Gravity Process

Define the parameters for a gravity sand casting or gravity die casting process.

Location: Gravity is an option on the Basic Setup icon on the Casting ribbon.

Gravity casting is one of the most common casting processes, as it can be used to produce a variety of parts, from simple gears and pulleys to complex components such as automobile engines. The process uses both expendable sand molds and permanent molds to form metal parts called castings, which can be made of nearly any alloy. The metal is melted in a furnace and then poured into the mold cavity. Once the casting is solidified, it is removed from the mold. Variations on gravity casting include investment casting and tilt pour casting.

Gravity sand casting has few limits on size, shape, and weight, with low pattern and material costs. However, it is generally less accurate than die casting and has a low production rate due to the destruction of the molds. Gravity sand casting generally uses ferrous metals such as stainless steel, carbon steel, and cast iron.

Gravity die casting is a type of permanent mold casting generally used for the production of small, simple metal parts such as gears, pistons, and wheels. It is similar to gravity sand casting but with a permanent mold, making it a better choice for high production volumes. Gravity die casting generally uses non-ferrous metals such as aluminum, magnesium, and copper alloys, although iron and steel parts can also be cast using graphite die molds.

Investment casting is a casting process in which the mold is created from a wax pattern, as follows:
  1. The wax pattern is created manually or by injecting wax in a mold.
  2. The ceramic mold (investment) is created by coating the wax pattern by dipping it into sand.
  3. The shell mold is dewaxed by heating the pattern.
  4. The molten metal is pored into the hollow mold.
  5. The shell mold is knocked out to get the final cast part.

Tilt pour casting is a permanent mold process where the mold is positioned horizontally and is gradually tilted upright during the filling process so that it is filled in a controlled manner with low turbulence and a moderate flow rate. This technique compensates for the effect of free fall at the beginning of the pouring process, and helps to avoid air inclusions.

Define Gravity Parameters

  1. Click next to the Basic Setup icon, then select Gravity.

  2. Select Constant Liquid Level on Sprue, Filling Time, Spoon Height, Flow Rate, or Tilt Pouring.
    Note: If you select Constant Liquid Level on Sprue:
    • When you click Select, you can then select the point on the sprue where the liquid level should remain constant.
    • If more than one ingate is present, you can select a liquid level for each ingate.
    • You can also change the initial pouring velocity of the material if necessary.
    Note: If you select Tilt Pouring, the Create Crucible button becomes active and a new dialog opens to enter details about the rotation.

  3. Optionally, you may select Investment Casting.
    The shell mold will be simulated allowing for analysis of mold temperatures over time. Use the fields to define shell thickness and initial mold temperature. Use the menu to select the type of material for the shell mold. Click the Materials Database icon to select the specific material for the shell mold.
  4. Define the parameters.

Gravity Options

Constant Liquid Level on Sprue
Select this option to maintain a constant liquid level on the sprue during filling. Click Select, then click the point on the sprue where the liquid level should remain constant. The flow rate will change during the filling by adjusting the inlet area to keep the selected level constant.
Use this field to specify the initial velocity of the poured material, or use the default. When the liquid level reaches the specified point, the velocity will adjust to keep the level constant.
Filling Time (s)
Select this option if you have calculated the exact filling time required for your process. Inspire Cast internally converts the filling time to velocity.
Spoon Height (mm)
Select this option when you have totally manual ladle operators. Spoon height is the distance between the ladle and the mold when the liquid is being poured. If you don’t know this value, use a value around 10–30 mm. Inspire Cast internally calculates the velocity based on the spoon height.
Flow Rate (Kg/s)
The flow rate is the poured metal volume in Kg divided by the filling time in seconds. This parameter can be calculated when using an auto-pour ladle, bottom-pour ladle, stop-and-rod ladle, etc.
Note: The size of the gate area affects the velocity, spoon height, and flow rate. To simulate a more realistic pouring, we recommend that you don't select the full area of the pouring cup when defining the gate.
Tilt Pouring
Rotation axis
Select X, Y, or Z to define the axis of rotation. The tilting rotation follows the same order as the XYZ coordinate axis; if you select Y as the axis of rotation, then Z will rotate over X; if you select Z, then X will rotate over Y, and so on.
Move the center of rotation. Right-click to return to the Tilt Pouring parameters.
Rotation table
Enter values in the time vs angle table. To set a positive or negative angle, check the sense of rotation from the final position to the original position following the right-hand rule to determine the sign.

Click Preview to check that the sense of rotation selected is the correct one.
Investment Casting
Shell thickness
As the mold in investment casting is only a thin shell, Inspire Cast will use a virtual mesh for it instead. Enter the shell thickness of the investment mold to simulate its effect on the part.
Initial mold temperature
Enter the shell temperature at the moment of filling the mold.
Mold material
Use the dropdown menu to choose the type of shell mold material, and use the materials database to select a specific material.