• Additive Process: Laser Powder Bed Fusion. The Laser Powder Bed Fusion (LPBF) process uses thermal energy from a laser or electron beam to selectively fuse powder in a powder bed.

• Inherent Strain (Yes or No): An option to use the Inherent Strain method. (If you used one of the AM custom systems in Workbench to set up your analysis system, this option is set automatically for you.) If No, the AM simulation uses a linked thermal-structural system in which strains are calculated from material properties and thermal loads. If Yes, an alternative method is used in which strains are based on an experimentally calibrated Strain Scaling Factor. Options under Machine Settings, Calibration Settings, Build Conditions, and Cooldown Conditions differ depending on whether Inherent Strain = Yes or No.

  If Inherent Strain = Yes (default if AM Inherent Strain custom system is used):

  • Inherent Strain Definition: Assumption about strain behavior reflecting the different ways inherent strain is calculated as an input to the structural solver.

    • Isotropic: Simplifying assumption that a constant, isotropic strain occurs at every location within a part as it is being built. A constant Strain Scaling Factor may be used to scale strain everywhere uniformly to account for calibration of the Mechanical application to a particular machine/material combination.

    • Anisotropic: Uses the same average strain magnitude as isotropic strain, but it subdivides that strain into anisotropic components in the X, Y, and Z directions based on the Global coordinate system.

    • Scan Pattern: Uses the same average strain magnitude as isotropic strain, but it subdivides that strain into anisotropic components based on the local orientation of scan vectors within the part. Scan vectors may be generated internally via a slicing function assuming a rotating stripe scan pattern or input via a build file.

    • Thermal Strain: A method that provides the highest level of fidelity and takes thermal cycling into account at each location within the part.

      • Thermal Strain Method: Machine Learning Prediction (only method available at this release)

        Uses a machine learning model prediction of the anisotropic Thermal Strain simulation result from the Ansys Additive application.—Thermal Strain simulations provide the highest level of fidelity by predicting how thermal cycling affects strain accumulation at each location within a part. The simulation follows the full laser path on every layer, and is based on the machine process parameters (power, scan speed, beam diameter, etc.).—The machine learning model has been trained to predict the Thermal Strain result much faster than simulation. It can be one to three orders of magnitude faster than Thermal Strain simulation in Additive Print in calculating the strain that is passed to the structural solver. Speedup increases with part size, scan area, and melt pool size. See Thermal Strain - Anisotropic in the Additive Print and Science User's Guide.

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        Important:  The Machine Learning Prediction feature requires a Structures AI+ license.

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      • Machine Learning Model: A list of materials that were used to train the ML prediction, in particular, the materials validated for the Additive application. Choose the material that most closely matches your material assignment in Engineering Data. ML models may be based on different material properties than those in Engineering Data. The ML models are used to generate loading strains. Materials in Engineering Data are used for the structural analysis.

• Layer Height: By default, the program uses the Layer Height specified when meshing as the super layer height. Occasionally you may want to increase the size of the super layer to something coarser than what was used when you created the mesh. Use the Layer Height option here to do that. Specifying a new Layer Height does not affect the existing mesh.

• If Inherent Strain = Yes (default if AM Inherent Strain custom system is used):

  • Scan Pattern Definition (visible if Inherent Strain Definition = Scan Pattern or Thermal Strain): How the scan pattern is defined, either generated using a rotating stripe pattern (default) or input via a build file.

    • Generated: Start Layer Angle and Layer Rotation Angle as defined above. Scan Stripe Width is also visible if Inherent Strain Definition = Thermal Strain. These inputs define an internally generated scan pattern.

    • Build File: Machine Type and Build File Path inputs become available with this option. These inputs specify an external build file to be used.

      • Machine Type: Specifies the machine or OEM associated with the build file specified. Options are Additive Industries, EOS, HB3D, Renishaw, Sisma, SLM, and Trumpf.

      • Build File Path: Location of a .zip file containing the scan pattern file(s), and an stl of the part geometry. See Build File Requirements.

  • Beam Diameter, Beam Power, Deposition Thickness, Hatch Spacing, and Scan Speed as defined above. If a build file is specified for Scan Pattern Definition, deposition thickness is determined from the file.

• If Inherent Strain = No (default unless AM Inherent Strain custom system is used):

  • Hatch Spacing, Deposition Thickness, and Scan Speed as defined above.

  • Dwell Time: The span of time from the end of the laser scan of one layer to the start of the laser scan of the next layer. It includes the time required for recoater-blade repositioning and powder-layer spreading.

  • Dwell Time Multiplier: The dwell-time multiplier accounts for more than one part in the build. If they are the same part arranged in the same orientation on the build plate, the multiplier is the number of parts.

  • Number of Heat Sources: For multiple-beam printers, specifies the number of lasers. This divides the amount of time it takes to scan a layer by the number of heat sources specified.

• Room Temperature

• Gas Temperature, Gas Convection Coefficient, Powder Temperature, and Powder Convection Coefficient as defined above, with an option to use Room Temperature for Gas Temperature and Powder Temperature.

• We define a build file as a .zip file containing, at a minimum: one .stl file for the part geometry and one machine-specific print file defining the scan vectors. Supported machine manufacturers include Additive Industries, EOS, HB3D, Renishaw, Sisma, SLM, and Trumpf. Ansys may add additional options as we continue to work with more machine partners.

• Build files from Additive Prep are automatically created with a file name of "ansys_additive_print.zip.

• The build file is a .zip file. Do not nest the files to be zipped within a folder, as a folder structure is not readable. Rather, zip the individual files together as shown in the following figure.

  

General requirements for the part geometry stl file

• Stl files within the .zip file must have units of mm and be positioned in the same location as the part in Mechanical.

• Multiple parts can be used, but they must all be within one stl file.

• The baseplate should not be included in the part geometry stl file.

• Supports should not be included in the part geometry stl file nor as a separate stl file.

General requirements for the machine file

• One laser head is assumed for the simulation. Build files with multiple lasers are not supported. When you import a build file with multiple lasers, the application handles it differently depending on the machine. In most cases, the application either generates an error or ignores the extra lasers upon import.

• One set of process parameters is used in the simulation. If the build file contains multiple parameter sets, such as different scan speeds and laser powers for the part hatches versus the support hatches, the part hatch parameters will take precedence.

• Only one part layer thickness (Deposition Thickness) is allowed.

• Only one support layer thickness is allowed, and it must be equal to, or a multiple of, the part layer thickness.

• Regardless of how they are defined in the build file, the scan sequence is always simulated from the inside out, that is, from hatch to contour scans. However, the appropriate order is maintained within the hatch area and within a contour. For example, if the build file order is: contour line 1 → contour line 2 → hatch line 1 → hatch line 2, it will be changed to be hatch line 1 → hatch line 2 → contour line 1 → contour line 2.

• Scan vectors marked as contour will not be simulated. The definition of contour/hatch is established by the software that creates the build file. If contour-like scan vectors are marked as hatch they will be simulated and results may not be as expected.

• Build files for simulations that use the Machine Learning Prediction strain definition only support stripe scan patterns.