How to Design Multi-Part Assemblies for 3D Printing
1. Why Split Into Multiple Parts?
Part exceeds maximum build size
Different sections need different materials or technologies
Easier printing (avoiding complex supports)
Easier post-processing or painting
Moving assemblies (hinges, sliders, gears)
2. Clearance Guidelines
For parts that need to fit together after printing:
Static joints (glued or press-fit):
FDM: 0.1–0.2mm clearance per side
SLA: 0.05–0.1mm per side
Industrial SLA: 0.05–mm per side
MJF: 0.15–0.25mm per side
Moving joints (hinges, sliders):
FDM: 0.3–0.5mm clearance per side
SLA: 0.2–0.3mm per side
Industrial SLA: 0.2–0.3mm per side
MJF: 0.3–0.4mm per side
3. Alignment Features
Always include alignment features so parts go together correctly:
Dowel pins and holes — Most reliable. Design pin 0.1mm smaller than hole.
Tongue and groove — Good for flat joints. Groove width = tongue width + clearance.
Keyed features — Asymmetric shapes that only fit one way. Prevents assembly errors.
Registration marks — Numbers or arrows on each piece for assembly sequence.
4. Bonding Methods
Cyanoacrylate (super glue) — Fast, strong, works on all materials
Epoxy — Strongest bond, gap-filling, longer work time
Solvent welding — ABS + acetone, creates a chemical bond
Mechanical fasteners — Screws, bolts, heat-set inserts for removable connections
Friction/press fit — Design interference fit with 0.0–0.1mm overlap
5. Print-in-Place Assemblies
MJF can print moving assemblies (hinges, ball joints, chains) in a single print because the powder supports the part during printing. Design with 0.4–0.6mm clearance between moving surfaces.
FDM and SLA generally cannot print-in-place due to support material between moving parts.
6. Tips
Always order a test assembly before committing to a production run
Provide assembly drawings or instructions with your order
Specify which dimensions are critical for fit
Send us your assembly files and we’ll review for printability.