|
Finnluxury
|
|
|
Group: Forum Members
Posts: 50,
Visits: 448
|
Hi!
We have decide in our company to start making a silicone vacuum bags. There is several reasons why we have end up to make these compared to the basic single use bags. One of the most important reason is that we have complex moulds shapes and we start to make bigger quantities of our products. So having a silicone bags is a real time saver, compared to basic single use vacuum bag that needs a lot of careful placement. Also savings in the material is another good reason for using silicone vacuum bags. After 6 parts, its cheaper to use silicone bags, and cost saving can be around 80%.
Last night I bought EZ-Spray junior spraygun and EZ-Spray silicone 20.This is a sprayable silicone which cures quickly to soft rubbers with high elongation and tear strength. Cures in about 20 minutes. Newly fabricated vacuum bags can be removed from the tool assembly in a matter of minutes and be put into production service immediately.
So have anyone else here made a Silicone vacuum bags?
There is two different ways to seal the bag to the moulds to make air tight seal. One option is to make a sealing channel to the mould, that the silicone goes inside the channel, and this way forms an airtight seal. Another option is to make a vacuum channel, that sucks the silicone bag tightly to mould flange and keeps the vacuum without any leakings. I am still thinking which method to choose.
|
|
|
|
|
Fasta
|
|
|
Group: Forum Members
Posts: 468,
Visits: 3.5K
|
The smooth on brand silicone has some neat videos on you tube of their spray and brush systems being used to make bags, seals etc. There are some neat ideas and I imagine the EC silicone could work in the same way?
|
|
|
|
|
Finnluxury
|
|
|
Group: Forum Members
Posts: 50,
Visits: 448
|
+xThe smooth on brand silicone has some neat videos on you tube of their spray and brush systems being used to make bags, seals etc. There are some neat ideas and I imagine the EC silicone could work in the same way? Yes, they do have lot of videos. I have watched all the videos. Actually in some of the videos, they use same spray gun and the silicone is the same.. Alan Harper from UK also make these bags. But they don't have much of information about the seal channels. I think the most professional way would be having the channel in the mould flange. The most important is that there will be no leaks. As we do resin infusion, so the leaking will ruin the parts. We always use micron meters to see the perfect vacuum. Basic vacuum gauge is too inaccurate. By the way, is anyone going for composite engineering fairs next week at Birmingham? I may go there, unless I must go to JEC Asia that is held in Korea.
|
|
|
|
|
oekmont
|
|
|
Group: Forum Members
Posts: 550,
Visits: 27K
|
I am curious how silicone bags will work with carbon in complex shapes. Everything i have seen so far was csm. The companies allways say that it will work just as fine with carbon. But unless the part is very simple I don't see that for a effective solution. They never use flow media in the videos. And I imagine it difficult to get a semi tacky silicone bag over the flow media of a complex part without messing it up. Sometimes even intensifiers are not easy to get into place. With all the preparations the time for producing one silicon bag easily exceeds the time I need for 25 regular bags. Even on the most difficult parts.
Have you considered to use intensifiers in your process? this might be a lot easier than the silicon bag.
|
|
|
|
|
Finnluxury
|
|
|
Group: Forum Members
Posts: 50,
Visits: 448
|
+xI am curious how silicone bags will work with carbon in complex shapes. Everything i have seen so far was csm. The companies allways say that it will work just as fine with carbon. But unless the part is very simple I don't see that for a effective solution. They never use flow media in the videos. And I imagine it difficult to get a semi tacky silicone bag over the flow media of a complex part without messing it up. Sometimes even intensifiers are not easy to get into place. With all the preparations the time for producing one silicon bag easily exceeds the time I need for 25 regular bags. Even on the most difficult parts. Have you considered to use intensifiers in your process? this might be a lot easier than the silicon bag. What is intensifiers? not familiar word for me. Is that same as "pressure strip"? Complex shapes and edges should not be any more problem that with basic vacuum bag. We have a solution that we use for tight corners (R=2.0mm). Also our panels are always a bit resin rich, so if there is small area where CF would not reach, the epoxy will fill it. Tiny area will not broke even the CF wouldn't be there. , unless hit by a hammer. Its true that I havent seen CF videos of silicone vacuum bags, but it can be also because the material itself is expensive just for demostration purpose. We also use Lantor soric, so it will help the resin to flow. We have lot of complex shapes, see: www.facebook.com/finnluxury
|
|
|
|
|
oekmont
|
|
|
Group: Forum Members
Posts: 550,
Visits: 27K
|
Intensifiers are just small silicone parts, wich you place on top of the flow media in tight corners, so the flow media gets pushed into the corners, so the bag can easily "flow" around complex areas.
Using soric might help, but my experiments resulted in a fairly small flow advantage compared to no flow media at all. Not nearly as good as a good flow media. But I have to say, that it was the 1,5/3mm lrc type and the 3mm sf version. Thicker ones and other types might work better.
