Just a bit of infusion help

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#1

Hey guys, fairly new here. Been mostly reading the last few days and I must say there is a HUGE amount of info here. I need some infusion help. We build fiberglass go kart bodies, each body is 3 seperate pieces. So 3 seperate molds for each body. Right now we are hand laying the body, but are looking at going with a silicone reusable bag method or LRTM. My question is I need help with the flanging part. I read all other flanging post, and have that part pretty much figured out, except what do I do about filling the wheel openings, and other void if I was going to mount it up to a table? I can email someone pics if that would help, I cant figure out how to attach them on here. Any help would be greatly appreciated. And pics would be even better.

Thanks in advance.

Chris.

#2

Pics can only be added to the posts after you make another couple of posts.

Can you tell more? Are your parts weight sensitive? Polyester or epoxy? How many per year?

#3

Herman is technically correct, pics can be added in the first couple of posts, you can use the paperclip icon in the reply to add them.

Your post will be moderated though so after you upload them sit tight until I get to the moderation queue.

And also post what Herman asked for. We do need that information to better answer your question! :smiley:

Thanks Herman!

#4

Thanks for the replies guys. I am going to attach a couple of pics of one of my parts. The one posted is put together already as you can tell from the bolts. I will try to get some better seperate pictures this weekend. As I said they are molded as 2 seperate peice, (nose and 2 sides). My weight now is about 15 lbs give or take, that is not really that crucial, as long as we stay within a pound or 2. Right now they are handlaid, 2 layers of 1.5 oz mat, with and extra layer in a few impact areas. They are laid with polyester resin. Thanks in advance and any and all help is certainly appreciated.

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#5

So what are your intentions to switch to resin infusion?
Less fumes? I bet it is no fun to do a wet lay up with polyester.
More consistent parts?

#6

Yes less fumes, more consistant parts, and also less resin ratio. Hoping for a lighter, stronger part. Really don’t make a ton of parts a year so not 100% sure LRTM is best for us. I’m leaning towards the bag, the only thing that I really really like about LRTM is being able to gel coat both sides. But the cost is a big factor. To stay competitive in the market, no the sure money spent on LRTM (unless I can do the tooling myself) will be worth it.

#7

If you already have the gel coat, glass, and resin you have just about everything you need to go LRTM. You would just need to make the tooling, get some fittings maybe, and the seals. Here are some good videos of LRTM http://rtmcompositestv.com/
You can also get all the fitting,seals, tubes, etc… https://rtmcomposites.com/store/

#8

Basicly 50 parts per mould is what you need to get the cost of a good LRTM mould back.

Your base mould should have 4-6" flanges, nice and smooth. Preferably no sharp corners. I somewhere have a document on making LRTM moulds. Will look it up on monday. It is relatively simple, but there are some tricks.

What you also need is a RTM machine. Look around to find a pre-owned one, and service it (basicly replacing some NRV’s (non return valves) and pump seals, and cleaning out everything. If you have bad luck, you will also need to replace some hoses.
I know Plastech (Now Venus) and Composite Integration machines. The latter are newer, as the company only started a few years back (out of Plastech personel) but both machines do the job.
Machines basicly do:
-suck up resin
-mix it with hardener
-inject it with a certain (adjustable) force into the mould cavity. The pressure is dependent on the mould. Flat moulds need low pressure (in order to prevent mould blowout) and more complicated shapes can use higher pressure, then the fill time decreases.

Advantages:
Very clean shop environment. Basicly you have 4 workstations:
-cutting fabrics
-applying gelcoats (brush or spray, if brush then you can leave the moulds in the infusion area, otherwise roll then to a spray booth, I saw a gelcoat spray machine for low dollars at boatdesign.net (a Binks unit, 900 dollar I believe)
-infusion. When using the Plastech “Turbo Autosprue” this is a very clean process. The output hose of the machine is connected to the mould via a Autosprue. Once infused, the button “flush” is pressed, and the residual (catalysed) resin is flushed into a bucket (make sure you can attach a bucket below the mould), then acetone rinsed (100cc or 1/8 quart, I am not good at imperial…) then blown dry with air. All without switching hoses or anything. Leave the autosprue on the mould, or attach it to the next mould. (it only connects with a safety pin to the mould). These are USD 130 or so.

-cutting area. A good mould generates “crack points” in your part. All you have to do is break off the extra “flesh” which basicly is the runner around the part, then sand the edges a bit.

And if you grow bigger:
-mould making dept. usually the domain of a senior worker, who skilfully makes moulds of whatever work you or your salesperson can get.

