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Hi All,
With my "doughnut" acrylic viewport all I plan to do is purchase a
24"x24"x4" and then cut a inside diameter of 20" and a outside diameter of 24"
thus having a 2" thick viewport to look through. This will give me a 360
degree view but only 4" high. Does anyone know if I need to heat this
piece of acrylic up first before I cut it so that any shrinkage that accurs will
not change my dimensions? According to the infor below that would seem to
be the case. Then would I need to heat it again after it has been
cut? Maybe I don't need to heat is at all?
Shrinkage
Because of the orientation imparted during manufacture, acrylic sheet shrinks slightly when heated to thermoforming temperatures. Manufacturing direction can be determined from the sheet label or print on the masking. The lines of print are perpendicular to the direction of manufacture. Original dimensions won't change in fabrication operations not requiring heat. However, sheet heated to thermoforming temperature changes dimensionally by about 3 percent maximum shrinkage in the manufacturing direction and approximately 0.5 percent maximum width increase (transverse direction). Measure the shrinkage in a preliminary test, if acrylic sheet isn't held in a retaining frame. Then, determine the size of material required to compensate for shrinkage before cutting any blanks.
Regards Brian Cox
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