Hi all, 
I have aluminium mould that I can heat. What is the best temperature to heat it to before vacuum infusion and what is the best temperature to hold it after and for how long for best results? I'm using carbon and epoxy resin.

I dont like to have my mould at a different temperature to my resin. If you heat the mould, I would heat the resin to the same temp - which you would only do if trying to lower the viscosity and you have a long pot life. 

If it is cold where you are working (ie, under 18°C), warm both the mould and the resin to 25-30°, infuse, and then keep the resin and mould at that temperature for at least 18 hours. Then ramp the temperature up if you want to do a post cure.

Gotta ask, if you have an aluminium mould you can heat, why not use pre-preg?

I agree it depends on tons of things.  Warmer is almost always better as long as you have the open time to fully infuse before things start to gel.  For normal epoxy, 30-35C is fine.  I am not opposed to infusing cooler resin into a warmer mold - just up-size the feed lines to allow the higher viscosity resin in the pot to meed the demand.  You can stretch the pot life a bit this way. 

One thing you shouldn't do is change the temperature before the resin is gelled hard - it can cause vapor issues and other stuff.  Let it gel and then raise the temp to post-cure.  Keep the vacuum on for this too... aluminum expands different than composite and it will probably demold itself.  

Dialing the vacuum back during/after filling the infusion is pretty useful for warmer temperatures where the vapor pressure of moisture makes it boil at full vacuum.  Even going down 25% helps a lot if your materials or resin is prone to volatile issues.