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Fasta
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+x+x+x+xThese are the two intensifier parts I have made. The large one has a core piece included so I could reduce the amount of silicone used and also have a bit more flexible plug to aid with releasing. This intensifier was cast inside a fiberglass shell that I pulled from the moulds. I have made 20 of these. The small one is a tubular foil section, this one was cast within the moulds using sheet wax to simulate the part thickness. I made 6 of these. No failures except for air in some corners which improved as I tailored the laminates to suit. The difference I see with the posters project is that my parts here are 1.5mm-2mm thick whereas the heli boom is probably much less so it would have less resin to go around?? Click To Enlarge Click To Enlarge Click To Enlarge Very cool! Actually not much thinner. Most likely I'll be about 1mm wall, maybe built up thicker in areas at the base. So it sounds like just simulating layup thickness for the plug with wax was all you really had to do. When laying up the foil, is it just left open at the back for the silicone to expand outward? Or do you cap it off to contain the expanding silicone? The smaller foil intensifier was just sitting in place whereas the larger one had an alloy plate bolted to the end of the mould to hold the silicone in place. It's really simple to make the silicone plugs, I guess the catch is that this method needs to be matched or tailored to some degree whereas air pressure/bladders can essentially conform to any mould shape. But then I would consider the building/design of a bladder system with with fittings etc and containing this in the mould and not leak to be a big challenge too. And time consuming. My small foil shaped one has had two silicone inserts snap/break when being withdrawn. A soft silicone releases easier as it stretches more/easier while pulling to release. But then with a stronger silicone this requires a little more pull and so also has the potential to snap. It broke about 100mm from the skinny end which was about 7-8mm thick. The larger one releases really well literally falling out as long as I used the Mann release on it. One mistake I made was to make the larger silicone intensifier without degassing the silicone as I ended up with bubbles left in the silicone, the bubbles that are in contact with the moulding surface get epoxy resin forced into them with the cure and that kind of keys the silicone to the inside of the new part making them really hard to get out. The new degassed version was great though. I think as long as you leave some space at one end of your mould you can use the moulds for either process. Sounds good. Thanks for the tips. I think I'll give the silicone plug a try first before going to a bladder. One more question, how are you preparing the silicone plug before inserting into layup? Are you applying anything for release? I'm using frekote sealer and release on molds. Should I apply that to the plug, or use something else?
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quinn
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Group: Forum Members
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+x+x+xThese are the two intensifier parts I have made. The large one has a core piece included so I could reduce the amount of silicone used and also have a bit more flexible plug to aid with releasing. This intensifier was cast inside a fiberglass shell that I pulled from the moulds. I have made 20 of these. The small one is a tubular foil section, this one was cast within the moulds using sheet wax to simulate the part thickness. I made 6 of these. No failures except for air in some corners which improved as I tailored the laminates to suit. The difference I see with the posters project is that my parts here are 1.5mm-2mm thick whereas the heli boom is probably much less so it would have less resin to go around?? Click To Enlarge Click To Enlarge Click To Enlarge Very cool! Actually not much thinner. Most likely I'll be about 1mm wall, maybe built up thicker in areas at the base. So it sounds like just simulating layup thickness for the plug with wax was all you really had to do. When laying up the foil, is it just left open at the back for the silicone to expand outward? Or do you cap it off to contain the expanding silicone? The smaller foil intensifier was just sitting in place whereas the larger one had an alloy plate bolted to the end of the mould to hold the silicone in place. It's really simple to make the silicone plugs, I guess the catch is that this method needs to be matched or tailored to some degree whereas air pressure/bladders can essentially conform to any mould shape. But then I would consider the building/design of a bladder system with with fittings etc and containing this in the mould and not leak to be a big challenge too. And time consuming. My small foil shaped one has had two silicone inserts snap/break when being withdrawn. A soft silicone releases easier as it stretches more/easier while pulling to release. But then with a stronger silicone this requires a little more pull and so also has the potential to snap. It broke about 100mm from the skinny end which was about 7-8mm thick. The larger one releases really well literally falling out as long as I used the Mann release on it. One mistake I made was to make the larger silicone intensifier without degassing the silicone as I ended up with bubbles left in the silicone, the bubbles that are in contact with the moulding surface get epoxy resin forced into them with the cure and that kind of keys the silicone to the inside of the new part making them really hard to get out. The new degassed version was great though. I think as long as you leave some space at one end of your mould you can use the moulds for either process. Sounds good. Thanks for the tips. I think I'll give the silicone plug a try first before going to a bladder. One more question, how are you preparing the silicone plug before inserting into layup? Are you applying anything for release? I'm using frekote sealer and release on molds. Should I apply that to the plug, or use something else?
