From: \ (rp@rapidprototyping.net)
Date: Sat Jun 28 2003 - 00:01:21 EEST
I have frequently used LOM up to a few years ago to produce Aluminum
Castings, a couple of dozen total but mostly very large pieces like
Hatch covers for ships and other dumb and clunky parts.
It is my opinion that if this Master is smaller than a bread basket or
even a bit larger don't use LOM.
These patterns have to be considered a one use master pattern to produce
a Matchplate or other tooling and NOT for more that one off plaster
molding.
In any case, a soft shell shellac, rubber or completely sealed water and
vapor tight these will in a very short time expand and crack and once
that happens it's all over.
Hard and brittle epoxies break from the inherent moister in the paper,
it expands and breaks the covering. No matter how well you seal these,
hard or soft use it fast.
I have gone back to traditional hand made patterns for parts over 3 feet
long, we used SLA two months ago to build 3 feet long street lamps and a
month before that 5 feet long Machine covers. SLA is getting to be a
pretty cost effective choice, even for the big stuff.
Ron Barranco
www.zcastings.com
www.stereolithography.com
-----Original Message-----
From: owner-rp-ml@rapid.lpt.fi [mailto:owner-rp-ml@rapid.lpt.fi] On
Behalf Of Makai Smith
Sent: Friday, June 27, 2003 9:23 AM
To: rp-ml@rapid.lpt.fi
Subject: RE: sealing of LOM masters
shooting from the hip..
I'd say either shellac or epoxy.
I've never used epoxy for this, but you could mix it thin. There are
some two-part paints and coatings (like the stuff used to finish floors
in harsh environments).
Shellac works for sealing paper because it has an alcohol carrier.
(Worked great for painting drywall from 1920!) It forms a vapor-tight
seal. The downside is that water attacks it, but you'd be done with it
before that matters provided you built up several coats first. Find a
shellac based primer with high solids like made by Zinzer. And mix the
plaster HOT.
Makai
-----Original Message-----
From: Kevin Lafferty [mailto:KevinHLafferty@avenew.com]
Sent: Friday, June 27, 2003 11:15 AM
To: rp-ml@rapid.lpt.fi
Subject: sealing of LOM masters
I'm planning on using LOM masters as patterns for plaster molds.
Obviously this will subject the pattern to very high humidity. Can
anyone offer suggestions on sealing the LOM patterns so they will not be
effected by the moisture?
Kevin Lafferty
mailto:KevinHLafferty@avenew.com
-----Original Message-----
From: Kevin Lafferty [mailto:KevinHLafferty@avenew.com]
Sent: Friday, June 27, 2003 11:15 AM
To: rp-ml@rapid.lpt.fi
Subject: sealing of LOM masters
I'm planning on using LOM masters as patterns for plaster molds.
Obviously this will subject the pattern to very high humidity. Can
anyone offer suggestions on sealing the LOM patterns so they will not be
effected by the moisture?
Kevin Lafferty
mailto:KevinHLafferty@avenew.com
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