces an interaction between frictional and impact forces, which releases high dynamic energies. The interplay between these forces produces the high and very effective degree of size reduction of the planetary ball mill, both, in ball to ball and ball to wall interactions.

Planetary mills with a single grinding station require a counterweight for balancing purposes. In the Ball Mill PM 100 this counterweight can be adjusted on an inclined guide rail. In this way the different heights of the centers of gravity of differently-sized jars can be compensated in order to avoid disturbing oscillations of the machine.

Any remaining vibrations are compensated by feet with some free movement (Free-Force Compensation Sockets). This innovative technology is based on the d’Alembert principle and allows very small circular movements of the machine housing that result in an automatic mass compensation. The laboratory bench is only subjected to minimal frictional forces generated in the feet.

In this way the planetary ball mill PM 100 ensures a quiet and safe operation with maximum compensation of vibrations even with the largest pulverization forces inside the grinding jars and therefore can be left on the bench unsupervised.