mold making

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#1

I’ve been trying unsucessfully to make several new set of molds. Previously i have had aluminum molds but polishing the inside is quite difficult so i have been experimenting with making an aluminum positive and making multiple fiberglass molds from that.

The first attemps were with using gel coat to create a nice mold surface but that has been sticking to the aluminum and ripping off from the fiberglass. I have tried several different release pastes and had the same sort of results with each.

Recently i’ve been trying just fiberglass and epxoy, using surface veil to avoid any bubbles and regular fabric for bulk them up. In this i have been getting bubbles under the surface that can crack through.

At this point i have put in more time and money than i would have liked so i’m wondering if anybody has a pretty fool proof way to do this. My positives do not have a flange and i would rather not buy a vacuum bagging system.

Any ideas would be appreciated!

#2

If you polish your plugs to a high gloss finish, almost every system should work. I regularly use aluminium, in combination with marbocote semiperm. release(227) for different products.
bu a regular wax like meguiars or honeywax should do well, apply at least 5 coats, preferbly 7, min. 15 minutes in between, and wait 24 hours after the last one(or read the instructions on your product)

after I read your post again, I found a possible problem: Are you using pe or epoxy gelcoat on your epoxy/glass laminate? Polyester gelcoats on a epoxy laminate can have some problems staying together. You could use a epoxy gelcoat, a skincoat between polyester gecoat and epoxy laminate(woundn’t reccomend that for moulds) or use polyester/vinylester resin(cheaper)

Some release trics:
Alu shrinks and expands more than most plastics, so heat up while curing, cool down after curing for a better release.
build up your moulds evenly, start with a light cloth, let cure, double cloth in weight, let cure, double that weight, let cure, etc. If you don’t cure completely, you don’t have to sand in between, just top the upstanding splinters off.

Hope it helps!

#3

have you tried semi permanent release agents? They will work perfect for this.

#4

Susho, i tried a polyester gelcoat with epoxy and fiberglass to hold the shape. I could use a polyester resin but i have lots of epoxy on hand.

The release agent is what worries me the most because i put on several layers of release wax but the gelcoat sticks like no other. I can’t chip it off or aything, the only way i’ve found that works is soaking it in acetone from a day or two and the gel coat slowly turns rubbery.

Hojo, I have not heard of a semi permanent release agent. Could you tell me more about it?

#5

Awww man I’ve been really hoping you’d get over this hump.

Ok let me get this straight you have an aluminum plug and want to splash molds off of it. Correct?

You are using poly gelcoat and then using epoxy to reinforce?

Your gel coat is not releasing and is coming off in strips when you try removing the part?

Ok ok let’s see here. First off sounds like you have everything there you need IMHO and a decent understanding! Your doing just fine! This is the proving ground for you. lucky for you were are all here to tell you one hundred thousand different things you should have done different , BUT WE ARE NOT!!! lets get you making some nice masks!

Ok let’s go get that nice aluminum tool and polish it real real smooth. Any compound you’d put on your car will do! Wipe it clean with acetone and bag it up!!! This is important!

Now let’s Make a trip to home depot or any hardware store and pick up a 24 by 24 piece or plexiglas! Unless you already got one! Clean it off and make a grid pattern of maybe 4x4 squares. Start applying each release wax free coat what have you and try to take some notes.

Now go ahead and mix up a bit of gel and spray the whole thing down. Lay up the materials like you plan to on the aluminum tool. Now you can determine which release is suitable for your gelcoat!!!

I would advise that you not mix poly with epoxy.

Here’s the thing when you a

#6

Ok where was I? Oh yeah . Some times I’ve learned you need to Pay close attention and take baby steps. A few jobs I can think of I used freecoat and would apply it two and 3 times before laying up. Sounds to me like you are not putting enough release on. The stuff also takes time to dry and settle in.

Come on man you got this! Try and slow it down a bit. Remember the parts are a reflection of the mold. And the mold reflects the time and care the builder put into it!

If you have poly gel coat get some bond-o and see if that will bind better than the epoxy will. If so you might not want to use that epoxy. Let’s roll with what you got and figure out the solution!

Btw let’s get a picture of what’s going on.

#7

Semi permanent release agents chemically bond to the mold surface. You will want to get a sealer and release agent. Clean the surface well with a mold cleaner, apply 1-2 coats sealer, then atleast 2-3 release depending on the release you choose. Always follow the directions supplied by the manufacturer exactly. Look in to Frekote release agents. you will have no problems with your parts/molds sticking.

