Hello there and thank you for your attention
English is not my main language so I apologise if my explanations are not as accurate as it should be.
I did my first mould and infusion since 10 years and it resulted as a disaster. I hope I can find help/solution and my experience could help other people.

I did the mould of a little tray with green tooling epoxy gelcoat and epoxy moulding paste on a glass. I used filling wax to fill the gap between the edges and the glass as you can see below:

So I did the mould, did my first infusion and had this as a result:


I forgot to take a picture but I had a looooot of bubbles  visibles behind the vacuum bag.
I did the infusion as this: [ -- Dry Reinforcement -- ] / Peel Ply / R100-MP22 Perforated Release Film / FM105 EasyFlow Infusion Mesh / Vacuum Bagging Film
I can see too there is a difference of thickness 



Perhaps I'm wrong but I think the problem comes from me doing too sharpen angles with the wax. I think it results with air traps.


What do you think guys? Am I right? Don't hesitate if you have any other clue to solve my problem, I wouldn't want to influence you

If yes, I was thinking about putting back in place the original tray (to protect the mould) and sand the gel coat where there was wax to flat this and to have this sharpen angles rounded.
I think it's possible to had the same gelcoat if I go too far or if I need to had a gap filled, can you please confirm?

Thank you mates, I have my other mould (unimould) done with the same way so I don't dare to do the infusion if it's for the same result

Definitely looks like a lot of bridging on that edge which has caused all the voiding issue you have.

As you suggested, its probably in part due to the rounded edge with the wax. 

You could round it a bit on those edges to reduce the bend radius which would help.

If you remade the mould, I would cut a recess into the baseboard so the tray edge can sit flush much closer to the baseboard so the area filled with wax is much smaller and much flatter. 

A simple fix that may work is using some snips, cut a relief cut into the corner of the carbon as you lay it so the fabric is not so taught on the edges.  Cut just shy of the finished parts edge line so nothing shows up on the finished part.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

thanks for your answer
I will follow your advices when remade a mould for sure, using polypropylene sheets for doing flanges in the same axis than the part edges.

Actually I try to same my 2 moulds sanding the egdes and adding gelcoat in the holes using a putty wedge to have in smooth, not easy but I will see.
Do you know how long it take for the unimould tooling gelcoat to cure at ambiant temperature (25°)?
I find for post curing on the technical sheet but nothing about ambiant. (I have one done with unimould to repair too)

If the problem remains for infusion, I suppose this mould will still be fully ok for classic vacuum bagging .

Cheers

Typically on Uni-Mould its a minimum of 4 hours before doing the coupling coat.

If the primary cause is bridging of the fabric, you won't get an improvement by vacuum bagging as the problem hasn't been solved.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

So as planned, I removed all the sharp angles by sanding until 240  on the mould and tried another infusion


but it was exactly like the first time



So I'm now trying to do another mould using polypropylene sheet than I putted almost flush with the edge of the tray.



I'm actually adding the release agent and thinking about what I will use to mould it.
I'm thinking about green epoxy gel coat, one or 2 coats of 200g black stuff carbon and 3 layers of 366g surplus carbon.
What do you think guys?

you just need to a lot more care when draping the fabric. i really needs to be in contact with the mould otherwise you will always get defects. use a fine mist of a spray tack that is made to be used on the moulded surface directly, then place the fabric in the mould while working it in all the crevasses from the center towards all the corners. Do this layer by layer and you will be golden with the mould you have!

Yeh I agree ^ 

How much time did you spend trying to get the reinforcement in position? You have a dramatic amount of bridging there, that isn't the fault of the mould. Of course mould shape will help/hinder you, but at the end of the day you always need to put the time and effort into really forcing the reinforcement into the corners when you pull a vacuum.

Thank you very much for your answer, because of you, I'm on the good way:

I did another infusion yesterday using the spray tack and taking more time to put the reinforcement in position and it looks really better: no bubbles at all on the surface


The problem is the fact that the tack stay visible on the surface even after an alcohol cleaning, looks like it's inside the resin.
On this photo, I used 2 layers of polish (coarse and fine) but no sanding, perhaps it would remove it if it s still on the surface....

I still have a problem , I think I have resin between layers so same problem than the beginning but not in the cosmetic layer. I thought did it well this time but the thickness is inegal on all the edge surface. That problem is a lot more visible on 2 corners :/

So what happened there is you still had bridging, but because you used spray adhesive the fibres were held against the mould surface and the resin has filled the gaps between the layers without the surface defects. That would indicate to me that your reinforcement layup was better, but your consumables layup had bridging in it still. So I would suggest cutting your infusion mesh at these radiuses where you have issues so that it can move around when you pull a vacuum.

I also feel like spray adhesive can hinder you with simple layups like this, because it doesn't allow anything to move around. You've got a better result here, so it may be worth trying again, but you also have the problem of it affecting your surface finish. So for me, I wouldn't use spray adhesive and just position everything loosely in the mould. Then when you pull a vacuum, draw the bag down until it is loosely against the layup and you can slide it around easily, and use this to slide the material on the flanges inwards towards the tray, and then firmly press it down into those corners. Use a blunt tool if it helps, just be careful not to damage the bagging film. This can take a lot of effort, like putting your whole bodyweight into pressing the material into the corners. It can be a workout, but on something this small it shouldn't be too hard. When you have done all the corners, pull a little more vacuum and repeat the process. Do this several times until you reach full vacuum, by which stage you should be able to put your whole bodyweight on the material in those corners and it should feel as solid as if you were pressing directly on the mould surface (because in essence you are). If you feel any 'sponginess' or can see the material move at all as you press on it then you still have bridging any you need to release the vacuum a little bit and keep repeating the process.

Easy Composites demonstrate the technique in this video at around 8 minutes in (whole thing is a useful watch if you haven't already):





The only thing I would do differently here is they used tape to hold things in place on the flanges, which I don't recommend. It does the same as using spray adhesive and can prevent you moving stuff around as much as you need to. Better to have everything loose and be able to slide things around easily.

Hanaldo is spot on here.

The simpler mould you are doing will help a little but still you need to concentrate on getting the fabric properly against the mould surface AND the bagging stack conforming too and not bridging.

I agree with taping for more complicated moulds or if you are struggling but for simple moulds like that vent, if you had enough fabric placed properly to begin with, it isn't an issue.  But yes being able to move the fabric around a little as you pull down the bag can help if things were not right to begin with.

With bagging stack, cut the mesh and peel into pieces if you need to as you can overlap bits and slide it around.  Certainly cut lines in the mesh and peel are great.

Have plenty of bag free as well.  If you've solved fabric and stack bridging you don't want to mess it up by not having enough bag! 

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant