Save as STL

Export your SMARS base for 3D printing with optimal settings

What We’re Building

Your SMARS base design is complete - now it’s time to turn it into a real, physical robot part! In this lesson you’ll:

1. Export the model as an STL file
2. Learn optimal 3D print settings
3. Understand common printing issues and fixes

Understanding STL Files

What is STL?

STL (Stereolithography) is the standard file format for 3D printing. It describes your model as a collection of triangles - the more triangles, the smoother the curves.

Why STL?

• Universal format - works with any 3D printer
• Simple - just geometry, no colors or materials
• Reliable - been the standard for decades

The Export Process

FreeCAD → STL → Slicer → G-code → Printer

1. FreeCAD creates the 3D model
2. STL export converts to triangle mesh
3. Slicer software (Cura, PrusaSlicer) creates print instructions
4. G-code tells the printer exactly how to move
5. Printer creates the physical part

Step-by-Step: Export to STL

1. Select the Model

In the Model tree, select the final body/feature of your SMARS base. This should be the complete model with all features.

Important: Select the body or part, not an individual sketch or feature. The export will only include what you select.

2. Open the Export Dialog

Click File menu in the top left corner.

3. Select Export

From the dropdown menu, select Export...

4. Choose STL Format

In the file dialog:

• Navigate to your desired save location
• In the Save as type dropdown, select STL Mesh (*.stl)

5. Save the File

Enter a filename like smars_robot_base.stl and click Save.

Naming tip: Use descriptive names with no spaces: smars_base_v1.stl, smars_base_final.stl

Recommended Print Settings

Material Choice

Recommendation: Start with PLA. It’s forgiving and produces great results.

Layer Height

For functional robot parts like SMARS, 0.2mm is ideal.

Infill

Recommendation: 20% infill with grid or gyroid pattern.

Supports

The SMARS base is designed to print without supports when oriented correctly:

• Print with the open top facing up
• The base bottom sits flat on the print bed
• All overhangs are under 45°

Print Orientation

Correct orientation:

        ┌─────────┐  ← Open top (facing up)
        │         │
        │  SMARS  │
        │  BASE   │
        │         │
        └─────────┘  ← Flat bottom (on print bed)

This orientation:

• No supports needed
• Strongest layer adhesion in stress areas
• Clean bottom surface

Slicer Software Recommendations

Free Options

Import Settings

When you open the STL in your slicer:

1. Scale: Should be 1:1 (70mm × 58mm × 32mm)
2. Position: Center on print bed
3. Orientation: Open top facing up

If the model appears tiny or huge, check that your FreeCAD units were in millimeters.

Pre-Print Checklist

Before starting your print, verify:

• Model is watertight - No holes or gaps in the mesh
• Correct size - 70mm × 58mm × 32mm (check in slicer)
• Proper orientation - Open top facing up
• No supports needed - Model should slice cleanly without them
• Print time estimate - Usually 2-4 hours depending on settings
• Filament estimate - About 15-25g of material

Common Printing Issues

“My print warped off the bed”

Cause: Poor bed adhesion, especially with PLA cooling too fast. Fix:

• Clean bed with isopropyl alcohol
• Use a brim (5-10mm) in slicer settings
• Ensure first layer is slightly squished
• Check bed leveling

“The motor holes are too tight”

Cause: 3D printers slightly shrink holes due to corner rounding. Fix:

• Use a 4mm drill bit to clean up holes
• Or increase hole size in FreeCAD to 4.7mm

“Layers are separating”

Cause: Print temperature too low or print speed too fast. Fix:

• Increase hotend temperature by 5-10°C
• Reduce print speed
• Check for drafts near printer

“Wheel stubs broke off”

Cause: Layer orientation creates weak point. Fix:

• Ensure you’re printing in the correct orientation
• Increase wall count (3-4 walls)
• Try PETG for more flexibility

“Surface is rough/bubbly”

Cause: Moisture in filament. Fix:

• Dry filament (food dehydrator or filament dryer)
• Store filament in sealed container with desiccant

Post-Processing Tips

Cleanup

• Remove any stringing with a heat gun (briefly) or knife
• Clean up support marks if you used any
• Test-fit motors and wheels

Test Assembly

Before building the full robot, verify:

1. Motors fit snugly in retention cutouts
2. Motor shafts pass through holes freely
3. Arduino slides into slots
4. Wheels attach to stubs properly

If Parts Don’t Fit

• Too tight: Sand with fine sandpaper, or drill out holes
• Too loose: Add tape, or reprint with adjusted dimensions
• Warped: Check bed leveling and try printing cooler

Try It Yourself

1. Export the STL following the steps above
2. Open in a slicer and verify the dimensions
3. Preview the slice - look for any issues in the layer preview
4. Print it! (if you have a printer)

Common Issues

“FreeCAD shows export errors”

Problem: The model has geometry issues preventing clean export. Solution:

• Check for overlapping faces in the Model tree
• Try using Part → Check Geometry to find problems
• As a workaround, export as STEP first, then convert to STL

“STL file is empty or wrong size”

Problem: Wrong item selected during export. Solution: Select the Body or Part in the Model tree, not a sketch or single feature.

“Slicer shows the model as too small/large”

Problem: Unit mismatch between FreeCAD and slicer. Solution: FreeCAD should be in mm. If the model is 1000x too big, FreeCAD was in meters. Scale by 0.001 in the slicer.

What You Learned

In this lesson, you mastered:

• STL export - Converting CAD models to printable format
• Print settings - Material, layer height, infill recommendations
• Orientation - Positioning for best print quality
• Troubleshooting - Common issues and their fixes

Next Up

Congratulations - your design is ready to print! In the final lesson, we’ll summarize everything you’ve learned and explore where to go next with your new CAD skills.

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