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"FIBERGLASS PLUGS", what's the deal?

 
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DarthVader1
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PostPosted: Sat Apr 16, 2011 6:54 pm    Post subject: "FIBERGLASS PLUGS", what's the deal? Reply with quote

Well, I've seen the infamous "Trooper Expert" doing a fiberglass plug tutorial on YouTube for about two years now.

My question is... does the fiberglass plugs (or molds, or whatever you call them) fresh out of the mold for vacuum-forming... can we use them just like that, or we have to do the talc powder thing to avoid the plug to adhere to the HIPS plastic casting?

If you really understand where or what I'm coming with, PLEASE let me know, since I'm running out of time QUICKLY into my OCP POLICE HELMET project, and I'm trying to save as much time as I could.


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jdougn
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PostPosted: Mon Apr 18, 2011 7:17 pm    Post subject: Reply with quote

Really can't offer a definitive answer to your questions but can offer a couple of personal experiences.

First, on the talc powder, it has the potential to destroy the seals in a refrigeration style vac pump since it is extremely abrasive. In a matter of minutes after using talc on a mold the pump would not hold vacuum. The pump had done fine for months & months before that.

Second, my experience with trying to use fiberglass molds is that 3/16" ABS heats it up to the point where autobody fiberglass gets soft and fails. HIPS may work better since it will cool quicker.

hth, DougN
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jegner
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PostPosted: Tue Apr 19, 2011 5:06 pm    Post subject: Reply with quote

Got any links to the video you refer to? I assume, a FG mold for a vacuum form part is what you are talking about? Usually PVA is used to release a pattern from FG. Without more details of your method in question, it's hard to tell.
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kayaker43
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PostPosted: Thu Apr 21, 2011 3:18 pm    Post subject: Reply with quote

Fiberglass molds are not ideal for vacuum forming. First they should be backfilled for support and to eliminate excess internal volume. Second, they are very prone to blistering and delamination from the sudden heating of the surface as compared to the layers beneath. If the surface is gelcoat or polyester resin, a release agent is rarely needed and a light coat of silicone or wax should prevent sticking and won't ruin your pump. A painted surface and many epoxy resins can get tacky when heated and cause more problems.

If I want to replicate an existing fiberglass part, I'll back fill with a ridgid urethane foam, (not the spongy stuff in a can), then wax and form one impression in fairly thin Styrene to keep heat transfer to a minimum. Then i'll use the styrene shell to cast a Kwik Kast resin pattern that can be used indefinately. If all you need is one or two parts, in thin plastic, you can skip the resin cast pattern.

In short, if you have a fiberglass shape you can work with it but I wouldn't start out using fiberglass for vacuum forming molds.
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DarthVader1
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PostPosted: Tue May 17, 2011 9:23 am    Post subject: Reply with quote

My vacuum method is similar to the one James have in his video... using a SHOP-VAC.

I've seen "TROOPER EXPERT" making castings with fiberglass plugs in his videos.

http://youtu.be/bBl-kA8ITlA

http://youtu.be/wc__KdmbEnw

After watching these videos... I realized that he made them out of bondo and some urethane resin. I might have to use a combination of different materials to do the plugs.
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jdougn
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PostPosted: Tue May 17, 2011 7:23 pm    Post subject: Reply with quote

Hey Robert, thanks for posting the video links. Fun watching someone else having a good time vac forming. TE is about as basic as you can get but it works for him! If I had to guess, the resin that he's talking about using is a high-temp product, especially since it keeps so much detail. In my experience, any traditional autobody style resin or bondo will get hot enough to loose detail as the mold heats up from repeated pulls. If the mold is only gonna be for a pull or two then autobody style products would be fine.

With repeated pulls consider going with something like BCC Products high heat urethane called Slo Kast BC8009. The BC8009 costs over $65 per gallon but using some type of filler helps. BCC also has a high heat "bondo", BC4570, that works great with the 8009. I use both these products on production runs of 3/16" ABS with repeated cycles and no signs of degradation. hth, Dougn
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DarthVader1
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PostPosted: Sat May 21, 2011 12:15 pm    Post subject: Reply with quote

Hmmm. interesting. Thanks Dough for the info. Unfortunately for me, those ideas you showed me are kind of expensive for what I'm doing (small parts for the helmet project you see in my sig banner), and I don't think I'll be making too many pulls due to the timeframe I have now.

I was trying to save work and money by not doing molds out of Hydrostone. which takes a lot of material and weight to make it happen, and on top of that, it will be difficult to make the detail holes while using such material, unless I make a batch to create a thick layer and then fiberglass to reinforce it below it.... that's just an idea.
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spektr
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PostPosted: Sat May 21, 2011 1:58 pm    Post subject: Reply with quote

Hydrostone can be face fact, just like anything else. you also need to acquaint yourself with pea gravel and chip rocks/agregate. You only need to face the tool with the expensive stuff, fill the 90 % left with rocks and a bit of epoxy, or plaster... FACE CASTING IS THE ANSWER TO REDUCING MOLD COSTS.
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DarthVader1
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PostPosted: Sat May 21, 2011 3:57 pm    Post subject: Reply with quote

spektr wrote:
Hydrostone can be face fact, just like anything else. you also need to acquaint yourself with pea gravel and chip rocks/agregate. You only need to face the tool with the expensive stuff, fill the 90 % left with rocks and a bit of epoxy, or plaster... FACE CASTING IS THE ANSWER TO REDUCING MOLD COSTS.


