Curta Calculator Mods

thingiverse

It looks like you've got a long post with some detailed notes about your experience building a replica of the Curta calculator. Here's a summary of the main points: **Case Design** * You recessed the top of the case by 0.1mm to prevent it from lifting off. * The case has a design for padding on the bottom and between the Main Crank and the Step Drum using ¼ inch foam. * You used high-density foam that had too much memory, causing issues with the screw mechanism. **Digit Transmission Gears** * You filed the ends of the digit transmission gears to prevent snagging on the Step Drum teeth. * You also filed out between the teeth for the same reason. **Lathe Work** * You used a lathe to clean up parts and trim transmission shafts. * You made a jig to hold the results dial and selector shaft tops, and turned them to put a smooth surface on them for lettering. **Screwing Issues** * Screwing the digits cover to the upper housing was a pain. * The digit lettering on the bottom of the upper housing didn't line up with the arrows. **Lettering** * You bought a Silhouette Cameo 3 to do the lettering. * The software has limitations, but it can generate tool paths from JPGs and other formats. **DXF File Issues** * Reading DXF files into programs resulted in garbage characters (Figure 11). * Mr. Wu used QCAD to generate the DXFs, which were then exported as R9 versions that imported correctly into the Silhouette software. **Main Shaft Alignment** * There is no alignment hole in the main shaft STL file for the step drum frame bottom. * You had to shorten the length of the zero positioning lever arm about 3 mm to compensate. **Vinyl Lettering** * You applied vinyl lettering directly, rather than using them as stencils and painting them on. * Only two results dial digits have been rubbed off, but you plan to paint them on long-term. **Update** * You generated the case artwork using the Silhouette software. * The calculator took a beating at a local maker fair, with one of the selector shaft bearings breaking and causing it to stop working.