From: Kirk Alcond (
Date: Fri Apr 18 2003 - 20:55:03 EEST

Hi Doug,

Sorry, no pictures. I'm from back in time when refrigerators were mostly
steel, sheet metal. They came with solid gaskets in the doors. For a low
vacuum draw they worked fine. I have worked in different shops where we set
these up for casting urethane into RTV molds. I will say though, our best
setup was a large old autoclave we got for fifty bucks from the UCLA
surplus inventory, warehouse. We could pull a vacuum then pressurize
without opening the door. I have also had a 75 gallon pressure tank made by
a local welding shop, in one afternoon, by using a surplus ship's tank
hatch and a surplus chunk of 36" diameter steel pipe from a salvage yard.

I've been away from this end of things for a while though. It sounds like
Andrew Miller is the man to check with for up to date information.

My best to you!
z Kirk
Kirk Alcond, UCLA Architecture, Shop Supervisor,
Phone: 310-825-1626

>Date: Thu, 17 Apr 2003 19:07:24 -0400
>From: Doug Groh <>
>Subject: Re: Pressure tank wanted
>To: Kirk Alcond <>
>X-Mailer: Microsoft Outlook Express 6.00.2600.0000
>you mentioned a refrigerator.
>Do you mean to use it as the chamber?
>Do you have pictures?
>----- Original Message -----
>From: <>Kirk Alcond
>To: <>Scott Moeller
>Cc: <>Rapid Prototyping Electronic Mailing List
>Sent: Thursday, April 17, 2003 6:23 PM
>Subject: Re: Pressure tank wanted
>Hi Scott,
>I have had better luck with the reverse approach. Instead of forcing the
>material into the mold suck the air out of the mold and the pour material
>will fill the empty space. First, you put your pour material into an
>oversize container and place it in a vacuum chamber. Draw a vacuum on it
>to off-gas or foam-off all the unwanted bubble forming gas. Then you place
>your RTV mold in the chamber, pour in the cleaned pour material and draw a
>vacuum on it. Any air in the mold will be vacuumed out and you will have a
>perfect casting. You don't need a super high powered vacuum chamber to do
>this. You could make your own using an old refrigerator and an old air
>compressor pump hooked up in reverse. After testing it to make sure it
>works, install a 1/2" thick lexan window and lights so you can watch the
>foaming process. For experiments you can use a bell jar over a small
>vacuum former table. This is just a suggestion, but I have had great
>results with it.
>Have a "Creative" day!
>z Kirk
>Kirk Alcond, UCLA Architecture, Shop Supervisor,
>Phone: 310-825-1626
>At 03:34 PM 4/16/2003 -0500, you wrote:
>>I'm interested in buying a used, 30 gallon(ish) pressure tank for the
>>purposes of pressurizing RTV molds. I'm having a heck of a time locating
>>any. If anyone has any leads, please let me know.
>>Scott Moeller
>>Progressive Engineering, Inc.
>>7741 Commercial Lane
>>Allenton, WI 53002
>>Phone: 262-629-4610 x35
>>Toll-free: 866-629-4610
>>Fax: 262-629-4625
>>E-mail: <>
>>web: <>

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