Fritsch PULVERISETTE 5, Operating Instructions Manual

Page: 34 / 72

6.4.2 Speed
Higher speeds shorten the grinding time and increase the percentage of
fine particles.
Lower speeds increase the grinding time and lower the temperature,
which can lead to fewer pauses. This means that the overall working time
may remain the same. The wear is increased in this case though.
Fritsch recommends however to use the maximum
speed and to plan for enough pauses so that the wear is
minimised.
For thermally sensitive materials, the optimal rotational
speed needs to be determined through experimenta‐
tion.
6.4.3 Reverse mode
n
Useful for mechanical alloying
n
Improvement of the homogeneity of the sample
6.4.4 Number and size of the balls
NOTICE!
It is not advisable to mix balls of different diameters. If
balls with different diameters are used, increased wear
and damage to the grinding elements is to be expected.
You can find the recommended number and size of balls
in Ä Chapter 6.1 „Choice of grinding bowls and grinding
balls“ on page 28.
Larger balls are used for pre-crushing. (See Ä Chapter 6.1.2 „Number of
balls per grinding bowl (independent of the material quan‐
tity)“ on page 31).
To increase the proportion of fine particles, the large balls need to be
replaced by smaller ball sizes during the course of the grinding process.
Using the device
- 34 -