RKT wrote:
"Richard Riley" wrote in message
...
On Wed, 3 Mar 2004 21:54:50 -0500, "RKT" wrote:
:I am trying to piece together the process of vacuum bagging a CF part
from
:several sources and comments. I am trying to achieve a glossy finish on
the
:mold side of the finished part.
:
:I though that the gloss that I saw on a purchased part was achieved from
:GelCoat. The manufacturer tells me no - not GelCoat. He tells me that my
:mold (aluminum) must have a 'mirror-like' finish and that I can get that
:easily by having it Nickel plated.
:
:But I'm not certain if that approach is compatible with my perception of
the
rocess:
:
:1. Nickel plate the mold.
:2. Wax the mold several times.
:3. Apply resin to both sides of the CF fabric.
:4. Remove execess resin.
:5. Apply CF to mold.
:6. Apply peel-ply.
:7. Apply breather.
:8. Apply vacuum bag, seal.
:9. Apply vacuum (18mm Hg) and slight heat to accel the cure (~110F)
:10. Remove piece.
:11. Buff or solvent (to remove wax?)
:12. Buff to gloss?
:
:What is confusing to me is why a mirror finish of the mold is 'absolutely
:required' to achieve gloss(acc. to source) if I am applying and buffing
the
:release wax. He says 'the wax is going to transfer to the part'. I
certainly
:believe him, but 'im not getting how the gloss is 'applied' in the
process.
:
:I have done this process using water soluble release w/o plating the mold
:and get a VERY dry-looking, matte finish on the mold side. The finished
part
:is indeed very light - so I thought I was removing TOO much resin to
achieve
:the gloss.
:
:I have a lot to learn. Can someone help me make sense of this process so
I
:will have confidence that Nickel plating the mold is magically (and
:counter-intuitively to me) going to yield this high-gloss finish?
The only way I've gotten it is with clear gel-coat. I suppose nickel
might work, if the resin you're using (polyester, epoxy, vinyl ester,
whatever) wets nickel and doesn't bead up on it.
But it's going to bead up on wax, anyway. So I *think* you're still
going to get pinholes.
Get a piece of adhesive backed nickel foil from McMaster-Carr - they
have it 15" wide, .004" for about $30 a foot. Lay up on it the way
you describe, see if it works. Just a thought.
Good idea. Will try. Thank you.
In my experience, the mold transfers everything to the product. So your
initial plug has to be basically perfect, although you can remove a few tiny
"high" spots in your mold that were low spots in the plug. A good, hard
molding gel coat helps a lot. You need to be at 2000 grit and buffed out to
be really smooth. I can't comment on nickel plating a mold, but you can get
very, very smooth with molding gel coats on complex surfaces. For flat
surfaces, or 2-D curves there are many more options.
Using wax then PVA release agent will usually transfer some surface
imperfections to a product. After a few releases, you should be able to use
mold release wax alone. A few good coats of wax properly applied will transfer
negligible imperfections to the product. Nothing that can't be buffed out --
as long as your resin is very hard and cured. Soft materials don't buff to a
high gloss nearly as well.
Scott Gettings