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Preparation for Cementing
Acrylic Sheet Preparation The first step is preparing the area to be
cemented. Edges must be cleanly cut and/or properly machined. If
a dull blade was used for a saw cut, resulting in a melted or
chipped edge, contact between the sawed edge and solvent may
result in crazing of the material. Finish all rough edges on a
jointer, shaper or edge finisher. If you cannot do so, wetsand
the edges with a flat surface or block. Do not polish edges which are to be
cemented. Polishing will produce a convex edge with rounded
corners and will result in an unsightly, weak joint. Also,
a flamepolished edge may craze when it contacts solvent cement. Crazing may also occur if internal stresses
from shop fabrication are high. To eliminate such stresses,
anneal the piece at 180°F (80 °C). Figure that the heating time
and the cooling time in hours should each equal the material
thickness in millimeters, up to 6 mm. For example, you would heat
a 3mmthick sheet (0.118") for three hours and allow it to
cool gradually for three hours. For thin sheet, the annealing (heating) time
should not be less than two hours. It is not necessary to heat
any piece for more than six hours, though it will not be harmful
if heating time is extended due to shift schedules, etc.
Remember-each hour of heating time requires a corresponding hour
of cooling time. SURFACE PREPARATION BEFORE CEMENTING
Solvent mixtures with low volatility should be
used. Solvent mixtures of this kind reduce air condensing and
humidity on the surface which causes whitening of the joint area. |
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Copyright © Plastiglas de Mexico 1999
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