Yeah, you are right, it is polyester resin.
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Really nice tutorial, regarding resin for the first time I suggest taking epoxy resin and hardener combination that turns jelly after ~120min, that way you will have enough time to work it arround properly, fill in/push out all the bubbles that will form near fillets. Also don’t mix up too big of a batches. I used small drinking cups from coffe wending machines and mixed about 1/3rd 1/4th of a cup at the time (you can use kitchen scales for propper proportions).
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Yeah, 120min epoxy is a way to go for a beginner. I personally picked up random epoxy for laminating. The datasheet said 40min to turn into jelly, but first time it turned into jelly under 20min. Maybe I have put too much hardener into it or it might have been too hot during summer day. On second try I knew I have to work fast, but if I was doing like 8 layers I would definitely not be able to do it on one go.
When mixing epoxy in multiple batches, is it ok if lower layers of fiberglass are jelly and you put new layers with freshly mixed epoxy on top of that? Will it hold well together?
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Nooo don’t do that.
Epoxy cures via an exothermic reaction. Meaning once the two parts are mixed, they start a chemical reaction that creates heat. The heat cures the epoxy.
Your best bet is to mix small, manageable batches. You can extend the pot life by mixing in your cup and then pouring the epoxy onto a plastic plate. This greatly increases the surface area and inhibits the exothermic reaction from happening too fast.
If you put fresh epoxy into a cup with epoxy that is already going off, the heat from the old epoxy will just make the fresh stuff cure quicker
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Ah, I understand. So doing multiple batches of epoxy hardener mix will mean the epoxy will turn into jelly later if I do it correctly.
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@Ac53n , do you mean the resin for the part or for finishing of the printed mould?
Are you going to vac bag it?
I haven’t used printed moulds, but expect some others on here may have, and could help with surface finishing tips.
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Gonna need to make sure the 3dp part is COMPLETELY sealed.
I’d be coating the part with epoxy dosed with microspheres/fumed silica to seal it and give a good mold surface to sand. Multiple coats may be necessary. If you tint the epoxy a different color from the part, it will help you know if you’ve accidentally sanded through.
Then you just need a proper mold release product. There are plenty of options available, i’ve always used honeywax
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Kinda both to be honest. Looking for recs for the part resin and any recommended methods for smoothing/sealing the mold. I made the walls pretty thick so im gonna sand flat the layer lines first, then id need to seal it with some kind of top layer before a mold release right?
And i dont have a vac bag, was just going to wet lay and let cure, but if vac bagging isnt too expensive and is worth it, im not opposed to it.
Carbon fiber fabric is 200gsm 3k twill
My patience and skill with wet layups led me to use vac bags on my first enclosures. They can give pretty good results. But there is cost for consumables as well as a pump. It’s not cheaper, but can give better strength and finish. All depends on your skill with wet layups and far down the rabbit hole you want to go in terms of process.
It was worth it to me, but everyone has different goals and expectations, and may not be worth the effort / cost. There is nothing wrong with an enclosure made using a traditional layup on a mould.
So if i did want to vac bag it, what would i need in total? Im guessing a vaccuum pump, a bag, some kind of medium between the vacuum bag and the carbon layup?
Picture of the mold so far, no post processing yet.
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Read this: Vacuum Bagging | WEST SYSTEM Epoxy
Need:
Flange on your mould around the enclosure
(Needed even if you don’t vac bag it I think)
Bag / plastic vac bag film
Sealant tape (butyl)
Peel ply fabric
Bleeder fabric/ polyester batting stuff
Vacuum pump and any fittings
Timer or control for vac pump if your bag isn’t going to seal well. (Which is quite likely)
Ummm
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Couldnt i just get a significantly larger vaccuum bag and put the entire mold inside of it, instead of trying to seal the vacuum bag to the mold flange?
Also, looks like im gonna get the west systems 105 epoxy and 207 clear hardener, any objections to that?
Yes, i’ve done this several times. I’ve used the vacuum storage bags with great success and you can just use a normal vacuum for those
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Is there any concern of the regular vaccuum burning out under that kind of load? How long do you need to hold vacuum pressure for? Are you able to pull enough vacuum to sufficiently press the composite into a negative mold? Do you still use breather/perforated layers?
Sorry for throwing so many questions haha, im on a tight-ish budget between all the other projects im working on, want to get it right the first time without burning through too much money 
Its just the same as if you were using the vacuum to shrink down clothes or whatever. You suck it til it won’t suck anymore and then disconnect.
However long your chosen resin takes to cure. Once you suck the air out with the vac, as long as you haven’t pierced the bag anywhere or compromised the seal, it should hold vacuum indefinitely.
Absolutely. Although it is advisable to lay it as proficiently as you can before vacuuming, you can’t just dump a bunch of wet glass in there and hope that the vac will sort it out
Yeah. You need peel ply/perforated film and breather fabric. Breather fabric allows the vacuum to distribute pressure evenly over the whole part and doubles as a ‘sink’ for excess resin. Peelply/perf allows you to remove the breather from the part ‘easily’ while providing a neat surface on the part
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West systems epoxy is my all time least favorite Epoxy to work with, but it has been 20 years since I used it. Stinky, thick, slow to wet out fiberglass, bizarre 4/5 to 1 ratio prone to error. I dont recall the pot life.
