Design for 3D Printing
Layer Orientation, Tolerances & Print Design
Design principles that make 3D printed automotive parts strong, accurate, and printable. Learn to think in layers.
Core Design Principles
Orient for Strength
Parts are weakest between layers. Orient so load direction is parallel to layers, not perpendicular.
Minimize Supports
Design with self-supporting angles (≤45°). Add chamfers instead of overhangs where possible.
Add Fillets & Radii
Sharp internal corners concentrate stress. Add 1-2mm fillets to prevent crack initiation.
Design for Tolerances
FDM has inherent variance. Design total gaps between mating parts: 0.1mm for nesting, 0.2mm tight, 0.3mm slide, 0.4mm clearance.
Print Orientation by Part Type
Clips & Snaps
Flex stress is handled by layers, not layer bonds
Flat Brackets
Maximum bed adhesion, strongest in plane
Bezels & Covers
Visible surface gets best finish from top layers
Tubes & Ducts
Circular cross-section is self-supporting
Complex Shapes
Support removal damages surfaces. Design around it.
Tolerance Guidelines
FDM printing has inherent dimensional variance. These are total gaps between mating parts (not per-part offsets).
Slip/Nesting Fit
0.1mm total gap
Parts nest together with light frictionTight Fit
0.2mm total gap
Super clean fit, stays in placeSmooth Slide
0.3mm total gap
Parts slide freely with light resistanceOpen Slide/Clearance
0.4mm total gap
Fully free movement, no resistancePress Fit (inserts)
-0.1 to -0.2mm diameter
For heat-set inserts, bearingsThreads
Use heat-set inserts
Printed threads are weak. Use inserts.Strength Best Practices
Add ribs to large flat surfaces to prevent warping and add stiffness
Use gussets at 90° joints for strength without bulk
Avoid long thin features that flex - add cross-bracing
Hollow parts with thick walls are stronger than solid thin parts
Add draft angles (1-2°) to vertical walls for easier demolding from bed
Design Pitfalls to Avoid
Sharp internal corners (stress concentrators)
Unsupported horizontal surfaces (need supports)
Very thin walls (<1.2mm for strength)
Long bridges (>50mm without support)
Features smaller than nozzle diameter
Printed threads (use heat-set inserts instead)
CAD Software Options
Fusion 360
Precise mechanical parts, parametric design
FreeCAD
Basic parametric modeling, community support
Blender
Organic shapes, modifying STLs, sculpting
TinkerCAD
Beginners, simple parts, quick modifications
SolidWorks
Professional engineering, assemblies
OnShape
Collaboration, browser-based professional CAD
Frequently Asked Questions
How do I know which direction to orient my part?
Think about where stress will be applied. Layers are strong in shear (sliding past each other) but weak in tension (pulling apart). Orient so the load pushes layers together, not apart.
Should I design for 0.4mm or 0.6mm nozzle?
0.4mm is standard and most versatile. Design minimum wall thicknesses as multiples of 0.4mm (0.8, 1.2, 1.6mm etc). For stronger parts, 0.6mm nozzle with thicker walls works well.
How do I make parts that screw together?
Don't print threads directly - they're weak and inaccurate. Use heat-set brass inserts for machine screws, or design for self-tapping screws into plastic bosses.
Can I modify an existing STL file?
Yes, but it's tricky. Blender, Meshmixer, or 3D Builder can edit STLs. For precise changes, consider recreating in CAD. STLs don't retain design intent.
What wall thickness should I design for automotive parts?
Minimum 1.6mm (4 walls at 0.4mm) for functional parts. 2.4-3.2mm for high-stress areas. Thin walls print faster but flex and break.
Troubleshooting
Part breaks at a specific point every time
Stress concentration. Add a fillet at that corner, or thicken the section. Check layer orientation relative to the failure.
Holes are too tight for bolts
Design 0.3-0.4mm total clearance for smooth slide. Or drill out after printing. First layer squish closes holes.
Part warps when removed from bed
Internal stress from cooling. Add ribs, use uniform wall thickness, let part cool slowly on bed.
Snap fit is too tight and cracks
Increase total gap to 0.2-0.3mm. Add stress-relief slots. Use PETG for more flex than ABS.
Ready to Design?
Upload your designs to the library or request a custom part from our design team.