|
Brian,
First you can rough cut to your desired shape, leaving extra.
You then ramp up to a shrinking heat, hold temp for a few hours and then
ramp down to near room temp. This will actually shrink and toughen the
acrylic. It will shrink 2 or 3% in size. Then, after your finished
machining, you do the same but to a lower temp to stress relieve the stresses
caused by machining.
If you think about what happens when your machining anything, there are
very high temperatures created at the tool tip. This heat is concentrated
at the surfaces being machined. The interior of the part gets warm but isn't
heated to the surface temp at the tool tip. The post machining heat evens
this out.
The times and temps can be found in PVHO. You need an oven with
precise temp settings and it takes HOURS if your dealing with a thick
piece. I did my 2 inch thick K-350 main view port. I don't remember
the temps I used off hand but I started the process one evening and finished the
next afternoon, changing temps every half hour for the ramp up and ramp
down.
Dan H.
|