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zappafile123
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Hi there, I'm new to making CF products and am after some tips on how to achieve a high gloss finish on the peel ply or B side of a small part made with resin infusion. Specifically I'm making custom road cycling shoes using a plaster casts of my feet. I successfully made my first sole on the weekend (laying up the carbon over the foot cast followed by peel ply and a full vacuum bag enveloping the entire foot cast), but have encountered the minor problem of requiring a smooth finish on the inside and outside of a part. I need a smooth finish on the inside so my foot is comfortable, and a neat finish on the outside so it looks good. As you can see from the first two images below, the peel ply leaves a pretty rough finish and I'm guessing from what I've read that thats just what peel ply does no matter what. What can do to make it look good like the third image below? I guess I could make a second carbon mould over the top and use that to sandwich the carbon, but that's too much effort, especially if I want to make shoes for local cyclists to get a bit of cash on the side of my day job. Would painting on some extra resin after moulding and then sanding and buffing it work? Further, I imagine I ended up with those big wrinkles on the outside finish because I wast careful about how I applied the peel ply. Tips on getting that smooth are also welcomed (just use adhesive? (cause I didnt!)) Thanks in advance!    notice the gloss finish inside and outside the shoe
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Chris Rogers
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That's a tough one! You'll need a mold or some kind of tooling to shape any surface you want to directly control. Given the shape this means a multi-part mold on the outside if you want a complete shoe shape like your bottom picture. This will be hard to make just with plaster - but you could build a part, fair it out with filler and make it shiny (and a uniform thickness) and then make an external mold - probably in multiple pieces with flanges - to shape the outside. If you are just trying to make the bottom of the shoe like the kevlar lined parts then it could be done with just single part inside and outside molds. The tolerances would have to be right to give the right thickness (infusion is more forgiving because resin will just add extra thickness) but having one mold be flexible would be best. Silicone would be a good material to make a flexible mold that would give a decent surface finish This would probably be the easiest way for producing many parts - metal or composite molds to shape the outside geometry with a silicone foot shaped intensifier/mold/liner to expand inside and give the inside compaction and a pretty surface. This could be inflatable (better) or solid (ok) and would ideally expand with heat or internal air pressure. Bike manufacturers have this process pretty well developed for frame parts.
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Warren (Staff)
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Trying to infuse the part to come out the mould as a single piece with double glossy sides could only possibly work with matched tooling and a core that can flow resin. Even then it would be difficult to achieve. The easiest way would be to resin coat the peel ply finish. A very quick sand back with 120 grit, avoiding cutting into the carbon itself, will smooth the finish out a bit. Then you can use something like our XCR Epoxy Coating Resin to apply a single coat over. Once cured, you can flat it and polish it. Alternatively, sand it as above, clean and then clear coat it with a clear PU lacquer. A couple of thick coats should get it nice and smooth with a gloss finish.
Warren PenalverEasy Composites / Carbon Mods - Technical Support Assistant
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zappafile123
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+xTrying to infuse the part to come out the mould as a single piece with double glossy sides could only possibly work with matched tooling and a core that can flow resin. Even then it would be difficult to achieve. The easiest way would be to resin coat the peel ply finish. A very quick sand back with 120 grit, avoiding cutting into the carbon itself, will smooth the finish out a bit. Then you can use something like our XCR Epoxy Coating Resin to apply a single coat over. Once cured, you can flat it and polish it. Alternatively, sand it as above, clean and then clear coat it with a clear PU lacquer. A couple of thick coats should get it nice and smooth with a gloss finish. Thanks for your help Warran, I'll give it a try and report back with the outcome. Barnes make Epoxyglass which appears to be basically the same product as XCR (I'm in Australia so unfortunately cannot import XCR). I think the example glossy shoe shown above wouldn't have been made with resin infusion. I reckon they've just used wet hand layup. The only issue is that if you do that... how do you get the carbon to stay in place around tight curves rather than draping off the mould? I chose infusion to avoid this problem and also to reduce weight.
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zappafile123
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+xThat's a tough one! You'll need a mold or some kind of tooling to shape any surface you want to directly control. Given the shape this means a multi-part mold on the outside if you want a complete shoe shape like your bottom picture. This will be hard to make just with plaster - but you could build a part, fair it out with filler and make it shiny (and a uniform thickness) and then make an external mold - probably in multiple pieces with flanges - to shape the outside. If you are just trying to make the bottom of the shoe like the kevlar lined parts then it could be done with just single part inside and outside molds. The tolerances would have to be right to give the right thickness (infusion is more forgiving because resin will just add extra thickness) but having one mold be flexible would be best. Silicone would be a good material to make a flexible mold that would give a decent surface finish This would probably be the easiest way for producing many parts - metal or composite molds to shape the outside geometry with a silicone foot shaped intensifier/mold/liner to expand inside and give the inside compaction and a pretty surface. This could be inflatable (better) or solid (ok) and would ideally expand with heat or internal air pressure. Bike manufacturers have this process pretty well developed for frame parts. Hey Chris, thanks for your thoughts. I'd always make the shoe in two parts and just use carbon adhesive to join the sole to an upper. I need to use an epoxy flexibiliser to make the upper portion malleable so I can bend it to get my foot in and out of the shoe as well as tighten it up with some laces when I'm wearing it. The silicone idea is interesting. But it's a little challenging to visualise how it would work/be practical particularly if it was inflatable. It could be reasonable to make a solid silicone outer mould if I had a set of standard shoe sizes. However, the whole point of this product is that it's bespoke to the individual foot so I would need to make a new mould for every foot. It's already quite time consuming making one shoe as it is. All I need is for the B surface to be wrinkle free, and be aesthetically pleasing. I plan to make shoes for myself primarily but then see if I can sell some shoes to local club riders so I can repay the outlay of the initial investment in materials and equipment which was around $2000 (AUD).
