Monitoring Laser Powder Bed Fusion Recoater Blade Vibrations For Collision Avoidance

Laser powder bed fusion (LPBF) relies on the precise spreading of powder by a recoating mechanism, such as a recoater blade, to build the next layer of material. One of the issues during fabrication is the thermal warpage of parts, which can collide with the recoating blade and cause print failures. As parts gradually thermally warp due to heat accumulation, the distance from the recoater blade to the parts decreases. If this is not mitigated in-situ, the blade eventually will crash into the part. Most LPBF machines have safety mechanisms in place to detect high current in the driver motor of the recoater mechanism when a part is obstructing the recoat path. This safety mechanism, however, detects when the blade has already collided with the thermally warped part, which damages both the part and the recoater blade and aborts the entire print job. Previous research has shown the ability to detect vibrations on the recoating arm due to thermally warping parts interfering with the recoater blade. However, the precise distance from the top of the part being printed and the bottom of the recoater blade edge when interference occurs remains unknown. This thesis aims to discover at what distance do measurable vibrations in the recoater arm occur. In addition, what, if any, vibrations occur due to forces caused by the resistance in movement of the powder before interference occurs? Lastly, what size of geometrical features drive the recoater blade vibrations? The findings of this study show that there were measurable vibrations in the recoater blade with as little as 3 μm after interference as well as measurable vibrations before interference. Signals indicating the recoater blade was in interference with a part were due to micro-scaled features located on the top surface of the part.

Date

2022-05-17

Resource Type

Text

Resource Subtype

Thesis

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