Title:

" Detecting and Reducing Build Defects in Laser Powder Bed Fusion through In-Situ Infrared Monitoring and Process Simulations”

ABSTRACT:

Additive manufacturing (AM) has seen rapid growth in the last decade and continues to evolve from prototyping to production. Laser powder bed fusion (LPBF), in particular, allows for complex parts that cannot be fabricated through conventional subtractive manufacturing methods. However, these manufacturing methods do not come without problems. Support removal, cracking, and defect formation all lead to costly trial and error runs to remedy the issues. Process modeling with finite element analysis (FEA) and an infrared (IR) camera can help reduce defects prior to printing and assist with finding these defects due to the complex manufacturing method.

The cost of support removal from complex shapes can exceed the actual AM cost of producing certain parts. Many parts have intrinsic details that require support structures to avoid build failures. Subtractive machining practices hinder the complexity because these methods require machine access to eliminate support structures. This work employs a hybrid style lattice structure as support to withstand residual stress and deformation in a part but will then be quickly dissolved away using a chemical recipe. Combining AM with dissolvable support makes complexity cost free compared to previous methods requiring traditional support removal. 

LPBF is a multiscale process that consists of a laser moving at high speeds for hundreds or thousands of layers, taking up to days or weeks to build parts. The part experiences rapid melting, solidification, re-melting, re-solidification, temperature buildup, and cooling throughout the build. This work develops a layerwise simulation to provide an accurate interpass temperature (heat accumulation) to any geometry. This provides helpful insight into predicting temperatures and even failures in the design stage. This work uses a GPU-based FEA model to provide these accelerated and accurate thermal simulations and validates against an IR camera.

Simulations are useful for designing and predicting thermal history in parts before printing; however, defects can develop due to unpredictable events during the manufacturing process.  Issues such as spatter and poor powder recoating can cause detrimental lack of fusion (LoF) defects. An IR camera captures information about laser intensity, interpass temperature, and spatter to indicate specific locations of interest. IR cameras have the ability to qualify parts as defect free. Defects can be minimized by correlating features such as interpass temperature or maximum temperatures and then using simulations to adjust the process parameters to reduce defect formation. 

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Meeting ID: 931 7375 6108