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How to Combine STL Files in Blender?

Published in Blender STL Combining 5 mins read

Combining STL files in Blender typically involves importing the individual models, positioning them as desired, and then using a Boolean Modifier to merge them into a single mesh object.

Here's a step-by-step guide based on the common workflow:

Step-by-Step Guide to Combining STL Files

Merging multiple STL models into one in Blender is a straightforward process using the powerful Boolean Modifier. Follow these steps for a clean combination:

  1. Step 1: Import Your STL Files

    • Begin by importing each individual STL file into your Blender scene.
    • Go to File > Import > STL (.stl).
    • Navigate to where your STL files are saved, select them (you can select multiple by holding Shift or Ctrl), and click Import STL.
    • See detailed instructions here: This initial import brings all your separate pieces into the workspace.

  2. Step 2: Move, Scale, and Rotate Objects into Position

    • Once imported, your objects might be scattered or overlapping incorrectly.
    • Use the Transform tools (G for Grab/Move, S for Scale, R for Rotate) to position each object relative to the others exactly how you want them to be combined.
    • Ensure the surfaces you want to merge are overlapping appropriately.

  3. Step 3: Select the Main Object and Add a Boolean Modifier

    • Decide which object will be the "base" or "target" object – this is the one that will receive the modifier. Select this object.
    • Go to the Properties Panel (usually on the right side of the screen) and click on the Modifier Properties tab (it looks like a wrench).
    • Click Add Modifier and select Boolean from the list under "Generate" or "Modify".
    • In the Boolean modifier settings, set the Operation to "Union". This operation is used to combine meshes, merging overlapping volumes.
    • Under Operand, select the other object you want to combine with your base object. You can do this by clicking the eyedropper icon and clicking on the other object in the 3D Viewport, or by selecting it from the dropdown list.

  4. Step 4: Delete the Object You Combined to Your Main Shape

    • After setting up the Boolean modifier and selecting the second object, you'll notice the base object now includes the geometry of the second object in the viewport (though the change is only visible in the preview until you apply the modifier).
    • To finalize the combination and remove the source object, first ensure the Boolean modifier is applied. Click the dropdown arrow on the Boolean modifier and select Apply. Note: Applying modifiers is permanent.
    • Now that the Boolean operation is applied to the base object, the original second object is no longer needed for the combined shape. Select this second object and delete it (X key, then Delete).
    • Pro-tip: If you have multiple objects to combine, you can add multiple Boolean modifiers (one for each object to union) to your base object and apply them sequentially, or combine them pairwise.

  5. Step 5: Go into Edit Mode to Check the Mesh

    • Boolean operations, while powerful, can sometimes create messy geometry (non-manifold edges, extra vertices, etc.).
    • Select your newly combined object and enter Edit Mode (Tab key).
    • Inspect the areas where the objects were joined. Look for unexpected edges, vertices, or faces.
    • You may need to use mesh cleaning tools like Merge Vertices (Alt+M) or the Clean Up menu (Mesh > Clean Up) to fix issues and ensure a clean, printable mesh.

  6. Step 5: Export the Modified STL File

    • Once you are satisfied with the combined mesh and have cleaned it up in Edit Mode, you are ready to export.
    • Select the combined object.
    • Go to File > Export > STL (.stl).
    • In the export settings, make sure Selection Only is checked (this ensures only the selected object is exported).
    • Choose a file name and location, and click Export STL.

Summary Table

Step Action in Blender Purpose
1. Import File > Import > STL Load models into the scene
2. Position Use Grab (G), Scale (S), Rotate (R) Arrange objects for desired combination
3. Add Boolean Modifier Select base object, add Modifier > Boolean, set Operation to "Union", select object to combine Prepare to merge shapes volumetrically
4. Apply & Delete Apply Boolean Modifier, Select & Delete combined object Finalize the merge and remove source object
5. Check Mesh Enter Edit Mode (Tab), use Clean Up tools Ensure geometry is clean and error-free
6. Export Select combined object, File > Export > STL, check Selection Only Save the final combined model as an STL file

Following these steps allows you to effectively combine multiple STL models into a single, unified object in Blender, suitable for 3D printing or further modeling.

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