Sweetheart Hamster

A palm-sized jewelry box shaped like a chubby chibi hamster cradling a heart. It prints in one piece — no assembly — and folds open along a living-hinge spine like a locket. Closed, it's a cute hamster hugging a heart; split down the middle, the heart parts between the two halves, and a heart-shaped pocket inside nestles a ring. A giftable little keepsake for a proposal, an anniversary, or a Valentine.

What you get

One print-in-place part — the two hamster halves come off the bed joined by a thin living-hinge web along the dorsal seam, so it prints already assembled and folds shut.

• sweetheart-hamster — the hamster locket, ~53 × 61 × 60 mm assembled; ring nest ~22 mm across. Prints flat/open, ~126 mm wide on the bed.
• sweetheart-hamster-coupon — a smaller "print this first" copy to dial in the hinge flex and seam fit before committing to the full print.

Print settings

• Material: PETG or PP recommended — the living-hinge spine flexes for many open/close cycles. PLA works but is brittle at the hinge: treat the halves as separable (the thin web is a tear-line) rather than a repeatedly-folding lid.
• Layer height: 0.2 mm.
• Infill: 10–15 % is plenty (decorative box). Default-density slicing runs ~36 g / ~2.5 h; low infill cuts both substantially.
• Supports: none for the body — it prints flat/open, cut-faces down, domes self-supporting. ~3 % of the surface (the ring-nest ceiling and a couple of underside curves) is technically overhang. Keep auto-supports OFF. The nest prints as a heart-shaped arch opening at the bed; only its small crown — where the lobes curl over — is a real overhang, and a sagging crown droops into the pocket and eats the headroom a ring's stone needs. If the fit matters, paint a support enforcer on the nest crown only — a global "enable supports" drops pillars into the 0.5 mm parting gap (re-welding the seam this design is built to keep open) and scabs the cheeks and the pocket the ring seats against — and no brim either: a brim laid across the two flat islands bridges the parting gap and welds the seam at layer 1, which no elephant-foot compensation undoes on the reprint (auto-brim rarely fires at this footprint, but switch it off to be sure). Note that PETG (the recommended material) sags on that crown more than PLA does, so a truly stone-flush ceiling is really a PLA job — at the cost of the hinge (see Material).
• Seam: set the seam to Back (or use a scarf seam) — the slicer's default aligned seam stacks a vertical ridge down the show dome (a scar on the cheek of a gift print); moving it to the back keeps the face clean.
• Orientation: as modelled — the default render is the print pose (both halves flat, cut-face-down, hinge in the middle). Don't re-orient.
• First layer & plate: the cut faces print as the first layer — and that's the heart-reveal surface the whole gift points at. On textured PEI it comes out matte (expected — it reads like a flocked jewelry-box liner); expect a faint elephant-foot flare around the seam silhouette (nose, brow, ears, tail), which 0.2 mm elephant-foot compensation cleans up. Enable it — on this part it isn't just cosmetic: a heavy flare can bridge the 0.5 mm parting gap, so if the halves won't part even after flexing (see Assembly & use), the flare is the cause, not part_gap. Don't chase a glossy reveal with PETG on smooth PEI without a glue-stick release — it welds to the plate and you'll chip the reveal face lifting the print. Textured PEI is the safe choice.
• Print this first: the coupon, to dial in the hinge flex and seam clearance for your printer before committing to the full print.

Parameters

The handful worth tuning; all parameters are at the top of sweetheart-hamster.scad, grouped in Customizer sections.

Two worth setting for your ring and printer:

• nest_w — size it to the ring. Set it to the band's outer Ø + ~0.5 mm so the ring seats snugly; the 22 mm default suits roughly a US-7 band, and a band looser than the pocket will roll, shift, and rattle in the closed box.
• web_t and layer height. At the pinned 0.2 mm layers, web_t = 0.7 mm is 3.5 layers, so a slicer rounds it to 0.6 or 0.8 mm (±14 % flexure stiffness). Pick 0.6 or 0.8 for a predictable hinge, and A/B it on the coupon.

Override on the command line, e.g. -D 'S=1.5' for a smaller hamster or -D 'fold=90' to preview it closed.

Assembly & use

Nothing to assemble — it prints as one piece, splayed flat and open. The hinge runs along the top of the spine (dorsal), so in the print/open pose both heart scoops face down. To load it: turn the open piece scoops-up, set the ring into a scoop, then fold the two halves shut about the spine. The reveal runs in reverse — unfolding parts the halves and the ring lifts free of the scoop as they open, so open it over a hand or the table, not in mid-air. The closed hamster carries a small tab along the top of the spine between the ears — that's the living hinge, printed flat and folded up, and it stays on the finished piece. A light tack across the seam at the very first layer is normal elephant foot — flex the halves gently to break it before first use (a non-event in PETG; in PLA expect a faint whitened crack along the seam). If the halves fit tight and won't part after flexing, that's almost always first-layer flare, not the gap — turn on 0.2 mm elephant-foot compensation and reprint — coupon first; only a seam that still binds after that wants part_gap raised, +0.1 mm on the coupon first. And when you give it, hand it over with "it folds like a locket — the spine's the hinge" (or fold it open once in front of them): a first-timer's instinct is to pull the halves apart sideways, which strains the thin hinge web — worst in PLA — at the one moment you can't redo.

The box has no catch — it holds shut by friction alone — so carry the print flat and empty, and load the ring at the table just before folding it shut: not in a pocket, and not pre-loaded in a bag, where an open box jostled in transit lets the ring hop its scoop (and a ring looser than the pocket rattles in the closed box — a tell). Print in PETG if you want the hinge to fold repeatedly.