Packing density: Packing density is the percentage of a powder bed build's volume filled by parts, and it decides how many parts share the cost of one build run.
When parts are nested in three dimensions in an SLS or MJF build, there is always loose powder between them. Parts need spacing so they do not fuse together or distort from heat, and real shapes do not fit together like bricks. Packing density measures how full the build is, by part volume or by bounding box volume. Even a well nested build is mostly unfused powder.
What it means for the price
Packing density sits behind every part’s build share. If a shop prices as if builds were dense and then runs half-empty builds, every part loses money; if it assumes sparse builds, it overprices and loses orders. The honest figure is the density the shop actually achieves, measured over its recent builds, and it varies with the mix of parts it gets.
Example: a run costs €500 and holds parts that fill 10% of its volume. If the build is only 5% full, the same €500 is spread over half as much part volume, doubling the cost per cm³. The figures are an example.
Common confusions
Packing density belongs to 3D builds. In sheet cutting the same idea in two dimensions is nesting and sheet utilisation. And a denser build is not always better: packing too tightly can cause heat build-up and distortion. Read how SLS pricing and nesting work.
Go deeper: SLS pricing: build share, packing density, refresh and cool-down