REPRODUCIBILITY, SAFETY AND EASY HANDLING

• 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 & OPTIONS

• Dry and wet grinding possible
• Suitable for long-term trials, 99:59:59 h max.
• Interval operation allows for cooling breaks
• Direction reversal helps to minimize caking effects

SAFETY FIRST: JAR CLAMPING

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 AND NANO-SCALE GRINDING WITH THE PM 200

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 barium titanate at 500 rpm in the PM 200. After 5 h of pulverization in heptane and oleic acid mixture with 0.5 mm grinding balls, the D90 value of the original sample was reduced from 15 µm to 95 nm. 

^{Grinding of barium titanate in heptane and oleic acid mixture with 0.5 mm grinding balls.
Blue curve: original sample; green curve: pulverized sample after 5 h.}

"COMFORT" GRINDING JARS FOR EXCELLENT RESULTS

The performance and the result of sample preparation are also determined by the choice of the grinding jar and its ball charge. The comfort range of grinding jars has been specially designed for extreme working conditions such as long-term trials, wet grinding, high mechanical loads and maximum speeds as well as for mechanical alloying. 

• Available jar sizes: 12 ml / 25 ml / 50 ml / 80 ml / 125 ml
• Pressure-tight and dust-proof O-ring sealing prevents material spillage, even after clamping is released
• Jars and balls available in 7 materials: hardened steel, stainless steel, tungsten carbide, agate, sintered aluminium oxide, silicon nitride, zirconium oxide
• Stainless steel protective jacket for agate, sintered aluminum oxide, zirconium oxide and tungsten carbide grinding jars
• A groove between jar body and lid allows for easy opening of the lid, e. g. with the help of a spatula, if there are underpressure effects inside the jar

JARS & LIDS FOR SPECIAL APPLICATIONS

• For colloidal or wet grinding, the use of a grinding jar with a special closure device is recommended
• Aeration lids are designed for working under inert atmosphere, for example if oxygen can influence the grinding process or the mechanosynthesis. The lids allow the introduction of gases like argon or nitrogen into the grinding jar.
• Optional pressure and temperature measuring system PM GrindControl

RECOMMENDED JAR FILLINGS

To produce optimum grinding results, the jar size should be adapted to the sample amount to be processed. The grinding balls are ideally sized 3 times bigger than the largest sample piece. Following this rule of thumb, the number of grinding balls for each ball size and jar volume is indicated in the table below. To pulverize, for example, 50 ml of a sample consisting of 3 mm particles, a 125 ml jar and grinding balls sized at least 10 mm or larger are recommended. According to the table, 30 grinding balls are required.

Grinding jar nominal volume	Sample amount	Max. feed size	Recommended ball charge (pieces)
			Ø 5 mm	Ø 7 mm	Ø 10 mm	Ø 15 mm	Ø 20 mm	Ø 30 mm	Ø 40 mm
12 ml	up to 5 ml	<1 mm	50	15	5	-	-	-	-
25 ml	up to 10 ml	<1 mm	100	25	8	-	-	-	-
50 ml	5 – 20 ml	<3 mm	200	45	10	7	3	-	-
80 ml	10 – 35 ml	<4 mm	250	70	25	10	5	-	-
125 ml	15 – 50 ml	<4 mm	500	110	30	18	7	-	-

The table shows the recommended charges (in pieces) of differently sized grinding balls in relation to the grinding jar volume, sample amount and maximum feed size.

TECHNICAL DATA

Applications	pulverizing, mixing, homogenizing, colloidal milling, mechanical alloying, mechanosynthesis, nano grinding
Field of application	agriculture, biology, chemistry, construction materials, engineering / electronics, environment / recycling, geology / metallurgy, glass / ceramics, medicine / pharmaceuticals
Feed material	soft, hard, brittle, fibrous - dry or wet
Size reduction principle	impact, friction
Material feed size*	< 4 mm
Final fineness*	< 1 µm, for colloidal grinding < 0.1 µm
Batch size / feed quantity*	max. 2 x 50 ml
No. of grinding stations	2
Speed ratio	1 : -2
Sun wheel speed	100 - 650 min-1
Effective sun wheel diameter	157 mm
G-force	37.1 g
Type of grinding jars	comfort, optional areation covers, safety closure devices
Material of grinding tools	hardened steel, stainless steel, tungsten carbide, agate, sintered aluminum oxide, silicon nitride, zirconium oxide
Grinding jar sizes	12 ml / 25 ml / 50 ml / 80 ml / 125 ml
Setting of grinding time	digital, 00:00:01 to 99:59:59
Interval operation	yes, with direction reversal
Interval time	00:00:01 to 99:59:59
Pause time	00:00:01 to 99:59:59
Storable SOPs	10
Measurement of input energy possible	yes
Interface	RS 232 / RS 485
Drive	3-phase asynchronous motor with frequency converter
Drive power	750 W
Electrical supply data	different voltages
Power connection	1-phase
Protection code	IP 30
Power consumption	~ 1250 W (VA)
W x H x D closed	640 x 480 (780) x 420 mm
Net weight	~ 72 kg
Standards	CE
Patent / Utility patent	SafetySlider (DE 202008008473)

*depending on feed material and instrument configuration/settings