The recoil pressure created by the vapor jet pushes the melt surface downward to form a vapor depression (also known as depression zone or keyhole) 12 the high-speed upward vapor flow of the vapor jet ejects powders and liquid droplets away to form spatters and induces ambient gas flow toward the laser beam to cause powder entrainment.ĭue to the strong dependence of the laser absorptivity on the incident angle 13, the nonuniform energy absorption leads to nonuniform vaporization that causes nonuniform recoil pressure on the melt pool surface (liquid-gas interface). As the high-energy laser beam impinges on the powder bed, the localized laser heating causes surface boiling to form a strong vapor jet 9. However, the focused laser heating of a powder bed creates severe process instabilities, which causes the formation of various defects 6, 7, 8, 9, 10, 11, as schematically shown in Fig. 1a, which has the potential to revolutionize many industries (e.g., aerospace, medical, defense) 3, 4, 5. The high spatial resolution stemming from the small focused beam size (about 50–100 µm) gives LPBF the capability to manufacture metal parts with complex geometries unachievable by conventional manufacturing routes 2, as shown in Fig. Laser powder bed fusion (LPBF) uses a focused high-energy laser beam to selectively melt thin layers of metal powders to directly convert a computer-aided design model to a part 1. The nanoparticle-enabled simultaneous stabilization of molten pool fluctuation and prevention of liquid droplet coalescence discovered here provide a potential way to achieve defect lean metal additive manufacturing. We reveal that two mechanisms work synergistically to eliminate all types of large spatters: (1) nanoparticle-enabled control of molten pool fluctuation eliminates the liquid breakup induced large spatters (2) nanoparticle-enabled control of the liquid droplet coalescence eliminates liquid droplet colliding induced large spatters. The elimination of large spatters results in 3D printing of defect lean sample with good consistency and enhanced properties. Here we report the elimination of large spatters through controlling laser-powder bed interaction instabilities by using nanoparticles. Particularly, the stochastic formation of large spatters leads to unpredictable defects in the as-printed parts. Rejected - A defect can be rejected for any of the 3 reasons viz - duplicate defect, NOT a Defect, Non Reproducible.The process instabilities intrinsic to the localized laser-powder bed interaction cause the formation of various defects in laser powder bed fusion (LPBF) additive manufacturing process. Reopened - When the defect is NOT fixed, QA reopens/reactivates the defect.ĭeferred - When a defect cannot be addressed in that particular cycle it is deferred to future release. Verified - The Defect that is retested and the test has been verified by QA.Ĭlosed - The final state of the defect that can be closed after the QA retesting or can be closed if the defect is duplicate or considered as NOT a defect. Test - The Defect is fixed and ready for testing. At this stage there are two possible outcomes viz - Deferred or Rejected. New - Potential defect that is raised and yet to be validated.Īssigned - Assigned against a development team to address it but not yet resolved.Īctive - The Defect is being addressed by the developer and investigation is under progress. Defect Life Cycle - Workflow: Defect Life Cycle States: It varies from organization to organization and also from project to project as it is governed by the software testing process and also depends upon the tools used. Defect life cycle, also known as Bug Life cycle is the journey of a defect cycle, which a defect goes through during its lifetime.
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