3D Printing Design Guide
Everything you need to know to design parts that print perfectly. File formats, design rules, and material selection tips from our Charlotte team.
File Format Guide
We accept several file formats, each with different advantages. Here's when to use each one.
STL (Stereolithography)
Most Common
The standard format for 3D printing. Represents your model as a mesh of triangles. Nearly every CAD program can export STL. Works for all printing methods.
Best for: Most projects. Simple to use, universally supported.
Limitation: No color or material data. Loses parametric design information.
STEP (Standard for the Exchange of Product Data)
Recommended for Engineering
A CAD-native format that preserves exact geometry, not just a mesh approximation. Gives us more information to optimize your print — especially for parts with curves, fillets, and tight tolerances.
Best for: Engineering parts, tight tolerance features, complex geometries.
Limitation: Larger file sizes. Not all consumer CAD tools export STEP.
OBJ (Wavefront Object)
For Visual Models
Similar to STL but can include color and texture data. Common in 3D scanning and artistic modeling workflows.
Best for: Models from 3D scanners, artistic projects, multi-color prints.
Limitation: Color data only useful for multi-material printers.
3MF (3D Manufacturing Format)
Modern Standard
The newest format, designed specifically for 3D printing. Includes mesh, color, material, and print settings in a single compressed file. Becoming the new standard.
Best for: Projects where you want to specify print settings, multi-material builds.
Limitation: Not yet supported by all CAD programs.
Design Tips for 3D Printing
Follow these guidelines to get the best results from your 3D prints. These rules apply to FDM (fused deposition modeling), which is our primary printing technology.
Wall Thickness
Minimum wall thickness of 1.2mm for structural walls, 0.8mm for thin features. For functional parts under stress, use 2mm+ walls. Our nozzle diameter is 0.4mm, so wall thickness should be a multiple of 0.4mm for best results (1.2mm = 3 perimeters, 1.6mm = 4 perimeters).
Overhangs & Support Structures
FDM prints layer by layer from the bottom up. Overhangs up to 45° from vertical print well without support. Steeper overhangs need support material, which leaves a rougher surface where it contacts the part. Design with self-supporting angles where possible — it improves surface finish and reduces cost.
Tolerances & Fit
Standard FDM tolerance is ±0.2mm. For parts that need to fit together, add 0.2-0.3mm clearance per side. Press fits need 0.05-0.1mm interference. For critical fits, we recommend ordering test pieces first. Hole diameters tend to print slightly undersized — design them 0.2mm larger than nominal.
Bridging
Horizontal spans (bridges) up to 10-15mm print well without support on most materials. Longer bridges may sag. If your design requires a longer bridge, consider adding a chamfer underneath or splitting the part to avoid it.
Orientation Matters
3D-printed parts are strongest along the X and Y axes (within a layer) and weakest along the Z axis (between layers). Orient your part so that loads are applied within layers, not pulling layers apart. We optimize build orientation for each project, but it helps to design with this in mind.
Infill & Strength
Parts don't need to be 100% solid. Standard infill of 20-30% is sufficient for most prototypes. Functional parts typically use 50-80% infill. Only load-bearing or impact-resistant parts need 100% infill. Higher infill = more material, longer print time, and higher cost.
Material Selection Flowchart
Not sure which material to choose? Follow this decision guide, or read our detailed materials comparison.
"Is this a visual prototype or presentation model?"
Yes → PLA. Best surface finish, widest color range, lowest cost.
"Does it need to function in the real world?"
Yes → PETG. Tough, chemical-resistant, good heat resistance. Our most popular functional material.
"Will it be outdoors or in a hot environment (80°C+)?"
Outdoor → ASA (UV-stable). Indoor heat → ABS.
"Does it need to survive heavy mechanical stress?"
Yes → Nylon. Highest strength-to-weight ratio, excellent wear resistance.
"Does it need to flex, compress, or seal?"
Yes → TPU. Rubber-like flexibility, excellent for gaskets, bumpers, and grips.
Common Design Questions
What is the minimum wall thickness for 3D printing?
Can I print threads and snap fits?
What is the maximum part size you can print?
How do I choose between FDM and resin printing?
Should I design my own supports?
Ready to print?
Upload your files and we'll review your design for free. Our Charlotte team provides a detailed quote with material recommendations within one business day.