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Hanaldo
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The mould is certainly key to getting good parts, but it is possible to sort out an imperfect surface on the final part albeit with a lot of work. If you're making more than one part then it's only logical to make sure that they are coming out of the mould with little to no finishing work required. For a one off, it is quite possibly more cost and time effective to just pull a part out and do what you can to make it acceptable. Dcfoster, what materials exactly do you believe you need for vacuum bagging? It is all very much the same stuff, infusion uses more materials than vac bagging so you should already have all the necessary stuff. The only material that is 'infusion only' is the flow mesh. In fact, all you REALLY need is vacuum bag. You'll get better results doing it properly with perforated release film and bleeder, but it's certainly possible to just wet lay a part and bag it up as is. Regarding sanding, there is no easy answer for how long to sand for. It comes with experience.
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dcfoster
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Hanaldo, I only have the peel ply, mesh, bag. I thought you needed peel ply, release film, breather fabric, bagging film. Seems to me I am missing 2 important pieces. If its better to vacuum bag then I guess I can watch some videos tonight and see if it will work, but there are no local places where I can buy the fabric that I know of. the composites place locally sells alot of that stuff in huge bulk which at this time is outta my price range.
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Hanaldo
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That is the ideal setup, yes. But I have vac bagged several successful parts where I just laid them up, put peel ply on the back and bagged them up. They come out resin rich sure, so you don't want to do it for structural parts. But for cosmetic items that don't need to be strong or as light as possible, it works fine. And you will likely get a better result doing that then trying to infuse with a resin that is too thick for infusion.
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dcfoster
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So my understanding is that I would appply mould release, brush resin onto the mould (or not), brush resin onto each layer of carbonfiber and lay them into the part smooth them out then lay the peel ply and then lay the bag down, then apply vacuum. how long do I run the pump? and am I missing a step? since I will only get one shot at this im really concerned about not screwing this up since I need the part ready by sunday morning, otherwise im going to infuse with a second feed in the middle. With vacuum bagging once im done pulling vacuum do I clamp off the line and let it sit like with infusion? Also does it need to stay bagged for 24 hours like the infusion process? The hardener with my resin is the standard which gives me a 17-18 minute pot life @ 72 deg F ... and the viscosity mixed is 500-600 cps (which i know is not in the low hundreds but I thought was still good for infusion, im assuming it needs to be more like 300 cps) and just to make sure if I am using lets say 3 layers of fiber that equals approx 8 oz, then I would want to use 4-5 oz of epoxy? and is that the same ratio for bagging and infusion? otherwise im going to infuse with a second feed in the middle.
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ChrisR
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with that short pot life you need to infuse or just wet lay without vacuum, by the time you've got it all bagged up it will have gone past it's workable time. you should be able to infuse with 500cps, link the data sheet on your post so we can see what its properties are (just for interest), you may be able to warm it a touch to reduce the viscosity. What you could try is wet lay with peel ply finish, it will just suck a touch of resin out and give a flat finish to the back of the part. If you're short on time, and want to infuse then do a test part on a sheet of glass and time (and mark off) the flow rate using your mesh and stack. It only needs to be 200mm wide and 500-1000 long depending. This will tell you how often you need new resin inlets into the part. So a couple of test parts 200x200 square for each method you want to try on a sheet of glass (with release agent) and see which works best.
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ChrisR
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Just read the last sentence, if you are going to infuse - weigh everything that will get resin on it, fabric, peel ply, infusion mesh; work on a 50/50 fibre/resin ratio so if you weigh 4oz total then use 4oz resin (at least) you may want to work on a 40/60 fibre/resin to get a nicer finish. Also measure the length of the infusion hose(s), calc the volume and convert that to weight, plus a bit for each pot. Add them all up and that's how much resin you need
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Hanaldo
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Can you post a photo of the infused part that failed? Might give an indicator as to whether there is any point trying to infuse with the mentioned corrections. The way you described the bagging process is pretty much it, except I prefer to wet out the fabric AFTER placing it in the mould. Less mess, and handling wetted fabric is a real nightmare. So basically, apply mould release, brush resin into mould, lay in first layer of fabric and stipple it with your brush to draw the resin that you applied to the mould surface through the fabric. This helps to reduce air bubbles. When you have drawn up as much of that resin as you can, apply more resin to the top. You want your first layer to be quite resin rich, so apply a bit more than it needs. Then repeat the process with the second and third layers, and finally the peel ply. Then bag, making sure there is no bridging anywhere as you pull the bag down. I recommend running the pump for 2 hours or so, just to give the resin a chance to go off. You can clamp it off and turn the pump off as soon as you have got full vacuum if you like, but then if you have a leak you will return to find a ruined part. Better to keep the vacuum running as long as you can. Leave it bagged for 24 hours ideally, but check your resin data sheet for demould time.
You are also going to want to get everything ready BEFORE you mix your resin. So have your release agent applied for the correct amount of time (preferably do this the day before, but a couple of hours after your last coat will suffice) fabric cut, your brush ready, and all your vacuum bagging stuff cut and read to go as soon as you have laid up the part. With a 17 minute pot life, you really need to make sure you are well organised and don't waste any time doing stuff that you could have had ready before you started.
For wet lay, you want a 50/50 ratio. So if you have 3 layers of carbon weighing 8oz, then you need 8oz of resin. Realistically, mix up 10-15% more to allow for wastage.
The resin I use for infusion is 400cps, and that is on the thick side. The infusion specific resin I have here is 220cps. So 600cps is too thick and quite likely won't wet out the fibres properly.
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dcfoster
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Here are some pics of the part and the data sheet of the resin |
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dcfoster
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So I did infusion again, but this time I ran the feed line the length of the part. Holy crap it went so fast I wasnt even prepared for it. I thought I mixed enough resin but ended up pulling some air into the line before I had a chance to clamp it off. Hopefully this will work out. while I was going through the sanding to fix the mould I found this thing has bubbles everywhere. That fiberglass resin was so bad. Im deffinately going to make a new mould. I was able to get the room upto 80 degrees F so hopefully I can help it cure marginally faster otherwise im going to demould around 6pm and that doesnt leave me much time to fix potential issues and to trim.
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Shaneer22
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Also slow down your infusion using the clamps,it helps especially on small parts.
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