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REFORMING Properly formed Chemcast® GP parts will retain their shape if
kept below 180°F. If exposed to higher temperatures, they tend
to revert to the original flat sheet form. This property, called
"elastic memory," prevents forming Chemcast® GP parts
in several stages as in sheet metal pressing, but permits the
fabricator to reheat and reform the sheet if he makes an error in
forming. When reforming, the sheet should be heated for
flattening and reforming at the same time to keep at a minimum
the total time the sheet is exposed to oven temperature. COLD FORMING Chemcast® GP can be bent while cold to simple shapes by
springing the material into a curved frame. The radius of the
curvature should be at least 180 times the thickness of the
sheet. Cold forming Chemcast® GP beyond these limits may result in
crazing of the material due to stresses beyond those recommended
for a continuous load. SLIP FORMING Chemcast® GP is usually clamped around the edges after
heating before it is formed. This puts the whole sheet in tension
and it stretches more uniformly and wrinkles are not apt to form.
In some cases, in order to obtain a thicker finished part, a
predetermined amount of Chemcast® GP is allowed to slip under
the clamping ring to reduce thinning out of the sheet. Wrinkles tend to form outside the ring around the edge of the
piece, limiting the amount of material which can be allowed to
slip in. When sufficient material has slipped in, the rings are
clamped more tightly and the draw is completed. Hot or insulated
clamping rings may be used to avoid chilling the material. Forming Temperatures and Cycles
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Copyright © Plastiglas de Mexico 1999
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