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Hojo
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+x+xThat's a tough one! You'll need a mold or some kind of tooling to shape any surface you want to directly control. Given the shape this means a multi-part mold on the outside if you want a complete shoe shape like your bottom picture. This will be hard to make just with plaster - but you could build a part, fair it out with filler and make it shiny (and a uniform thickness) and then make an external mold - probably in multiple pieces with flanges - to shape the outside. If you are just trying to make the bottom of the shoe like the kevlar lined parts then it could be done with just single part inside and outside molds. The tolerances would have to be right to give the right thickness (infusion is more forgiving because resin will just add extra thickness) but having one mold be flexible would be best. Silicone would be a good material to make a flexible mold that would give a decent surface finish This would probably be the easiest way for producing many parts - metal or composite molds to shape the outside geometry with a silicone foot shaped intensifier/mold/liner to expand inside and give the inside compaction and a pretty surface. This could be inflatable (better) or solid (ok) and would ideally expand with heat or internal air pressure. Bike manufacturers have this process pretty well developed for frame parts. Hey Chris, thanks for your thoughts. I'd always make the shoe in two parts and just use carbon adhesive to join the sole to an upper. I need to use an epoxy flexibiliser to make the upper portion malleable so I can bend it to get my foot in and out of the shoe as well as tighten it up with some laces when I'm wearing it. The silicone idea is interesting. But it's a little challenging to visualise how it would work/be practical particularly if it was inflatable. It could be reasonable to make a solid silicone outer mould if I had a set of standard shoe sizes. However, the whole point of this product is that it's bespoke to the individual foot so I would need to make a new mould for every foot. It's already quite time consuming making one shoe as it is. All I need is for the B surface to be wrinkle free, and be aesthetically pleasing. I plan to make shoes for myself primarily but then see if I can sell some shoes to local club riders so I can repay the outlay of the initial investment in materials and equipment which was around $2000 (AUD). You can get fairly smooth surfaces using bladder. You wouldnt likely infuse, but use prepreg or wetlayup.
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Hanaldo
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I agree infusion is not the most suitable method for this. Nor is trying to bond the upper and lower sections of the shoe with a butt join, if that was your intention? That would be very weak, especially if the shoe needs to flex.
Wet-lay would be easier, and pre-preg even easier again. Pretty much everything Chris, Warren and Hojo mentioned is good advice. This is not an easy project, especially for someone with limited experience, I dare-say you are going to atleast double your investment by the time you have a product you can sell.
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zappafile123
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+xI agree infusion is not the most suitable method for this. Nor is trying to bond the upper and lower sections of the shoe with a butt join, if that was your intention? That would be very weak, especially if the shoe needs to flex. Wet-lay would be easier, and pre-preg even easier again. Pretty much everything Chris, Warren and Hojo mentioned is good advice. This is not an easy project, especially for someone with limited experience, I dare-say you are going to atleast double your investment by the time you have a product you can sell. The problem with wet layup is getting the carbon to tightly adhere to the mould - basically the carbon needs to envelop about 65% of the foot, and it will just drape at the oblique surfaces; at least that's what happens with fibre glass - no fibre glass sole has matched the mould 100%. Do you have any suggestions for how to solve this problem? As for prepreg... I don't have an oven so its not feasible at this stage. Even then I'd still have the problem of a rough B-side given the need to use a male mould (rather than a female mould). Below are a couple of photos of the structure of the upper. I've bond it to the sole using 3M DP 420 NS black. My understanding is that this adhesive is designed specifically for bonding carbon parts and is so strong that the rest of the shoe would fail before the bond fails. Correct me if I'm wrong. I used an additive to make the epoxy flexible so I can fold the upper back over so I can get my foot in. As for the cost of getting a product I can sell, you could be right. But after my second attempt I've already got a functional shoe. Once I have a pair I'd test them for a month to make sure they can handle the stress of riding. Probably need to do some sprinting on a trainer to make sure the upper doesnt rip off under load.  cleat nut holes were moulded in and are not drilled.    Note that those lines on the sole are because I didn't use a flow media to infuse and consequently there is resin buildup around the spiral tubing line. I'm still trying to get the placement of spiral tubing right. But next time I'll use a flow media because it worked much better for the upper.
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Hanaldo
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I do mean wet-lay vacuum bagging, not just wet-lay with no vacuum. You can wet the reinforcement out in between two sheets of plastic film, and then allow it to cure to a b-stage before placing it into the mould. In this way, you can work with the material almost exactly as you would a pre-preg.
Getting a smooth b-side is much easier with wet-lay and pre-preg than infusion because you dont need the flow media. So you can then use a matched mould, whether that is a rigid matched mould or a silicone matched mould - either way it is easy. Infusion it is very difficult and virtually impossible, you would be looking at more of an RTM process to achieve the same thing.
As for bonding, your choice of adhesive is fine, thats not the issue. All structural adhesives will be stronger than the laminate - provided the bond joint is designed correctly. I'm not sure what your bond joint looks like, it is hard to tell from the photos. My first comment was based on your photo where it appeared like you would be butt-joining the upper to the lower. If that is not the case and you have a good overlap between the two components (at least 25mm, which looks to be the case in your latest photos), then that is fine, it will be strong. The only thing that could be an issue is elongation - is the 3M DP420 a rigid adhesive or a flexible adhesive? You would want a very flexible adhesive to bond will with a flexible epoxy, otherwise all of that movement will either be made impossible by the adhesive, or it will cause the adhesive to fail over time.
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