Week 17

This week I needed to design and digitally fabricate something (including computer design and fabrication) that had not been covered in any previous assignment. I read through the possible options for this week and ended up choosing the last option in the list: Composites 😅

This one immediately caught my attention and I really wanted to try it because I also needed to design the body of my car for my final project. So I decided to use this week as another opportunity for interesting experiments.

I should also mention that a few months ago Anush, one of our lab staff members who is also a FabAcademy and FabriAcademy instructor, brought a book from Amsterdam specifically about creating car composites from a humorous perspective. That book inspired me even more, and with Anush’s help we started working on this week's assignment.

First, I needed to understand how I would design my car and wheels. Since I no longer wanted to work with FreeCAD and Fusion 360 could not be installed on my computer because of operating system issues, I downloaded Blender. However, Blender is not really a precise CAD software, so I found a nice workaround to keep the dimensions accurate.

I downloaded all the 3D objects in .stl format and imported them into Blender so I could create my car using their real dimensions.

Here are the links where I downloaded all the models from: the motor, battery, button, and for the self-adhesive caster wheel, since I could not find a model online, I quickly generated one in OpenSCAD by asking AI to create code similar to a self-adhesive caster wheel. Then I measured my real wheel and replaced the dimensions in the code. Here is the final result.

// Exact 34x34mm Ball Transfer Caster Wheel Model
$fn = 60; // Smoothness factor
// Parameters
base_w = 25;      // Width (mm)
base_l = 25;      // Length (mm)
base_h = 1.6;     // Base thickness (mm)
corner_r = 4;     // Corner rounding radius (mm)
hole_d = 3.5;     // Mounting hole diameter (mm)
hole_offset = 4;// Distance from edges
ball_d = 15;      // Metal roller ball diameter (mm)
shroud_d = 18;    // Plastic housing dome diameter (mm)
shroud_h = 13;    // Height of housing dome (mm)
difference() {
    // Main Body
    union() {
        // Rounded Square Base Plate
        linear_extrude(height = base_h) {
            offset(r = corner_r) {
                square([base_w - 2*corner_r, base_l - 2*corner_r], center = true);
            }
        }
        // Central Housing Dome
        translate([0, 0, base_h])
            cylinder(d1 = shroud_d, d2 = shroud_d - 3, h = shroud_h - base_h);
    }
    // Cutout for the Steel Ball (Sphere Cavity)
    translate([0, 0, shroud_h - (ball_d/3)])
        sphere(d = ball_d + 0.4); // Added 0.4mm tolerance for print-in-place spacing
    // Diagonal Corner Mounting Holes
    translate([-(base_w/2 - hole_offset), -(base_l/2 - hole_offset), -1])
        cylinder(d = hole_d, h = base_h + 2);
    translate([(base_w/2 - hole_offset), (base_l/2 - hole_offset), -1])
        cylinder(d = hole_d, h = base_h + 2);
}

For the PCB and NFC reader models, I used the 3D model exported from my already finished KiCad PCB project, where I had already integrated the NFC reader model.

Now let’s move to creating the wheel.

Since the wheel needs to directly fit into the motor shaft, I selected the corresponding motor section and entered Edit Mode. Then I selected all the external points and captured the shape of the motor connection area.

After that I pressed Shift + D to duplicate it and moved it forward. Then I pressed Ctrl + E and scaled it along the X axis to give it depth so I could subtract it from my cylinder object.

To remove it:

• Switch back to Object Mode
• Select the cylinder first
• Open Modifier
• Select Add Modifier → Generate → Boolean
• Use the eyedropper tool and duplicated object
• Press Apply

Now I could see that the shape was removed successfully.

Next, I selected the outer surface of the wheel cylinder and pressed Ctrl + I to invert the selection and isolate the area where I wanted to add depth.

Then I selected the isolated region and pressed: Ctrl + E → move along X axis

To create holes in the wheel, I selected: Add → Mesh → Cone

I placed the cone where I wanted and duplicated it as many times as needed. Then again I used the Boolean operation to subtract these cones from the main wheel cylinder.

Afterward I selected the curved cone surfaces and modified them using the same process: Ctrl + I → Ctrl + E

Let’s stop here with the wheel section and move to designing the main body.

First I will show the version that I had already designed and printed for testing purposes, then continue with the main design process.

I started by arranging all the internal components that would fit inside the car body.

Once everything was positioned correctly, I created a Cube, then pressed Ctrl + R to create loop section so I could shape the body by moving the generated sections.

