3D Slot-Together Christmas Ornaments - Star, Tree, Bauble, Bell, Print Flat, No Glue

Flat to print, 3D on the tree. Each ornament is two flat halves that slide into each other at 90° and click in place: a star, a tree, a bauble and a bell. They print in minutes, need no supports and no glue, and look great in two colours, for example a gold half and a red half.

What you get. Four ornaments, each made of half A (slot from the top) and half B (slot from the bottom, with the hanging loop). Built, they are 79 to 82 mm tall including the loop and 61 to 76 mm wide: star 76 × 79 mm, tree 61 × 82 mm, bauble 69 × 82 mm, bell 64 × 79 mm. The cut-outs catch the light of the tree lights. The loop has a 4.4 mm hole for a thread or a hook.

Why it prints well. Flat print, 2.4 mm thick, no supports. The slot has 0.2 mm clearance per side, a 0.4 mm lead-in at the entry and a 0.4 mm chamfer on the first layer against elephant foot. The tips next to the slots are trimmed, so there are no thin slivers. Two small ribs in the slot of half B click into a window in half A, so A does not slide off when the ornament hangs by the loop on B.

Colours. Each half is a separate file, so you can mix them: gold and red, green and gold, silver and blue, white and red. The pictures show some combinations. One colour works too.

IN THE FILES

- star-A-gold, star-B-gold: star halves (76.1 × 68–79 mm, 2.4 mm thick)

- tree-A-green, tree-B-green: tree halves (60.8 × 71–82 mm)

- bauble-A-red, bauble-B-red: bauble halves (68.8 × 71–82 mm)

- bell-A-gold, bell-B-gold: bell halves (64.0 × 69–79 mm)

- slot_3d_ornaments.scad: the parametric source. You can change the size (60 to 100 mm), the plate thickness and the slot fit.

PRINT SETTINGS: PLA, 0.20 mm layers, 3 walls, 100 % infill (the parts are 2.4 mm thick), no supports, flat on the bed. All 8 halves fit one 250 mm plate, or print in two batches of 4 halves on a small bed (two ornaments per batch). Silk gold, red and green PLA look festive.

ASSEMBLY: Hold half B with the loop up. Slide half A from below into the slot of B, crossing the halves at 90°, until the two ribs in the slot snap into the window in A. Hang the ornament by the loop on B.

Honest notes:

- The hanging loop on the tree is the thinnest spot, about 1 mm wide where it meets the tip. It is fine for hanging, but do not bend it sideways.

- The images are 3D renders made from the same files you print. This set has not been test-printed yet.

- What we checked numerically on the exported STL files: every half is a closed single solid; fully assembled, the halves of all four ornaments do not overlap; moving A down by 1 mm from the assembled position runs into the ribs of B, so A is held when the ornament hangs by B; upwards A rests against the end of the slot in B; nothing is thinner than 0.8 mm.

- The ribs press 0.1 mm into A, so how firm the click is depends on your printer. If it is too tight, sand the ribs lightly; if it is loose, a drop of glue is the fallback.

- The design is original: no licensed characters, no brands.

SLICED (Bambu Lab P2S, 0.20 mm, PLA, 3MF included):

- gold: 21.0 g, about 36 min

- green: 8.7 g, about 17 min

- red: 16.2 g, about 26 min