Binary Adder and Subtracter

This is binary counter which can perform both addition and subtraction. It can be useful during Computer Science and Math lectures, in order to teach how to convert a binary number in decimal number and to show how addition and subctraction works in the binary system.

This is my personal version of a similar instrument i saw from someone who built it using wooden board, but this also includes the subtraction and a bottom feature for keeping track of the positions of the digits. 

(The position numbers should be in inverted order for the teacher point of view!)

I used 5 green PLA washers in total for spacing every 2 pieces and one of them at the beginning and one of them at the end.

I suggest you 20% infill.

No supports are required for this print.

To build this are required:

1. A drill with a small drill bit in order to enlarge the hole where the little screws should fit.
2. 14 self-tapping screws 10mm (for plastic or wood)
3. An iron bar 8mm diameter 190mm length
4. Glue for placing the numbers (digits and positions) onto the pieces. I used epoxy transparent glue but you can also use cyanoacrylate.