My all time favorite for laminating to wood is System3 clear coat. It is very thin, penetrates wood deeply, wets out cloth nearly instantly, long potlife, though a bit stinky, but not as rude as West system.
System 3 general purpose resin is nothing special, SB112 is good, but phased out i think.
When I lived in Socal, Id drive to surfsupply in iceanside and pick up Apex brand epoxy. Was cheapest around, pretty fast,. prone to fisbeyes on secondary bonding. They seemed to improve the formulation over the years. Ive gotten really used to it, gone through about 5 1.5 gallon kits in the last decade, and recently ordered another 1.5 gallon kit from them last year.
Basically No stink, wets out cloth quickly, pretty fast setting, 2:1 ratio by volume, 100:45 by weight, shipping eats up the savings but cost wise is among the least expensive brands available.
I see they offer a few different pot life versions. the quickset is probably too fast for vaccum bagging, with which I have no e experience
Epoxy does not stick to the plastic, like zipock freezer bags. One can lay this plastic atop curing epoxy, and use the squeegee to push bubbles from middle to edges, and as epoxy slowly thickens, one can time it right and mold it i to place when it has gotten thick. I call it the poor mans vaccuum bag technique, and it can save a lot of sanding.but there is a learning curve.
Use distilled white vinegar to clean up uncured epoxy from tools/skin.
Avoid epoxy on skin, getting sensitized to it is a fear of mine. Some people instantly react to it. Never use acetone.
Get a digital scale. weigh the ratios. The correct ratio is very important. Mixing by volume is error prone with the graduations in mixing cups being inaccurate, air in the pumping systems causes improper ratios to happen so frequently that many surfboard factories ban their use.
With apex epoxy the ratio is 100:45 by weight. pour resin in cup on scale, read weight, multiply by 0.45, hit tare button on scale , pour that much hardener tk the tenth of a gram. Small batches with my 300 gram scale, I will.pour to the hundredth of a gram.
I weigh JB weld too, 50 50 even though it is very tolerant of improper ratio, but it will bond far stronger,and have far greater strength when the ratio is exact.
Laminating epoxies vary, but basicalky 3% max. 10% off and it will remain soft, gum sandpaper, bond poorly. Avoid!
Make sure it is thoroughly mixed. no swirlies when shi ing a strong light into mixing cup.
Make sure mixing stick can fit into mixing cup corners. sand to shape.
Wipe all 5 sides of flat mixing stick on top of cup edge when mixing, multiple times, making sure to not fling it into eyeballs.
Do not allow any to drip down out sides of cup as it will screw the ratio.
Once thoroughly mixed, mix .some more, and dont’t keep it in the cup, spread it wide in a baking tray or similar to increase working time.
Exotherming in the cup will ruin your day.
It is not so easy to see when carbon fiber is fully wetted out, and a dry lam will ruin your day.
Inexact ratio A and B, and not mixing them thoroughly, can ruin your day week month and turn into a tool throwing curse fest, then later quiet sobbing, then back to the tools being thrown.
So take every step possible to prevent the occurrence.
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Ratios are definitely important!!!
There are some resins out there that specifically demand ratio by volume or weight. I’ve always thought the 2 were basically interchangeable in this circumstance, but I think its possible to get into trouble using one when it calls for the other.
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i believe most say mix exactly by volume, or by weight.
But mixing by volume leaves tons more room for error, with cup graduations being off, dealing with meniscus, and viscosity at different temoeratures
Digital scales are cheap, cheaper than the good mixing cups.
other benefits of the scale are ot needing to slow pour to tbe line.
My biggest regret working with epoxy is nkt switcbing to weighing it sooner, especially as i do so many small batches, like less than 7.5ml.
Ive had repairs fail, and find when re repairing them, that the epoxy below was soft and bonded poorly and caused the repair to fail, all cause i was trying to mix small.portions in a mixing cup by volume.
Some resin systems are more tokerant of imorooer error than others, but maximum strength and adhesion and sandability are achieved by exact ratios mixed thoroughly.
Also, epoxy can be sanded at 98.5% cured, but the dust is toxic until 100% cured.
my Apex brand epoxy says minimum working temo is 60f. If i get 4 hourz of time above 60f, ut then it fLls below tbis, and then warms uo the next day, it seems to harden fine, but sands poorly, and 5 to 6 more days are required.
I have found it important that the epoxy stay well above its minimum working temperature for at least 12 hours. when it falls below, nkt onky does it then take forever for it to cure 100%, at which point the dust is inert, but that it does not seem to cure properly either seems a bit soft, and does not bond quite as well either.
Its another variable I do my best to control.
Also amine blush… much worse in higher humidity, even on the ‘blush free’ epoxies.
A fog rolling in during the cure can cause all sorts of issues with epoxy clouding and secondary bonding, and dew collecting on the surface is guaranteed to as well.
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Alright so i managed to find these for my breather, peel ply, and a vacuum bag. Would that work out? Should i be concerned about the thickness of the vacuum bag not getting into the crevices of my negative mold?
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Thay all lopks good!
So some vacuum films have a certain amount of stretch to them but ot would be foolish to rely on that to get all the way into your corners. You need to ensure that as you are pullimg the vac, you are also pushing the bag imto all of the corners. It doesn’t matter if the bag ends up all bumched up or whatever, just as long as its not stretched.
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