Printing performance in laser powder bed fusion (L-PBF) is heavily dependent on the energy density of the laser spot used to produce the necessary heat for powder fusion. Laser spot characterization technologies exist today to characterize laser spot size and shape, but are generally engineered for applications outside the context of printing beds, or indirectly measure the effects of laser performance from process by-products, within the context of printing beds. For L-PBF a tool for characterizing the laser spot across the entire bed is critical as as galvanometer scanning and F-theta lens effects can distort the spot size as a function of position across the bed. The device presented here, developed and patented by EWI, showcases hardware and data analysis techniques on how to map position-linked laser spot characterization data, and outlines the requirements for commercial machines to implement the technology. The hope is that this device can help users identify system deterioration, diagnose root cause for abnormal part results, and eventually play a role in machine certification standardized procedures.
- Define what causes laser sources to degrade over time
- Understand what causes laser sources to vary across manipulation through an F-theta lens
- Describe the disadvantages of current laser characterization technologies when implemented on additive manufacturing machines
Why Is It Important?
A lack of standards for machine certification is currently plaguing additive manufacturing processes including laser powder bed fusion (L-PBF). This void is resulting in part qualification procedures that are limited to a specific manufacturing machine; this makes part qualification an even more time-consuming and expensive process for additive manufacturing centers. Partial justification for this lack of standardization is centered on an inability to acquire the necessary data for certification. Laser spot characterization exemplifies the most critical measurement inability. No tool is available to measure spot size and shape at multiple locations across the build area.
The solution developed under this work provides a path forward for multi-location laser beam characterization. For machine manufacturers, it provides an opportunity to understand the data necessary to characterize their lasers. For standards development agencies it provides an opportunity to start including essential variables into machine certification specifications. For end users, it provides the potential capability to finally certify machine performance.