absorption or for other unexplained reasons.
U WARNING: Although the Abraser is designed to
operate at normal room temperature, it may be
used at temperatures as low as freezing. In
atmospheres approaching 0°C (32°F), allow the
motor to warm up until it reaches normal speed
before lowering the abrading arms. When the
Abraser is not in use, keep it in a room at normal
temperature.
Determining the Test Procedure – Standard
test procedures for a number of materials have
been established and, in the interest of
uniformity and the ready exchange of
information, are very generally accepted. To
ensure that test results will be comparable, the
procedure described should be followed exactly.
In the absence of a standard specification, the
technician must work out his or her own test
procedure. They may begin by referring to the
general recommendations for various materials
shown on pages 32 - 37. Final choice of
abrading wheels, load weights, method of
mounting the sample, kind and duration of test,
and other details may best be decided by
preliminary testing of the specimen material.
Begin by estimating the nature and degree of
wear that the specimen would receive in actual
service. Select an abrasive wheel that will most
nearly reproduce this wear, but will not clog with
the material being tested. Past experience must
guide in choosing the load weight. Under
ordinary conditions a load and wheel
combination should run on a specimen a
minimum of 300 cycles before the end point
occurs, otherwise the test may be too harsh. In
certain instances there may be exceptions to
this rule since there are many varieties of
material that can be tested with the Abraser.
When setting up a test procedure, always keep
in mind to avoid wearing the material too fast as
this will result in ripping and tearing action.
Recording the Test Procedure – It is essential
that careful record of every phase of the test
procedure be kept for purposes of comparison.
This will also enable others to duplicate the test
at a later date. An example of a standard form
for test record is shown on page 48.
Selecting the Method of Evaluating Test
Results – Test results are commonly expressed
as a wear factor or numerical abrasion index of
the test specimen. The most common methods
for calculating this index are by measuring a
visual or physical change. It should be noted
that the wear factor arrived at by any one of the
following four methods is not directly
comparable.
METHOD OF EVALUATION
A single test may correctly indicate the
material’s resistance to abrasion, but it should
not be accepted as a final answer. A minimum
of three to five tests should be made of any
given material and the average result taken to
represent the true value.
A. Visual End Point Method – Certain
materials are best adapted for testing to a
clearly marked change in appearance or
physical breakdown of the specimen. This is
especially true of materials with a plated, glazed,
polished, or printed surface where the end point
is sharply indicated; of materials that withstand
less than 300 abrasion cycles before reaching
the end point of test; and of textile materials.
The visual method is a subjective test that
requires examination of the test specimen, and
should be conducted under controlled lighting.
The test results will be a description of the wear,
and must be as thorough as possible to ensure
all the details of the wear mechanism are
captured. For example if the test specimen is a
coating, one suggestion is to monitor when the
surface coating has worn down enough so that
the substrate material is visible (this is defined
as ‘breakthrough’). For printed specimens,
breakthrough is when a portion of the printing
has fully worn away. Breakthrough testing
should be quantified by recording the number of
cycles it took for breakthrough to occur.
Other examples of Visual End Points:
1. Loss of Luster
2. Changes of Surface Appearance
3. Color Changes
4. Appearance of a Hole
Another option is to compare the abraded
specimens with a measured abraded standard.
A rating scale of 1 – 5 is commonly used to
assist with this type of evaluation, and often
includes a photograph depicting each ranking.
B. Weight Loss Method
– The weight loss test
method is a quantifiable method in which you
record the weight loss of your test specimen due
to abrasion. To perform this method, you will
need to have access to a precision balance,
preferably one that can measure to the milligram
range since some tests may yield very low
weight loss. Weigh your test specimen before
and after testing to obtain your initial and final
weight values. The difference between these
two values will be your weight loss.
29 5135 / 5155 Operating Instructions ver 1.1
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