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casting [2012/10/06 21:50]
admin [Actually Casting]
casting [2018/03/06 08:59] (current)
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 ===== The Setup ===== ===== The Setup =====
  
-  *A small(ish?) coffee can with a large hole/​opening in the side so that a small hairdryer can be positioned to blow air in through the side. Aluminium tape was used to seal space around the dryer, permitting as much positive pressure as possible. We initially had the hair dryer standing up vertically under the entire rig, but very quickly realized this is a bad idea; when our earliest (steel can) crucibles failed, the molten metal had a tendency to drip straight down and, as you might imagine, flow into the hair dryer - and trust us, molten metal can make very short work of a $7 hairdryer. Luckily we only had one hair dryer ruined this way and quickly restructured the rig so it wouldn'​t happen again.((We also used a rubber band to hold down the "​cooL"​ button on the dryer - it makes absolutely no sense to blow hot air into a 1000K+ furnaceand after a while the dryer would overheat and shut down, thus lowering the efficiency of the furnace to that of a Webber grill.))+  *A small(ish?) coffee can with a large hole/​opening in the side so that a small hairdryer can be positioned to blow air in through the side. Aluminium tape was used to seal space around the dryer, permitting as much positive pressure as possible. We initially had the hair dryer standing up vertically under the entire rig, but very quickly realized this is a bad idea; when our earliest (steel can) crucibles failed, the molten metal had a tendency to drip straight down and, as you might imagine, flow into the hair dryer - and trust us, molten metal can make very short work of a $7 hairdryer. Luckily we only had one hair dryer ruined this way and quickly restructured the rig so it wouldn'​t happen again.((We also used a rubber band to hold down the "​cooL"​ button on the dryer, ​because if not, after a while the dryer would overheat and shut down, thus lowering the efficiency of the furnace to that of a Webber grill.))
   *A normal steel paint can with a hole cut in the bottom, made to mate with the coffee can. This acted as an adapter and an ash trap.   *A normal steel paint can with a hole cut in the bottom, made to mate with the coffee can. This acted as an adapter and an ash trap.
   *Another paint can, this one with many holes punched in the bottom. We used a large nail and making holes about 1/8" in diameter. We probably punched around 20 of these in various radial patterns. The holes needed to be big enough to allow for ash to regularly sift down, but small enough that no pieces of still-burning charcoal would make their way down. Too few holes would not allow enough air to get through at regular intervals, while two many would cause the bottom to lose its structural integrity - and remember, it needed to be able to hold the weight of the charcoal, the crucible, and all the metal being melted - all while being heated to extreme temperatures.   *Another paint can, this one with many holes punched in the bottom. We used a large nail and making holes about 1/8" in diameter. We probably punched around 20 of these in various radial patterns. The holes needed to be big enough to allow for ash to regularly sift down, but small enough that no pieces of still-burning charcoal would make their way down. Too few holes would not allow enough air to get through at regular intervals, while two many would cause the bottom to lose its structural integrity - and remember, it needed to be able to hold the weight of the charcoal, the crucible, and all the metal being melted - all while being heated to extreme temperatures.
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 ===== Actually Casting ===== ===== Actually Casting =====
 Once we had the molten metal, we had to do something with it. We pursued two types of casting for a few weeks and had semi-decent results at best.((See: [[acceptable results]])) Once we had the molten metal, we had to do something with it. We pursued two types of casting for a few weeks and had semi-decent results at best.((See: [[acceptable results]]))
 +
 +One of the hardest parts of handling molten metal is that it's really, really, hot. Like, indescribably hot. We had a proper handle for the crucible we inevitably bought, but because of the way the crucible had to be lowered nestled into the coals it was impossible to use it properly. What we usually did was use a pair of channel lock pliers to raise the crucible, by the lip, about 10" out of the furnace. This was an astoundingly challenging process simply because of the sheer weight of what you were lifting, and the fact that it was literally hot enough to melt solid metal. The other guy would hold the proper handle thing a short distance away, and as soon as the crucible was clear the coals he had to swoop in and grab it from the pliers, which would inevitably be slipping at this point. Then, the guy with the crucible-holder and crucible would have to get to the mold as quickly as possible and dump the metal in there before it cooled too much and hardened. ​
 ==== Greensand Casting ==== ==== Greensand Casting ====
  
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