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Gabe 034 · Joined: 22 May 2006 Posts: 3

hey all,

i am new to the forum, and farley new to vaccumforming (very new Razz

)

i am having a prob with some bly holsters for an epIII CT costume. i made 2 wooden molds (front and back) of the holsters, and made them a little tall. i put them on my 1x1 table with a 4.5 HP shopvac, and heated the pladtic up in an oven set on 500 until it tunred all wavy. i put the plastic on the molds, with the vaccum running. got a good pull, then went to take it off the table, and the molds are stuck in the plastic!

it took a while, but i finnally got the molds out. (at the expense of part of the mold) i made sure there wasnt any undercuts or anything in it.

i added risers to it... same thing happend. what am i doing wrong? i have an order to fill for these, and i need it done this week. i fear i'm screwed......

ANH trooper · Master Joined: 20 Oct 2005 Posts: 305 Location: UK

Hi there

This is a common problem that I think we all suffer from.The plastic shrinks slightly as it cools so it's gripping your moulds.

What I do is reheat the plastic gently with a heat gun when the mould gets stuck,or cut the excess plastic off first then gently pry the mould out.You can try demoulding straight after the part is formed before the plastic starts to cool.

You can also screw handles onto the bottom of your wooden moulds to help with releasing too.I hear thet a light coating of baby powder on the moulds helps too,though I haven't tried it personally.

Hope this helps Wink

-Paul.

thebluecanary · Posted: Tue May 23, 2006 7:53 am Post subject:

You could also try a sock full of baby powder, and dust them a little. This might also help. And I think someone also mention using pam spray, but I don't think they had wood molds tho.

crashmann · Guru Joined: 27 Sep 2005 Posts: 501

After pulling the parts, I cut them from the sheet with at least a 2" border around them. Then I take the whole thing and whack one 2" edge on a 4"x4" piece of wood. A couple of whacks are usually enough to get the mold coming out, then you just pry the rest of the way with your fingers.

It's even easier if your using risers with a tapered edge (at least 15 degrees). Then you just pull out the riser, and drop the whole thing on the floor. Again, the mold starts coming out, and you pry the rest of the way with your fingers.

Demolding always seems to take much longer than actually forming Shocked

Good luck!

Charlie
TI-386

Gabe 034 · Joined: 22 May 2006 Posts: 3

thanks for the help! i will try it today, and see what happens.... i'll keep you updated!

jegner · Posted: Wed May 24, 2006 7:45 am Post subject:

The molds sticking in the plastic, as others have commented, is a common problem. Here is what I do:

Add risers, and if you can put a 15 degree angle on the risers, this will help the demold. Also, if your part has a hard straight edge, add a taper. This is a piece of wood, that tapers the hard edge down to the platen. It also acts as a removable wedge, that you can pry out and get a finger hold on the mold. Also, demold as soon as you can, while the plastic is still warm. For some molds, talcum powder works wonders.

You can tweak your molds until they demold better. Chances are, there is a part of the mold that is slightly undercut causing the trapping. Hard straight edges with no taper will do this.

Jim

Gabe 034 · Joined: 22 May 2006 Posts: 3

seeing as i didnt have any of the powder lying around, i tried demold when the plastic was still warm. it worked!

one problem though, i couldnt get a sharp pull.... is there a fine line i walk between succesful demold and sharp pull? or do i sacrifice one?

ANH trooper · Master Joined: 20 Oct 2005 Posts: 305 Location: UK

I wouldn't sacrifice a good pull for easy mould release.It sounds like you only got an easy release due to a weak pull,which is not gripping tight to the mould like it should.

It can be very tricky getting the moulds to release but the quicker you do it after the pull,the better.

Some of my moulds,mainly the 02 canister end caps,take forever to get off the moulds.If I am too eager they will split in a second,very unforgiving!I have to basically heat them up again gently,then twist and pull until the plastic moves a bit,then reheat and repeat until they are free from the moulds.Very time consuming for a few little bits of plastic but that's how it is sometimes Confused

-Paul.

Mattax · Expert Joined: 09 Mar 2006 Posts: 160 Location: Virginia

I am looking into using silicon spray. Also your local body shop paint supplier should have release compounds. But I think silicone spray would work best.
_________________
Mattax
TK487
Garrison Tyranus

jegner · Posted: Sat May 27, 2006 1:11 pm Post subject:

I do not recommend any sort of liquid, lubricant or petrol based products unless you want a greasy mess on the insides of your pulls. Talcum powder works great.

knightshade · Posted: Wed Jun 21, 2006 12:56 pm Post subject:

Sounds like something to try.

My fear of liquid lubricants is that they would help to form a tighter vacuum seal to keep the molds locked into the formed plastic

ROYAL RED · Newbie Joined: 18 May 2006 Posts: 21

Post deleted.

TKBIG · Guest

Talc powder is always the ticket for a sticky mold barring the search for undercuts.

I prefer the fresh scent of Dollar Store "After Shower" in the Fresh scent. Laughing

Seriously! Beats the heck out of that melting plastic smell, plus its only $1 for a big container!!! Cool