After that I selected the cube and applied: Add Modifier → Generate → Subdivision

Then I set Levels Viewport = 5 to get the desired smooth curved shape.

Afterwards I started subtracting spaces from the main body according to the dimensions and positions of the imported models.

Let’s start with the Toggle Button.

I placed it where I wanted the opening to be, selected the button model, switched to Edit Mode, duplicated the required points, gave them thickness, filled the surface by pressing F, and repeated: Add Modifier → Generate → Boolean

Then I selected the duplicated object with the eyedropper and pressed Apply.

Then I repeated the same subtraction process for all the objects.

For the self-adhesive caster wheel, I again selected the surface and to fill the inside I chose: Add Modifier → Generate → Solidify

Then I increased the Thickness value until the inside became filled. However, I noticed that some surfaces were facing inward while others were facing outward, so I pressed L to select all connected surfaces and then selected: Mesh → Normals → Recalculate Outside to correct the directions.

After that, I duplicated only the inner ring sections and performed the Boolean operation on the car body.

Next, I moved to creating the corresponding holes for the NFC Reader from the bottom side of the car, because I planned to mount the NFC module on the lower part.

Since I was also planning to mount the motors on top of the NFC board, I created a new Cube and adjusted its Scale so it would create support holes matching the inside dimensions for mounting the NFC properly.

Then I created another cube and adjusted its scale so the motor could be mounted to it with bolts using the motor's mounting holes. I duplicated this setup symmetrically.

Here is an image of the bottom section of the car.

Then I created another similar cube that would be placed above the motors to mount my PCB on top of it. For that, I duplicated the hole positions from my PCB and subtracted them from this platform.

Then I also subtracted this new cube from the inside of the main car body so it would extend outside the car and create something like a small door-line effect.

Next, for allowing the wheels to rotate freely outside the motors, I selected the corresponding motor hole area and enlarged it enough so that rotation would not interfere with the body, then subtracted the resulting shape from both sides of the car.

Here is an image of the USB hole in the car.

Now it was time to split the car into two parts for printing.

For that, I created a panel: Add → Panel.

Then I positioned it where I wanted the cut and again performed a Boolean operation.

Here are the two parts of the car after splitting.

Here are the final parts of the car.

Here is the complete car shown in video format.

Afterwards I exported all required parts as .stl files for printing: File → Export → STL (.stl)

Here are the screenshots from OrcaSlicer.

And here are all the components that need to fit inside and the printed models.

I placed all components inside and checked the fitting — it looked like everything fit properly.

However, while trying to place the PCB, I noticed that I had forgotten to leave space for the pin headers. Because of that, I printed a corrected version.

And now it finally looks like everything fits.

I am planning to connect the two car body parts using magnets, which I will show later.

My car actually looks really beautiful 😍😍

Composite Creation Process

Now let’s move to the composite creation part.

For this, Anush helped me — the same person who inspired my interest in that book mentioned earlier, and who is also a FabAcademy and Fabricademy instructor and generally a wonderful person ❤️

Anush suggested creating a biomaterial with the following composition:

• Gelatin - 38g
• Glycerin - 19g
• Water - 190ml

Before pouring the biomaterial into the ring-shaped section, I wanted to create some design using wool available in the lab.

After pouring the material, we waited for one hour and then closed the car using fabric material.

Also I should mention that one of the advantages of working with biomaterials is that you do not need to wear a mask and can even work directly with your hands.

After waiting for one hour, I separated the material from the wooden ring using a knife. Then I tried placing it on the top section of the car, but it cracked and got damaged.

So we made some conclusions. First, the material layer was too thick. We also decided that using fabric to reinforce it on the car body would be a better approach. Because of that, we cut the material into smaller pieces and heated it again until it became a homogeneous mixture, and I removed the wool material.

Then we decided to perform one more experiment and added 1.5 g of Xanthan Gum and a small amount of colour powder to make it more visually interesting.

After that I selected two different types of fabric for testing.

The first one was fiberglass cloth / glass fiber fabric.

For this experiment I first applied the biomaterial onto the outer surface of the car, then attached the fabric to the car body, and finally applied another layer of material on top of the fabric.

After one day it was ready to trim around the edges. This version was not very strong, but the shape was clearly visible. I will wait a few more days to see how much more it dries.

But I already like it.

Then I took linen cloth, soaked it in the material, and attached it onto the car body using the matrix material.

After one day I removed the car again, and the result was much better, although it will still continue drying.

Here is how beautiful and stable it turned out.