I have just encountered a problem that I am sure has been answered many times before but somehow a search in the forum brings back nothing. oops Apple iMac posted only part of the question. I have just produced a small curvy part and have a fairly bad case of insufficient resin penetration. The Vacuum was perfect, held for 12 hours before infusion and perfect afterwards. My suspicion is that the IN2 resin was not warm enough, it was below 20C and I used an electric blanket after infusion to bring the temperature up. I noticed on infusion a lot of de-gassing going on which settled after about an hour. Is it possible the resin was too viscous for the gas to be extracted fully and therefore prevent full resin take up. On the course we de-gassed and this gave a marvellous result. If a higher temperature can be achieved i.e. warming mould and resin up first what would be a good temperature to ensure a better penetration. I don't really want to have to buy a de-gassing setup if it can be avoided.



Retired - Thank heavens, and still don't have enough time during the day

Hi David

Unless the temperature was quite a bit below 20 degrees, I doubt that it was the cause of your issue, which sounds like insufficient wet-out of the fabric. It sounds like you kept the mould at a good temperature afterwards also. Warming the resin prior to mixing helps lower the viscosity in lower temperature conditions and can aid in the wet-out of your fabric, but take this into consideration when estimating your likely pot-life.

Voids on a, seemingly 'perfect' infusion are sometimes caused by the infusion being a bit too quick and can occur on small moulds, in particular. A resin break is recommended to ensure that the infusion is slowed a little prior to reaching the edge of your stack to ensure all areas are wetted-out sufficiently and highly recommended on smaller moulds. This is a deliberate gap of around and inch or so between the infusion mesh/flow media prior to another strip of mesh at the edge of the stack where your exit port is situated.

On very small parts where the infusion will usually complete quickly, you might want to consider increasing this gap to ensure that all parts of the stack are thoroughly infused before the resin meets the exit port and leave the resin feed open for, at least, 30 seconds after closing the vacuum port.
Ensure that all areas have been infused, including any excess release fabric at the edge of the stack to prevent the risk of this thinning-out the overall infusion of resin across the part once shut-off.

Some might have a different view, but I've done hundreds of infusions now on various shaped/sized moulds and the use of a degassing chamber is not required to achieve perfect cosmetic results. Ensuring complete wet-out is the key factor and most of the necessary de-gassing will occur during the infusion. I have used a chamber in the past but, even after 20 minutes or so there will still be gas left in the resin and, in my opinion, it cuts into your pot-life unnecessarily. I've even made very small parts almost immediately after mixing where the resin has been visibly aerated and, with some control of the speed in which the resin works through the mould, this has not led to any visible imperfections

There are different opinions on degassing. On simple parts (plain or curved) there is really no need for degassing chamber. But -in my opinion- on complicated parts (sharp edges, edges, unavoidable "flow front traps" or with less permeable sandwich cores) degassing is an essential step forward in impregnation quality.
But an other essential factor is the viscosity of your resin. The thinner, the better. And viscosity highly depends on temperature. Depending on the part, I usually work with at least 40 °c temperature within my infusion chamber (wich contains the mold and the resin reservoir). This saves time (But shortens pot life significantly) and leads to lighter parts and better visual quality. The procedure is the following: I heat up the unmixed resin within the chamber during the layup process (on small parts), then pace the mold inside the chamber,  mix up the resin, degass it (takes only a minute with "hot resin (I use the professional ec degassing system)) and infuse afterwards inside the chamber.

Thank you both for your very quick responses. Just to say also to Mark, I did have a resin break of a good inch and I let the resin run through to a short way up the exit tube. The actual infusion took about 20 mins over 6 inches and by the time the front arrived at the break the cloth appeared to all be infused. is it possible by leaving the vacuum on test for leaks over night that I had compressed the cloth too much. Also I think Paul said on the course that leaving the infusion mesh out is OK on small parts. I will try again with a warmed resin. De-gassing noted. Thanks for your help.

Retired - Thank heavens, and still don't have enough time during the day

You didn't use flow media? I just searched in my process datas for some older infusion without mesh at lower temperatures. I found one several years ago. 20cm (8") in about 18:43mins, result was good, but I degassed. Temperature was 21°C.
Without degassing I really would recommend using a flow mesh. My thoughts: in a regular infusion with mesh but without degassing, the degassing mainly happens at the flow front, within the flow media. You can see that. Before the resin enters the actual cloth, most trapped air already left the resin. Without flow media the degassing happens within the cloth (where else should it? There is trapped air, and the resin front is under full vacuum), and not all the gas leaves the part though the flow front.
Btw. : without flow media you certainly don't need a resin break. Most here will disagree, but I don't "believe" in resin breaks even when using a flow media. At least not to get a better finish. That was not the purpurse this technique was invented for.

It sounds like you had slowed things sufficiently on what, I'm guessing, is quite a small part

Even if looking to slow things further, I'd still recommend having the infusion mesh at the front edge of the part, at the very least, to allow the resin to distribute through the part evenly. Maybe a warmer resin will help achieve the results you're after so a little bit of experimentation is all part of the process, as every mould/part will throw up its own particular challenges and requirements

Apologies if confusion, yes I did use a flow mesh. I kept the flow rate slow by clamping on the resin intake tube, hence the 20 mins. It was curious that for quite a while after the resin had flowed through that gas bubbles were evident at the front and also actually forming in the outlet tube in the excess resin. Feeling fairly convinced it’s a viscosity issue related to temperature. Will try again in a couple of weeks when back in the workshop - got to go and do some flying around the Med. Thanks chaps.

Retired - Thank heavens, and still don't have enough time during the day

Ok, if  you use flow mesh and restricted the feed line the issue is clear: you build yourself a degassing chamber!
A regular infusion has a pressure gradient: (almost) vacuum at the flow front, atmospheric pressure at the resin pot. The flow resistance of the hoses, the mesh and the fabric work against the instant equation. In reality there is steep pressure gradient at the resin front, and almost none over the rest of the part.
You restricted the resin feed line (pretty hard, 6 inches regularly takes me about a minute) so the (dynamic) flow resistance of the resin didn't build up a pressure gradient. Basically there is only one, steep gradient: at the restricted point of the hose. And this means, that your whole part is under almost full vacuum. Like in a degassing chamber.
In a regular infusion (Without degassing) the pressure is only in a small stripe  behind the flow front low enough to draw gas out of the resin.  In your case, the gas contaminated resin passes the clamped off section, degasses, and the gas is drawn through you part.
In my opinion there is no need to restrict the resin flow,  unless there are sharp edges in your part. And with proper degassing, there is no need at all to restrict the feed line. The faster, the better.

Good answer! A good lesson in fluidics I think. So combined with a less viscous resin as well means that the resin with an insignificant pressure difference won’t actually de-gas. All makes a lot of sense. I have quite a lot of small parts to make as well, so will get this correct one way or another. Thanks very much.

Retired - Thank heavens, and still don't have enough time during the day