Advantages:
-clean process. Less fumes, less waste, less grinding
-constant quality
-fast. Both cutting (usually only 1 mat) and infusion are fast.
-both sided smooth, or even gelcoated
-cheaper labour can be used, the skill is removed from the worker, to the engineering.
-safer. No open buckets with rollers, brushes, etc.

Disadvantages:
-more expensive moulds
-need machine, compressor and vacuum system
-materials slightly more expensive (mat) per lbs (but you use less)
-need different resin (infusion resin, same price as hand laminating resin)
-need more knowledge slightly more up in the pyramid. (shop supervisor, mould making)
-on high strength parts: lower fiber/resin ratio. Usually only 18% or so.

#9

If weight is not the most important thing he can work with a double sealed closed mould and only vacuum
here a video
[ame=“http://www.youtube.com/watch?v=HxFaDKRkoEc&feature=youtube_gdata_player”]Lange&Ritter LRTM[/ame]

and how they made the mould
[ame=“http://www.youtube.com/watch?v=zTfQG6qY2eo&feature=youtube_gdata_player”]Mould making[/ame]

But for less than 50 parts a year or a good fibre to volume ratio I would prefer resin infusion with a bag. But than you dont have a smooth finish on both sides.

#10

I only watched the last video. It is a good video, up to 90% of the runtime. After that things go too fast. You need to reinforce the sides of the top mould considerably, and the part where the seals are installed is missing completely. The dynamic seal (the closest to the product) needs some extra care.

As for the use of wax: During production you will see the tendency of the resin not to cure completely in the thin line along that inner seal. There are waxes which dissolve these residual waxes (Ferro FR17 comes into my mind, but there are others).

Also, the resin feed line around the perimeter is something that must be done with care. Plastech has a half-round silicone seal to produce this cavity in the top mould, but the resin mass is quite high, causing high peak exotherms, attacking the mould. (cracking). The Composite Integration silicone seal for the same purpose is much shallower, and causes less problems.

#11

OP, can you please post pics of your moulds, personally, I would not go the route of LRTM on these for a few reasons:

  1. As a business, providing a “class A” finish on both sides of the part should only be done when you can charge enough for it. On go-cart skins I would highly doubt the buyers care what the other side, the one nobody looks at, looks like. Besides, you can paint that out if needed and it is smooth enough if you bag it and lay your peel ply and flow media right (no bridging).

  2. VARTM is the right process for this in epoxy, it will increase the value of the part, increase the quality, reduce the weight, provide a VOC free infusion process, provide a cleaner set-up for you to work in, will end up increasing your material costs (not by much) but will also reduce the time it takes in producing it a bit (not a ton of time, but it should be faster for you since you don’t have to “wet-up” the layers)

  3. LRTM for us requires way more than 50 parts to yield a return on the mould process. It is essentially two moulds you are building and if you not use to doing VARTM and skip that process to jump into LRTM you may find it a bit of a struggle learning the ropes of doing it right. I am not trying to say you should not do it, but there will be costs involved and lost time in learning, be prepared for that…

  4. Ideally, as oppose to going to a more advanced process, jump up to VARTM and spend a little money and time on building an oven to cure the parts faster and turn the moulds around quicker. I often am surprised that people spend so much time perfecting the process of infusion only to let the part “hang-out” for 16 to 24 hours on cure. Building a mould to handle up to 175 degree’s does not cost much more than a low-temp version, a garage-built oven can be done for $1,500 to $2,000 with a PID and some elements and bringing the infused part into heat can reduce your turn-around by 75%. Meaning you have a fully cured part in 3 to 4 hours that you can pull from the mould.

  5. Turning your parts quicker and cycling the mould faster means quicker invoicing and higher volume, with the volume you maintain your current pricing and you will find a higher percentage of profit being yielded.

Just my two-cents, if it were my job we would do it that way…after you post pics of the mould it will be easier to suggest flanging techniques because seeing a “finished” part doesn’t show us your trim lines presently unless you are doing these to net shape in the mould by hand.

Hope I didn’t come off sounding like a commander but really, I would go for increased quality through VARTM and turn-around time to free-up more production and keep costs down while increasing profit at the same-time.

:slight_smile:

#12

Thanks for all the help guys. Here are a few things, I don’t want to invest in a injection machine, I’m looking to do this with Vacuum. You guys could be right about the second side, but nobody in my industry is doing it so I think it would be a good selling point.

My biggest concern here right now, is the flanging of the parts and how to do this where I can build a good A sides mold ready to do infusion from. Any and all help with how to flange these parts would be awesome. I also already have a trim mold ready (a quick mold with no flanges) that we will use for a pattern for trimming. Any help with the flanging is greatly appreciated.