RTM process?

General Composites Discussions Composites Talk
#1

How does it work? What type of equipment is involved for doing small parts, and what type of molds? From what i understand the advantage is time savings.

Here is an article about a company that is going to be making composite roofs for the new VW Vans in Europe. They are using RTM and nickle plated molds… freaking expensive to nickel plate such a huge mold. We have some medium sized plates nickel plated at my day job, it costs $150 per aluminum plate(2"x20"x20"). But i’m sure to that company doing VW parts it’s no big deal to pay out for a nickel plated mold.

http://www.compositesworld.com/ct/issues/2004/February/367

#2

its fibers that are pressed under pressure with two or more mold halves then injeted with a resin sytem using an injection machine. the advantage is fast repeatable production for high volume, also gives you a a-class finish on bothsides.

#3

how is the problem of bubbles bing injected into the part avoided?

#4

Hojo, what resins are used with RTM? What is the cure time for each part?

#5

it really depends on the requirements of the part but they all are low viscosity. cure time depends on the resin system and the temp the mold gets heated at. its a very expensive investment and is good for very high volume parts, or parts that require a a-class finish on both sides.

#6

Are there any websites that show and discuss the RTM process. About how much $ would you guess a basic RTM set up would cost?

As far as production i can see making one hundred or so of each part. Infusion takes a long time, I like it but something more streamlined would be nice.

#7

i dont know of any websites, i am sure if you google it you could find something. as for the machines, I am unsure of the exact price, but I know they get expensive, glass craft makes one I would guess it must be around $15k but I trully dont know. in all reality you could make your own manual injection for the resin. you could make two mold halves, one which is offset for material thickness, and have a injection point which you have a cylinder with your resin that you force down into the part with a lever. I dont know how well it would work, but I would imagine if you built it right and thought about your injection point(s) well it should work. but I have never done it

#8

I did a youtube search on RTM and saw the video GlassCraft made on the subject. They say it takes about 7-10 minutes to inject enough resin to wet out an area about 7ftx3ft. I wonder how they ( or any RTM mold) heat the molds?

#9

I believe they run heated water through piping in the mold?

#10

a disadvantage to rtm is the high RC

#11

hot water, or oil, electric heating elements, etc. many ways.
as I was discussing slightly with BustedBlade, and easy way is make 2 mold halves with some sort of gasket between. Like for blades, acrylic blocks machined out (you can see then when to stop injecting, etc.)
Get a paint pressure bucketfor your resin, and inject a regulated pressure into it, which pumps your resin into the part.
There are of course, several ways to do all this. Mixing the resin, and injecting. You can inject both parts of the resin at once as well.