What am I forgetting? (Sandcasting Aluminum)

Going to give sandcasting aluminum a go. Probably will 3d print or CNC some 'round tuits' or coasters or something easy to start as patterns. Below is the start of and status of equipment and materials. Please let me know if I am missing any 'showstoppers'. I have welding type safety gear and full face shield. Thanks in Advance!

--propane furnace kit on order

-propane furnace,

-crucible

-crucible tongs, firebrick


--on hand at home

-propane

-scap metal for melting (cast alu)


--need to make

-flasks

-ramming tool (started)

-vent wire rod

-patterns


--bought on order

-Petrobond

-parting dust


--need to buy

-hand sieve

-refactory cement for furance fiber

 

Sounds like you've got the essentials covered. If you're concerned, do a few cold runs i.e. ram up a mold, simulate a melt, pour and shake out to see how your work area and set-up will perform and throughout every step of the process, ask yourself what could make this easier, safer or more efficient.

 

??
Ingot molds for leftover melt
Pyrometer to measure melt temperature
Some method to maintain the Petrobond
Sprue/riser cutter/rods
Straight edge for striking off the rammed mold top
Rapping rod/tool
Soft brush and source of air to clean any loose sand

A bench to work on. Working on the ground SUCKS. It has been a long time since I did so but I haven't forgotten.................

Fridge with cold beverage of choice for after the pour

 

Thanks Everyone!
Jeff, I love that 'tuit', I was totally picturing that in my head while typing...
Rocco, great idea to try a dry run or two.
Smoking Stone, I appreciate the details, the little things. Also the creature comforts of a bench and a beverage. In my case it's still cold/wet/snowy outside so coffee might come first.

Here is the rammer so far, based on an Ebay sale and drawn in CAD and ported to CNC via STL. Happy with the shape, handle could be just a little longer:

 

Thanks Jeff.

To the group-would I be better off trying a different shape for a first go rather than something that is supposed to be thin and flat?

 

Damn right! Once it’s been used a few times it becomes more cooperative in the finer riddle, but 5 per inch works pretty well for me.

Pete

 

Have you got weights or clamps to hold your cope and drag together against the hydraulic pressure of the molten metal?. Also a camera to record video of your furnace operation and pours for further viewing afterwards to spot any mistakes.

I was able to score a 1 metre square sheet of some stainless woven mesh to make a riddle with, it has 6mm holes or 1/4". I'll mount it in a frame on springs and drive with a motorized shaker.

 

Thin and flat should be just fine. For a first casting, do yourself a favor and stay above 1/4” in thickness and pour the metal on the hot side. As you may or may not know the metal can’t be just molten. It needs what’s known as super heat so it can flow completely into the mold without freezing prematurely. Once I’m completely molten I might give an additional 5 minutes or so to ensure it’s hot enough. I use a pyrometer these days, but that’s about how it works out.

Pete

 

Thanks Mark. I have some clamps and SCUBA weights. With small homemade wooden flasks, would a couple-few gypsum board or decking screws do the trick?

 

Thanks Pete. I don't think I'll get a pyrometer for the first pour but will for sure get a riddle and make sure my pattern is not too delicate.

 

Thanks Kelly. I am new to sprues, risers, pour basins, and gating. I would appreciate the feedback.

I did get the rammer sanded this morning and the next round of packages should arrive today. Getting excited to see it come together.

 

The Petrobond came yesterday. I am not good at equating weight to volume for sand and clay products. I needed to go into the Cities for something else so I arranged some 'personal time away' at work. I stopped by the 'clay store' and got some Mizzou refractory cement and some bentonite ( very inexpensive if you buy 5 or more pounds) and a couple firebricks. The trip was eventful, my car would not start at two stops (intermittent electrical thing) , got to visit another specialty shop for a different hobby, and had an awesome burger and fries with my kid who came out to jump start my car. Picked up a couple groceries and came home to the email from Amazon that the furnace would be delayed. I guess that means I'll have more time for the patterns and flasks...I will grab some sand for the bentonite and see about a riddle.

 

The furnace arrived, I bought sand at the local home improvement store, and found some secondhand kitchen stuff as accessories.


I started in on the flask. Long story short is that I almost glued it together permanently while attaching the plywood guides and I came to realize I did some 'new math' and made the cope and drag one size too big to use with the one bag of sand...I am thinking I'll knock together another flask one size smaller and save the larger until I have homemade green sand. I also made a riddle, sending the CNC after routing 1200+ holes in some scrap 1/16" FR4 board from work. I also had the speed turned down on the feed so it was taking forever until I saw it was not right. All about normal in a day of projecting at my place. The rammer is looking and smelling good with a coat of polyurethane, I should probably give it a couple more.

 

I can't tell for sure from the picture but it looks like the ceramic fiber insulation in the furnace is uncoated, if that's the case, you should coat it with something like Satanite to prevent airborne fibers and erosion by the burner.

 

Thanks Rocco. Yes, it is uncoated, sorry about the harsh early morning light in the pictures. I bought some Mizzou castable refractory at the same place I got the bentonite and firebrick. Now I just need to figure it out, convert the mix chart into smaller units, etc. Does anyone know how thick is about right for this application? Square area of wool looks like about 273 sqin or 1.9 sqft. Use the whole 5 pound bag?

Worked on the smaller flask. I ended up cutting out pieces for 2 of them just working with scraps I had in the garage. Then I thought I should play with the laser...it is my 'least' favorite CNC in that it has to be tethered to a PC and that it does not home or focus and repeat pieces count on the user not bumping the machine. Once you get your objected positioned x and y and have the head set to z it can do some neat stuff including burning photographs. Since this was real wood, the house now has a nutty / campfire smell to it. If I am cutting 'plasticy' things I set it up in the garage.

 

I called into tech support at HWI and got a call back about Mizzou. I used the whole 5 pounds and added 10% water by weight. The first two pounds were on the lid and floor, the remaining three along the sides. I should have mixed/waited a bit more on the lid. Furnace is a '6kg' model.

I tried putting some small steamer trunk type hardware latches on the above flask but they do not close tightly at rest.. I will plan on weights (as suggested) and maybe screws.

 

I saw those latches in the photo above. I had those bale type latches on a couple of my flasks and although convenient for their purpose, they tended to get in the way so I’ve removed them. I usually put a board across the top covering as much of the sand as possible without covering any holes and then use cheap squeeze-grip bar clamps. Depending on the thickness of the mold cavity and the depth of the flask not only is it possible for the flask halves to separate, but the sand can actually heave as well so I make a habit of covering it.
HWI also makes a refractory mortar product called Satinite. It’s very popular here and among forge builders. It’s relatively inexpensive and available online. It would be helpful to have if and when your mizzou coating needs servicing or modification. One advantage of using it in your application is that it would protect your still-exposed wool, and allow for a decent mating surface with your lid since it doesn’t have the gravelly component in it like the mizzou, but at this point you would probably need to chisel away the mizzou from the lid around the contact surface which could get a little dicey.
Hopefully the weight of the mizzou on the lid won’t cause it to pull away from the wool, but time will tell.
Keep up the great work! You’re almost there!

Pete