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Stephen.Pritchett
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oekmont
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With such extremely dry areas I would guess your bag is not fully airtight. Make shure there is no leak in your bag by performing a drop test before starting the infusion.
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Hojo
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yes, best to use a digital absolute pressure gauge at the resin inlet for checking part vacuum level(lower than 20mbar) and integrity(0mbar drop in 5 mins or more for a part this size). This is the best way to ensure successful, constant infusions everytime
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MarkMK
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Yes, as above, the picture does seem to show a part that has suffered air ingress, either during the process or in the cure stage. It looks particularly bad at the tight corners, which shows that the bag has bridged here quite a lot. It looks like air has done it's worst on other areas also, indicating quite a big leak
This should have been evident, though, when infusing the part or prior to removing the materials during de-moulding? If it happens during the infusion, you might have a chance of quickly pressing down the tape in the relevant area (usually around one or more of the pleats).
It's quite a contoured part and relatively small, so make sure that your pleats are big enough to allow for plenty of slack before pulling down the vacuum. If it's over-stretched then that'll increase the chances of an unreliable seal and also lead to more unwanted bridging around the angles. I've no doubt that the pleats get pulled inwards quite a bit on that kind of shape, so making them a bit longer might help reduce some of the stress on the pleats when vacuum is applied. Ideally, you should try to get them sitting as 'upright' as possible once vacuum is applied, so it will call for plenty of excess bag to alleviate excessive pulling on the base of them. When testing out the seal prior to infusing, back off the vacuum a little and re-adjust the way the pleats sit so that wrinkles in the bag are spaced out as evenly as you can
If the problem area is around the inlet/exit connector, I find that a little 'doughnut' of tape on top of each connector can help keep the bag from wrinkling excessively when inserting the pipes, so this might help?
Infusing the part across it's length (the shortest route) is usually always the best option, but just take your time to ensure that the bag is created as neatly as you can. Using a woven infusion mesh with some perforated release film to aid de-moulding might also be a worthy consideration, given the shape of your part, as sometimes the tougher nylon mesh can distort quite a lot on complex-shaped parts (even with relief cuts) and create quite sharp little peaks that can, sometimes, create a small hole in the bag, especially if it's stretched tightly.
If, however, you just can't get things sealed reliably, there is always the option of envelope bagging the whole mould. Not ideal if you want to make multiple parts, as there will be unwanted resin cured on the underside to deal with, but it might help things if you're only looking for one or two? Just smooth the underside first as best as possible and consider using some breather cloth covered in bagging film to further reduce the risk of punctures here
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Stephen.Pritchett
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+xYes, as above, the picture does seem to show a part that has suffered air ingress, either during the process or in the cure stage. It looks particularly bad at the tight corners, which shows that the bag has bridged here quite a lot. It looks like air has done it's worst on other areas also, indicating quite a big leak This should have been evident, though, when infusing the part or prior to removing the materials during de-moulding? If it happens during the infusion, you might have a chance of quickly pressing down the tape in the relevant area (usually around one or more of the pleats). It's quite a contoured part and relatively small, so make sure that your pleats are big enough to allow for plenty of slack before pulling down the vacuum. If it's over-stretched then that'll increase the chances of an unreliable seal and also lead to more unwanted bridging around the angles. I've no doubt that the pleats get pulled inwards quite a bit on that kind of shape, so making them a bit longer might help reduce some of the stress on the pleats when vacuum is applied. Ideally, you should try to get them sitting as 'upright' as possible once vacuum is applied, so it will call for plenty of excess bag to alleviate excessive pulling on the base of them. When testing out the seal prior to infusing, back off the vacuum a little and re-adjust the way the pleats sit so that wrinkles in the bag are spaced out as evenly as you can If the problem area is around the inlet/exit connector, I find that a little 'doughnut' of tape on top of each connector can help keep the bag from wrinkling excessively when inserting the pipes, so this might help? Infusing the part across it's length (the shortest route) is usually always the best option, but just take your time to ensure that the bag is created as neatly as you can. Using a woven infusion mesh with some perforated release film to aid de-moulding might also be a worthy consideration, given the shape of your part, as sometimes the tougher nylon mesh can distort quite a lot on complex-shaped parts (even with relief cuts) and create quite sharp little peaks that can, sometimes, create a small hole in the bag, especially if it's stretched tightly. If, however, you just can't get things sealed reliably, there is always the option of envelope bagging the whole mould. Not ideal if you want to make multiple parts, as there will be unwanted resin cured on the underside to deal with, but it might help things if you're only looking for one or two? Just smooth the underside first as best as possible and consider using some breather cloth covered in bagging film to further reduce the risk of punctures here Thanks for replies, the vacuum appeared to hold over the full 24 hour cure and I did do a leak test. However I don't have a gauge fitted. Your comments on the flow mesh are very valid, perhaps I am pulling a small hole. Will try larger pleats and combining with breather layer on corners. Was thinking about a resin break as well to slow flow down and possibly two inlets for resin but thought with full length spiral this would negate the need for that. Another go is on the cards! Will let you know how it goes.
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oekmont
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You really don't need a second resin inlet. This is a fairly easy part. I have done parts the size of half a car with only one inlet. A second one will only make it more difficult to solve the real problem. If your flow mesh punctures the bag, I would suggest to get better bagging material. The switch to pa/pe/pa was one of the best decisions I've ever made.
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Stephen.Pritchett
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+xYou really don't need a second resin inlet. This is a fairly easy part. I have done parts the size of half a car with only one inlet. A second one will only make it more difficult to solve the real problem. If your flow mesh punctures the bag, I would suggest to get better bagging material. The switch to pa/pe/pa was one of the best decisions I've ever made. ok fair point, had also thought about placing inlet in centre of part. Going to try a new layup with advice given. Some good points to note here. Its often the small details
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MarkMK
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The sound that your pump does/doesn't make when testing your vacuum should be enough, especially after 24 hrs, so a gauge isn't always essential Didn't spot this previously, but on such a small part using a resin break would be be ideal. In warmer temperatures especially, the resin can shoot across very quickly so slowing things down to allow for adequate wetting-out will help a lot. Leave the inlet side open until you're certain that all areas of the part are infused well.
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