[PSUBS-MAILIST] Pre-machined Acrylic Prep

[Alan James via Personal_Submersibles]

Jon,I bent some thick acrylic that I was going to attach to a dome for mounting.The acrylic ring was in 2 pieces & fitted in a standard oven, from memory mounted on wood.I drilled a hole from the warming tray through to the main oven to heat the oven with the warming tray element & monitored the temperature with a probe & external monitor. I was able to keep the temperature within the required parameters by manually monitoring it & infrequently turning the oven off and on.Just mentioning this as it can easily be done, however I was up all night while it cooled.There are lots of kiln temperature controllers on the market where you can program the heating and cooling profiles. You would need a fan (from an old oven) to distribute the temperature evenly & maybe a few temperature monitors to check that the fan is keeping the temperature even.Alan

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  On Sat, 3 Sep 2022 at 2:56 am, Jon Wallace via Personal_Submersibles<personal_submersibles at psubs.org> wrote:   Anyone out there normalizing their acrylic?
Section 15 of Stachiw's Handbook of Acrylic is dedicated to stress relieving processes for acrylic viewports.  Stachiw states that such stress relief is required to reduce the premature crazing and failure of acrylic surfaces.  Section 15.2.1 discusses "normalization" of the material and how it both relieves stress and changes the physical properties of it.  The amount of time required to heat, bake, and cool the acrylic material depends upon thickness, but is lengthy in all cases.  I have reached out to numerous acrylic molders in New England and found that none of them have ovens that meet the technical requirements for proper normalization or annealing as described by Stachiw.  That leads me to the conclusion that I'm probably/definitely going to have to build my own oven for such purposes.  I think Hank did build such an oven but I haven't heard of anyone else doing so.

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