www.TK560.com

crashmann · Guru Joined: 27 Sep 2005 Posts: 501

Here's a photo gallery of a kit that we've been working on.

http://tk386.com/aws/bird_of_prey_mold_box/

The goal is to create a negative mold where the surface detail of the ship would be transferred to the plastic as it is being formed.

Another artist created the master, then we cast the parts in silicone, making female molds. We sprayed the molds with a generous helping of Mann's Ease Release, then poured in silicone. The Ease Release did its job of preventing the silicone castings from bonding to the molds. Now we're ready to create the mold box.

I started with a sheet of MDF the same size as the forming platen and attached walls four inches tall. Then I cut 2"x4" boards down to 45° angles. These were installed in the box using lots of silicone caulk. Then the entire box was coated with a layer of silicone caulk.

The only thing silicone sticks to is itself, so while the caulk was wet, I pressed the male molds into the goop.

After allowing the caulk to cure for a few days, we mixed BCC Slow Kast resin and poured it into the box.

Extracting the box from the casting took a good bit of wrestling, but we were rewarded with a beautiful mold!

Now we had to smooth out the ripples from the silicone caulk, and drill LOTS of tiny vac holes to encourage the plastic to draw down into the cavities.

We created a gasket on the bottom of the mold using silicone door sealant strips. This will seal the mold to the platen surface during the pull.

Finally, our first successful pull!

This endeavor had a very expensive up front cost with all of the silicone and resin used to create the mold. But the final results are beautiful, and the plastic pops right out of the mold!

Charlie

jegner · Posted: Tue Dec 23, 2008 7:35 am Post subject:

Great info, thanks for sharing! Say, that looks like a TOS Romulan Bird of Prey from Star Trek?

I too am looking at making a female mold for a project. Re-creating the vintage GIjOE 6-wheel ATV in vacuum form. A female mold will be the perfect way to get the detailing on the OUTSIDE of the formed part, and not the usual inside.

Jim

ahillworks · Master Joined: 18 Nov 2007 Posts: 308 Location: Orlando FL

Yeah I my self is learning female molding is better than male molding and forming. Get better detail and less likley to webb.

TK 109 · Guru Joined: 11 May 2007 Posts: 712 Location: Galena, Ohio

perfect for a stormtrooper bucket...... Idea

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-Alex

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Stomper · Posted: Sun Dec 28, 2008 2:41 pm Post subject:

NICE WORK!! I bet you have AT LEAST $200 worth of silicon, not even counting the resin and other materials! Sheesh, and people wonder WHY prop-builders charge what they do!!

BTW- When I first saw this thread's title... I was half-expecting to see something with softer and rounder curves! Razz

_________________
Tony Krewson
FEAR... is not my god!!

fast_monte · Novice Joined: 17 Aug 2005 Posts: 40

Do you have a picture of a ship that has been built from your mold yet?

crashmann · Guru Joined: 27 Sep 2005 Posts: 501

Not yet

We've sent the vac formed parts to the person who made the master. He's in the middle of building it up, adding some internal structure with foamcore, and creating the instruction sheet.

Here's a thread on Resin Illuminati about the prototype he built up for a client. REL does absolutely incredible work with tiny bits and pieces of plastic!

http://www.resinilluminati.com/showthread.php?t=2537

Charlie

jegner · Posted: Fri Jan 16, 2009 7:56 am Post subject:

WOW! Very nice! I'd love to see that against a dark background. Cool stuff.

CrazyFool · Expert Joined: 07 May 2008 Posts: 203

That is extremely cool. Fantastic job!!

I also have fond memories of the yellow, 6-wheeled G.I. Joe ATV and my sandbox behind our house. It was a prized possession and I'm still not sure exactly how my little brother dispatched it.

spacephrawg · Novice Joined: 02 Jul 2010 Posts: 42

question: did the vent holes show up on the final vacuum formed cast? If not, why? They didn't appear to but my screen is small so i cannot tell. I would think if you're sucking into a female mold, it would pick them up more so, right?
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please pardon my apparent newbie ignorance!

crashmann · Guru Joined: 27 Sep 2005 Posts: 501

Yes, some of the 1/8" vent holes did appear in the plastic as small dimples which can be easily sanded down. If you use a smaller drill bit, then the dimples do not show up. However, smaller drill bits are more fragile.

Another factor is the thickness and type of plastic you are forming. Thicker plastic will not stretch to enter a small hole very easily, but thinner plastic will. We are pulling these using .060 HIPS (high impact polystyrene).

Charlie

DarthVader1 · Posted: Mon Jul 19, 2010 8:12 pm Post subject:

spacephrawg · Novice Joined: 02 Jul 2010 Posts: 42

How many vacuum casts can you get out of a female mold?
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please pardon my apparent newbie ignorance!

spektr · Master Joined: 07 Jan 2008 Posts: 425

this is a question without an answer because there are too many variables. Normally I never need to ask the question because I tool in a manner that will exceed my needs. Cheap tools with limited lives are a different story.

Try asking the question a little differently, like this...... I plan to make
X number of these parts. Heres a picture of the part. What tool would you recommend, and how would you make it.

This is SO MUCH easier to do than to get all hypothetical all the time.

Scott.

spacephrawg · Novice Joined: 02 Jul 2010 Posts: 42