Because of the increase in the number of calculations at each point in a part, Thermal Strain simulations take much longer than Assumed Strain or Scan Pattern simulations. Additionally, while the Voxel Size and Voxel Sample Rate determine the mesh used in the Mechanics Solver, the Additive application uses a much finer mesh in the Thermal Solver. This mesh sizing is controlled internally. (See Thermal Solver Default Settings.) An option is available for simulations that use the Thermal Solver to increase the speed of your simulation—or to increase the accuracy of the melt pool— by scaling the mesh for the thermal strain portions of the calculation. The Mesh Resolution Factor (MRF) allows some user control over mesh size. Valid inputs are integers between 1 and 12. We recommend you use the default value of MRF = 5, in which case you should see comparable run times to the pre-2019 R1 release, but the results are being generated at better than twice the resolution in X and Y.

MRF is inversely proportional to run time and fidelity. If the MRF is too low, the simulation will take a long time to complete. If the MRF is too high, you will see a warning message, such as The Mesh Resolution Factor (MRF) used is too coarse to accurately resolve the maximum melt pool width. For more accurate results, adjust settings to satisfy (MRF * 0.021 mm) < max melt pool width. This means the element size is too large to fully capture the heat transfer phenomena in the melt pool. Either lower the MRF or increase the energy density into the system to increase melt pool width.

Energy density is the energy being put into the material at the melt pool location per unit volume. The most significant factors contributing to energy density are the laser power, scan speed, hatch spacing, layer thickness, and the material's absorptivity. So for a given material, to increase the energy density you can increase Laser Power, reduce Scan Speed, reduce Hatch Spacing, and/or reduce Layer Thickness.

Should you see a similar warning message regarding MRF in a simulation that does not have MRF as an input parameter, such as a Microstructure simulation, adjust one or more of the machine parameters mentioned above.