Why

After a summer of creating a variety of projects, from small metal art pieces to large 3D-printed models, I noticed that many of them lacked a final level of refinement. When I examined my completed projects, I realized that they were often missing a smooth, polished finish. I decided to reuse parts from previous high school projects to design and build a belt sander that could help me finish future 3D-printed items and small metal parts.

Constraints

Time Limit: 6 days — I needed to complete the project before leaving for college.

Budget: $50 — This did not include parts and materials I already had available.

Personal Constraint: To challenge myself, I was not allowed to research or look at belt sanders designed or manufactured by other people or companies.

Usage Requirement: The belt sander needed to be designed for safe operation when plugged directly into a wall outlet rather than using a variable power supply.

How

Day 1: I began by sketching concepts for my small tabletop belt sander, focusing on its overall design and how it would connect to the motor I already had (Figure 1).

Figure 1

I decided to use a pulley system to transfer power from the motor directly to the sanding belt. To accomplish this, I created an extruded hole in the larger pulley wheel that matched the gear shape on the end of the motor (Figure 2).

Figure 2

I also created holes with a diameter of 1.19 in and a depth of 0.25 in on each side of the wheel to house ball bearings. The bearings would reduce wear and allow the pulley to rotate more smoothly.While the wheel was printing, I worked on the electronics that would be housed inside the belt sander. I began by recreating the circuit from a previous project, an automated curtain, because I believed the same system could be adapted for the belt sander. The circuit uses a programmed Raspberry Pi Pico connected to an Arduino motor controller, allowing a potentiometer to adjust the motor’s RPM and control the sanding speed. After creating and testing the circuit, I purchased the components needed to make the system independent of my computer and variable power supply. I spent $34 on wire ($16), a soldering iron ($10), and DC power jacks ($8), which allowed the circuit to be safely connected to a power cord.

Days 2–4: With the circuit components ordered, I designed and printed the remaining parts. I started by designing around the dimensions of the components I already had, using their measurements to determine the dimensions of the housing. The completed parts are shown in Figures 3–8 (Note: All units are inches).

Figures 3-8

Day 5: After completing the design and printing all of the parts, I finished the circuit by connecting the remaining components and soldering them into place (Figure 9).

Figure 9

I then tested the circuit and motor for safe operation by connecting the system to a surge protector and running the motor.

After testing each component individually, I secured the completed circuitry inside the housing and attached the back lid using screws.

Adjustments & Problem Solving

As I fabricated and tested the 3D-printed components (Figure 10), I encountered several fit and durability issues that required adjustments to the design.

Figure 10

One of the first issues was that parts printed with different types of filament did not always fit together as expected. I found that using the same type of filament throughout the project provided more consistent dimensions and fit.

The biggest challenge was the tolerance of the gear-shaped hole in the pulley wheel that connects to the belt sander. The hole was initially too small to properly fit onto the gear. I adjusted the dimensions of the opening and reprinted the part until I achieved the proper fit.

I also had issues with the wiring connecting the motor to the Arduino motor controller. The vibration and kickback that occurred when the motor started and stopped caused the connections to come loose. I solved this by soldering the connections and securely fastening the motor to the housing to prevent it from moving.

There are still improvements I would make to the design. Ideally, I would replace some of the 3D-printed components with metal parts. In particular, I would like to make the spools that hold the sandpaper out of metal because the plastic can wear down over time from contact with the moving sandpaper. I would need access to a CNC machine to fabricate these parts, which was not available to me for this project.

Figures 11-14

Result

Working within the given constraints, I developed a fully functioning belt sander by combining 3D modeling, 3D printing, mechanical design, and electronics while primarily utilizing parts and materials I already had available.