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DOCERAM Roughness Measurement
according to DIN EN ISO 4288288 |
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Roughness
Measurement Equipment |
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Principle of Roughness Measurement |
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A tactile cone with a
chamfered tactile tip is pulled (traversing) over the
surface of the ceramic. In this way, the deviations of the
surface in a rectangular angle to the tactile direction are
measured. The standard
traversing length (lt) consists of the pre-travel (lv),
five sampling lengths (le) and the post-travel (ln).
According to DIN EN ISO 4288, the sampling lengths (le)
equal the cut off wavelengths (λc),
so that 5le = 5λc =
evaluation length (lm). |
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Pre-travel (lv) and post-travel (ln) are to
provide for the transient and attenuation effects of filters.
They have the same length as the individual sampling (lv
= λc = ln). The cut
off wavelength (λc)
determines the traversing length lt of the tactile. DIN
EN ISO 4288 stipulates that the cut off wavelength for
non-periodic profiles has to be selected according to Ra
or Rz in the following way: |
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Non-periodic Profiles |
Cut off |
Sampling / Evaluation Length |
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Rz (µm) |
Ra(µm) |
λc
(mm) |
le (mm) / lm (mm)
(with Z = 5) |
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Rz ≤ 0.1 |
Ra ≤ 0.02 |
0.08 |
0.08 / 0.4 |
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0.1 < Rz ≤ 0.5 |
0.02 < Ra ≤ 0.1 |
0.25 |
0.25 / 1.25 |
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0.5 < Rz ≤ 10 |
0.1 < Ra ≤ 2 |
0.8 |
0.8 / 4 |
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10 < Rz ≤ 50 |
2 < Ra ≤ 10 |
2.5 |
2.5 / 12.5 |
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50 < Rz |
10 < Ra |
8 |
8 / 40 |
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Traverse length lt = lv + lm + ln
= lv + 5 x λc + ln
= 7 x lc The norm suggests, that for special
purposes (e.g. the measuring area is too short for the
traversing length), the next shorter cut off or a free cut off
(values between 6 and 70) may be employed instead of the
standardized one required by the DIN EN ISO 4288.
Apart from the standard traversing length prescribed above,
special traversing lengths of any size can be adjusted. In the
case of special traversing lengths, filtering is performed on
the basis of the cut off wavelength related to the next shorter
standard traversing length (see table). Example: For the
traversing length lt = 20mm, the cut off wavelength
λc = 2.5mm results. |
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The Arithmetical Average Roughness Ra |
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In
order to calculate Ra, the profile has to be changed into a
rectangle of area equal to the square and of equal length.
The Arithmetical Average Roughness Ra is equivalent to the
height of the resulting rectangle. |
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Mean Roughness Depth Rz |
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DOCERAM Measurements according to
DIN EN ISO 4288 are carried out with a German "Mahr
Perthometer" measuring instrument.
Ra of satinated surfaces equals 0.4-0.6
µm.*
Ra of polished surfaces equals 0.2-0.3
µm.*
*Guideline values, gauged on test pieces! |
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DOCERAM Hardness Measurement according
to Vickers |
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The “Impression Hardness” is
defined as: The resistance of a crystal surface (ceramic)
against a plastic deformation inflicted through a form- and
size-normed test piece under a certain pressure.
For Vickers Hardness, the penetrator consists of a diamond,
ground in the shape of a tetragonal pyramid. A certain
pressure is applied on the diamond needle to let it
penetrate the test piece. This results in an impression in
the surface of the ceramic with a certain size.
Vickers Hardness is calculated as
Hv = P / F
... the test load in relation to the size of the impression
in the ceramic surface.
Hv = Vickers Hardness, P = Test Load, F =
Impression Surface
DOCERAM measures with a German
Hardness Tester from Leitz, Wetzlar. The Test Load is 0.5
kilo pond (Hv0.5). For hardness values of the different
materials, please refer to the "Technical Parameter"
section! |
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Hardness Measurement
Equipment |
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DOCERAM Density Measurement |
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The buoyancy-flotation method makes use
of the fact, that a buoyancy-flotation acts on a body in a media
equally to the weight of the liquid displaced by that body.
The buoyancy-flotation is assessed through weighing the test
piece in air and in liquid. Knowing the density of the displaced
liquid, the volume of the test piece can be calculated. Volume
and mass of the test piece make its density.
For density values of the different materials, please refer to
the "Technical Parameter" section! |
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DOCERAM Surface Inspection |
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| Mantis
Magnifying Instrument (x 2/4/6/8) |
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Microeye Inspection (x 40-140) |
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REM
Surface (x 1,000) |
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DOCERAM Surface Inspection includes
usual visual inspection, inspection with German "Mantis"
magnifying instrument, inspection by electronic "Microeye"
inspection equipment and REM surface examinations. |
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TOP |
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