Material pixel-based process planning for layered manufacturing of heterogeneous objects

Layered manufacturing (LM) is emerging as a feasible technology that enables the fabrication of three dimensional heterogeneous objects such as multi-materials or functionally graded materials (FGMs). In this paper, we present a new material pixel-based processing planning method that takes into account not only the geometry, but also material variation along the build direction. The continuous material distribution on each 2D slice is first approximated by a set of material pixels. Iso-material regions for tool path planning are then computed by applying marching square algorithm to these material pixels. Next, the layer thickness at the current z-height is adaptively determined by calculating both the geometry-dependent and the material-dependent layer thicknesses. Once the slicing is done by repeating the previous steps (calculation of material pixels, iso-material regions, and layer thickness) for each slice, extra contours serving as support structures are added to each slice to obtain a complete LM model. We first introduce the representation scheme for heterogeneous objects and the new process planning method is then described in detail. Examples are shown to illustrate the overall procedure.