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INFRARED RADIANT HEATING The principal advantage of radiant heating over airoven
heating is speed of heating. Radiant heating time cycles for
.125" thick Chemcast® GP heated from one side only may vary
from one to three minutes, depending on the type of heater and
the distance from the heating surface to the Chemcast® GP,
compared with about 10 minutes for airoven heating. Temperature uniformity varies with the type of heater used.
Heaters with more uniform surface temperatures can be held closer
to the Chemcast® GP. Chemcast® GP is opaque to much of the infrared radiant energy
and absorbs most of the energy on the surface exposed to the
heater. The rest of the sheet is heated largely by conduction
from the exposed surface. Thus, radiant heating should not be
used for sheets over .125" thickness when heated from one
side, or .250" thickness when heated from both sides,
because the surface exposed to the heater may become overheated
before the opposite surface or the center of the sheet has
reached forming temperature. Infrared heating time is critical and must be controlled
within a few seconds because of the high surface temperatures
(usually 600°F. to 1,000°F.) of the heaters and the large
amount of energy radiated from them. Infrared heaters are usually
controlled by a timing switch on a relay circuit, varying the
onoff cycle to meet the requirements of particular forming
operations. Infrared radiant heating is not recommended for heating large
areas where the most uniform heating is necessary in order to
obtain excellent optical properties in the formed part. With
infrared heaters, power required is approximately 10 watts per
square inch of sheet area. |
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Copyright © Plastiglas de Mexico 1999
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