SFP Planner

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Cells fully inside the STL are planned as in a box. Cells across its surface are packed sand against the mould wall (or gaps), so they need no mould and keep every labyrinth open for washout.

Fit: the unit size nearest yours at which the box is a whole number of lattices, walls through cell centres. For the truncated octahedron and the rhombic dodecahedron every cut unit is then a half, a quarter or an eighth.

Whole units: nothing is cut by the floor or the top. The box top is the pour line: top units stand up through it and the cast stops there. Sand bed: the bottom units stand whole on the real floor and dry sand is poured round them up to the bed line (the cast's flat underside). Cast to the floor: no bed; the cast runs down between the bottom units to the real floor.

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Units cut by the box walls are exact trimmed edge units; each distinct shape is a mould. The units the surface crosses are left out: those gaps are the cast.

Dowels stand upright, half in each of two units, because every unit is lowered straight down. Every face: a hole on each face that can take one, so a mould serves the most units; the holes that face the cast are plugged before the pour. Joined only: holes only where two units meet, so nothing to plug but more moulds. Pins in the mould: the holes are planned but not cut into the mould STLs; each mould gets numbered pin bores, and each unit is cast with the pins its row lists pushed in, like sliders in an injection mould. The fewest moulds and nothing to plug. Fit is the hole's extra diameter; wall is the least material left round a hole.

Marks: each mould's name, debossed in the master: on a box face when one is big enough (a box face never meets the cast), otherwise on the face that meets the cast least often.

Instructions: a printable page per layer, with a picture, a numbered top-view map, the parts to place and the support flags.