How do I import STL and OBJ files from Blender or other 3D software for CNC carving?

Overview

The software can import 3D models from other programs and convert them into carvable components. That opens up free downloads, models you make in Blender, ZBrush or similar, and scanner data. Because the software works with base relief, a fully 3D object (front, back and sides) has to be oriented and sliced at a zero plane before it becomes a component.

Supported Import Formats

• STL: the standard format for complex 3D models, based on a triangular mesh. Many programs export it. If you read data from a 3D digitizer or scanner, STL is typically the best format, and it is a common choice from Blender.
• OBJ: a native format from Wavefront and many other animation-oriented packages.
• 3DS: a native format from 3D Studio Max and other animation-oriented packages.
• DXF (3D): from AutoCAD and other CAD packages. It must be a 3D mesh, not just wireframe data of the vertices.
• SKP: SketchUp's native format.
• V3M: a proprietary format for Vector Art 3D and Design and Make files (purchased 3D clipart). It imports as a new component with the same name as the file, at the size and position it was saved.
• 3DClip: 3D clipart exported from Aspire, which keeps the component structure and imports all its components. This one is Aspire only, as is CRV3D (a single component made from the visible 3D components in an Aspire project file).

STL, DXF, OBJ, 3DS and SKP files use the Orientate form. V3M, 3DClip and CRV3D do not. If a file will not open at all, or you are not sure a format is supported (STEP is not), see the entry on which 3D formats can be imported.

Step-by-Step Import Process

1. Go to File > Import > Import Component/3D Model (or use the import icon on the Modeling tab).
2. Select your file. For STL, OBJ, 3DS, DXF and SKP files, the Orientate form opens so you can set up the model before it becomes a component.
3. Step 1, Orientate:

• Initial Orientation: pick the option (6 are offered) that puts the face you want carved on top. Five Rotation about Z Axis options turn the part in 90 degree steps.
• Interactive Rotation: drag the red, green and blue circular handles in the 3D view to rotate about X, Y and Z (the central gray sphere rotates about all three at once). A handle turns yellow when it is active, and you can type an absolute angle in the floating field that appears. Picking a different initial orientation cancels these adjustments.
• Model Size: keep Lock XYZ ratio ticked to stop the model being distorted, enter the size, and click Apply.
• Units and Scale mm/inches: mesh files usually carry no units. If the model arrives about 25.4 times too big or too small, set the Units to match your job and use Scale mm/inches.
• Center Model: moves the center of the model's bounding box to the XYZ datum.
• Apply Perspective along Z: optional slider that makes the model appear to come out of the screen.
• Segment (Aspire only): opens the segmenting form for models with undercuts.

4. Click Position & Import.
5. Step 2, Position & Import:

• Zero Plane Position In Model: a slider that sets where the model is cut off when it becomes a component. Anything that is an undercut (goes under another part of the model) is discarded, and a vertical wall is created down to the plane from the silhouette edge.
• Create both sides: in a two-sided job this makes one component looking down from above and one looking up from below.
• Discard data below zero plane: tick it to remove data below the zero level, which is normal for a relief. Untick it for a negative model such as a dish or recess with a flat plane, so the data below the plane is kept.
• Highlight Undercuts: turns the parts of the model that will lose detail dark purple in the 3D view. It also highlights parts with normal (inside-out) problems in the original file. Large purple areas on the top surface mean the source model needs checking in the program that made it.

6. Click Import. The model appears in the Component Tree as a component named after the file.

Once imported, you can re-import to adjust the size, position and slicing plane: right-click a component of the imported model in the Component Tree and choose Re-import.

Orientation is Critical

The face you want carved must point up in the Orientate form. For a bust, the face should point up. For an animal figure, the front or top should face up. For a model that is already a bas-relief, the raised surface should face up. If the result is wrong, go back and choose a different initial orientation or use the rotation handles.

Blender to STL to Import Workflow

Blender is a free 3D modeling and sculpting program.

1. Create or clean up the model in Blender.
2. Use File > Export > STL (tick Selection Only if you only want certain objects).
3. Check the units setting in the exporter if you work to real-world sizes. If the size is wrong after import, fix it with Units and Scale mm/inches on the Orientate form.
4. Import as described above. The orientation is chosen in the Orientate form, so you do not need to match axes exactly in Blender.

The mesh should be solid and whole: no holes and no parts that are inside out. Highlight Undercuts will show normal problems in dark purple. In Blender, Mesh > Clean Up (Fill Holes, Merge by Distance) and Mesh > Normals > Recalculate Outside help repair a problem file.

Polygon count: the model is converted to a height map at the job's Modeling Resolution, so extra polygons beyond what the resolution can represent do not add detail.

Combining Several Models

To get several models into one component, import them all into Blender, position them as you want, export the whole scene as one STL (without Selection Only), and import that single file. You can then use Create Vector Boundary from Component and Clear Component Outside Selected Vectors to isolate individual pieces if needed.

After Import: Working with the Component

The imported model behaves like any other component:

• Adjust Shape Height in Component Properties to fit your material depth.
• Use Fade or Tilt to change the depth distribution, and combine it with other components using combine modes.
• Use Smooth Components to reduce stair-stepping, and Scale Model Height to adjust the overall height.
• In Aspire, use Sculpting to refine the surface, Emboss Component to reduce the height while keeping surface detail, and Add Draft to Model to soften a hard vertical edge.

Toolpathing an Imported Model

You do not need to draw vectors to toolpath a 3D model.

1. Use Create Vector Boundary from Selected Components to make a boundary vector (optional but useful).
2. Calculate a 3D Roughing toolpath, using the boundary as the machining region.
3. Calculate a 3D Finishing toolpath.

Two-Sided Import (Full-Round Models)

For objects with significant geometry on both sides, set the job type to Two-Sided before importing, tick Create both sides in Position & Import, and design the toolpaths for each side independently. For a rotary job, the Orientate form is different. See the entry on the Orientate 3D Model gizmo for rotary jobs.

Quick Fixes

Common Mistakes

• Wrong orientation: the model comes in upside down or sideways. Fix it in the Orientate form before importing, or re-import.
• Units mismatch: a model made in millimeters can arrive tiny in an inch job. Use Units and Scale mm/inches.
• Leaving Discard data below zero plane unticked on a solid model, which keeps unwanted data below the plane (untick it only for dish or recess designs).
• A mesh with holes or flipped normals: check Highlight Undercuts and repair the model in the original program.
• Expecting more surface detail than the job resolution can hold. Detail is limited by the Modeling Resolution in Job Setup, not just the STL polygon count.

Where to Find 3D Models

• Thingiverse and Printables: large free libraries where quality varies. Search for "bas relief" for relief-style files.
• Design and Make and Vector Art 3D: sources of V3M 3D clipart.

Check the license of any model before you sell carvings made from it.