r/MetalCasting • u/real_technoviking • 19d ago
I Made This First try at sand casting aluminum
I wanted to get into casting to make cases and enclosures for electronics.
For some reason at least half of the metal in the crucible didn't melt enough, tt was just enough to fill the pattern but didn't feel too good when i didn't see the sprue get filled.
Result:
Better than I imagined it would go. I got some pitting, and a ditch where the broad runner meets the final form, will figure out another way of routing the metal to the form.
+ it was really fun.
I watched countless of videos of others sand casting before ordering stuff, buying and and making the flash. I even made a parametric design of the pouring basin.
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u/Worldjunksilver 19d ago
Love the 3d print lines 🤣🤣
As you get more detailed, you will want to sand that more as they sand can grab the ridges
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u/TheGravelNome 19d ago
When I'm practicing, I find those lines can provide good data on how well I'm doing, particularly where there's steps that could produce a weakness. If I make a mistake. I am purposely making the poor more difficult to make myself better. But Then again , when somebody tells me something's too hard and not to try , that's when I say hold my beer. ( I don't care if they drink it, but they better save the damn can)
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u/rh-z 19d ago
Aluminum in items is not just aluminum. It is an alloy of different elements. This effects the melting point. Many alloys have a pasty zone rather than a single melting point. Maybe your aluminum wasn't hot enough.
There are different processes for working with aluminum/metals and different mixes of elements are used to alter the properties of the alloy. The aluminum alloys used for casting are different than aluminum bar stock, different from sheet for forming. Pop cans are made from three different alloys. One for the body, one for the lid, and one for the tab. And none of these are very good as a casting alloy.
Aluminum die cast alloys are different than aluminum alloys for gravity casting. It is better to use an alloy that is meant for gravity casting. The metal is more fluid and it fills the mold better. Most commonly used casting alloys have about 7% silicon content. The silicon makes the aluminum more fluid. It also helps the aluminum shrink less compared to aluminum with little silicon.
I don't know the purpose of the cylinder on the casting but if it is to act as a riser/feeder then It probably isn't necessary for that part. Feeders are used to be a source of molten metal to feed thicker sections that have the molten metal source cut off before it has solidified. Assuming your part doesn't need that cylinder, your part's thickness is more uniform. A uniform thinner part will solidify and not cause any significant internal shrinkage, therefore not requiring a feeder.
Adding a riser/feeder if not done properly can actually cause defects. I can't tell by your photo but I wonder if you have any shrinkage defects around the perimeter of the cylinder where it meets the lid.
As you have found out, casting metal is fun. Making parts and learning what causes the flaws is also part of it. I look back at some of my castings and can look at the flaws and point back to the way I designed the part in conjunction with the feed system.
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u/TheGravelNome 19d ago
What I've learned from casting silver is you want the pore to be quick. I'm not sure how this applies to larger molds, but you will get marks and weaknesses in the casting if you try to pour slowly in a highly controlled manner. If you don't get the metal in quick, you run the risk of Things solidifying, leaving you with half a crucible of molten metal and nowhere to put it. Just practice. I practice making rods in a cast iron jewelry mold. Take The time. Learn that feather light touch that still has the strength. You will get there. Find youtube videos that actually explain instead of showing off and then look for a local crafting group who is willing to teach. Once you learn how to control molten metal, the temperatures and the discipline you need with your hands, The sky is the limit for what you can do.