Blender Workflow for Cleaning CAD Meshes for ROS 2 / Gazebo

This guide explains how to fix common mesh problems when importing CAD models, for example from Onshape, into Blender before using them in ROS 2 and Gazebo.

Typical problems this workflow fixes:

• Missing faces in Gazebo
• Flipped normals
• Extremely large mesh sizes
• Broken CAD mesh geometry

The goal is to produce a clean visual mesh (.dae or .obj) and a simple collision mesh (.stl) for use in URDF.

1. Open the mesh in Blender

1. Start Blender.
2. Go to File -> Import.

3. Import your mesh file:

4. Collada (.dae)

5. STL (.stl)
6. OBJ (.obj)

If importing from CAD:

• OBJ is usually the most stable format.

2. Select the mesh object

Look at the Outliner in the top-right panel.

Select the object with the triangle icon. That means it is a mesh.

Example:

Collection
 └ robot_part

3. Enter Edit Mode

With the mesh selected, press:

Tab

Or use:

Object Mode -> Edit Mode

Now you should see vertices, edges, and faces.

4. Select all geometry

Press:

A

Everything should now be selected.

5. Remove duplicate vertices

CAD exports often contain duplicated vertices.

Press:

M

Then choose:

By Distance

Blender will merge overlapping vertices.

Example message:

Removed 12000 vertices

6. Fix face normals

Incorrect normals cause missing faces in Gazebo.

Press:

Shift + N

This recalculates all normals to point outward.

7. Check face orientation

Enable the overlay:

Viewport Overlays -> Face Orientation

Colors mean:

• Blue -> Correct orientation
• Red -> Flipped faces

Goal:

Outer surfaces should be BLUE

8. Flip incorrect faces if necessary

If some faces remain red:

1. Select those faces.
2. Press:

Alt + N

1. Choose:

Flip

9. Triangulate the mesh

Gazebo works best with triangular faces.

Press:

A
Ctrl + T

Now all faces are triangles.

10. Reduce mesh size

CAD models often contain millions of polygons.

1. Go to the Modifiers panel.
2. Click:

Add Modifier -> Decimate

Recommended settings:

Ratio: 0.2 - 0.4

Apply the modifier.

Example result:

1,200,000 faces -> 40,000 faces

11. Apply object transforms

Return to Object Mode:

Tab

Then press:

Ctrl + A

Choose:

Rotation & Scale

This prevents scaling issues in Gazebo.

12. Export the visual mesh

Export the cleaned mesh:

File -> Export -> Collada (.dae)

Recommended options:

• Apply Modifiers
• Selected Objects
• Triangulate

Example file:

robot_visual.dae

13. Create a collision mesh

Duplicate the object:

Shift + D

Rename it:

robot_collision

Apply heavy simplification:

Decimate Ratio = 0.05

Export as:

File -> Export -> STL

Example file:

robot_collision.stl

14. Use in URDF

Example URDF link:

<link name="base_link">

  <visual>
    <geometry>
      <mesh filename="package://robot_description/meshes/robot_visual.dae"/>
    </geometry>
  </visual>

  <collision>
    <geometry>
      <mesh filename="package://robot_description/meshes/robot_collision.stl"/>
    </geometry>
  </collision>

</link>

Recommended mesh sizes

Mesh Type	Recommended Faces
Visual	< 50k
Collision	< 5k

Best practices for robot simulation

Avoid including small CAD details.

Remove:

• Screws
• Threads
• Fillets
• Decorative logos

These increase simulation cost without improving physics.

Typical robotics pipeline

CAD (Onshape / SolidWorks)
        v
Export STEP / OBJ
        v
Blender cleanup
        v
Visual mesh (.dae / .obj)
Collision mesh (.stl)
        v
URDF
        v
ROS 2 + Gazebo

Summary

This workflow helps robot meshes:

• Render correctly in Gazebo
• Load faster
• Simulate more efficiently
• Avoid flipped normals and missing faces