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Finnluxury
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I will test this silicon today. I bought Loctite SI 5926 blue as u menthioned. Thanks everyone for a good tips. If this silicon works well for the split mould, I may use it for the roof part also. The roof part will be a huge mould, I am going to use EC uni mould system for it. Never tried uni mould system before, but looks to be good when watched some of the EC videos of it. Usually all my moulds are made from epoxy tooling gelcoat, and epoxy putty, but this part is way too big for that method. I must design a good steel structure, and wheels under the mould, so i can easily move the parts of the moulds side ways. |
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VVS
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If you put some break points in the flanges you will have no problem splitting it after.  don't know how clear this shows one but build if using wax same as you make location pegs from wax.
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Hanaldo
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Have attached a photo of my split mould channel. The channel is essential to the accuracy of the split mould, sealant tape won't work without it. The trouble is as you say, the bolt holes need to be on the outside of it. This means you cant make the holes close to the part for the tightest fit, so the split isn't quite as tight as it would be if you could have the bolts close to the part. However we are splitting hair there, as you're talking a 0.25-0.5mm gap. Either way, you are going to get a flash line that requires polishing out. As for the silicone gasket, I just use an automotive product. Same stuff used to make inlet gaskets etc. This is the easiest way because you can just build your mould as per normal with no special considerations. Then apply the silicone to one flange, making sure you encircle the bolt holes, and then bolt the mould pieces together. It's important to do this while the silicone is wet and hasn't started to set up. The silicone will squeeze out to virtually nothing, so you can get the same split accuracy as you would without it. Be aware that if you apply a huge amount of silicone, you may get it squeezing out the parting line and onto the mould surface. So you don't want too much, just a small consistent bead. If you are using wax or a chemical release agent, this won't release the silicone easily. I normally have to wedge the flanges open and slice the silicone with a knife. PVA would be the only way to make it easy.
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VVS
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Ok so different process using a sealed mould but you can see how they make the mould with wax and a rubber seal. https://m.youtube.com/watch?v=f-vBw3HH7uIRegarding using silicon the diy type will stick your mould for good so you need the soft automotive type. I use Loctite SI 5926 blue that's available at general car supplies shops, you can put a very fine line behind the surface edge of the mould and then clamp it down wet, any that comes out into the mould can simply be wiped with your finger. only thing to watch is semi permanent release agent slightly dissolves it so just go easy.
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Finnluxury
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Hanaldo (16/04/2016)
Silicone liquid gasket is the easiest. The only issue is that it tends to 'bond' a little bit to the flanges, which makes demoulding and cleaning up the mould a bit difficult. But not impossible. What I do on my split moulds now is use 2mm sheet wax to create a 20mm wide channel on one side of the flanges. This allows me to place regular 3mm bagging sealant tape in the channel, and the exposed mm is enough to seal the flanges. This does however take a bit of thinking to ensure all the channels meet up and form a complete seal. It is also important to not stretch the bagging tape at all when placing it, as this reduces it's thickness and can cause it to not contact the opposite flange. So it isn't fool proof. Thanks for really fast reply. I tried sealant tape, but problem is that it will make splitting the mould parts really really hard (but i didnt have the channel, and it made the splitting really inaccurate) . I have thinking about idea of making a channel, and using a silicon d-profile or something. this channel sounds good way, and i have thinking it a lot. I guess the channel must be before the bolt holes, or else the bolt holes may leak the vacuum. Do u got any photo of the channel? Did the mould parts closed perfectly together, leaving no gap between? Tell me more about using this silicone liquid gaspet, i guess u dont need a channel for it? Will u let it dry in other side of the gasket before bolting parts together? or will u bolt them when they its still in liquid form? I got one split mould which i dont have the channel, so i could test this method for it. and if i would add a good surface of mould release between the flanges, the silicone would not stick too much, I guess.
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VVS
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Ive just done a 4 part mould and being much smaller but complicated used the silicon to seal . To help when demoulding i use wax to give split points at the edge of the flange joins, this allows me to get a bar in between the mould parts and break the silicon seal.
like Hanaldo says you could use strips of sheet wax to give a gasket groove that could use vac tape or even a rubber seal similar to the rti light, might be rtm I'm unsure of the name but videos on you tube.
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Hanaldo
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Group: Forum Members
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Silicone liquid gasket is the easiest. The only issue is that it tends to 'bond' a little bit to the flanges, which makes demoulding and cleaning up the mould a bit difficult. But not impossible. What I do on my split moulds now is use 2mm sheet wax to create a 20mm wide channel on one side of the flanges. This allows me to place regular 3mm bagging sealant tape in the channel, and the exposed mm is enough to seal the flanges. This does however take a bit of thinking to ensure all the channels meet up and form a complete seal. It is also important to not stretch the bagging tape at all when placing it, as this reduces it's thickness and can cause it to not contact the opposite flange. So it isn't fool proof.
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Finnluxury
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Hi! I would want some new ideas for a split mould. My last mould was leaking between the flanges. I am going to use resin infusion, so its critical that there is no air leaking. I included a photo of the part. It will be a three part mould. I will make splits above the door. Second photo has one idea I got, that the flanges would have 90 degree angle at the end, so i could put vacuum tape on it. blue and white line are different part of the mould. black line is plug. Top of the blue and white line is the vacuum tape. Its impossible to vacuum bag the whole part, as its so huge. And I really wouldn't want to hand laminate this.
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