Hello ,
This is a great forum and I have gained immense knowledge here . Thank you guys !
After getting all supplies from easycomposites
I infused many carbon sheets on glass and a perfect glossy finish.
This is my first part I’m infusing in a mould.
Attempt 1 - pinholes towards the inlet side and relatively very less towards the vacuum side
( pinholes exactly between the fabric weave pattern )
It’s a 26”x 20” mould vacuum spiral was all around the flange of the mould and inlet in the center.
Mesh was right till the edge of the carbon fabric and spiral over the mesh.
This infused very fast approx 8-10 mins
Attempt 2 - pinholes all over the part. This time I infused from the side. Resin inlet spiral along the 26” side. I cut the mesh short and the spiral was over the peelply and carbon fabric. On the opp side I used two layers of the mesh on the flange and silicon connector in the middle.
This took about 20-25 mins to infuse.
Both times it was a perfectly sealed bag leak tested for 30 mins.
Where am I going wrong ? How do I get a pinhole free finish ?
Also which is the ideal way to place the inlet and vacuum on such a mould .
Really appreciate some help, thanks in advance

I’m not able to upload pictures.

On a mould of those dimensions it's always best to choose the shortest path to the outlet and there's likely no need to place the inlet in the middle of the part. So going between the 20' (45cms?) sides sounds ideal. 

When applying your infusion mesh, you need to ensure that your spiral sits on top of it at the inlet side, to get the resin flowing across the part well and place it up to the part's edges. On that size, there's likely no need to run the spiral up the sides as well, but this can be beneficial when making very large panels, especially flat ones that might be over a metre wide

Placing a deliberate break in the infusion mesh just before the outlet, no wider that about an inch or so, should also help to slow things down a little if the side sections of the part haven't quite infused when the resin approaches the outlet. Place the outlet connector on a separate strip of infusion mesh, which helps provide a good path for any gas to escape whilst the infusion is in progress. Even if you opt to de-gas your resin prior to infusion, you'll still likely see gas escaping at the flow front.

If necessary, allow a little resin to travel up the outlet tube and even into the catch pot if there's still significant areas at the sides still to infuse. If there's only a small section to infuse, you can usually close the outlet and leave the inlet open until all of the part is visibly infused. Leaving it open for another 30 seconds or so can provide certainty that everything is properly wet-out, at the cost of an ever so slightly more resin-rich part (which you'd probably not notice)

Over time, as you make smaller/bigger parts, you can experiment with the mesh placement to help slow things down or increase the resin flow speed in certain areas (using additional strips on larger parts where the sides might usually infuse more slowly). Either way, the area on which your inlet connector sits should always have mesh underneath, even if you decide to make you resin break a large one to control things better on a small mould

If there were no visible signs of air entering the parts during the infusion or during the cure cycle (usually very apparent in the infusion mesh) then, perhaps, the issues you've experienced might have just been down to insufficient resin in the part.  Ensuring complete wet-out by delaying the closing of the inlet side and controlling the speed of infusion better should help things

Thank you Mark for your valuable time and inputs on this.
Tomorrow I’ll try another infusion and let you know.
Why am I not able to upload pictures.
Thank you .

I’ve found that slowing the feed rate to a slower pump help not trap the micro pin holes, just have to be cautious of pot life, and also de-gassing the resin before infusing helps eliminate a lot of the micro pin holes you see on the surface.The smoother the mold surface is the better the finish aswell, as you know what a glass surface will do for you part. Still haven’t been able to get a flawless part, we usually have one or two quarter size areas where the pinholes appear. Can’t figure out why. No expert but these are just things that have helped me out along the way.

this could very well be the issue. Since it happens in a different area everytime it’s hard to pinpoint what’s going on in that location. Could very well be the weave got bunched up on some of the middle plys or yes the peel ply has been overlapped.

+x

 

Xtreme - 7/10/2020 6:50:31 PM

Hello , This is a great forum and I have gained immense knowledge here . Thank you guys ! After getting all supplies from easycomposites I infused many carbon sheets on glass and a perfect glossy finish. This is my first part I’m infusing in a mould. Attempt 1 - pinholes towards the inlet side and relatively very less towards the vacuum side ( pinholes exactly between the fabric weave pattern ) It’s a 26”x 20” mould vacuum spiral was all around the flange of the mould and inlet in the center. Mesh was right till the edge of the carbon fabric and spiral over the mesh. This infused very fast approx 8-10 mins Attempt 2 - pinholes all over the part. This time I infused from the side. Resin inlet spiral along the 26” side. I cut the mesh short and the spiral was over the peelply and carbon fabric. On the opp side I used two layers of the mesh on the flange and silicon connector in the middle. This took about 20-25 mins to infuse. Both times it was a perfectly sealed bag leak tested for 30 mins. Where am I going wrong ? How do I get a pinhole free finish ? Also which is the ideal way to place the inlet and vacuum on such a mould . Really appreciate some help, thanks in advance

Degassing first and perhaps a MTI hose is the next step in my opinion. Not sure whether you have done it already. You'll be amazed at the amount of air that comes out with a vacuum chamber. Do it about 3 times. I.E. bring it to vacuum, let the bubbles reach near the top of the vessel, let in a tiny bit of air, close the valve again ..... and so on.

I've tried MTI hose and found it to be an unnecessary expense and not needed where just a refinement of basic approaches is all that's required.

It's been covered many times before, with a variety of opinions, but after de-gassinng the resin for quite a period I've found no discernible benefit to adding-in this step. I'm doing infusions every day and even where the resin is quite freshly mixed and showing visible bubbles, there is no visible effect on the finished part, as the resin will de-gas as it's drawn through the part and anything left in the resin at the end will shrink to virtually nothing once the vacuum level equalises across the part. 

There will still be gas drawn out, even after a prolonged period of de-gassing and weighed against the reduced pot-life time, it's not a step that I've found to be necessary in achieving perfect cosmetic results. I don't think that either is the answer to the OP's current issues where it feels like some tweaking of approach will be all that's needed. 

Exactly ^ 

Degassing is not necessary. It can help in situations where other things are wrong, like excess resin collecting in areas of bridging etc. But on a perfect infusion, you wouldnt be able to tell between a part that had the resin degassed and a part that didn't.