Adjusting the Height of the Vacuum
Pickup Nozzle
After the specimen has been mounted, the gap
between the vacuum pickup nozzle and
specimen surface should be set. It is extremely
important that the height of the suction nozzle be
adjusted properly, especially when evaluating
specimens of different thicknesses.
Figure 53
The height of the vacuum pickup nozzle is
referenced in many test methods. If it is not, you
must consider the material being tested. For
most materials, a gap of 6.35 mm
(0.25 inch) is
sufficient. However, a setting of 3.17 mm
(0.125
inch)
has been found to be more effective on
certain rigid materials.
To adjust the vacuum nozzle height, first lower
the vacuum pickup nozzle from its rest position.
A precision adjustment knob located next to the
nozzle is used to adjust the distance between
the nozzle and specimen. Each full rotation of
the knob represents a 1.27 mm
(0.05 inch) height
adjustment.
î NOTE: To facilitate resetting the nozzle for a
given thickness of material, a shim may be inserted between
the nozzle and specimen, provided care is taken not to
damage the specimen surface.
Setting the Vacuum Level
The vacuum suction level should be set high
enough to remove debris from the specimen
surface, but not lift flexible samples. A visual
inspection of the wear path can usually indicate
if debris is adhering to the specimen surface and
the vacuum level (or vacuum pick-up nozzle
height) needs to be adjusted. For test control
and standardization of vacuum suction, the
vacuum level is calibrated to values of 50 â
100%.
Modified Vacuum Pick-up Nozzle
A modified vacuum pick-up nozzle is available
for materials that are evaluated using a change
in haze. It has been found that many materials,
such as transparent plastics, may generate
static electricity during testing resulting in an
attraction of loose grit and debris to the
specimen surface. The orifice openings of the
modified vacuum pick-up nozzle are 11 mm
(0.4375 inch) opposed to the nominal opening of 8
mm
(0.3125 inch). This assists with the removal of
debris that has adhered to the specimen as a
result of this static attraction.
If transparent materials are the only material that
you intend to test with your Taber Abraser, you
may elect to permanently modify the vacuum
pick-up nozzle (see below diagram).
21 5135 / 5155 Operating Instructions ver 1.1
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