Parts that snap together without glue
Printed parts hold without glue when snap-fit joints sit on the seams: the springy plastic clicks in and holds the connection itself. BunnySplit adds these joints automatically and sizes them for the material — clearance for shrinkage and deflection against the strain limit — so parts meet and do not crack on assembly. Glue becomes optional, not required.
Why it holds without glue
Snap-fit works on elastic deflection: as it clicks, the catch briefly flexes, clears an undercut and springs back, locking the joint. To make that work on an FDM part you have to hit two numbers at once — clearance (or it jams or rattles) and deflection (or the beam cracks). The engine computes both for the chosen plastic.
- Upload a model or a finished assembly of parts.
- Cut the model by color or by size — or mark the existing seams.
- The engine places joints on the seams and computes clearance and deflection per material.
- Download the 3MF, print the parts and snap them together — no glue.
The numbers the joint stands on
BunnySplit engine defaults, not vague advice:
- Clearance: releasable (reusable) clips get 0.2–0.5 mm per side, permanent press-fit 0.1–0.3 mm. By default the engine uses a 0.30 mm fit plus material shrinkage compensation (PLA 0.3%, PETG 0.5%, ABS 0.7%).
- Strain margin: clip deflection is designed to ≤50% of the material's limit. Strain limits: PLA ~4%, ABS ~6%, PETG ~7% — so brittle PLA is given less deflection while flexible PETG can hold a grippier catch.
- Beam geometry: the cantilever length-to-thickness ratio stays in the 5–10 range and the catch height is at least 0.4 mm (one nozzle extrusion width), or the clip either fails to engage or breaks.
Which joint to pick for which load by hand is covered in how to join printed parts; why PETG beats PLA for clips is in the wiki on material for snap-fit assembly.