Struers Prepamatic-2, Instruction Manual

Page: 45 / 242

Prepamatic-2
Instruction Manual
41
Prepamatic cannot distinguish whether the stock removal takes place
on the sample or on the grinding stone. Therefore, a smaller stock
removal than the set one can take place. In order to compensate for
this a higher removal can be set - how much higher only tests can
show, as the removal is dependent on the sample material.
Therefore, where a very accurate stock removal is required, it is
recommended to make a series of tests and then measure the actual
removal. Where an accurate removal is required, it is not
recommended to prepare more than one sample at a time.
Another source of inaccurate stock removal is the zero setting of the
measuring system, as this does not take place until after one rotation
of the sample holder head (13 rotations, when grit sizes finer than or
equal to 2400 are specified). If the sample is very soft some removal
will take place during the rotation. This inaccuracy can be
compensated for if the above-mentioned measuring series is carried
out.
In general it is recommended to use grinding forces and grinding
bases/grain sizes which give relatively slow removals, i.e. more than
20 seconds when grinding on stone or more than 180 seconds on
MD-Allegro.
When grinding on the grinding stone, the set stock removal may be
higher than what the stone can grind off without dressing (opening).
Therefore, an automatic dressing of the grinding stone takes place
when the stock removal has been reduced to less than 15 µm per 10
sec. If many dressings are necessary a reduction in accuracy must
be anticipated.
If a set stock removal e.g. on MD-Allegro is too big and therefore will
take a very long time (and is maybe even impossible to obtain) the
grinding stops automatically after 20 minutes.
Error sources when using
stock removal