Re: More info on freeze cast process (FCP), ATTN: Andy Scott

From: Bradley VanDike (
Date: Fri Apr 09 1999 - 16:09:38 EEST

I have seen water freeze in a vaccum chamber. What takes place that causes that to happen? Does the extraction of air molucules cause the temperature of the vaccum chamber to drop?

Brad Van Dike
Yazaki North America
Canton, Michigan
phone: 734-844-6994

>>> "Monica & Glenn Whiteside" <> 04/09 12:12 AM >>>

Your ideas would probably work OK. I think one of the toughest areas would
be in designing the mold correctly, figuring out the "expansion factor"
necessary to accomodate for the water-to-ice transition multidirectional


Glenn Whiteside

>Glenn & Andy,
>I wonder if following will make for a repeatable process, without air
>1. place the mold and water in a vacuum casting machine (Kugelgen, MCP,
>2. degass the water in a vacuum chamber
>3. after degassing, but before the water freezes, pour water into mold
>4. contiune applying vacuum until frozen
>Any thoughts?
>Dan Davis
>PROTON Rapid Prototyping & Manufacturing Center
>Hicom Industrial Estate, Batu Tiga, PO Box 7100
>Shah Alam, 40918 Selangor MALAYSIA
>+60 3 515-2380 phone/fax
>> -----Original Message-----
>> From: Monica & Glenn Whiteside []
>> Sent: Thursday, April 08, 1999 8:57 AM
>> To: Rapid Prototype Mailing List
>> Subject: More info on freeze cast process (FCP), ATTN: Andy Scott
>> Andy:
>> In reply to your question I have quoted some more information from the
>> article that might answer
>> some questions that people may have:
>> "Fine-tuning the process:"
>> "Not surprisingly, many problems were encountered during the
>> development
>> of the freeze cast process.
>> Mold design was particularly challenging, because water expands as it
>> freezes. Fortunately, ice exhibits the same linear expansion
>> repeatability,
>> if frozen at the same temperature. However, the expansion is
>> multidirectional (I take this to mean that water is isotropic - GW).
>> Therefore, the elastomer mold must be designed to provide enough extra
>> volume to absorb multidirectional forces. Moreover, the thickness and
>> consistency of the elastomer must be correlated with the different
>> modules
>> for the different shapes of the castings".
>> "After conducting hundreds of tests and measurements, problems
>> involving
>> the morphology of castings and the induced stresses were resolved. A
>> system
>> was developed in which several basic geometries were designed, to
>> which
>> certain semi-constants could be applied in the design of a specific
>> mold. A
>> major breakthrough came when directional solidification was viewed in
>> terms
>> of expansion rather than shrinkage".
>> "Another major problem was how to prevent the cracking caused by
>> stresses induced in the ice pattern by constricted freezing. This was
>> studied and attacked from three different directions: mold design, the
>> freezing medium's velocity and temperature, and air content in the
>> water/ice
>> system. It was discovered that
>> extremely low temperatures trigger cracking, particularly when the
>> patterns
>> are stripped at higher temperatures. This problem was adressed by
>> "conditioning" the ice, just as wax is conditioned prior to being
>> injected.
>> Conditioning involves controlling the air content of the ice and
>> regulating
>> additives (amount and chemistry) in the water".
>> "Warmer mold temperature was found to be crucial for fast, clean
>> stripping of rubber molds. Parting sprays that do not freeze,
>> pre-chilling
>> the water solution, and higher temperatures are used for
>> fast-stripping of
>> the molds".
>> "Air bubbles trapped on the surface of the ice were a recurring
>> and
>> persistent problem, in spite of molds designed to permit air bubbles
>> to
>> escape. Unfortunately, these bubbles would be reproduce on the
>> surface of
>> the casting. This problem was minimized by controlling turbulence and
>> counter pressure within the mold, through proper mold design and
>> venting. A
>> vacuum was also applied in a sealed chamber, prior to and during the
>> mold-filling procedure. A combination of these methods, along with
>> special
>> additives for the water, finally eliminated the air bubbles".
>> Fascinating process!!
>> Hope this additional information helps.
>> Best Regards,
>> Glenn Whiteside
>> >In a message dated 99-04-05 19:39:55 EDT,
>> writes:
>> >
>> ><< Then water
>> > (with "special" additives to minimize air bubbles) is poured into
>> the
>> rubber
>> > mold and frozen. >>
>> >Water expands when it freezes. Is it isotropic? Then you need to
>> compensate
>> >for the metal shrinkage as it cools. Sounds to me, it might take a
>> few
>> >iterations to get the numbers dialed in.
>> >Andy Scott
>> >Lockheed Martin Aerospace
>> >
>> >For more information about the rp-ml, see
>> >
>> For more information about the rp-ml, see
>For more information about the rp-ml, see

For more information about the rp-ml, see

For more information about the rp-ml, see

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