Castle keep box — a fortified keep that opens at the wall-walk

A fortified keep, 112.2 × 112.2 × 120.5 mm, that opens at the wall-walk. Lift the battlements, the four corner drums and their tiled conical roofs off in one piece, and what is left is a box with a 70 × 70 × 64 mm cavity.

Six STLs, two prints, and nothing to assemble — no screws, no magnets, no glue, no elastic, no bearings. The colours are coordinate-locked solids the slicer prints as one object, and the lid simply lifts off.

70 × 70 × 64 mm is a fistful of dice, a sleeved deck, keys and coins by the door, a watch, or a gift you would rather not wrap.

The lid rests — it does not latch. The tongue locates it precisely and it sits flush without rocking, but nothing grips it: tilt the keep and the lid comes off. This is a box that lives on a table or a shelf, not one to carry in a bag. If you need it to travel, glue a pair of Ø5 × 3 mm magnets into the tongue and the groove, or pack it lid-up.

Materials

• Filament: PLA, ≈183 g for both prints at 0.2 mm / 3 walls / 15 % infill — 102 g for the base, 80 g for the lid, under 3 g for every accent combined. Four colours: stone grey, tile red, dark brown, gold. Single-filament builders use ≈150 g.

• Non-printed parts: none. No screws, magnets, glue, elastic or bearings. Every locating feature is printed.

• Tools: none. A deburring blade is handy for the tongue if the lid ends up snug, nothing more.

The six parts

Step 1 — slice print A, the base

1. Import castle_base_stone.stl, castle_base_dark.stl and castle_base_gold.stl together.

2. Bambu asks "load as a single object with multiple parts?" — answer Yes. They arrive coordinate-locked; do not move them relative to each other.

3. Assign a filament per part: stone grey, dark brown, gold.

Never merge these into one file and use "Split to Parts." It divides by connected component and ignores solid names — castle_base_dark.stl is 35 separate shells (34 arrow loops and the gate), so you would get 35 parts to colour by hand instead of 3.

Step 2 — slice print B, the lid

Same again with castle_lid_stone.stl, castle_lid_roof.stl, castle_lid_gold.stl → stone grey, tile red, gold.

The colour boundaries here are touching faces, not overlaps: each cone sits on the flat top of its eave, 0.8 mm inside the lip, so a stone rim shows all round under the red.

Step 3 — one colour, if you prefer

Print just castle_base_stone.stl and castle_lid_stone.stl and skip the rest. Every accent is a pocket that its plug fills from behind, so without the plugs you still get the whole design as crisp engraving: 1.8 mm deep arrow loops, a 3.4 mm gate passage, a recessed escutcheon. ≈150 g sliced for the pair.

Step 4 — print

Do not rotate either half. The base stands on its battered plinth; the lid's flat deck underside is already its lowest face, so it lands on the bed with the roofs pointing up. The cones are 32° off vertical and self-support, and every tile course is cut into the cone rather than stacked on it.

• 0.2 mm layers, 1.2 mm walls or more. The thinnest stone anywhere is 1.8 mm (behind an arrow loop); the curtain is 3.6 mm.

• Two lid features bridge, both deliberately narrow: the 1.0 mm seam collar step 1 mm above the bed, and the 2.8 mm tongue-groove ceiling 4.2 mm above it. Neither needs support.

• Masonry is cut, never added, and every bed joint lands on a vertical face, so no course is a stacked ridge waiting to delaminate.

Step 5 — assemble

Drop the lid on. The base's tongue rises 4 mm above the seam and enters the lid's groove with 0.2 mm clearance per side — it locates the upper works with no push-fit at all. The joint sits at the bottom of a 2 mm recessed shadow line, so it reads as a masonry drip course rather than a print seam.

If the lid rocks, deburr the elephant's foot on the tongue rather than sanding the groove: the groove's ceiling is a bridge and is the softer of the two.

It is a friction-free fit by design, so remember it holds by gravity alone — see the warning above before you use it as a travelling case.

The .scad source is included if you want a different size, a plain roof or a deeper cavity.