Mold Making Surface Coat Questions

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#1

So far I have only used Smooth-On Epoxycoat Red for making molds. I was wondering what others use. Is there a benefit or disadvantage to using epoxy for my molds? It is also about $100 for a gallon of the Epoxycoat Red so I was wondering is there are any cheaper options?

My next question about surface coats is about degassing. Do you degas? I actually tried and the second I pulled a vacuum the cup overflowed and covered the inside of my vacuum chamber. I was wondering if I should just pull some vacuum but only enough to make it foam, or is degassing is not needed. I have noticed that if I sand a mold it uncovers a lot of pin holes which I am guessing are air bubbles.

As always, thanks for your help!

Daniel

#2

I like epoxy surface coats because they are more durable than polyester based surface coats. For open molds like you’ve been using for infusion a polyester gelcoat is just fine. For two piece molds that form a seam with a sharp cornered mold the extra durability increases the mold life. The downside to most epoxy based molds is that they are more difficult to polish and many don’t polish up as nice as a polyester based gelcoat. I don’t polishing my molds but pull them off nice plug to get a nice mold surface.

I put my epoxy based surface coat down in two coats. The first one goes down as thinly as possible (dimensional thickness). This allows bubbles to easily escape. Then I pass a torch on low over the surface in quick passes. This super heats the bubbles and causes them to pop. After this first coat tacks up (tacky to touch but doesn’t transfer) then I add second thicker coat. I wait a few minutes for any bubble to rise near the surface and then zap this with a torch. When the second coat tacks I move on to the reinforcements.

Adam

#3

+1000 - Adam has said it best, the only way to have a polished epoxy mould is a high gloss plug to pull the mould off of. Typically, duratech ez sand primer is your best bet to paint the plug. Wet sand 400/600/800/1000/1200/1500/2000 then hit it with a compounding cream, I use Presta 1200 and then finish off with 3M finish cream and a swirl remover if necessary. The plug looks like it got a few hits of clear (but didn’t) and basically you can seal the plug in if you fell it necessary and begin on your mould after waxing it.

Once the mould is pulled, we wet sand the surf e of the mould to a high gloss epoxy finish, not the same as a polyester but not far off. Then seal the mould and start the wax applications.

I recently tried a polyester gelcoat on a high polished plug, let it dry (waxed version) and sanded it with 80 grit and wiped it with acetone then did a lay-up of epoxy afterwards. It worked and does provide a high gloss finish. I doubt I will do it again, it was just a test to see how it would work and done on a low volume part.

Regardless, if you want glossy parts it starts with the plug, it has to be 100%, and when you have there, go the extra 10% and you will not regret it.

#4

^ Those two guys hit the nail on the head.

I personally would not use Smooth-on’s products if you plan on being anything more than a hobiest. Smooth-on is your overpriced dealer that sells, “ok” quality products. In my professional opinion that is…

For example, their red epoxy gel coat has a heat deflection temp of 133F. If you plan on post curing epoxy parts that won’t work. It also depends on how high your post cure is.

I look at it this way though. If I’m going to make a mold, I want to make it twice as strong, and twice as resistant to heat than it needs to be.

Right now we’re working on a mold for a CAI. The part will be made of VE resin so post curing is not necessary, however if we ever switch to epoxy or pre preg for that product, I don’t want to have to remake the mold to work with the higher temperature cure.

Just something to think about :). A good VE tooling gel coat goes up to 250F.

Where to get that VE tooling gel coat is beyond me…

#5

I prep my plugs with PPG DC3000 clear-coat, use Frekote FMS sealer and Frekote 770-nc as the mold making release, make the mold with epoxy, and then NEVER touch the mold surface with sand paper or polish. Sometimes I’ll hit the fresh mold surface with Meguiars Swirl Remover 2.0 by hand to make it sparkle. Then I’ll apply the Frekote system and put the mold into service. I think polishing a plug is usually faster and easier then polishing a mold. I put my effort into the plug and never have to touch the mold surface. If I need to make another mold to speed up production then I reuse the plug…now that two molds I didn’t have to polish.

If you ever make a multi-piece mold for hollow structures then sharp corners for seaming are really important…at least for in mold paint applications. If you ever have to sand and polish a two piece mold the corners will get rounded which makes the seam wider, more difficult to trim, and visually unappealing. I have a different perspective though. Almost everything that I do is hollow molded and I don’t do any post mold painting or prep. Pop the part out of the mold, trim the seam and openings, package, and ship.

