5. 3D Scanning and printing

group assignment:

  • test the design rules for your 3D printer(s)

individual assignment:

  • design, document, and 3D print an object
     that could not be made subtractively
     (small, few cm3, limited by printer time)

  • 3D scan an object (and optionally print it)

For this week, the group assignment was to test the design rules of our 3D printer. This involved checking tolerances, minimum wall thickness, overhang limits, and clearances between moving parts. These tests helped us understand the physical limitations of our printer and informed the design decisions for the individual assignment.

Group Assignment

Group assignment

Individual Assignment

For the individual assignment, I designed and 3D printed an object that cannot be made subtractively and cannot be assembled after fabrication. The object is a ball enclosed inside a box. This design demonstrates the power of additive manufacturing because the ball is permanently trapped inside the box and can only be produced in a single print.

Designing the Object

I began by creating a sketch on the front plane. Using the center rectangle tool, I drew a square with dimensions of 80 mm by 80 mm. This square formed the base profile of the cube.

After finishing the sketch, I used symmetric extrusion with a distance of 40 mm. I chose symmetric extrusion instead of one-sided extrusion because it pushes material equally in both directions from the sketch plane. This keeps the cube perfectly centered at the origin. Since I extruded 40 mm on each side, the total depth became 80 mm, forming a complete cube. Keeping the cube centered makes the revolve operation precise and balanced.

Next, I created a new sketch on the top face of the cube. I drew two center circles: one with a diameter of 97 mm and another with a diameter of 80 mm. The larger circle was designed to intersect the cube corners, while the smaller circle touched the middle of the cube’s sides. The reason for creating two circles was to define the outer curved cavity and the inner sphere.

I then drew a vertical construction line along the Y-axis. This line was important because it would serve as the axis of revolution. The revolve tool requires both a profile and an axis to create 3D rotational geometry.

Using the trim tool, I removed half of both circles. I did this because the revolve tool works on a closed profile. By trimming half of the circles, I created clean half-circle profiles that could be rotated around the axis to form smooth spherical geometry.

I selected the outer half-circle profile and revolved it 360 degrees around the Y-axis. This operation created the curved internal cavity and circular openings on the cube’s faces. The revolve operation was necessary because it generates smooth spherical geometry, which cannot be achieved using simple extrusion.

axis,

This is how it looks like after revolve, you can see there are circle holes in all sides of the square box.

To create the internal sphere, I selected the inner half-circle profile,just enabled the second sketch to see it and revolved it 360 degrees around the same axis. This formed a complete ball inside the cube. Because the sphere was created within the enclosed geometry, it became permanently trapped.

The final result is a cube with circular openings on all sides and a fully enclosed internal sphere. The ball is free to move but cannot be removed without breaking the cube. This object cannot be manufactured using subtractive processes like milling, and it cannot be assembled after fabrication. It demonstrates the advantage of additive manufacturing.

After completing the design in Fusion 360, I exported the file as an .STL file. I chose the STL format because it is the standard file type used for 3D printing. STL converts the solid model into a mesh made of small triangles, which slicing software can interpret and convert into machine instructions.

Slicing using -Prusa Slicer

I then opened PrusaSlicer to prepare the file for printing. In PrusaSlicer, I switched to Expert Mode. I chose Expert Mode because it gives access to all advanced printing parameters such as layer height, infill, supports, and print speeds. Even if I did not modify many settings, working in Expert Mode allows better control and understanding of the slicing process.

I clicked the Add button and imported the STL file from my folder. The model appeared on the virtual print bed.

At this stage, I checked the orientation and size. The slicer allows scaling, but I kept the original dimensions since they were already correct and within the printer’s build volume.

Next, I clicked Slice Now. Slicing converts the 3D model into layers and generates the toolpaths the printer will follow. This step also shows estimated print time and material usage.

After slicing, I exported the file as G-code. The G-code contains the machine instructions for the printer. I then transferred this file to the 3D printer for fabrication.