Gas Flow Velocity Calibration in Tool Steel Powder Bed Fusion
Calibrating cross-flow velocity to 2.2-2.8 m/s prevents laser plume attenuation and condensate redeposition in tool steel powder bed fusion.
Hot-Wire Anemometry
Meaning
Thermal sensor technology uses the cooling rate of a heated thin wire to measure local fluid velocity with high temporal resolution. Implementing hot-wire anemometry allows researchers to map the precise velocity distribution of protective gas streams in additive manufacturing chambers. The sensor operates on the principle that fluid flow removes heat from the wire by forced convection.
This method is particularly effective for detecting rapid changes in the gas flow pattern that other, slower sensor types might miss.
Working Principle
A tiny sensor element made of platinum or tungsten is kept at a constant temperature by an automated control circuit. In hot-wire anemometry, the electric current required to maintain this temperature correlates directly with the gas velocity. Because the wire has very low thermal mass, it responds to changes in flow speed almost instantaneously.
System Calibration
Calibration must be performed in a controlled nozzle flow to relate the measured voltage to specific velocity values. Accurate hot-wire anemometry requires compensation for temperature variations in the gas stream itself. This is typically achieved by integrating a second, unheated sensor to monitor background temperature.
Turbulence Analysis
High-frequency data collection allows the evaluation of turbulent fluctuations close to the powder bed surface. This analysis helps optimize the gas delivery nozzle design to ensure a laminar, stable flow. Devices with lower turbulence levels minimize powder disruption during the printing process.