Week 05 – 3D Printing & 3D Scanning

Additive Manufacturing and Digital Capture

Group Assignment: Computer-Controlled Cutting – HedgeDoc

1. Objectives

  • Design a 3D printable object that cannot be manufactured subtractively
  • Document the design and printing workflow
  • Perform 3D scanning of a physical object
  • Process and evaluate scanned mesh data

1. Design Concept – Trapped Sphere Inside a Cube

For this week’s assignment, I designed a trapped sphere inside a cube using Autodesk Fusion 360. The objective was to create an object that cannot be manufactured subtractively. The sphere is fully enclosed inside the cube but remains free to move after printing.

To understand the geometric strategy behind trapped designs, I referred to a Fusion 360 tutorial on designing a sphere trapped inside a cube. I recreated the model step-by-step and adjusted parameters according to my design requirements.

Step 1 – Creating the Base Cube

I started by creating a sketch on the Top Plane. Using a Center Rectangle, I created an 80 mm × 80 mm square, constrained at the origin for proper alignment.

Base square sketch 80x80

The square was then extruded symmetrically to create a total height of 80 mm. Since symmetric extrusion splits equally on both sides, I used a value of 40 mm on each direction.

Step 2 – Creating Sphere Profiles

To generate the sphere cutout, I created a new sketch on the Front Plane. Two center-diameter circles were drawn:

  • Outer Circle: Ø100 mm
  • Inner Circle: Ø80 mm

The 80 mm diameter matches the cube width. A center line was drawn through the origin to act as the revolve axis.

Extruded cube 80mm

Unnecessary sketch portions were trimmed to create semicircular profiles.

Revolve cut creating spherical cavity

Step 3 – Revolve Cut (Creating Hollow Cavity)

The outer profile was revolved 360° around the center axis using the Cut operation. This removed material from the cube and created a spherical cavity inside it.

Inner sphere creation

At this stage, the sphere is fully enclosed within the cube but not connected to the cube body.

Final trapped geometry

Step 4 – Creating the Inner Sphere

Next, the inner circular profile (Ø80 mm) was revolved around the same axis using the New Body operation. This created the internal sphere body.

STL export

Step 5 – Exporting STL

After verifying the geometry, I exported the model as an STL file:

  • File → Export
  • Format: STL
  • Unit: mm

Download Final STL File

The final processed 3D model can be downloaded below:

Download STL File

Step 6 – Slicing in PrusaSlicer

The STL file was imported into PrusaSlicer. Settings used:

  • Material: PLA
  • Infill: 15%
  • Supports: Manual (painted support)
  • Estimated Print Time: ~2 hours

Since the sphere touches the bottom surface, manual support painting was used to stabilize the sphere during printing.

PrusaSlicer preview

Why This Cannot Be Made Subtractively

This object cannot be manufactured using subtractive methods such as milling or drilling because:

  • The sphere is fully enclosed inside the cube.
  • There is no tool access to remove internal material.
  • The internal sphere is a separate moving body.
  • It requires additive layer-by-layer fabrication.

This demonstrates one of the key advantages of additive manufacturing: complex internal geometries and trapped assemblies can be printed in a single build.

Printing Status

Status: Work in Progress
The object has been sliced successfully and is ready for printing. Final results, tolerance evaluation, and movement testing will be updated after printing.

Scale Reduction Test (Factor ×0.25)

To further test the design limitations, I reduced the overall model dimensions by a factor of 4 and printed the smaller version. The purpose was to evaluate minimum feature size, tolerance, and printer capability at reduced scale.

Observed Issues

  • Support structures became difficult to remove at smaller scale.
  • Internal sphere movement was restricted due to reduced clearance.
  • Thin structural walls showed deformation and partial layer defects.
  • Surface quality decreased, especially around circular cutouts.
  • One things i am sure that these are not the issues of support.

At this reduced scale, the tolerance between the inner sphere and outer cube was no longer sufficient for smooth movement. This demonstrates how scaling directly impacts mechanical clearance, printer resolution limits, and structural stability.

Conclusion: While the original design works at full size, significant redesign of tolerances and wall thickness would be required for reliable miniaturization.