I'm kinda understood 50% of what you've just said... but I have the idea... if it's what I think it is... pretty much what I had in mind before. I'll try this method you've said.

I wish I had the knowledge and resources to work better with MDF, but that will be in the future... but not for this kind of molds.
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DarthVader1
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PostPosted: Thu Nov 10, 2011 4:14 pm    Post subject: Reply with quote

Well, after spending a good deal of time searching on the internet about this... I've found the answer: a mix between BONDO and FIBERGLASS RESIN together, which some people call it the "MILKSHAKE", due to it's color and texture. I just hate the "roto-casting", since you have to actually spend time moving around the mold, for the resin to cover specific areas and such. BTW, you could use either hardener (liquid one prefered) for the "part-b" process, regardless of the mix.

This is what I've done so far in regards of my mold, my latest experiment/project... AN/PVS-5 Night vision goggle frame, which is used as the base for the ECTO-GOGGLES in GHOSTBUSTERS:





Looks all good; no webbing, and perfectly detailed. Only problem I'm facing is... it's sticking to the surface of the plugs, even though I'm using baby powder as mold release.

Question is... Can I use the "spray" MOLD RELEASE instead of the powder for this issue? Since I'm dealing with polyester resin (aka. BONDO) and fiberglass resin mix. After the cast, it has some kind of a sticky texture, but once I sand the hell out of it, it doesn't look like a problem, except that I have to actually make slits in some corners of the mold in order to release the casting from the mold... and that takes time.

Any suggestions?
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jdougn
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PostPosted: Thu Nov 10, 2011 7:18 pm    Post subject: Reply with quote

Great looking goggles and very nice pulls!

First suggestion is to keep a good pull still in the plastic sheet and plan on casting with high temp urethane or similar. Fiberglass resin is not temperature resistant and it sounds like it is melting. I tried the same thing some time ago and had the same results. On long runs I've had problems even with regular bondo overheating. BCC Products makes a high temp bondo and high temp urethane that works well for me.

It may also be that the plastic is locking onto the near vertical sides. How are you removing the mold from the plastic? Here are some things to try:
- Look for black scuff marks on the mold surface from the plastic rubbing too hard. Try to sand down those areas so the plastic doesn't drag as bad.
- You can try to remove the plastic before it is cooled all the way too since the plastic shrinks as it cools causing it to "lock" onto near vertical surfaces.
- Magic Wet is a good lubricant that was recommended to me by Spektr and doesn't mess up vac pumps. I hate baby powder since the talc from it got in my first vac pump and destroyed the seals.
- Another option may be to mount the mold to a dedicated platen. This allows mulitple parts to always be perfectly positioned for maximum efficiency and they stack very cleanly. Most importantly, since the mold is mounted to the platen it does not lift off with the plastic.

hth,
DougN
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kayaker43
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PostPosted: Fri Nov 25, 2011 10:43 am    Post subject: Reply with quote

Fiberglass resin comes in more than one flavor. Resins used for laminating cure with a slightly tacky surface so the next layer will stick. resins used for casting have a small amount of wax added to cure with a non tacky surface. If its not specified you'll get laminating resin. After sanding the surface away they are both the same. There are much better materials to use besides resin and bondo.

The big issue I see is deep draw and no draft angle. I'm very surprised you aren't getting webbing. There's not much you can do about difficulty removing the part due to shrinkage with no draft angle. Just force it off with compressed air while warm or slit the corners and glue back together. Release agents wiil only help a little, the problem is a physical interference with the plastic gripping the mold.
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ANH trooper
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PostPosted: Thu Dec 01, 2011 2:51 am    Post subject: Reply with quote

I have certain forming tools that were almost impossible to get the plastic off once formed. What I did was make a handle or grip inside the tool so I could pull it out. You have to heat the plastic again to release it from locking onto the tool and then pull it out.

This can be a pain to do, but I always get perfect forms and no damage to either the tool or forms. Cracking the plastic trying to release it from the tool can be so disheartening. I find the extra effort removing the plastic from the tool is a small price to pay for successful forming.
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spektr
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PostPosted: Thu Dec 01, 2011 2:22 pm    Post subject: Reply with quote

this is where the platen/form style of molding shows its true colors. You cannot use positive pressure to pop the plastic off the mold.

Watch the car release from the mold using blow off ait thru the tool....

http://www.youtube.com/watch?v=GF0Bm3Uf94M
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DarthVader1
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PostPosted: Thu Dec 08, 2011 10:21 pm    Post subject: Reply with quote

As I've posted in another forum my progress... now, I've finally figured out the way to take the mold out of the casting without making the slits on the corners… by cutting away the “mouth” area of the casting, that way will allow me to manipulate the castings and remove the molds (with a little muscle power, though) without damaging either one,







Then, a light rough trim, just for a better look,


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