Centrifugal Casting
Centrifugal casting is a casting method in which molten metal is poured into the mold using the centrifugal force generated by the rotation of the mold, and is the method with the highest casting capacity among the three types of casting solutions used in precision casting.
When centrifugal force is used, centrifugal force is applied almost at the same time as the start of rotation, so the molten metal is poured into the mold in a very short time. For this reason, it is effective for metals that solidify quickly, castings with thin meat, and complex shapes.
During casting, the molten metal moves outward due to centrifugal force and is released in the opposite direction (oblique 45°) to the direction of rotation under the influence of the law of inertia (the force by which the object tries to stay in its place). As a result, the molten metal enters the mold in a swirl in the hot water passage of the mold cavity. The gas inherent in the mold is forcibly discharged from the center of the molten metal vortex in the direction of molten inrush. This allows for faster replacement of molten metal with internal gases.
The casting capacity can be adjusted by adjusting the rotation speed, but the longer the turning radius, the higher the peripheral speed and the stronger the centrifugal force, so a casting machine with a long arm is generally advantageous.
On the other hand, however, the high velocity and swirl of molten metal can cause turbulence, which can cause gas entrainment. In particular, thick-walled castings tend to have nesting problems, and large cavities may occur near the Yudo Weir.
In addition, since the casting in the opposite direction due to centrifugal force and inertia is weakened, the wax tree must be placed at an angle that does not oppose the direction of rotation and centrifugal force.
There are two types of block molding casting machines: horizontal centrifugal casting machines that rotate horizontally and vertical centrifugal casting machines that rotate vertically.
Horizontal centrifugal casting machine
The mold is placed on a rotating arm that rotates around the axis of rotation, and it is rotated horizontally to obtain centrifugal force. A balance weight is placed in a concentric circle of rotation, and the center of gravity of rotation is adjusted so that it is on the central axis of rotation to stabilize the rotation.
The metal is melted with a crucible placed in front of the mold, and rotation begins after the melting is complete.
In an external melting (a device that is not equipped with a melting function), the metal in the crucible is melted with a burner flame or the like, and rotation starts when the melting is completed.
In equipment equipped with a melting function, such as an induction type, metal is placed in advance in the crucible in the heating coil to start melting.
When the melting is completed, the heating coil is lowered and the crucible and mold rotate. Vacuum centrifugal casting machines are equipped with a sealed vessel (chamber) that can vacuum the entire melting chamber so that melting and casting can be carried out in a vacuum.