#8

Frekote, marbocote, just to name a few. I found that semipermanents are the most reliable. But I get a better result using wax(but the marbocote 227 isn’t intended for good surface quality, or the use of gelcoats.)

Could you tell us more about the steps youre going trough? what kind of wax are you using, how do you prepare your surface, do you use any other products with the release?
The only problems I got with wax was mainly the surface, mainly to rough, or a chemical reaction with the paint. What also happens is using a paintbrush to apply the gelcoat, wich is used before and was cleaned with acetone. The acetone offcourse damaged the release coat…

(clean aluminium is usually a pain in the ass to stick things to, the oxidation happens quite fast, and forms a greasy layer on wich no resin will stick. Sanding and degreasing a few times is recommended if you like to bond anything to it. So with a smooth surface and a good release agent used in the right way, everything should come loose very easily.)

#9

http://www.freemansupply.com/datasheets/15sealer.pdf

http://www.freemansupply.com/datashe...leaseOneFS.pdf

http://www.freemansupply.com/ChemleaseOneFSEZSe.htm

#10

Yesterday i took a second look at the release paste i am using (TAP plastics standard release paste), its says to apply the paste then let it dry for 5 minutes before polishing it off with a cloth. In previous molds I have previously been applying it and polishing it off almost immediately to save time and that has been working so far with epoxy and carbon fiber and never thought twice.

So after reading that i tried a little sample piece using the release paste as directed and so far so good. I’m going to try one last time with this release paste before trying a semipermanent release.

I’ll let you guys know how it turns out!

PS another thought i’ve had is that i needed to scrap the old gelcoat off in spots so i’ve repolished the molds and most likely did not give the aluminum time to oxidize so between that and the improper gelcoat use could be the reason it stuck on so well

#11

also using polyester resin instead of epoxy

#12

You can use pva. It will add some insurance that nothing with stick.

#13

yeah, but it will xxxx up your finish. you shouldn’t use PVA when building moulds, or when you want a high quality finish on your product. The only use for PVA is on products wich don’t need a good finish, and wich you need fast, or, when you have 2 reacting materials.(styrene in polyester and most paints)
Other than that, PVA is a (quick and)crappy method for crappy products.

#14

completly agree, hate PVA with a passion. It has its applications, but not too often. Semi permanent release are the best for both molds and parts IMO.

#15

For aluminium, glass and polyesters:

either use a hard wax, like Meguiars Mirror Glaze 87, or use a semiperm system, but do not forget that it needs a sealer.

Also, read the instructions. For instance, M87 needs to be applied as thin as possible, after a minute break the surface with a polishing cloth, then let cure for 15 minutes, then polish. Change cloth often.

PVA: great for some applications, but not for production work. I have used it 3 times:
-when making a mould off a towing tank model, which absolutely should not be damaged, and which had unknown paint. (remember, Susho?)
-when making trailer moulds on a boat that was sanded to get the final coat of paint. I applied a couple of layers of PVA, which bonded nicely with the boat. The trailer moulds popped right off. The guy that had to wash off the PVA was not happy…
-when making moulds from plugs which have “Gibco Flexmold” applied for anti-skid surfaces. This is a great product, but needs PVA for proper release.

Add some dye to your PVA, so you can see what you are doing.

As for mould making materials: Do not mix systems. So either use a polyester system, or an epoxy system.

#16

offcourse, my first infusion :smiley:
But that mould wasn’t that bad, was it? ( I have some pictures, somewhere…)

#17

The mould was OK, but the plug was a towing tank model, owned by HoCo. I was just borrowing it…

#18

i use pva when i want to make sure there is no sticking. I can also spray it without much texture. After the mould is popped. I quick wet sand is all that is needed to get rid of any texture from the pva. I hate pva as well. but i do still use it on plugs. I just don’t have a lot of trust in semi perm yet. I use it on seasoned moulds and it works great.

#19

i use pva when i want to make sure there is no sticking. I can also spray it without much texture. After the mould is popped. I quick wet sand is all that is needed to get rid of any texture from the pva. I hate pva as well. but i do still use it on plugs. I just don’t have a lot of trust in semi perm yet. I use it on seasoned moulds and it works great.

#20

Alright so i’ve tried the molding again.

This time the molds came off much easier this time around but the surface was a little blemished. I’m thinking about trying a different release paste…

Also got a bubble in one and the gelcoat cracked because it was not supported from the back with fiberglass. Its in a concave curve and the fiberglass likes to go straight across it rather than stick to it. Any tricks to that?