Mechanical Calculator with 4 Functions (Compliant Mechanism)

This is a protoype of a mechanical calculator that can add, subtract, multiply and divide made entirely as a compliant mechanism. It is just a single 3D-printed part that can perform all four basic math operations!

How does it work?

The calculator has two sliding inputs, A and B, which can each be set to 0, 1, 2 or 3.

Their movements are transmitted through an arrangement of flexible beams and linkages. All four results are displayed at the same time. this is done by two straight scales that indicate addition and multiplication and two rotating scales which indicate subtraction and division. The sliding inputs must stay parallel to each other.

For example, set A to 3 and B to 2, and the calculator displays:

• Addition: 3 + 2 = 5

• Subtraction: 3 − 2 = 1

• Multiplication: 3 × 2 =6

• Division: 3 ÷ 2 = 3/2

Division results are displayed as fractions so you can calculate results such as 1/3 or 2/3.

There is one limitation though, i could not figure out how to divide by 0. Because of this multiplication and division is designed for inputs from 1 to 3 only. If either input is set to zero these two displays must be ignored. Addition and subtraction work with all inputs from 0 to 3 though.

Technical details:

• Dimensions: 150 × 150 × 4.8 mm

• One single part no assembly required

• Four arithmetic operations

• Two adjustable numerical inputs (0–3)

• Four simultaneously readable results

• Fractional results for division

• Completely mechanical

How to use it

1. Start: Hold the outer frame and move both input sliders from their parking positions (P) to 0. The P position is only for storage and is not a numerical input.

2. Set A: Move the A slider to the right until its indicator points to the desired number (0–3).

3. Set B: Move the B slider to the left until its indicator points to the desired number (0–3).

4. Read the results: All four calculations are displayed simultaneously. The straight scales show addition and multiplication, while the moving angular scales show subtraction and division.

5. Reset: Carefully return both sliders to their parking positions (P) when you're finished.

That's it! You can now perform all four basic arithmetic operations without a single electronic component :)
Be careful not to break it though.

How do you print it?

Tbh I used a printing service with an SLS printer to print this. If you want to try it on FDM I would recommend starting with the following settings:

• PLA

• Nozzle: 0,20 mm

• Layer height: 0,10 mm

• Infill: 100%

The design also contains bridging sections with spans of approximately 10 and 15 mm. These are important for successful printing because the moving parts need to remain separated. I recommend checking your printers bridging performance beforehand...

After printing:

Allow the print to cool completely before moving the mechanism. Check for stringing sagging bridges or accidentally fused sections. Start by carefully moving both inputs between P and 0. Then try the remaining positions one at a time. Don't force the mechanism if something doesn't move freely and avoid pulling directly on the thin flexible sections...

Have fun experimenting!

What I like about this design is that you can actually see the mechanical relationships between the inputs and the results. I wanted to design this for many years now and I'm glad I finally did.

If you print one yourself i'd love to see your results! Feedback, suggestions and ideas for improvements are always welcome.

I hope you have as much fun with it as I had designing it :)