Converting 3MF to STL for 3D Printing: A Complete Guide

The STL file format has long been the standard for 3D printing. However, a newer format called 3MF aims to improve on STL’s limitations. If you need to convert 3MF files to STL, this guide will walk through everything you need to know.

What is a 3MF File?

3MF stands for 3D Manufacturing Format. It is an XML-based file type developed by Microsoft and other companies to be an enhanced standard for 3D printing and CAD applications.

Some key features of 3MF include:

• Full color and texture support – STL files are single color only.
• Multiple materials/colors within one model.
• Non-mesh objects like curves and solids.
• Hierarchical object structure instead of a single mesh.
• Smaller file size due to XML compression.
• Encryption and digital rights support.
• Extensibility for future features.

In summary, 3MF allows much greater complexity and design flexibility compared to basic STL files. But it’s not yet as widely adopted across 3D printing software.

Why Convert from 3MF to STL?

If 3MF is superior, why would you need to convert to the older STL format? There are a few reasons:

1. Software Compatibility – Many slicing softwares like Cura and Simplify3D still only support STL files for importing and processing. So 3MF models may need conversion to be printable.

2. Online Printing Services – Most consumer printing services such as Shapeways and Sculpteo ask for STL files to place orders. They may not accept other formats.

3. Full Color Limitations – While 3MF supports color, most home FDM printers can still only print single color models. Converting to STL strips away unnecessary color data.

4. File Size – STL files tend to be smaller than 3MF for basic models. This makes them easier to transfer and store, especially if color data isn’t needed.

For these reasons, converting 3MF to STL remains common practice for preparing prints until 3MF sees wider adoption.

How to Convert 3MF to STL

Several methods exist for converting 3MF files to STL:

Online File Converters

Many free online tools will convert between 3MF and STL:

• Online-Convert – Supports drag-and-drop 3MF to STL conversion up to 50MB. Also optionally optimizes STL after conversion.
• FileZigZag – Converts 3MF to STL and vice versa. 50MB limit for free users.
• CloudConvert – Converts hundreds of file formats including 3MF and STL. Free tier has daily limits.
• FileConverterOnline – Supports 3MF to STL conversion with 50MB file size limits.

The advantage of these tools is fast, automated conversion without downloading any software. But file size limits may block very large 3MF sources.

Mesh Editing Apps

Popular mesh processors like Meshmixer, Blender, and MeshLab all support importing and exporting both 3MF and STL file types.

The basic workflow is:

1. Import your 3MF file.
2. Optionally edit, repair, or modify the 3D model.
3. Export out as an STL file.

This works for simple format conversion needs. But also allows performing model corrections and improvements before export if needed.

Slicing Software

Many 3D printer slicing apps can open 3MF files, then export STL versions. Common examples include:

• Cura
• IdeaMaker
• Simplify3D
• PrusaSlicer
• Slic3r

The process is:

1. Open your 3MF file in the slicer.
2. Select “Export as STL” or similar option.
3. Save the output STL file.

This leverages tools designed specifically for 3D printing. The downside is slicers focus on printing-related features rather than in-depth modeling tools.

CAD Software

Full CAD packages like Fusion 360, SolidWorks, Rhino, and FreeCAD support both importing 3MF and exporting STL. But they are overkill for only file conversion.

The complex interfaces make simple format conversion more frustrating than necessary. Use CAD software for designs needing modeling power rather than just conversion.

Scripts and Code

For developers, writing code to convert 3MF to STL is possible using XML and 3D parsing libraries for Python, JavaScript, C#, and more.

But custom coding is only practical for batch processing many automated conversions rather than one-offs. This approach requires comfort with programming.

Conversion Software

Dedicated file conversion utilities like polytrans and 3D_Tool offer GUIs tailored specifically for converting various 3D file formats.

They make the process seamless by just selecting the source 3MF and output STL filenames. Advanced options are also available for power users.

For one-off manual conversions, these specialized tools provide the best experience without learning complex modeling apps.

What Gets Lost Converting from 3MF to STL?

Since STL is a less advanced file format, some data will be lost or simplified when converting more complex 3MF files. Here’s what typically gets discarded or changed:

• Colors and textures – STL only supports a single color/material for the entire object. Any color variations defined in the 3MF are lost.
• Curved geometry – STLs can only represent shapes made up of triangles. Curved faces get approximated as many tiny triangles.
• Multiple objects/parts – The hierarchical “groups” of parts in 3MF combine into one giant mesh in STL.
• Animation/articulation – Any moving components defined in the original 3MF become static parts after conversion.
• Metadata – All metadata like units, author, and general properties are removed when saving to STL.
• Compression – STL files are typically 2-5x larger than compressed 3MF files for the same model geometry.

For basic single-color prints, an STL can retain the key physical shape at the cost of simplified data. But any color, animation, or rich data will not transfer over fully into STL.

Tips for Converting 3MF to STL

Follow these tips when converting 3MF files to STL for the best print results:

• If color isn’t needed, opt for monochrome STL output to reduce large files.
• Repair and simplify STL files after conversion if they have issues importing to your printer software.
• For multi-part assemblies, export each component as a separate STL to retain distinct objects.
• Try different conversion tools if your first try yields problems – quality varies.
• Print a test part before a long print to verify dimensions converted accurately.
• For poor quality STLs, re-export higher resolution or use mesh healing tools.
• If file size balloons too much, run STL files through an optimizer before printing.
• Resize overly large STLs within your slicer software for your particular printer.

With some experimenting, you can fine tune your conversion process to get clean STLs that print accurately.

Future of 3D Printing File Formats

While STL has dominated 3D printing historically, the limitations are clear when converting from more advanced formats like 3MF. New file standards aim to strike a balance.

AMF – Additive Manufacturing File format developed by ASTM International seeks to integrate the benefits of both 3MF and STL.

GLTF – The Graphics Language Transmission Format spearheaded by the Khronos group covers both 3D assets and full scenes/environments.

USDZ – Apple and Pixar’s take on 3D scenes as a package format supporting AR/VR and 3D printing.

Over time, broader adoption of these or other newer file types could displace STL and make conversions unnecessary. But for now, expect STL to remain the baseline format for affordable home 3D printing.

Conclusion

As a modern replacement for STL, the 3MF format enables much more complexity and functionality. But converting 3MF to STL remains necessary for software compatibility and online printing until wider adoption occurs.

Thankfully there are many conversion options from online tools to desktop apps. With some experimenting, you can find an optimal converter that retains the most detail and reliability.

While newer formats will continue evolving 3D printing, STL endures as the tried-and-true standard. Learn how to leverage both formats for an ideal workflow.

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