Im trying my hand at aluminum casting tomorrow and I was wondering what the best material would be to make a mold for it.
I’ve used Plaster of Paris for casting aluminum. I use “Pam” cooking spray as a parting compound to help release the pattern. I also use Wax paper as the “Parting Line” break in-between front and back half’s of the mold. I’ve used old Tupper ware to cast the pattern into or made up wood frames to pour the plaster of Paris into. I then submerge the m=pattern ~ half way into the plaster. I then use a spatula to level the mold to the top of the frame/Tupper ware. I let the plaster cure about 30 minutes and place wax paper cut the patter to allow a separation of the two plaster half’s. I then make the top half of the pattern my pouring more plaster of Paris on top of the bottom half of the mold. After the plaster has cured ~ 2 hour, I remove the pattern and gently wash out the “Pan” with dish soap. I then cut my fill and vent holes in the Bottom half of the mold. Note I usually pour into the back side of the mold to allow for the removal of the spruces with out damaging the casting. I let the plaster cure over night. On the day of the pour I start early by pre heating the houses oven to 200 Degrees F. I cook the plaster for 2 hours and then when I’m starting the forge, I heat the oven up to 500. I hold the two half of the mold together with c-clamps. The pre-heating of the plaster help to prevent the aluminum from forming cold pour lines in the final item. Yes the plaster of Paris will pop and crack as it cools off, but it works. Charles
once you find out let me know ! hahaha only thing i know so far is to make a forge and they have vids on your tube with some inexpensive homemade ones. as far as the foil idea.. that works plus soda cans and junk yards too for scrap pieces.
I'm considering on doing the same to make various motorcycle parts. Did some research and noticed there are several brands of specialty plasters designed for use as reusable metal casting molds. I'll be using one of those when the time comes to avoid wasting time and material.
Casting Aluminum In Plaster
First... this is science so, if you want specific answers, you need to ask specific questions. Second... The melting point of aluminum is NOT 3600°F, it is 1220°F for pure Al. Third... It is unlikely that you want to cast pure Al. A more common Al casting alloy is 360, Al-Si eutectic with a mp 1070°F but it really depends on what you will do with this casting. Fourth... What shape do you want to cast? and how many castings do you want to make? The answer will be different if you want to make 2 castings vs 2 million castings. If you want a simple shape, a right circular cylinder or a rectangular block, you have many choices for permanent molds: steel, cast iron, graphite, copper, among others. If the shape is more complicated or if the dimensional requirements are tight, the mold design may be much more complicated. There are graduate level college courses on the design of castings. One consideration is how long do you want it to take to freeze. You should, at minimum, do the thermal analysis to be sure that the heat load (superheat and latent heat of solidification) can be absorbed by the mold so that the equilibrium temperature is below the solidification temperature of the alloy. Regarding previous answers... If you wet the mold with water or any other volatile liquid immediately before pouring, it is very likely that the molten alloy will create a steam explosion and blow that molten metal right back in your face. If you plan to do this, please be considerate of others and do it by yourself so you are the only one injured by your stupidity. A little knowledge is a dangerous thing and the most dangerous person is the one who does not know that he/she does not know. Consult your friendly neighborhood metallurgist or someone who has actual proven experience.
