Building a DIY 7 Segment Mechanical Counter

This 3D-printed mechanical 7-segment counter is an awesome weekend project. It operates using internal cams, gears, and segment plates that respond to a linear input when you press the top button, cycling through numbers 0 to 9. Designed by Flower-3D, this is the latest version, 3.0, which has been enhanced and refined from earlier versions. The entire design has been revamped, and in this update, you can even reverse the counting by swapping the springs and drums in the mid-plate to count from 9 back to 0.

What you’ll need:

Printing and Material:

We’re using SUNLU PLA filament to print all the parts. I’ve set up the Bambu Lab A1 to handle all the black components, including the case and mid plate. Meanwhile, the A1 Mini is printing the colored parts in red and green, such as the cams and segment plates. Using two printers significantly reduces print time; while it would take about 9 hours with one printer, the time is now halved with two.

Assembly:

Once all the parts are printed, we’ll begin the assembly. It’s a pretty straightforward process, guided by the build video. We’ll use a total of 31 printed parts, along with some springs and rubber bands. For my build, I sourced the springs from pens, but if you don’t have any, a rubber band will work as well. It’s also important to lubricate the moving parts; you can use a synthetic oil safe for plastic or rub candle wax on them. The entire assembly process takes about 20-30 minutes, after which it’ll be ready for its first test!

Below: Springs or Rubber Band option – Springs work best

Final Thoughts:

The mechanical counter is a satisfying project featuring a sequential counting system that works exceptionally well. After completing this one, I’ve also built a second one with white digits, and maybe I’ll make a green display as well!

If you’re into 3D printing and interested in mechanical engineering, this is a really fun project to tackle.