Please show us some results. The guys who wanted to sell me silicone bagging equipment seemed to have no clue about carbon manufacturing that I just not trust in their promises.
|
|
|
|
|
oekmont
|
|
|
Group: Forum Members
Posts: 550,
Visits: 27K
|
I believe they only show csm processes, as csm allready has got decent flow propertys. In my opinion the bagging is not the annoying and labour expensive step they allways proclaim. The process just looks that much easier, because they don't use peel ply/release film and flow media. Basically everything that is difficult to get into complex areas and hold down firmly. And the shapes are allways as easy as you can get without using a glass plate. Considering the preparations you have to do for a silicone bag I would recommend (For this easy shapes) making a matched mold and do the part via vari or "light rtm". That is just as expensive, will last forever and gives you a better part.
|
|
|
|
|
Hanaldo
|
|
|
Group: Forum Members
Posts: 2.5K,
Visits: 28K
|
Silicone vacuum bags work fine with carbon infusion, you just need to use flow mesh and factor that thickness in when making the bag. This is as simple as just infusing your first parts in the regular fashion with conventional vacuum film, then making the silicone bag prior to demoulding or removing the consumables. In the videos they are likely using CSM that has flow media incorporated into it, which is quite common.
For your sealing method, I actually recommend combining both the channel in the mould, AND then channel in the bag. I've never had success using one or the other, but a combination does work well. Just make sure not to use too much reinforcement when you make the channel in the bag, as if it is too stiff then the channel won't draw down and seal against the mould surface.
Also yes, silicone bagging is SIGNIFICANTLY quicker once you've worked it out. It is literally a case of throwing the bag on, getting the sealing channel in place and pulling vac. It's a 1 minute process, every single time. The bag seals itself consistently so theres no need to leak check, bridging is never a concern... It is definitely a great way to save time on production runs. But it does take a bit of time and effort to get it working nicely.
|
|
|
|
|
Finnluxury
|
|
|
Group: Forum Members
Posts: 50,
Visits: 448
|
+xSilicone vacuum bags work fine with carbon infusion, you just need to use flow mesh and factor that thickness in when making the bag. This is as simple as just infusing your first parts in the regular fashion with conventional vacuum film, then making the silicone bag prior to demoulding or removing the consumables. In the videos they are likely using CSM that has flow media incorporated into it, which is quite common. For your sealing method, I actually recommend combining both the channel in the mould, AND then channel in the bag. I've never had success using one or the other, but a combination does work well. Just make sure not to use too much reinforcement when you make the channel in the bag, as if it is too stiff then the channel won't draw down and seal against the mould surface. Also yes, silicone bagging is SIGNIFICANTLY quicker once you've worked it out. It is literally a case of throwing the bag on, getting the sealing channel in place and pulling vac. It's a 1 minute process, every single time. The bag seals itself consistently so theres no need to leak check, bridging is never a concern... It is definitely a great way to save time on production runs. But it does take a bit of time and effort to get it working nicely. Hi! Do U have the channel in the mould at inner or outer side of the mould flange? I were thinking that I could have mould channel at inner side of flange, and then the bag channel at outer side of the flange. Have u tested is there difference which one is outer and which one in inner side? Would u have any photos to share? 
|
|
|
|
|
Hanaldo
|
|
|
Group: Forum Members
Posts: 2.5K,
Visits: 28K
|
+x+xSilicone vacuum bags work fine with carbon infusion, you just need to use flow mesh and factor that thickness in when making the bag. This is as simple as just infusing your first parts in the regular fashion with conventional vacuum film, then making the silicone bag prior to demoulding or removing the consumables. In the videos they are likely using CSM that has flow media incorporated into it, which is quite common. For your sealing method, I actually recommend combining both the channel in the mould, AND then channel in the bag. I've never had success using one or the other, but a combination does work well. Just make sure not to use too much reinforcement when you make the channel in the bag, as if it is too stiff then the channel won't draw down and seal against the mould surface. Also yes, silicone bagging is SIGNIFICANTLY quicker once you've worked it out. It is literally a case of throwing the bag on, getting the sealing channel in place and pulling vac. It's a 1 minute process, every single time. The bag seals itself consistently so theres no need to leak check, bridging is never a concern... It is definitely a great way to save time on production runs. But it does take a bit of time and effort to get it working nicely. Hi! Do U have the channel in the mould at inner or outer side of the mould flange? I were thinking that I could have mould channel at inner side of flange, and then the bag channel at outer side of the flange. Have u tested is there difference which one is outer and which one in inner side? Would u have any photos to share? I keep the mould channel on the outside of the mould, reason being that it works as more of a locator than a seal. Ill try to find some photos for you
|
|
|
|