Fritsch PULVERISETTE 23 Bedienungsanleitung PDF herunterladen (Seite 23)

6.3.2 Vibration frequency

Higher vibration frequencies shorten the grinding time and increase the

share of fine particles.

6.3.3

Number and size of the balls

Pre-grind course, hard material with large balls:

Reduced percentage of fine material!

Many small balls increase the percentage of fine material during

extended running time.

6.3.4 Weight of the balls (type of material)

A higher mass (specific weight) of the grinding balls accelerates grinding.

(see table in

Chapter 6.1 ‘Choice of grinding bowls and grinding balls’

on page 19).

6.4 Dry grinding

During dry grinding a bed of material with a fineness of approx. 20 µm

forms on the balls and the walls of the grinding bowl after approx. 5-10

minutes, which prevents further comminution. The grinding stock begins

to stick because the surface forces become too big.

If surface-active substances are added to the grinding stock, comminu-

tion can be carried out for longer and it is possible to achieve a higher

share of fine material.

Examples (maximum amount to be added in mass%):

n Stearic acid 2-3%

n Aerosil (fine-particle silicic acid) 0.5-2%;

n Quartz sand 2%

n Glass powder 2%

Highly flammable and flammable liquids such as ketone and benzine

with boiling points <80°C must not be used.

Using the planetary mill

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Fritsch PULVERISETTE 23 Bedienungsanleitung Seite 23