1. in-plane accuracy (= in-layer = x/y plane parallel to building substrate),
2. accuracy in the z/building direction.
Small features (thin walls, holes, sharp angles/corners, …) accuracy or volume/dimensions variations after heat treatment will be discussed separately.
In-layer dimension accuracy - x/y plane
· HWI offset: found in the PSW 3.6 software in the HWI window, this parameters can be positive or negative in value. It reflects an offset between original CAD file and the one being machined.
· Presence or absence of contour parameters: optional, the presence of contour parameters can improve surface roughness. These parameters are scanned along the CAD outer contour of the component in each layer.
· In-layer scaling factors x,y in the HWI window: here to take into account volume variation after heat treatment – not usually needed (values = 0) for as-built dimension accuracy. Also the offset may be used to compensate for phase change volume variation if the component is subsequently heat treated. These scaling parameters may also compensate for distortion generated by internal stresses.
· Pre- or Post-Contour parameters: Power, scanning speed used to scan the outer CAD contour (offset optional) of the component.
· Contour offset: given that the contour laser track has its own track width, an additional contour offset (in addition to HWI offset) may be used to ensure the overall dimensions of the components are within tolerances.
· Skywriting: recommended, this option ensures the laser is Off as the scan head redirect the beam path at the end of the path and starts processing the adjacent track. If the laser is on, material is melted during positioning and superfluous material is processed that decrease dimension accuracy.
Dimension accuracy in the vertical/build direction
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