Hi,
It's long time since I have wrote anything and I wanted to share some of my experiences now. 

As many of U may know, I have been working with carbon fiber and fiberglass parts for a long time. Mostly every composite part that I have been making, is made by resin infusion. Problem with resin infusion have been always the fact that sealing the vacuum bag takes a lot of time and it is very easy leave it to have a leak. As I have wrote in some older thread, the micron meter helped a lot to get reliable sealing. Basic vacuum gauges are not enough to determine 100% reliable that is the bag leaking or not(unless u wait long time and check vacuum drop). Since we need to make so many parts and we need a fast cycle for the parts we have been going more and more to reusable silicon bags. Basically we no longer make basic resin infusion with nylon bags. There is several reasons for it:

-Silicon bag is reusable (some companies have used it for cycle of 3000)
- No Waste
- 100% reliable sealing (never vacuum leaks)
- Can hold vacuum for days without running vacuum pump
- Seals in matter of seconds
- Made in the shape of the mould, so there will be no corners that the bag wont be reaching.
- Environmentally friendly.

Of course it's a investment to make the silicon vacuum bag, so its not good for one off items, but if u make more than 2 parts, it will definitely be worth of making it. Negative thing of the bag is that it wont be lasting for long with epoxy parts. Lifetime will be 25-100 cycles. I made a 1,3 meter long miniature boat hull mould with silicon bag for demo purpose and it took just minutes to infuse the part. After I have add the fiberglass, I just add the silicon bag over it and I will get perfect vacuum in matter of seconds and its ready for infuse. I never had any leaking issues with the silicone bag. Also with a Morph runner I can make a channel for resin flow, that after infusion I am able to get it disappear. No traces of flow channel, so no need for removing hardened resin, like normal channels would leave. 

I am not promoting anything or selling anything with this text. I just want to give u all my honest opinion of silicon vacuum bags. Highly recommend for testing it.

Yeh silicone vacuum bags are great. Biggest problem with them for me is they don't work with split moulds, at least not without sealing the flanges in another manner which makes it a pain. But for single piece moulds on any production run making more than 10 parts - hands down better than conventional vacuum bags.

Resin infusion aside, you should try it with pre-pregs! Now that's a treat! Biggest production run I've done was on a part for a go-kart, I had to make 150 of these little things. Initially I started out out resin infusing them with regular vacuum bagging, they took about an hour and a half each to make. Switched to pre-preg with regular vacuum bags and I dropped that to about 45 minutes. Made a silicone vacuum bag and I dropped it to 15 minutes for each part - with only the release film as wastage. 

+x

 

Hanaldo - 11/16/2018 2:24:48 PM

Yeh silicone vacuum bags are great. Biggest problem with them for me is they don't work with split moulds, at least not without sealing the flanges in another manner which makes it a pain. But for single piece moulds on any production run making more than 10 parts - hands down better than conventional vacuum bags.

Resin infusion aside, you should try it with pre-pregs! Now that's a treat! Biggest production run I've done was on a part for a go-kart, I had to make 150 of these little things. Initially I started out out resin infusing them with regular vacuum bagging, they took about an hour and a half each to make. Switched to pre-preg with regular vacuum bags and I dropped that to about 45 minutes. Made a silicone vacuum bag and I dropped it to 15 minutes for each part - with only the release film as wastage. 

Nice to hear your experiences!  
Actually I have a sealing profile that works perfecty with split moulds. When U make a split mould, u just add this " square" profile between flanges and once the mould is ready, U remove it and add different proper size round sealing permanently to that channel. So when U tighten the flanges together this sealing profile will seal the flange perfectly and the sealing will be connected to the silicone bag vacuum channel. 

Did that release film extended silicone bag lifetime? Did u use Silflon to protect the bag with prepregs?

Yeh I tried the sealing profiles but I just couldn't get them to work reliably. I'd love to see some pictures of yours if you have any you can show?? 

I would expect the release film extended the life of the bag a little bit, but it's hard to tell - it's still as good as the day I made it, but it's also only done 150 pulls. In any case, it has very little contact with the resin, so I cant see the resin degrading the bag too much.

It is good to hear your experiences with a silicone bag system.  Do you have any pictures on how you are making the bags?


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

There is an Alan Harper workshop about his silicone bags taking place at work next month. Check out the link, its a free event and I will hopefully attend it as i get to have some hands on with the technology

https://nccuk.com/reusable-vacuum-membrane-technology-workshop

Hi Warren. I would recommend to go Alan Harper workshops. Or ask Blaise from Alan Harper to visit your company. They are super friendly and very professional with silicone bags. I think it would be good idea for Easy Composites to start selling the silicone that Alan Harper provides. Its quite simple to make the bags, when U see how it works. 

Hanaldo, I can send U some pictures later on. I have silicone square profile that I use to make the channel and after mould is ready, I change it to round one to get perfect finish. Are U doing the same way? Both ends of the silicone profile must end to the outer vacuum channel of the bag, This prevent any vacuum leakage to happen. 

I liked knowing this method, I have great difficulty with micro leakage in the vacuum bags.

I have some doubts:

In this method is still necessary the use of resin flow media, peel ply?

The other question , is there any way to make the vacuum bag without being sprayer? Here in South America you do not have any such equipment yet.

 Thanks!

You dont need anymore infusion media, thats one of the many benefits.

If you look at the smooth on.website in America it has materials similar to alan harper. You will need to spray it to get a decent coverage on anything other than flat.