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3D Printing Guide

This page provides detailed instructions for 3D printing all custom structural components of PrintExo.

CAD Files

All CAD files required for 3D printing PrintExo are provided as open-source resources.

  • Printable STL files for all structural components
  • Editable Fusion 360 parametric models (.f3d)
  • Optional parametric export script for shoe-width customization

👉 Download CAD files:
Google Drive – PrintExo CAD Release

1. Overview

Key points:

  • All custom parts are designed for consumer-grade FDM printers
  • Primary material: PLA (PETG or carbon-fiber–reinforced filaments also compatible)

The following subsystems require 3D-printed components:

Subsystem Components
Actuation module Planetary gear stage, protective casing
Shank structure Shank body, passive hinge
Shoe interface Dorsal component, plantar guides

Printing Estimates (per leg)

Item Value
Total print time 1 day 23 hours 51 minutes
Model filament 928.70 g
Support filament 21.22 g
Total filament 949.92 g
Estimated cost $23.74

Note: Estimates based on 70% gyroid infill with supports. Actual values may vary depending on printer, slicer settings, and filament brand.

2. Required Printing Equipment

Printer

  • Recommended: Bambu Lab X1C (or equivalent enclosed FDM printer)
  • Any consumer-grade FDM 3D printer is compatible

Nozzle

  • Diameter: 0.4 mm (standard)
  • Hardened steel nozzle recommended for abrasive filaments

Slicer Software

  • Bambu Studio (for Bambu Lab printers)
  • PrusaSlicer, Cura, or equivalent

Optional

  • Filament dryer (recommended for hygroscopic materials like PETG)
  • Enclosed chamber (improves print consistency)

3. General Print Settings

Parameter Recommended Value Notes
Layer height 0.20 mm Balance between speed and strength
Nozzle diameter 0.4 mm Standard
Infill pattern Gyroid Good omnidirectional strength
Infill ratio 70% For structural rigidity
Perimeters (walls) 4 Increases shell strength
Top/Bottom layers 5 Ensures solid surfaces
Support Part-dependent See Part-by-Part notes
Material PLA PETG or CF-PLA also compatible
Bed temperature 60°C For PLA
Nozzle temperature 210°C Adjust per filament brand

4. Print Orientation & Strength Considerations

FDM prints exhibit anisotropic strength — they are weakest along the layer lines (Z-axis).

Guidelines

  1. Load-bearing parts should be oriented so that primary stresses act parallel to the print bed (X-Y plane), not perpendicular (Z-axis).

  2. Planetary gears require careful orientation to ensure tooth strength and smooth meshing.

  3. Use brims (5–10 mm) for parts with small footprints to prevent warping and improve bed adhesion.

  4. Avoid rafts unless absolutely necessary — they can affect dimensional accuracy on mating surfaces.

Critical Orientations

Part Recommended Orientation Reason
Shank body Vertical (standing) Maximizes bending strength
Gear components Flat (teeth facing up) Preserves tooth geometry
Shoe interface Flat Ensures accurate mounting surfaces

5. Part-by-Part Printing Notes

Part Name Quantity Orientation Support Infill Special Notes
Sun gear 1 Flat No 70% —
Planet gear 3 Flat No 70% Print bearings separately
Ring gear 1 Flat No 70% Check inner teeth quality
Carrier 1 Flat Yes 70% Remove supports carefully
Motor casing 1 Upright Yes 50% —
Shank body 1 Vertical Yes 70% Orient for bending load
Hinge component 2 Flat No 70% —
Dorsal interface 1 Flat Yes 70% Size-specific
Plantar guide 2 Flat No 50% —

Note: This table is an example. Refer to the CAD files for the complete part list.

6. Post-processing

After printing, perform the following steps:

6.1 Support Removal

  • Use flush cutters or needle-nose pliers
  • Be careful around gear teeth and mounting holes

6.2 Surface Finishing

  • Light sanding (220–400 grit) on mating surfaces
  • Focus on surfaces that interface with bearings or fasteners

6.3 Hole Preparation

  • Reaming: Use appropriately sized drill bits to clean up holes
  • Tapping: M3 holes may require tapping for secure bolt threads

6.4 Dimensional Verification

  • Check critical dimensions with calipers
  • Gear mesh should be smooth without binding
  • Bearing press-fit should be snug but not overly tight

7. Common Printing Issues

Issue Possible Cause Solution
Warping Poor bed adhesion, no enclosure Use brim, increase bed temp, use enclosure
Layer delamination Under-extrusion, low temp Increase nozzle temp, check filament quality
Poor gear tooth finish Too fast, insufficient cooling Reduce speed for outer walls, increase cooling
Holes too tight Over-extrusion Calibrate flow rate, or ream holes after printing
Holes too loose Under-extrusion Increase flow rate, or use smaller drill bit
Stringing High temp, no retraction Lower temp, enable/increase retraction
Z-seam visible Slicer settings Set seam position to "sharpest corner" or "rear"

Next Steps

After completing all prints and post-processing:

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