Hi- I've been learning a little bit about casting aluminum objects from a home foundry- I've come across the topic of shrinkage and this raises concerns:Suppose I want an aluminum copy of an object that is an exact match in size and shape.Say, the your intake manifold in your carWhat method of casting do I use? Close to the same size is nice but a 2% size difference would likely cause functional problemsLost foam? Pressing one half of the object into one half of a flask, then the other half of the object into the other?
The two metals, carbon and aluminum would reactIf you could coat the aluminum with an electric insulating material before applying the carbon then you would be fine.
Well, in the strictest terms the bonding between carbon fiber (CF) and aluminum (AL) had better be at least a bit reactive or else you won't get a good bondThere are many AL parts that have a CF overlay but there are some things that you'll need to do for good success: 1) The AL must be phosphatized to exacuate the oxygen from the metalIt should be laminated immediately afterwards without touching the metal with your bare hands to avoid contamination; 2) The CF must be cured onto the AL using some kind of vacuum system, perhaps a strong plastic sealable bag into which the AL/CF item is placed, then the air pumped out using a vacuum pump; 3) You'll need to use thermoset epoxy that activates with peroxide to bond the CF to itself and the two objects togetherIt will be a rather high ratio, perhaps 20% to 25% epoxy to CF- makes for a messy day I know the answer because I design bike frames and parts utilizing this method.
Aluminum shrinks at a rate of 1.5% when castThey only cast aluminum parts when the tolerance is not a factorWhen close tolerances are a factor, they will mill the part rather than cast itIt's just a matter of physics that hot things expand and cold things compressThe only exception that I'm aware of is cast iron which expands when initially cast and cooled.
