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sin03 Profile
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Dark Knight
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Re: A Molding Question


Hey thanks guys! That's some really useful info there.

I think I'm going to stick with Oomoo because its a one:one mix silicon which will make it easier to work with. I've never done a mold before so I think it would be best to stick with something easy for now.

I'm going to do a "practice" mold (for my tdk knuckle guards) before I attempt the fins.

I'll likely go with Oomoo 30 because it has a bit higher tear-resistance and longer pot-life.


The Mold Box: I probably should have provided more info. on my plans. The mold box is going to be 12" x 4" and 6" deep. I was thinking of pouring to about 4.5" deep, which will make the mold 1" think on every side of the mold (including from the highest tip of the fins).


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Not the best drawing but that's what I want to go for.

Jason

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3/11/2009, 10:42 am Link to this post Send PM to sin03
 
Proximo Profile
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Caped Crusader
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Re: A Molding Question


If you do a block mold for the fins you might get problem during the casting and demolding, Especially because the fins you're molding have undercuts.

Due to undercuts you can damage the mold when you demold it, And you also need to get air bubbles out from the tips while casting. A bent steel rod to reach all the way down can help to get the bubbles out so thats no big deal, But the hard part will be demolding due to the huge undercuts.

I think most people would do a 2 piece mold for this.

Personally i would do a brush-up mold as you would do with a cowl, which usually has lots of undercuts wich is why a glove mold is used for easy demolding and to save materials. Someone suggested if you do a brush up mold you can use Plaster as a shell (block) wich is cheap and it will in the end work out just as good as a solid piece of silicone would, If not better since you will be able to demold alot easier with a glove mold.

Just my thoughts, There is obviously a lot of ways to do it and you have to do what you feel is right and within your budget.

Last edited by TheKingaSwing, 11/29/2011, 6:22 am
3/11/2009, 10:59 am Link to this post Send PM to Proximo
 
sin03 Profile
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Dark Knight
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Re: A Molding Question


Proximo: You just stated exactly what my concern is!

If i was to do a paint on mold, I was thinking of grabbing the Silicone Brush-On Starter Kit which includes the following:

Trial Kit Rebound 25 Silicone Mold Rubber
Trial Kit Smooth Cast 300 Urethane Resin
Trial Kit Plasti-Paste support shell plastic
1oz. Sonite Wax
Thivex II Silicone Thickener

Guys please keep coming with the advice (it's really appreciated :up )

Jason.

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3/11/2009, 11:07 am Link to this post Send PM to sin03
 
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Re: A Molding Question


For something thin like fins I would opt for a mold box and just pour it. YES, you'll use more silicone (and we all know silicone is one of if not THE most expensive material we all use) but if you opt to brush it then you need a mother mold and you're having to mix another material and then the sil mold will have to be held to that somehow to make your castings. IMO it's more trouble than it's worth in saved material. A cowl is a different story, a box mold on something that big would use a HUGE ammount of silicone. Just my 2 cents

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3/11/2009, 11:08 am Link to this post  
 
sin03 Profile
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Dark Knight
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Re: A Molding Question


Quote:

Proximo wrote:

If you do a block mold for the fins you might get problem during the casting and demolding, Specially because the fins you're molding have undercuts.

Due to undercuts you can damage the mold when you demold it, And you also need to get air bubbles out from the tips while casting. A bent steel rod to reach all the way down can help to get the bubbles out so thats no big deal, But the hard part will be demolding due to the huge undercuts.



That is my concern (just in case it doesn't stand out).

Jason.



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3/11/2009, 11:14 am Link to this post Send PM to sin03
 
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Caped Crusader
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Re: A Molding Question


this is all good info- any way will work.

and honestly, we have already thought way too much about it LOL.

BUT- my point with the glop on/ no mold box was for flexibility.. if you run a mold that has 1" around every part... you may have some issues getting the parts out.. where as if you have a more flimsy mold, 1/4" around everything, it will be a lot more pliable.

Now- i have never made a jacket for a mold.. i just dont see the need on the stuff i have done, including a cowl.. But with that said-- if i know the mold needs to be flexible, i make it a bit thinner.. and vice versa if it needs to hold a shape well.. make it thicker.. But in this case.. a small plaster slip on/in jacket might be bang on.. Good idea! It would hold the thing upright.. you dont have to worry about parts being shaped wrong as you will be using so little resin.. it wouldnt have the weight to flex the mold..

You can get a trial of MM30 for about [sign in to see URL]. You could probably make 2 box molds that size with it.. or 6 the paint on way..



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3/11/2009, 11:24 am Link to this post Send Email to Kbillan   Send PM to Kbillan
 
sin03 Profile
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Dark Knight
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Re: A Molding Question


Quote:

this is all good info- any way will work.

and honestly, we have already thought way too much about it LOL.



I know and I do apologize for thinking way too much about this, but I do want this to work as I have been dealing with these fins for the last 4 months or so! lol

From the sounds of it doing a pour mold into a wooden box will be easier but will end up being a hassle after the resin copy has fully cured (my fear was I wouldn't be able to get the copy out or end up breaking the fins trying to).

I have the Smooth-on pourable starter kit already but I will need more molding rubber to do this. And from watching the instructional DVD filling the box full of oomoo (and probably moldmax as well) will will make it far to difficult for demolding (proximo said it best: the fins are too rigid). Oomoo requires at least 1/2 inch space between the model and the walls of the molding container (in this case the wooden box).

That's why I mentioned the brush-on starter kit as another option since it has paint-on rubber (rebound 25) and the stuff to do a support shell.

Keep the thoughts coming though!

Jason.
 

Last edited by sin03, 3/11/2009, 11:32 am


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Caped Crusader
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Re: A Molding Question


EDIT..

Last edited by Proximo, 3/11/2009, 11:35 am
3/11/2009, 11:32 am Link to this post Send PM to Proximo
 
sin03 Profile
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Dark Knight
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Re: A Molding Question


And by glove mold you mean painting the silicon directly onto the row of fins right?

Jason.

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Gauntlets: http://www.runboard.com/bbrotherhoodofthebat.f4.t204452
3/11/2009, 11:34 am Link to this post Send PM to sin03
 
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Caped Crusader
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Re: A Molding Question


No one in their right mind would do a block mold for something big as a cowl.
My concern is the undercuts. Making a glove mold is not really that much more of a hassle than a block mold. You still have to make a mold box on both, So why not spend a few extra hours of letting the material set and do a mother mold and save some bucks on the silicone. Making keys on the silicone to grab on the mothermold is very simple and least to worry about.

IMO, The cons by doing a block mold for this is that you get two problems.

1. Huge Undercuts wich make it hard to demold and you can damage the inside of the mold when you demold the resin fins, Unless you use a very low shore Silicone which flex alot, then you have nothing to worry about rather just a issue of how much you wanna spend.

2. Get any air out that get trapped in the tips while casting.

If you do a glove mold, You will only have one thing to worry about, Getting the air out while casting.

Last edited by TheKingaSwing, 11/29/2011, 6:25 am
3/11/2009, 11:35 am Link to this post Send PM to Proximo
 


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