Vacform on Fiberglass mold NEED HELP

[Gorgot3000]

Hi Guys

I was wondering if someone know if I can pull a vacform styrene parts from a fiberglass mold ?

As you know I'd make the dark helmet dome , and my mold was made from paris plaster with pieces of foam inside to light weight a bit ... but today the mold was broke by the heat ( separate in 2 where I pour the layer of plaster ) :cry

So I would like to make it in fiberglass and reinforced with plywood inside the mold to make it lighter and harder than paris plaster ... I have made a silicone negative matrix of my dome when I created it with a plasti-paste shell ( my safe ) and make the corrections with bondo

I don't want to go with ultracal or hydrocal because it's to heavy to put on the vacform table ( only the mold for this dome in paris plaster weigh 60 lbs )

So Can Fiberglass and bondo mold support styrene heat from the vacform ?

Any help please ? ! ?

Thank you

Joe

 

[IEDBOUNTYHUNTER]

You can do it, but the Bondo will soften after a few pulls. and the fiberglass will crack.

hate to say but ultracal is the best bet. i use it for all my Vac patterns. never have a problem. they are heavy but worth it.

my 2 cents.

Al

 

[Gorgot3000]

@Al :Thanks for your fast response ...

*sigh* ... I have some mold in ultracal , I know it the best bet for small /medium parts ... the faceplate and the rest of the suit was made in ultracal ... but the dome would be a 100 pounds if I made it in ultracal ... :confused

 

[cavx]

What are you using for suction? If you have a Vacuum Pump and Surge Tank, the following probably won't be an issue, but if your using just a vacuum cleaner for the pull, then you really want solid bucks so you don't have to evacuate too much air from the cavities.

Plywood frames would be OK, but as mentioned, there are limited pulls with certain materials. I made a buck using a combo of 10mm Perspex (heat formed), Bondo and wood. There is a slight crack forming on the edges. I don't think the Vac Forming is heating the Perspex up anywhere near enough for "plastics memory" to straighten the heat formed part out, but maybe the heat has affected the Bondo to the point where it now beginning to let go.

If you want or need to make the buck hollow to keep the weight down, then I suggest adding a base to it.

 

[Gorgot3000]

For now I'm using a 5.0 HP vacuum cleaner and sometimes I'm adding another 4.0 HP to the first one when just in case if the first one doesn't pull enough. ( I never had to use the 2 vacuums in the same time )

For the new mold, I thinking about that : Making A Fibreglass Mould - YouTube

If I use Gel coat as bondo to fulfill the imperfections after the mold was created... maybe it's going work better than if I use bondo .. I don't know .. I have to test it ..

 

[CaptCBoard]

Use the Ultracal, very thick. Coat the mold with the Ultracal so you have it about an inch thick all over. Mix plaster, add styrofoam chunks and fill the remaining cavity. The Ultracal will certainly take the stress and the plaster and styrofoam chunks will take up the rest of the space, but remain very light.

Scott

 

[cavx]

I never had to use the 2 vacuums in the same time )

I've been using a VAX (wet/dry unit) and today started setting up my Vacuum Pump and Chamber (to be used as a surge tank for Vac Forming). I was going to block the VAX hose hole, but was advised to keep it and just add a new one for the Vacuum Pump. So basically the VAX evacuates most of the air and the surge tank just gives it that final whop (is that even a word?) of suction to really pull tight.

I ran a few tests tonight. I need to replace my main hose from the chamber to the pump as I got to about 20inHG when the hose crushed in.

 

[Gorgot3000]

Thanks guys for the tips ! , this is a good idea to slush with ultracal before ... my mistake is I poured one batch of paris plaster , add a big square of styrofoam and pour a another batch of plaster in the silicone mold ... This is where the mold was " separated" in two ( the 2 junctions of the pouring )

for the Vac pump and chamber .. I'm curious to see the result ... of course if you want to share how you made it

 

[cavx]

for the Vac pump and chamber .. I'm curious to see the result ... of course if you want to share how you made it

I bought the Vac Pump off Ebay for $108 landed. Like so many things these days, it is Chinese made and I am having a few issues getting fitting for the inlet as it does not seem to be standard metric threads.

The Chamber is made from 250mm [10"] PVC pipe and has a 20mm PVC base welded to that. A local plastics fabricator did the work for me. The lid is 20mm Perspex. The seal at the top is made from a 5mm thick rubber mat that I've cut an 8" hole out the middle.

My plastic fittings and ball valve came from a local pump shop. The clear hose they sold me crushed under vacuum at about 20inHG last night, so today I went and bought some steel reinforced hose and is rated at 1500 PSI. The issue I am now having is that I can't get a good seal on the inlet from this hose where it attaches to the pump and can only pull about 5inHG until I sort that.

The Chamber cost $110 and the fittings and hose about $35 so far.

I have a thread about specs for Vacuum and Pressure Pots and all my images are there.

 

[Gorgot3000]

Cool ! Thanks Cavx !

 

[Gorgot3000]

Hi all

I've made some test this week , Finally I'd try in fiberglass with a gel coat on it. Here is the result of the mold

I've pulled 9 dome non stop on this mold ... the 4 last one were amazing ... and no damage on the fiberglass mold .

 

[SChristides]

Very good. Pretty sure a member on here, Thorssoli, quite commonly uses fibreglass bucks for vac forming. I guess it comes down to how often you'd use it as to how long it would last.

Lookin a little darth vaderish there. Be interested to see the resulting pulls you did with it.

 

[Gorgot3000]

Good guess ... wrong movie Dark Helmet ( Spaceballs )

 

[cavx]

So this is a ply wood frame or support. What is the actual shell under the glass made from? And what is that whitish foam stuff - Expanda foam?

I want to do a Pedator mask and was thinking it had to be solid and this idea is looking great.

 

[Gorgot3000]

this is a gel-coat with 7 layer of fiberglass and resin , reinforced with plywood frame and yes it's expanding urethane foam to fill the inside ,stick the plywood together and a strip of auto-adhesive seal foam in between the fiberglass shell and the wood . ( to reduce shock on the mold )

this was cast inside my "safe" silicone negative mold .

 

[SChristides]

may the schwartz be with you.