5. 3D Scanning and Printing

Overview

This week combined two distinct digital fabrication skills: designing and 3D printing an object that takes advantage of additive manufacturing's unique capabilities, and capturing a physical object as a 3D digital model through scanning. For the print assignment I built on design work already completed in Fusion 360 during Weeks 2 and 3.

Both tasks connect to my final project: understanding how to move between the physical and digital world is essential for the wearable haptic system I am designing.

Group Assignment

1. Test the design rules for your 3D printer(s).
2. Document your work on the group work page and reflect on your individual page what you learned about characteristics of your printer(s).

Individual Assignment

1. Design, document and 3D print an object (small, few cm3, limited by printer time) that could not be easily made subtractively.
2. 3D scan an object (and optionally print it)

Understanding the Prusa Mk3s+

To understand the capabilities and limits of the printer I am working with, I printed a test object designed to reveal key printer characteristics.

I printed the Nano All-in-One 3D Printer Test by majormuppet (Printables). This single small object tests a wide range of printer characteristics at once (overhangs, bridges, fine detail, tolerances, and surface quality).

What the test revealed

Feature	Value	Why
Printer	Prusa MK3S+	The Lab's Primary 3d Printer
Material	PET	Material I'm using in my final project
Layer Height	0.2 mm	It's the standard layer height for prints and I hope it reveals real world perdformance
Infill	15%	I use 15% infill for most of my prints.
Supports	Organic (tree style) supports	I wanted to test removal of organic supports and see how it impacts the quality of the print
Nozzel Diameter	0.4 mm	Standard Nozzle

Discoveries related to my final project

1. The Nano test object exposed the MK3S+'s real-world limits across several fabrication characteristics I need to understand before designing parts for my final project.
2. Clean results up to 45°. Stringing and drooping begin noticeably at 50°. At 60° and above, significant sag occurs and supports become necessary.
3. Any holes designed for press-fit motor components need to be drawn 0.3mm larger than the target diameter in Fusion 360 to compensate for PLA undersizing. Minimum clearance for any moving joint in a print-in-place assembly is 0.4mm.
4. Bridges between 25–30mm show minor surface roughness on the underside but are structurally sound. Beyond 30mm, visible sag increases. For spans over 50mm, redesign with an arch, add a mid-span rib, or enable supports.
5. 0.3mm is the reliable minimum clearance for two printed surfaces to be separable after printing. At 0.2mm, PLA surfaces fuse and cannot be separated. For print-in-place hinges, use 0.4–0.5mm clearance.
6. Embossed or debossed features need at least 0.6mm height/depth and 0.5mm stroke width to resolve at 0.2mm layer height. Features smaller than the nozzle diameter (0.4mm) will not print.
7. Vertical walls (90°) print with excellent surface quality. Sloped surfaces below ~20° from horizontal show visible layer stepping at 0.2mm layers.
8. Thin towers under ~5mm diameter above 10mm height begin to show layer deviation. Above 20mm, thin towers can develop visible lean. For tall thin features, slow the print speed or add a sacrificial pillar.

Why Not Subtractive for my final project?

The Fab Academy requirement is that the printed object must include geometry that could not be easily made by a subtractive process (such as CNC machining or milling). Subtractive manufacturing removes material from a solid block using a cutting tool. Most cutting tools on the market cannot reach into enclosed spaces, cannot make internal voids, and cannot create geometry that traps the tool path.

What makes my project require additive manufacturing

My wearable is very small and includes the following features that prevent subractive fabrication:

1. Interior "seats" : My future PCB, and battery need to fit inside of a small verticle space. A milling tool entering from the top would have no way to cut the underside of these ledges without destroying the surrounding walls.
2. Overhangs: Because of the interior "seats" there are also interor ledges that are needed for vertical stacking of components. These are undercuts by definition. They feature geometry that faces away from every possible tool entry direction simultaneously.

Scanning and 3D Printing

Capture Process

I scanned the vibrating disc motor that is the core output device of my final project, to practice capturing small, irregularly-shaped objects and to explore whether a scanned mesh could be used as a reference for designing a fitted enclosure.

Capture Process

1. I used polycam to scan my motor
2. Placed the motor on a matte white surface under diffuse lighting.
3. I rotated the motor to get a 360 scan
4. After capturing, I uploaded the photos to Polycam for photogrammetry processing. I exported it as an OBJ.
5. I opened the OBJ in meshmixer and removed all the floating fragments and reduced the noise
6. I used filter to reduce and bring the polygon count down a bit.
7. I exported the cleaned mesh as an OBJ

Scan Result

The top and sides of the motor captured cleanly. The flat bottom face had a small hole in the mesh because it was resting on the table during capture. I tried to fix this by filling the hole manually in Meshmixer. The coin-cell surface texture came through clearly at standard quality but fine edge chamfers were slightly rounded off.

Gallery

Reflection

What I learned about 3d printing this week

The most useful insight this week was understanding why design-for-printing matters before you even open the slicer. Redesigning the PCB clip from 65° to 45° took ten minutes in Fusion 360 and eliminated the need for supports entirely. Thinking about the printer's constraints during design, not after, changes the whole workflow.

What I learned about 3d scanning

I learned how much the scan quality depends on preparation: matte surfaces scan cleanly, shiny surfaces do not.

How this connects to my final project

The printed enclosure this week is a real component of my final project.

Files

File	Description
Printer Test	3D Printer Test - Gcode File