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Fasta
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Group: Forum Members
Posts: 468,
Visits: 3.5K
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+x+xThese are the two intensifier parts I have made. The large one has a core piece included so I could reduce the amount of silicone used and also have a bit more flexible plug to aid with releasing. This intensifier was cast inside a fiberglass shell that I pulled from the moulds. I have made 20 of these. The small one is a tubular foil section, this one was cast within the moulds using sheet wax to simulate the part thickness. I made 6 of these. No failures except for air in some corners which improved as I tailored the laminates to suit. The difference I see with the posters project is that my parts here are 1.5mm-2mm thick whereas the heli boom is probably much less so it would have less resin to go around?? Click To Enlarge Click To Enlarge Click To Enlarge Very cool! Actually not much thinner. Most likely I'll be about 1mm wall, maybe built up thicker in areas at the base. So it sounds like just simulating layup thickness for the plug with wax was all you really had to do. When laying up the foil, is it just left open at the back for the silicone to expand outward? Or do you cap it off to contain the expanding silicone? The smaller foil intensifier was just sitting in place whereas the larger one had an alloy plate bolted to the end of the mould to hold the silicone in place. It's really simple to make the silicone plugs, I guess the catch is that this method needs to be matched or tailored to some degree whereas air pressure/bladders can essentially conform to any mould shape. But then I would consider the building/design of a bladder system with with fittings etc and containing this in the mould and not leak to be a big challenge too. And time consuming. My small foil shaped one has had two silicone inserts snap/break when being withdrawn. A soft silicone releases easier as it stretches more/easier while pulling to release. But then with a stronger silicone this requires a little more pull and so also has the potential to snap. It broke about 100mm from the skinny end which was about 7-8mm thick. The larger one releases really well literally falling out as long as I used the Mann release on it. One mistake I made was to make the larger silicone intensifier without degassing the silicone as I ended up with bubbles left in the silicone, the bubbles that are in contact with the moulding surface get epoxy resin forced into them with the cure and that kind of keys the silicone to the inside of the new part making them really hard to get out. The new degassed version was great though. I think as long as you leave some space at one end of your mould you can use the moulds for either process.
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quinn
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Group: Forum Members
Posts: 155,
Visits: 992
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+xThese are the two intensifier parts I have made. The large one has a core piece included so I could reduce the amount of silicone used and also have a bit more flexible plug to aid with releasing. This intensifier was cast inside a fiberglass shell that I pulled from the moulds. I have made 20 of these. The small one is a tubular foil section, this one was cast within the moulds using sheet wax to simulate the part thickness. I made 6 of these. No failures except for air in some corners which improved as I tailored the laminates to suit. The difference I see with the posters project is that my parts here are 1.5mm-2mm thick whereas the heli boom is probably much less so it would have less resin to go around?? Click To Enlarge Click To Enlarge Click To Enlarge Very cool! Actually not much thinner. Most likely I'll be about 1mm wall, maybe built up thicker in areas at the base. So it sounds like just simulating layup thickness for the plug with wax was all you really had to do. When laying up the foil, is it just left open at the back for the silicone to expand outward? Or do you cap it off to contain the expanding silicone?
