Specify the Thermal Conditions

Specify the thermal conditions for the build part, the build tray, and the supports.

The thermal conditions include the initial temperature for each analysis case, the moving heat flux that represents the laser, and the heat transfer conditions that control cooling of the assembly.

This task shows you how to:

Define the Initial Temperatures

An additive manufacturing simulation is a thermal-structural analysis, and you must specify the initial temperature conditions for both the thermal and structural analysis cases.

In the thermal analysis case, the initial temperature is the initial temperature of the incoming powder material before it is spread from the powder bed reservoir. The initial temperature for the thermal analysis case is often the room temperature for the powder bed process.

In the structural analysis case, the initial temperature represents a relaxation temperature above which thermal strain induces negligible thermal stress. This initial temperature is typically much higher than room temperature. After material activation, this initial temperature is the temperature from which the initial thermal contraction occurs. The initial temperature for the structural analysis case depends on the material properties of the powder; it is no higher than the melting temperature of the material.

  1. From the context selector, select Thermal Analysis Case.1.

    Thermal Analysis Case.1 is activated.



  2. From the Starting Temperatures section of the Assistant, click Starting Temperature Setup .
  3. Click the Parts and supports field to verify that the bridge structure is selected.
    The selection is highlighted in the tree and in the model view.
  4. Click the Build tray field to verify that the build tray is selected.
    The selection is highlighted in the tree and in the model view.
  5. Enter a chamber temperature and build tray temperature magnitude of 300Kdeg.
  6. Enter a melting temperature of 1200Kdeg.
  7. Click OK.
    The Chamber Temperature and Build Tray Temperature appear in the Thermal Analysis Case.1 > Initial Conditions category of the tree. The Melting Temperature and Build Tray Temperature appear in a parallel location in Structural Analysis Case.1.

Create the Moving Heat Flux

Define the moving heat flux that simulates the heat addition in the additive manufacturing process. In the powder bed process, the moving heat flux encapsulates the information required for the laser motion over time. The laser path data is generated from the slicing data in the Powder Bed Fabrication app, and the laser path data is converted to an event series.

  1. From the context selector, select Thermal Analysis Case.1.
    Thermal Analysis Case.1 is activated.
  2. From the Moving Heat Source section of the Assistant, click Moving Heat Flux .
    The Moving Heat Flux dialog box appears.
  3. For the Laser distribution, select Concentrated, if it is not already selected.
  4. For the Absorption, enter 0.45.
  5. Click OK.

    The Moving Heat Flux dialog box closes, and a glyph appears on the bridge indicating the moving heat flux.



Create the Free Surface Heat Transfer

Define the free surface heat transfer condition to enable convective and radiative cooling of the current free surfaces as the printed part evolves over the course of the printing process.

  1. From the Cooling section of the Assistant, click Free Surface Heat Transfer .
  2. Enter a Reference temperature of 300Kdeg.
  3. Enter a Convection coefficient of 18W_Kdeg_m2 and an Emissivity of 0.25.
  4. Click OK.