Re: [PSUBS-MAILIST] acrylic dimension change

Dan,

That's very interesting about the acrylic faces not being even, I'm only familiar with the plexiglass that is commonly purchased which is "sheet" acrylic. The cast acrylic is a new one for me, I assumed the cast was similar to the sheet but I guess not. So then you probably had to machine the faces perfectly flat and the sand and polish them to get them crystal clear. How smooth were you able to get the acrylic with just a machine tool?

Thanks

Brian

----- Original Message -----

From: Dan H.

To: personal_submersibles@psubs.org

Sent: Monday, January 23, 2006 10:46

Subject: Re: [PSUBS-MAILIST] acrylic dimension change

Brian,

I first shrunk my viewports with a higher heating process. This was before final machining. I probably did have some thickness shrinking then but I didn't have an exact measurement of the thickness before hand. When you get your acrylic it won't be exact thickness anyway. My pieces were all different thicknesses. I don't remember the exact variations but I'm thinking they varied about .030 thousants of an inch. They even very from one edge to the other of the same piece.

I was told that thick acrylic sheets is made by pouring the liquid acrylic between two sheets of glass and there is always some bulging of the glass form.

If you need exact thickness you should have your acrylic in hand before you machine your housings.

Dan H.

----- Original Message -----

From: Brian Cox

To: Personal_Submersibles@psubs.org

Sent: Monday, January 23, 2006 11:34 AM

Subject: [PSUBS-MAILIST] acrylic dimension change

Hey Dan H,

When you annealed your viewports did you have any change in the thickness ? I'm getting ready to machine my viewport flanges but I haven't purchased the acrylic yet, I'm just wondering if that dimension is going to change on me.

Thanks,

Brian