vacuum bagging or vacuum infusion

[Eisa Hasan]

hi all

I just started my own bussiness in fiberglass , we manufacture fiberglass products and another bussiness of building fiberglass boats .

i read about vacuum bagging and vacuum infusion

-Which one is the best? will both give me lighter weight and higher strength?

-Will i save some material cost by these two method?knowing that the labor charges is exteremly low ($160-$270 a month).

-Vacuum infusion seems to be a very complicated method while vacuum bagging seems to be much easier.correct me please if im wrong


thanks

[spartin]

what is the size of your hull

[Eisa Hasan]

size about 27 feet

[spartin]

baging can work for you but you better learn on smaller parts first things like bulk heads to start out to learn just how much to wet out
and you may want to cut back on you m.e.k. and work fast once you have it down and have done you fisrt hull
when you go to pull off the bag the lam will still be green i dont care if it sets for 1 or 2 days it will still be green it has to gas off
be very carful not to pull you peel ply

[8knots]

Look into infusion with a UV cure resin. more expensive but easy and more consistant results. I'm not plugging this company but this will give you an idea.
http://www.sunrez.com/
good luck 8Knots

[JV_Comp]

Infusion is nice but you have to eliminate any leakage in both the mold and the vacuum bag. A leak will ruin the part because air will beome entrained in the laminate. Leaks are the biggest problem.

You also have to postion the feed lines properly. It is not hard to figure that out but it takes practice and some trail & error before you get the positioning right for your particular project. Positioning is detemined by how fast the resin flows through the laminate and how far it has to travel.

Speed of flow is determined by resin visocity and the laminate stack and whether there is a core in the laminate (sliced and perforated) or an interlaminar flow medium or a surface flow medium.

You have to make a lot of test samples to get the technique down and to learn how to eliminate leaks in the hose connections and bag. I recommend buying the Vacuum Infusion DVD at:

http://www.gurudvds.com/site/index.asp

The full DVD is $500 but it is worth it. You can spend a lot of time and money doing trial and error tests on your own. I bought one a while back and it was very useful.

Also, for more info see:

http://www.grpguru.com/vipupdate.asp

[Buckle]

They key to both processes is vacuum pressure. Both processes require a good bag. So if you can vac bag, RI ain't much harder. Its just a bit of plumbing.

Astrome has writting a very good book called Manufacture of polymer Composites. Its very good and worth the money. Have a read of it, and all your prayers will be answered.

I wouldn't faff around with vac bagging. Go to RI. The results are so much better.

shaun

[rxcomposite]

Hi,

Infusion is a method of transfering or introducing resin into the reinforcing layer. To transfer you need pressure or create a difference of pressure from the atmosphere to the part.

Resin Transfer Method (RTM) is a method wherein the resin is transferred or infused to the reinforcing fibers by a pressure pump, no vacuum. This requires a heavy inner and outer mold.

RTM- VAT is resin transfer using both pressure and vaccuum assist to pull the resin in. A closed mold or vacuum bag is used.

VARTM- Vacuum Assist Resin Transfer Method is purely vacuum to transfer the resin under a closed mold or vacuum bagged mold. I beleive this is a patented system and inquiry to the process will bind you to an agreement to use the process. At least that is what i have read when it was introduced.

A variation of the VARTM is available from another material supplier but i understand you have to use their flow medium material.

Vacuum bagging- prepreg molding is a process where there are no resin transfer because the resin is already impregnated into the reinforcing material. You have to cook it in an oven though. A variation of this is VARTM- UV curing, another vacuum bagged process.

As with all of the process described, not ordinary off the shelf material will work. Resins and fabric works hand in hand to make the process work as well as the correct vacuum pressure profile over a period of time.

This is the problem that is being discussed in another thread where the part they were getting is heavier than a wet laid up part.

When overdone, another problem creeps in. The laminate becomes thinner due to reduced resin content than was originally designed for. a thin laminate flexes more. Stiffness is a function of thickness.

Care must be exercised that there is no major deviation from design.

[rxcomposite]

[quote=Eisa Hasan]
[-Which one is the best? will both give me lighter weight and higher strength?

-Will i save some material cost by these two method?knowing that the labor charges is exteremly low ($160-$270 a month).]

There are many factors that affect "lightness". Reducing resin content will reduce weight but will make panel thinner and more flexible. Flexibility is a function of the support span of the stiffeners so you might have to reduce your stiffener spacing. As you pack the laminate with more glass (to make it thick) and less resin you get a heavier boat. Remember, resin is lighter than fiberglass.

To have stiffness, you need thickness. to build up thickness, you need CSM with lots of resin content.

To have strength, you need WR. Just enough strength to do the job, combine WR and CSM in the right proportion.

If labor cost is low, why not go for wet lay up? Wet lay up is labor intensive but VARTM is more expensive to run even if it uses less labor.

In production run, what is important is the turn around time of the mold. The more part you can pop out in a mold at a given time, the better.

[rxcomposite]

More technically correct terms

LRTM- Light Resin Transfer Molding came into development in Belgium about 20 years ago. It is a process where pressure pump was used to transfer resin and vacuum was used to assist. Vacuum was low, about 20 in.

RTM VAT- Resin Transfer Molding Vacuum Assist Transfer (or technology) was the common term when it was slowly being adapted in the U.S.

RTM VIP- Resin Transfer Molding Vacuum Infusion Process is now the most widely used term by the composite industry.

[War Whoop]

A couple questions:

Is your molding area Air-conditioned?

and do you have a plumbed in regulated vacuum system? (needed in wet bagging production)

Resin Infusion is the better of the two systems in terms of a finished product/speed Also the only material used is what in feed into the manifolding/distribution system and that stops when the resin front reaches the end/edge of the work. Where in wet bagging you are compressing a wet laminate and excess resin is in the breather to be thrown out Ie the waste is greater but this can be reduced with a Impregnator

However I have a “Quick bag” system I used in Kuwait and it worked well on the military stuff I was doing there.

Here is a picture of a custom made vacuum regulator I built (it is controled by weights on a slide)problem is Wetbagging with Ester resins it's very critical to keep the vacuum around 24-36 inches of Water in daily production runs it is better to regulate the entire system to the Max vacuum to avoid a problem my Glass shop there was perimeter plumbed and hooked into a 1000 cfm pump outside.Oop's also 40 tons of AC

Infusion is a different story.