Learning Reflection

Through this exercise, I learned:

  • How to use revolve-cut operations to create spherical cavities
  • How to manage multiple bodies in Fusion 360
  • How additive manufacturing enables trapped geometries
  • Basic slicing and manual support generation in PrusaSlicer

This assignment strengthened my understanding of design-for-additive-manufacturing principles.

3D Scanning Process

Part 1 – Scanner Setup and Software Overview

For the 3D scanning task, we used a structured-light 3D scanner setup connected to a laptop. The system included:

  • 3D scanner mounted on a tripod
  • Motorized turntable
  • Calibration board
  • Laptop with scanning software

The scanner was connected via USB and controlled using Creality Scan software.

The scanning software interface allowed selecting:

  • Object type (Normal / Face / Body)
  • Object size (Small / Medium / Large)
  • Tracking mode (Geometry / Texture / Marker)
  • Accuracy settings

Software Issues Observed

During scanning, we experienced multiple software stability issues:

  • The tracking frequently lost alignment
  • The mesh appeared fragmented or floating
  • The scanning process froze multiple times
  • We had to restart the application several times

This showed that scanning quality heavily depends on lighting, object texture, and stable tracking.

Part 2 – Scanning Test Objects

Test Object 1 – Small Printed Cube

The first object we scanned was a small 3D printed cube. It was placed on the rotating platform to allow full 360° capture.

The scanner captured approximately 488,000 points during scanning. However, we observed:

  • Noise around the base
  • Incomplete capture on sharp edges
  • Surface irregularities

The final mesh required post-processing for cleaning.

Test Object 2 – Triangular Pyramid Model

For the second experiment, I scanned a small orange triangular pyramid model mounted on the motorized turntable. The object consists of:

  • A triangular pyramid top
  • A rounded triangular base
  • Flat surface regions with small geometric details

The scanner was configured in Normal mode with Small object size and Texture tracking enabled.

Scanning Stage

During scanning, the system captured approximately:

  • 943 frames
  • 112,312 points
  • Frame rate around 12 fps
  • Scanner temperature between 32°C – 38°C

The turntable allowed full 360° coverage. However, some unwanted point clouds were captured around the circular platform.

Mesh Processing

After completing the scan, I used the following mesh processing tools:

  • Fusion to merge captured frames
  • Resolution adjustment (~0.31 mm)
  • Noise removal set to 50%
  • Remove isolated parts (20%)
  • Fill small holes (5 mm perimeter)
  • Mesh smoothing (Medium)

The meshing process generated approximately 2.2 million triangles.

Challenges Observed
  • Unwanted geometry captured from the turntable surface
  • Noise around object boundaries
  • Small mesh fragments around the circular base
  • Minor surface roughness after fusion

The Clipping Plane tool was used to remove the turntable geometry and isolate only the scanned object.

Final Result

After cleaning and smoothing, the triangular pyramid model was successfully reconstructed. The final mesh preserved the pyramid edges and base geometry with acceptable surface quality.

This demonstrated that shiny and reflective materials are difficult to scan accurately.

Part 3 – Mobile App Exploration

The mobile 3D scanning application was briefly explored to understand its interface and available scanning modes.

The application provides different scanning categories:

  • Small Object – food, toys, pets, flowers
  • Medium Object – people, vehicles, furniture
  • Large Object / Area – rooms, buildings, outdoor spaces

It also offers two main scanning modes:

  • Splat Mode – Lifelike scans that can be shared to the map
  • Mesh Mode – Classic mode with more export options

However, full mobile scanning was not performed. Initial testing showed that processing required significant time and device resources. Due to time limitations and performance constraints, the primary scanning workflow was completed using the desktop-based system.

Reflection on 3D Scanning

From this exercise, I learned:

  • How structured-light scanners capture geometry
  • The importance of stable tracking
  • How surface properties affect scan quality
  • Common issues such as noise and mesh fragmentation
  • The difference between desktop and mobile scanning workflows

3D scanning is highly dependent on lighting conditions, object texture, and careful movement during capture.

4. Learning Outcome

  • Understanding additive vs subtractive manufacturing
  • Hands-on experience with slicing and 3D printing
  • Understanding mesh structures and 3D scan processing

Assignment Overview

Task Status
3D print designed object Completed
Design object that cannot be made subtractively Completed
3D scan an object Completed
Document process Completed
© 2026 Dinesh Kumar Sah | Fab Academy