How to Prepare Files for 3D Printing Service: STL Checklist

Proper STL file preparation for 3D printing is the difference between a perfect print and a failed one. Whether you are using Zbotic’s 3D printing service or any other provider, correctly prepared files save time, reduce costs, and ensure your parts come out exactly as designed. This checklist covers everything you need to verify before uploading your files.

Table of Contents

• Accepted File Formats
• STL Export Settings
• Wall Thickness Requirements
• Print Orientation
• Support Structures
• Common File Errors
• Final Pre-Upload Checklist
• Frequently Asked Questions
• Conclusion

Accepted File Formats

Most 3D printing services accept these file formats:

• STL (STereoLithography): The industry standard. Contains only geometry data without colour or material information. This is what most services prefer
• OBJ: Includes colour and texture data, useful for full-colour 3D printing
• 3MF: The modern replacement for STL, includes colour, material, and build information in a single file
• STEP/STP: Preferred for CNC machining, some services accept it for 3D printing as it preserves exact geometry

When in doubt, export as STL in binary format. Binary STL files are 5-10x smaller than ASCII STL files while containing identical information.

STL Export Settings

When exporting STL from your CAD software, these settings matter:

• Resolution/Deviation: Set to 0.01-0.05mm. Too coarse (0.5mm+) creates visible faceting on curved surfaces. Too fine (0.001mm) creates unnecessarily large files
• Angular tolerance: 5-15 degrees works well for most prints
• Units: Always export in millimetres. If your design software uses inches, convert before exporting or note it clearly
• Binary vs ASCII: Choose binary for smaller files. ASCII is human-readable but 5-10x larger

In Fusion 360, use File > Export > STL with “High” refinement. In SolidWorks, use Save As STL with deviation set to 0.01mm. In FreeCAD, use the Mesh workbench to export.

Wall Thickness Requirements

Minimum wall thickness depends on the printing technology and material:

For functional parts that need to withstand force, double the minimum wall thickness. For decorative prints, the minimum is usually sufficient.

Print Orientation

How your part is oriented on the build plate significantly affects strength, surface finish, and support requirements:

• Layer lines run perpendicular to the strongest direction. A bracket that needs to resist downward force should be printed upright so the layers stack in the direction of the force
• Minimise overhangs. Any surface angled more than 45 degrees from vertical needs support material, which leaves marks when removed
• Flat surfaces on the build plate. Orient the largest flat surface downward for best bed adhesion and dimensional accuracy
• Consider post-processing. If one side needs to be smooth, orient that surface facing upward (top surface is typically smoother than sides on FDM)

Support Structures

Most printing services generate supports automatically, but understanding them helps you design parts that need fewer supports:

• Design self-supporting angles: Surfaces up to 45 degrees from vertical print without supports on most FDM printers
• Use chamfers instead of overhangs: A 45-degree chamfer prints without support; a 90-degree shelf does not
• Bridge short gaps: FDM can bridge horizontal spans up to 10-15mm without sagging
• Add support blocker notes: If you know certain areas should not have supports (like internal cavities), communicate this to the service provider

Common File Errors

These are the most frequent file issues that delay 3D printing orders:

• Non-manifold geometry: Edges shared by more than two faces, or faces with zero thickness. Use the “Check Mesh” tool in your slicer to identify these
• Inverted normals: Faces pointing inward instead of outward, causing the slicer to think the inside is outside
• Zero-thickness walls: Surfaces that look like walls in CAD but have no actual thickness in the STL
• Intersecting bodies: Multiple objects overlapping without being merged into a single solid body
• Scale errors: Models designed in inches but exported as millimetres (or vice versa), resulting in parts 25x too small or too large

Use free tools like Meshmixer (Autodesk), Microsoft 3D Builder, or the NetFabb online repair service to fix common mesh errors before submitting your files.

Final Pre-Upload Checklist

Run through this checklist before sending your files:

• File format is STL binary (or as required by your service)
• Units are in millimetres
• Mesh has no errors (run mesh analysis in your slicer)
• All bodies are merged into a single solid (unless multi-part is intended)
• Wall thickness meets minimum requirements for your chosen material
• No internal voids that trap support material
• Drain holes added for hollow resin prints
• Scale verified — check a known dimension against the original design
• File size is reasonable (under 100 MB for most services)
• Part orientation noted if critical for strength or finish

Frequently Asked Questions

Should I include supports in my STL file?

No. Most services generate supports automatically using their optimised slicer profiles. Including supports in your model file can cause conflicts and wasted material.

What resolution should I export my STL at?

A deviation of 0.01-0.05mm is ideal for most 3D printing. Higher resolution does not improve print quality because the printer itself has a minimum resolution (typically 0.1mm layer height for FDM).

Can I send a Fusion 360 or SolidWorks file instead of STL?

Some services accept native CAD files, but STL is universally supported. Exporting as STL also protects your design IP since the original parametric data is not included.

How do I check my STL file for errors?

Import the STL into any free slicer (PrusaSlicer, Cura, or Bambu Studio) and it will automatically flag errors. Meshmixer and Microsoft 3D Builder can also analyse and repair mesh issues.

Conclusion

Proper STL file preparation ensures your 3D prints come out perfect on the first attempt. Follow this checklist, pay attention to wall thickness and orientation, and fix any mesh errors before uploading. These steps save both time and money, whether you are printing a single prototype or ordering in bulk.

Need 3D printing services or filament? Visit our 3D printing section for materials, tools, and accessories.