Casting Problems
The most common casting problems involve thickness of the casting and thickness of the gating system.
Castings of aluminum, brass and bronze should be 3/16" thick or more. If your pattern is too thin, you can tape cardboard to the back for a quick fix. Castings can be made 1/8" thick, but can be no larger than 4"x 4".
When making your gating system, the runner must be at least 3/4" thick and 3/4" wide.
2. Into the runner
3. Across the gate
4.Fills the casting
5. Up the pop-up when full
This casting is 11" long and 2.5" wide.
Note distance from runner to casting (gate) is only about 1/2".
Deep 3/4" runner allows the metal to stay molten longer. This casting is 1/8" thick.
Runner is almost as long as the casting.
A pop-up vent is located near the end of the runner, but not at the end. The pop-up tells you when the mold is full.
Gate is the same thickness as the casting to allow metal to flow in as fast as possible. Gate to runner (square edge) must also be rounded to prevent erosion, use a molding spoon or your finger.
No vents are needed on the casting.
Even with small castings, a thick 3/4"x 3/4" runner will keep the metal hot until it reaches the casting.
Gating is wide, deep and smooth.