Curta Calculator Type I scaled at 3:1
by mwu, published
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The Amazing Curta Calculator is now 3D Printable!
I am doing an Ask me anything on Reddit /r/3Dprinting on Tuesday Sept 19th at 3pm EST / 12pm PST!
New group for discussion, bragging rights, and help with Curta builds: https://www.thingiverse.com/groups/curta
Bill of Materials
Assembly Video (The build manual contains more details, but this is a good visual guide)
See video of the Curta in action.
See for my original build for details on the project.
The CAD files are shared on OnShape
Updated the BOM to fix the size of the upper carriage spring and eliminate confusion in description of the main body.
Updated the BOM to add a file name column to make it easier to find the correct files. Also removed the remaining references to the old 0.25mm nozzle requirement.
Added a split step drum to reduce the required printer print volume! Minimum print volume is now 160x160x170mm!
Fixed some naming problems with files and in the BOM. Also added the two files I had missed below into the BOM.
Added missing bolt sleeves for zero positioning lever and anti reversal pawl.
After manually aligning all the 5mm number stencils on the lower and upper housing and then messing up the paint, I decided to create stencils for it (lower_housing.dxf and upper housing numbers.dxf). Those stencils are now uploaded.
Also, I have added a group for those building the Curta. I will be answering questions there and I look forward to seeing pictures of people's in-progress builds: https://www.thingiverse.com/groups/curta
Updated the main axle and step drum model. The old one works, but the hole for the crank handle pin was 90 degrees off. This change is basically cosmetic.
- Updated a few files that were requiring too much manual fitting work.
- The zero positioning disk is updated for easier printing / better teeth for the anti-reversal pawl.
- Added missing crank pin file.
- Adding dxf files representing paint masks for numbering and lettering. I cut these from vinyl with a Cricut machine.
- Updating the BOM because the torsion springs for anti-reversal pawl and zero positioning lever recommended in the BOM were way too strong. I ended up making these springs by hand. The BOM is now available as PDF and XLS files.
- Adding the initial draft of the build manual. This covers the entire build process -- including making the springs mentioned above. Feedback on this build manual is desired and welcome -- help me improve it for others please.
Update 3/29/2017 -- In the process of preparing the build manual, I have a list of several files which need correcting to get correct assembly and functionality out of the Curta. I recommend waiting until I can get these changes published before doing much printing if you haven't yet. Particularly, the mount hole for the crank handle on the main shaft was 90 degrees from where it should have been.
While the build manual is taking me some time, I am excited by the progress on it so far. In the process I have disassembled and reassembled the second Curta which helped me find and eliminate extra friction. I will have another video of the Curta going up soon which will cover a simple, but difficult calculation that has eluded a correct result on the 3D printed Curta until now. That calculation is simply starting at 0, adding 1, then subtracting 1. The result should be a completely zero result with zero showing on the turns counter as well. Since the Curta utilizes addition for subtraction, the calculation requires the Curta to rotate every result and turns counter dial to 9 and a carry operation to cascade all the way around bringing each digit back to 0.
Update 3/9/2017 -- I have assembled a second Curta and taken loads of pictures along the way. I can now either work on a build manual utilizing the photos I took or a series of build videos. There are a LOT of photos and a lot of steps involved. What would you prefer (google form poll)?
Update 1/18/2017 -- I have updated the transmission gear and lockout parts to be printable using a 0.4mm nozzle instead of a 0.25mm nozzle. Thanks to the feedback from MikeHenry. I also updated a repaired Lower Housing.stl due to non-manifold edges.
Update 01/06/2017 -- I found that the tens bell also had non-manifold edges causing problems when slicing. A repaired copy has been uploaded.
Update 12/30/2016 -- I found that the main axle and step drum had non-manifold edges that may cause problems when slicing (Simplify3D skips a few layers in the next to last row of teeth). I uploaded a repaired copy.
Update 12/17/2016 -- I found a part I had missed uploading a file for. It's the securing spring for the zero positioning plate. I have now added the file and added it to the BOM.
Update 12/12/2016 -- I just added layer height, infill, orientation, and support notes to the printed files in the BOM. First step in getting actual build instructions.
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Curta Calculator Type I scaled at 3:1 by mwu is licensed under the Creative Commons - Attribution license.
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