When it comes to preparing your models for additive manufacturing, two file formats often take center stage: STL (Standard Tessellation Language or STereoLithography format) and 3MF (3D Manufacturing Format). 

Both formats are well-regarded and fully supported by PTC’s Onshape, but they cater to different needs and come with unique advantages and challenges. 

Let’s explore the benefits of each format, their significance in modern additive manufacturing, and how Onshape seamlessly facilitates both the exporting and importing of STL and 3MF files. We’ll also share some expert tips to streamline your workflow and enhance your experience.

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STL vs. 3MF Files

What are STL Files?

STL has been the backbone of 3D printing since its creation in the late 1980s by 3D Systems, which jumpstarted the 3D printing market with its innovative stereolithography and resin-based printers. STL is still one of the most widely used formats to share data for 3D printing, and other industries have picked up on it for several reasons. 

STL files are:

  • Universally Accepted: STL files are supported by virtually every slicer (the software that generates the instructions for a 3D printer), ensuring compatibility regardless of your hardware or software.

  • Lightweight for Simple Models: STL files remain an efficient choice for straightforward designs without intricate details or metadata.

  • Easy to Generate: Onshape’s export tools make it simple to create STL files with adjustable resolution, letting you balance file size and model fidelity.

Exporting an STL File

To export an STL file from Onshape, follow these steps:

  1. Open the Part Studio or Assembly: Navigate to the tab containing the 3D model you want to export as an STL file.

  2. Right-Click the Part: Locate the specific part or assembly in the Parts list or Graphics area, then right-click on it.

  3. Choose “Export”: From the right-click menu, select Export.

  4. Set the Export Options:

    • Format: Choose STL from the dropdown menu.

    • Resolution: Select the desired resolution (Custom, Fine, Medium, or Coarse). Fine resolution is recommended for detailed models.

    • Units: Specify the units for the STL file (e.g., millimeters or inches).

    • Options: Choose whether to export in Binary or ASCII format. (Binary is more common for 3D printing.)

    • Include Options: Check if you want to include only visible parts, hidden parts, or both.

  5. Name the File: Enter a name for your STL file in the Filename field.

  6. Select Destination: Download the file to your computer or store it in a linked cloud service.

  7. Click “Export”: The STL file will be prepared and downloaded to your specified location.

If you’re exporting multiple parts as a single STL file:

  • Create an assembly of the parts first.
  • Or multi-select the parts from the Parts list in a Part Studio and follow the export steps above.

When to Use STL Files

STL is ideal for quick prototyping, simple single-material prints, and legacy workflows where compatibility is key. Export file sizes can grow fast, if working with complex parts with fine export resolution, causing performance slowdowns in downstream software such as slicers.

What are 3MF Files?

3MF was developed to address STL’s shortcomings, making it a modern and robust format for additive manufacturing. 3MF files have:

  • Rich Metadata: 3MF files store material properties, colors, textures, and even slicing settings, eliminating the need for multiple files or manual adjustments.

  • Smaller File Sizes: With built-in compression, 3MF files are more efficient to store and transfer compared to STL.

Exporting a 3MF File

Follow the same process as STL files. 

When to Use 3MF Files

3MF shines in advanced workflows, such as multi-material or multicolor printing, and when precision and efficiency are critical. For example, I personally use a BambuLab X1 Carbon for my projects at the home office, which accepts 3MF files exported from Onshape. I find it tremendously handy to export from Onshape as 3MF and use that same 3MF as the project file containing all the settings for the print job. I can re-import the 3MF file into Onshape to organize my project in the cloud or share it with another user who wants to use the same printer profile settings, material choices, etc.

Tech Tip: Automate Filename Standards to Exported Files

Onshape allows users to automatically apply file naming standards to exported STL and 3MF files. This ensures consistency across teams and reduces manual effort. For example, a concatenated file name such as 100-0001-FORM4-01-CLEAR-A.stl could be applied where:

  • 100-0001 is the part number,

  • FORM4 is the printer name,

  • 01 is the printer’s designation,

  • CLEAR is the material choice, and

  • A is the revision. This level of control ensures that all company users can maintain consistent naming conventions when exporting files.

These rules can be set up in your personal preferences or company settings for every user.

  1. Add custom export rules based on object type, category, and file format to automatically generate metadata-driven file names when exporting objects.

  2. Select a Scope that is the type of part for which this export rule will apply: Part, Assembly, Drawing, or Part Studio. In this case, a Part.

  3. Optionally, select a previously defined Category (see Tech Tip here). If a Category is selected, the export rule applies to all applicable objects within that category. For example, I have a Category for Additive Manufacturing, and then if I select STL, I get the name formatted for my STL-based printer. If I select 3MF, I get the filename rule set for that file type.

Onshape Supports STL, 3MF Files

Both STL and 3MF have their place in additive manufacturing, and Onshape’s support for both formats makes it an excellent platform for preparing and importing 3D models. While STL’s simplicity and universality make it a reliable choice for straightforward workflows, 3MF’s advanced features and efficiency pave the way for the future of 3D printing.

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