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Fasta
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Group: Forum Members
Posts: 468,
Visits: 3.5K
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These are the two intensifier parts I have made. The large one has a core piece included so I could reduce the amount of silicone used and also have a bit more flexible plug to aid with releasing. This intensifier was cast inside a fiberglass shell that I pulled from the moulds. I have made 20 of these. The small one is a tubular foil section, this one was cast within the moulds using sheet wax to simulate the part thickness. I made 6 of these. No failures except for air in some corners which improved as I tailored the laminates to suit. The difference I see with the posters project is that my parts here are 1.5mm-2mm thick whereas the heli boom is probably much less so it would have less resin to go around??
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Hanaldo
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I just got a quote back from Vac Innovation; £18.40 per kg for the Silicone 60. Comes in a 3kg slab, slab size is about 350mmx500mm, so about £55 a sheet.
That price isn't actually bad, its significantly better than I was expecting. I have ordered some, very much looking forward to trying it. Thanks for the source Rob!
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scottracing
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I can reccomend the material that rob has suggested, ive used it and reused the same intensifier several times on many complex parts like oil tanks and aircraft interior parts.
Its not cheap iirc as we all used to nab a big chunk and hide it in our toolboxes.
I would suggest with the size of the part you are making to get a threaded bar and wrap it in the silicone before putting into the mould. If you put it onto the laminate make sure you use non perf release film.
The threaded bar will help you pull the cured silicone out of the part. Of its still playing up stick the whole thing in a freezer.
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quinn
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+xWell I wasn't sure about the actual bulk modulus of silicone rubber. Hard to find actual data. I was just assuming from the formula k=E/(3-6ny) that it's bigger than you might think, since poissons number is close to 0,5 for elastomers. Now I looked it up, and I found K~2 Gpa for basic silicone rubbers. Considering that the thermal expansion is about 10 times greater compared to aluminium, you can easily get pressures that aren't optimal for composite compression. A bladder seems the most reliable an easiest way in my opinion. That's basically how it has been done since the beginning of small diameter composite tubes, and still how it is done today. Seems like a good process to me. I'm definitely curious about the bladder method. A nice heavy duty reliable bladder would be almost as quick as the silicone plug, assuming you just blow it up and leave it, no leaks. I've done research on that and couldn't find much specific info on that either, mostly just companies that will make bladders for you. What kind of material is used for this?
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Hanaldo
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It sounds great. I didnt realise you could mould it like plasticine, I thought it was a 10mm sheet and you stuck it where you wanted it and that's it. I like the idea of using it to fill voids on the outside of moulds where the bag might bridge and fail during cure as well. Got a couple of molds with deep recesses on the outside that are a pain to bag without nagging or bridging. I shall be getting some if they'll ship to Aus.
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f1rob
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+xStuff looks interesting, would love to try it. Waiting on a reply from Vac Innovation. Do they have a MOQ Rob, do you know? Quinn, I wasnt saying do a small scale part to save on pre-preg costs, I know pre-preg is cheap in this instance. But at around AU$85 a Kg, those silicone plugs are going to cost you a packet if you need to make them several times in trial and error. Your labour time in laying up each piece is also worth something, and it would be quicker to layup a smaller scale piece. Anyway, there is a better way than 20 trial and error processes - do the maths, work out the actual expansion to expect for your silicone across its specific form, put that into CAD and then CNC machine two moulds. One that you use as your actual pre-preg mould, and one that you use as the mould for casting your silicone plug. If you've done your maths right, that will be accurate enough to work reliably. But to get the maths right, you'll need to get some silicone and test it for its expansion rate. Don't think they do Comes in a flat sheet,about A5 size Thickness is variable between about 10-15mm. Very handy on detailed parts you just fill or cover the detail an you have a smooth area to bag an don't have to worry really
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