The book says do it, I would.
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
----- Original Message -----
Sent: Tuesday, December 07, 2004 1:01
PM
Subject: [PSUBS-MAILIST] Thermoforming
acrylic sheet (domes)
Thijs Struijs