Kotta Calculator Type I

The Curta Calculator, a purely mechanical handheld calculator invented and manufactured in the 1950s, is presented here.

Boasting an ingenious design and unique mechanical charm, it stands as a significant milestone in human mechanical engineering.

This project is a 3x enlarged FDM-optimized model of the Curta Type 1 calculator, meticulously modeled from engineering drawings.

Validated Filament: PETG/PETG-CF

Finished Dimensions (approx.): 300*150*150mm

Additionally, a mold for creating springs and torsion springs is included for optional printing

Notes:

Requires metal components; refer to the assembly instructions and BOM for details.

Due to varying material shrinkage, pre-cut and test-fit components with holes for shafts to determine appropriate hole compensation.

Printing Instructions:

1, This model requires significant dexterity and some mechanical aptitude.

2, For the B2/C1-1/C1-2 plates, high-strength CF material is recommended (requiring hardened steel or similarly durable nozzles).

3, Sacrificial supports have been added to certain parts for easier printing and require removal.

4, Multi-color print sections include recesses for single-color printing followed by hand-painting (due to layer lines, the effect is slightly diminished).

Special Thanks:

To Marcus Wu's work on Thingiverse, which greatly aided my understanding of the internal structure.

Update v1.2 (2024/11/06):

1, Addressing user feedback on difficulty removing supports from A1-1/A2 plates: A1-1 support structure is now tree-like and organic; A2 is now split into separate printable components.

Update v1.3 (2024/11/12):

1, Shaft hole tolerances increased by 0.1mm for improved fit, ensuring smooth operation.

2, Corrected the parameter error for the nut mounting area of part F1 (original diameter 4.2mm, corrected to 3.8mm) for better M4 nut compatibility. Reprint this component, or carefully modify the existing part.

Update v1.5 (2024/11/18):

1, The long shaft B2-1 is now split for XY plane printing, increasing torsional strength. Reprint if insufficient strength is observed.

2, Due to changes to B2-1, the internal hexagonal connection in I1-1 has been modified. If reprinting split shaft components, I1-1 must also be reprinted.

Update v1.7 (2024/11/26):

1, The H3 cylindrical thrust rod has been reinforced to improve strength. Reprint if breakage is experienced.

Update v1.8 (2025/04/20):

1, Resolved support issues with Bambu Studio 2.0 software; support settings for E1 optimized for easier removal.

2, Minor adjustments to B2-2 (no assembly impact; reprinting unnecessary).

3, Removed auxiliary supports from J2, achieving the same aesthetic result through slower wall printing.

Assembly Instructions: