We are using 0.03” thick white
thermoform plastic to make our piece. There are 6 pinwheel sections that will
be raised during thermoforming, and each of these sections has a projected area
of 0.964in2. The total surface area of each raised segment will be
1.2218in2 which means that the thickness of the thermoform plastic
will decrease on average 21.1%. This means that the
average thickness of the stretched plastic is expected to be 0.0237in.
The
plastic does not stretch evenly and is expected to be somewhat thick on the top
of the extrusion than on the sides. With this in mind, the mold has been
constructed with a 0.0225in margin between the mold and expected edge of the
extruded part. This is an upper estimate of the ultimate thickness of the
plastic along the edges to allow re-machining if necessary once the prototype
has been produced and measured.
The extrusions are
0.205in tall as the final height of the extrusions is expected to be 0.23in
above the top surface of the mold. The thickness of the plastic on the top
surface is expected to come out to about 0.027in and an estimated eventual 1%
shrinkage from the initial molded height, the part should be meet the required
dimensions at 0.23in.
Goal Maximum Height: 0.23”
Height of mold: 0.205”
Original Thickness of Plastic: 0.03”
Stretched Thickness of Plastic (top
surface): 0.027”
Maximum Height (prior to cooling and
shrinking): 0.232”
Maximum Height (after cooling and shrinkage):
~0.2296”
-> Expected part dimensions are within the 0.005”
tolerance of the designed part dimensions
No comments:
Post a Comment