VE resins require a heat treatment/post cure at 250*F to get an HDT that high.

Take a look at the .pdf for the Crystic 14A tooling gel coat. All the strength tests were done from samples cured at 80C (176F). The HDT data was taken from a sample cured at 120C (248F). It takes a heat treatment to get those kind of numbers. VE resin manufacturers rarely post stats from room temp cured samples.

It’s pretty common to be able to get them to 180F to 190F though without a post-cure.

#6

Thanks everyone. I have used up all of my Smooth-On stuff and am looking to try something new. It is what I can get locally but I would rather try something new that isn’t as expensive and is better quality.

What what brands does everyone recommend?

#7

We use #1154 surface coat from PTM&W, that is for low temp moulds, maximum post cure 150 degree’s F. They another version for 275 degree’s F. Both will give a high gloss provided the plug is highly polished.

#8

I always make my own gelcoat,i never use polyester only epoxy,reason no shrinkage and much stronger,regarding degassing your gel coat,as long as temperature is about 20c where your working you should not have a problem I do have some mold with small pin holes usually when you wax your mold the wax will fill them.

#9

I too either make my own with epoxy laminating resin or use Adtech ES-221.

#10

Hi

Has anyone among you tried PE/VE zero shrink tooling resins like the neumold from DSM, the RM2000/3000 from Nord Composites, or Riechhold’s POLYLITEx33542x25.

If tried and discarded, why?

Just curious.

N

#11

Also some parts I only use one gel coat but two usually two and fillet any area’s that are deep,this way you make the materials more compliant around plug,just make’s life easier,especially useing powder bound fiberglass.

#12

Anyone care to exaggerate on making your own gel coat? I am assuming you add something to an epoxy resin? thanks.

#13

I use 27% West Systems 404 high density filler and 9% graphite powder by weight.

#14

Thats news to me :eek:. My suppliers told me post curing is vener needed :confused::(.

#15

I’ve done it before a few times mixing regular gel coat with ceramic powder and ground fiberglass.

#16

So is it cheaper I make your own or buy premade surface coat?

#17

On RM2000 and other rapid tooling systems:

I have used them myself a couple of times. Nice stuff. Just do follow the instructions though. Many need a minimum layer thickness to generate enough heat to cure without shrinkage. Also the wet film thickness of polyester gelcoat is more important than with epoxy gelcoat. Also important is temperature (between 18 and 25 C) and avoid direct sunlight.
If you are used to toss your moulds outside after use, protect them with a decent topcoat.

I am most familiar with the RM2000 and 3000, and lately also with RM2550 and RM5000.

RM2000: relatively cheap tooling system. Can be used with a (cheap) iso gelcoat (GC200) or VE gelcoat (GC206). Over here it is all GC206 (or 207 for the spray version). Make sure it does not bulk up in inner corners, and catalyse properly. (not the 0,8% a customer tossed in. Ruined both mould and plug. Well done. Datasheet and label told him 1-3%. I would say: use 2% at all times.
Tg of 85C. Gelcoat has 135C

Apply 4 layers of CSM450 (1.5oz) wet in wet. Not more, not less. Bristle rollers are great for bubble busting.

RM2550: same as RM2000, but can use regular catalyst.

RM3000: VE based. Tg 110C. use regular catalyst. Not as picky on the 4xCSM450.

RM5000: infusable. Use hi-flow mat, like Rovicore or Polymat.

#18

Hello Herman,

Didn’t know of 5000, now how can one infuse it? Don’t the additives get filtered out? How is that prevented? Or are the additives now embedded in the glass? Whats the shrinkage of 5000?

Another question, since you’re from NL, have you not tried the neumold resin from DSM?

Thanks

#19

I haven’t tried neomold, but basicly they are all the same. In the past DSM used to sell RM2000 in repackaged containers.

RM5000 can be infused onyl through very open fabrics. Shrinkage is nil.

There is also an infusable VE version, RM6000. Never worked with that one though.

#20

Thanks. What is the realistic exotherm temperature with a typical layup using 5000, one of my plugs is a polystyrene base, with a .7mm glass epoxy laminate (basically 2x400gm/sqm twill) on top, which is finished with duratec. Could the exotherm from 5000 destroy my plug?