Layer Thickness
A wide range of process parameters build up a successful material parameter set, and optimizing these parameters is critical to achieving successfully results.
The layer thickness is a key parameter which plays a large role in both quality and productivity. Typically, fine layers will yield improved surface finish and higher feature resolution compared to coarse layers where higher productivity is achieved.
Desired layer thickness should be linked to melt pool penetration depth to ensure a good weld between layers and therefore mechanical performance
Inskin, Upskin and Downskin
For a given layer thickness, a part geometry is sliced into 3 main regions:
- Inskin – the bulk of the part/layer which also includes borders
- Upskin – the upper most surface
- Downskin – the lower most downfacing surface with powder below
A parameter set specifies what energy is applied (Laser Power), how it is applied (Scanning Speed) and where it is applied (distances & stitching).
The definition of regions allows different parameters to be applied in these areas, for example lower energy densities applied to downskin regions to improve surface finish and enable for lower unsupported overhangs.
Hatch Distance and Offset
Hatch distance is a function of laser spot size. It defines the overlap between weld tracks and has a significant impact on productivity.
Hatch offset if a critical parameter to ensure the hatch vectors are properly connected to the borders.
The number of borders, the distance between each border and the order in which they are scanned can be used to eliminate subsurface porosity.
Hatching Patterns
Various hatching patterns can be deployed in a process parameter depending on material characteristics and requirements, the more common strategies are stripes, chessboard or total fill.
No Pattern
Straight line vector path from each side of the border.
Stripes
The area within the border is split into strips and a meander technique is used a within each strip.
Chessboard
A further advancement on Stripes. Instead, the area is split into squares like a chessboard.
Total Fill
The complete area is filled by offsetting Additional Borders. No hatch pattern is applied.