What tools can be used to monitor the melt pool?
meltpool:
Pyrometer (2 Photdiodes): measure energy of themal (electromagnetic) radiation
fast
estimate temperature
Camera: size and shape, behaviour
What properties of the powder bed are monitored?
uneven powder distribution
missing powder
powder layer thickness
What tools are used to monitor temperature and how do they differ?
Pyrometer (Meltpool Monitoring):
Uses photodiodes to measure the intensity of thermal (electromagnetic) radiation emitted by the melt pool.
Very fast measurement.
Used to estimate melt pool temperature.
Thermographic Camera (Buildspace monitoring):
Measures temperature distribution in the build area.
Detects overheating and thermal abnormalities.
Difference:
Pyrometer: Radiation intensity of a small spot
temperature estimation
Thermographic Camera: Infrared image of area
temperature distribution
In-Process QA - commercial established monitoring in AM
1. Process Conditions
Position of axes (build platform, laser/ nozzle system)
Cooling system (flow rates)
2. Melt Pool Monitoring
Pyrometer
Camera (instead of Photodiodes)
Measures:
Melt pool size
Melt pool shape
Melt pool behaviour
3. Powder Bed Monitoring
Camera system
Takes images after each powder coating step and/or each built layer.
Detects:
Uneven powder distribution
Missing powder
Layer defects
4. Build Space Monitoring
Thermographic Camera
Optical Coherence Tomography (OCT)
Uses light-based imaging to analyse:
Surface structure
Layer quality
Defects
Which strategies for process control are introduced in this lecture?
realtime control (constant comparison):
layerwise control (layer-wise comparison)
challenges:
relationship between defects and process parameters is complex
Sensors need high resolution & fast detection
Process parameters must be adjusted quickly
real time data processing requires high computational power
Last changed13 days ago