Re: [PSUBS-MAILIST] Acrylic Molds

["Mark Steed" <plutomark@mail.astate.edu>]

Doc: Wow, excellent and thanks. Mark Steed


---------- Original Message ----------------------------------
From: Doc <doc@bionicdolphin.com>
Reply-To: personal_submersibles@psubs.org
Date:  Wed, 08 Jan 2003 01:56:41 -0800

>Hi guys, just got in, I've been out exploring in the boonies around here.
>
>I'll put together a drawing of the backwoods acrylic oven soon and post a link.
>
> The basics of it are simple, picture a shoe box the size you need without the lid, line it with
>aluminum foil using double faced tape around the edges then stapled through the tape and foil.
> Now in the side cut an inspection hole about  1/4 of the way down and centered, 6" X 10" and
>cover it with 1/4" plate glass.
> At the bottom of the 2 ends cut several small breathing holes and a heater access door.
> Place your heater in the center of the box and build a metal rack that is about 3" higher than the
>top of your propane barbecue (without the legs) or propane heater, and place a sheet of 1/8" aluminum
>or sheet metal, (somewhat larger than your heat source) on the rack to evenly distribute the heat throughout the box.
> Around the top edge on the outside of the box attach a framework of 1x2 or or angle iron (bed frames work nicely)
>to clamp your former sheet and acrylic to. And finally, mount an oven thermometer on the wall across from
>your inspection window.
>
> Now here is where the different techniques determine which way you need to go. For AquaNuts we really only
>have two choices ambient or 1atm. If it's non structural you can blow it, if it's structural it should be draped which
>will require a male mold, coffin like handles clamped along the sides of the acrylic and a few strong helpers.
>
>To blow mold requires a box top of sturdy plywood with a air fitting centered and countersunk flush on the bottom
>side and fitted with a shut off valve and quick connector at the top side. Around the bottom border attach a gasket of
>weather stripping.
>Now with another sheet of plywood cut out the shape you want to make but make it a bit larger than the planned finished
>part. Paint the top side around the cut out with polyester resin or primer/ surfacer about 3-6" wide and sand smooth.
>Then polish with 2 or 3 coats of a good automotive car wax.
>
>Your acrylic sheet will now be sandwiched between the former sheet and the top and secured firmly with either clamps
>or preferably bolts and wing nuts.
>
>Now light up the ol barbecue and place your wood and acrylic sandwich on top of your box and secure it to the flange at
>the top of the box and you're cookin!
>
>At around 175-300º F (depending on the thickness & particular properties of the acrylic used) the plastic begins to sag,
>this is where you begin to add a little air pressure (on large canopies you can draw your projected profile with a permanent
>marker on the back wall of the box as a reference), slowly increase the air pressure until the plastic is just slightly larger
>than spec and turn off the heat while maintaining your pressure and let slowly cool.
>
>That's about it.
>
>To make a simple bend you just need a strip heater available at most places that sell acrylic, solvents and tools.
>Or if you're really good and quick you can use a heat gun,,,,, I'm not!
>
>I hope this helped, I'm off to dream about my next baking soda and vinegar powered Psub! Night all.
>
>Doc
>
>Reference;
>http://www.plaskolite.com/fabguide/pg11.pdf
>http://www.chemcastacrylic.com/technical/mx4b.htm
>www.tapplastics.com/plastics/ plasticsinfo/hi-acrylic.html
>www.sdplastics.com/acrylit1.html
>www.sunlight-tech.com/acrylic_tech_data.html
>www.manufacturing.net/esec/Article_85859.htm
>
>
>DJACKSON99@aol.com wrote:
>
>> Doc
>>
>> I need to bend a 35 degree turn in a 1 inch thick sheet of Acrylic that is 4 feet by 4 feet. I found a couple of helpful web sites (below) but I'd really like to see a photo and description of your oven.
>>
>> http://www.chemcastacrylic.com/technical/techinfo.htm
>> http://www.bayplastics.co.uk/product%20guide/Altuglas-guidenavbar/prod-altuglass-tech(bending).htm
>>
>> Please keep it online.
>>
>> Thanks
>> Doug
>>
>> >Mark;
>> > I've done considerable research and testing on different ways to form
>> > acrylic in the barn, from gravity to blow molding to drape forming of
>> > up to 1 inch thick over a male fiberglass mold. For blow molding or
>> > gravity forming, you can coat your separation points (ring) with a
>> > layer of epoxy resin or gelcoat and a thin coat of car wax. You can
>> > build a 4'X8' forming oven out of plywood or chip board, aluminum foil
>> > , a piece of 1/4" plate glass and a propane barbecue!
>> >
>> >Doc
>
>