In this step, specify the settings and conditions related to the machine and the process, grouped into the following three categories:
Machine Settings refer to process parameters that vary for each DED machine as well as for the material used in the deposition process.
Material Deposition Rate: The feeding rate of the melted material, in mm3/sec. This value can be determined by multiplying layer thickness (mm) x weld width (mm) x deposition speed (mm/sec).
Build Conditions are the settings pertaining to the environment in the build chamber around the part as it is being printed, including the preheat temperature. Multiple convection coefficient and emissivity inputs are available to allow for the possibility of different materials and/or conditions for the part and the base plate.
Preheat Temperature: The starting temperature of the base plate.
Scoping Method: Choose to select geometry directly in the geometry window or use a named selection to identify the bottom of the base plate that will be preheated.
Preheat Geometry: The bottom face of the base plate.
Preheat During Printing: If set to “Off (default),” the preheat temperature is applied in only the first load step. Option “On” maintains the preheat temperature throughout the complete build process.
Heating Method: Controls how new clusters are heated in the transient thermal analysis. Choose Temperature Based (default) or Power Based.
Temperature Based: Heating is based on the process temperature.
Process Temperature: The temperature of the feed material as it is exiting the nozzle—usually melting temperature or above. (When using the DED Process wizard, this value automatically defaults to the build material's melting temperature.)
Power Based: Heating is based on laser power and material absorptivity.
Power: The power of the laser in Watts.
Absorptivity: The average fraction of energy that is absorbed by the deposited material and contributes to the heating process. Value must be between 0 and 1. Defaults to 0.4, or 40%.
Room Temperature: Temperature of the gas in the build chamber during the build.
Gas Convection Coefficient: Convection coefficients from the part and base plate surface to the surrounding gas in the chamber during printing. Convection is applied to the element surfaces of every element cluster, which can be especially relevant in the case of a bulky structure.
Radiation: Set to Off (default) or On to include the effect of radiation in the simulation. Define emissivity if Radiation = On. Turning on radiation effects may provide higher accuracy but at significant computational cost.
Thermal Calibration: Off (default)/On - If set to Off, default heating and cooling behavior is used for cluster deposition. Setting the option to On allows you to change the Cluster Cooling Time Ratio, essentially using it as a calibration factor.
Cluster Cooling Time Ratio: A value between 0 and 1 (default). The total deposition time, t, for each cluster is determined by the volume of the cluster and the deposition rate. By default, a very tiny fraction of this total time (1e-6 seconds) is used to raise the temperature to the Process Temperature, and the remainder is used for cooling. Use the Cluster Cooling Time Ratio to adjust the heating and cooling distribution. Lowering this value from the default of 1 has the effect of lowering cooling time, thereby increasing heating time. For example, a value of 0.8 means 20% of time, t, is used for heating and 80% for cooling (during printing). The lower the number, the higher the temperature spikes that will exist in the thermal history across the part.
Cooldown Conditions are the settings pertaining to the environment in the build chamber around the part in the cooldown step after the last layer is printed.
Room Temperature: Temperature of the gas in the build chamber during cooldown.
Gas Convection Coefficient: Convection coefficient from the part to the surrounding gas in the chamber during cooldown.
Time: The duration of the cooldown process.
Tip: To neglect convection for testing purposes, set the Gas Convection Coefficient for both the build and cooldown conditions to very small values.
Cooldown Between Layers are options to adjust the dwell time, which is the pause, in seconds, between layers as measured after the last cluster in a layer is deposited, not including laser travel time. Two methods are available, Time Based and Temperature Based.
Time Based is a method allowing direct input of dwell time, in seconds or milliseconds, from the G-Code file which is then interpreted through the element clustering process. Dwell time for individual clusters is modifiable in the cluster settings table. You can use the convenient "List only last cluster in each layer" filter to manually adjust dwell time between layers.
Temperature Based uses a Target Temperature together with time step and convergence options to automatically adjust dwell time. See Cooldown Between Layers options in the Build Settings object. With this method, the ability to manually adjust dwell time for individual clusters is disabled.