Coin Sorters

thingiverse

In lower elementary school, students need to learn how to count money, and United States coins are particularly challenging because their size does not indicate value. This confusion is heightened by the fact that the dime (10 cents) is smaller than the penny (1 cent). In this project-based learning initiative, students are tasked with working with the most common United States coins: the penny, nickel, dime, and quarter. To achieve this, they must first use a ruler to measure the widths of these coins, then design a device that allows a handful of mixed-up coins to be sorted using gravity. In the real world, individuals such as bank tellers, cashiers, PTA Treasurers, kids running school stores, and kids operating lemonade stands all sort large quantities of mixed-up coins so they can be bagged and taken to the bank. To effectively utilize gravity in this project, students must incorporate some form of inclined plane (slope) or level, or a mechanism that allows gravity to pull the coins from the mixed group by size. One example design features an inclined plane with holes for the coins to fall through into a separate cup or bag. Another example uses pins to knock the coin off the front of the inclined plane into a cup or box. When creating the 3D print, students should be mindful that "thin" is not necessarily optimal due to the raft and warping of thin flat panels. Instead, thicker designs will yield better results as they allow for waffle/hollow spaces. Because I am limited by my MakerBot Replicator Mini printer, I had to replicate my design and split it into two batches. Alternatively, I could have printed it vertically in a single run. My initial print of the top portion with holes successfully sorted dime and penny combinations but was too thin. Some raft material became stuck, requiring me to hold or lean against something for support. To address this issue, I thickened up my design in subsequent iterations. It is essential to remember that these sample designs are intended as inspiration rather than templates for direct copying. To make the challenge more engaging, consider having students use only measurements from the US Mint's website to create their gravity sorter devices.