Open bottles effortlessly with 30 mm plastic caps. No clamping force required - the opener clamps the cap while turning.

Most PET bottle caps are either 30 mm or 40 mm in diameter. Because the diameter of the caps does not always correspond exactly to the nominal size, an opener must be able to adjust itself. This is the adaptive 25 to 32 mm version of my adaptive 38 to 42 mm PET bottle opener athttps://www.thingiverse.com/thing:7281693.

How to use:

1. Lower the opener over the cap and turn it clockwise.
2. Turn the opener counterclockwise to clamp and loosen the cap.
3. Remove the opener, then unscrew the cap.

While lowering the opener over the cap in a clockwise direction, you may hear a creaky noise. That's okay. With caps larger than 30 mm, tilting the opener while turning clockwise may help. Do not fully lower the opener over the cap if (a) the cap is very short and the bottle has a flange immediately below the cap, or if (b) the cap itself has a flange at its lower end with a diameter greater than or equal to the ridges; otherwise, the rollers may extend around the flange and fail to perform their intended function.

It loosens almost any plastic cap (preferably having fine ridges around its circumference), but may fail on metal caps. Do not use it on crown caps (e.g. beer bottles) as these may damage the opener. And do not leave the opener hanging on the cap, because the opener's spiral - acting as a spring - may permanently lose tension if you do so.

The cage element comes in two versions:

• With the text "Max. 50 °C" for materials with low glass transition temperatures such as PLA or PETG. This will remind users that they must not clean the opener in the dishwasher. My design has PLA or PETG in mind.
• Without the "Max. 50 °C" text if printed with materials with a higher glass transition temperature, such as polycarbonate, ABS, or ASA. But I haven't tested these materials for their suitability.

The cover element comes in two versions:

• Screw-on for three 2.2 x 9.5 mm or (preferably) 2.2 x 6.5 mm or 0.1 inch sheet metal screws
• Glue on with positioning stubs. I use Revell Contacta Professional glue.

Both PLA and PETG work well. I prefer PETG due to its lower friction coefficient, which makes it easier to lower the opener over the cap. I printed the opener on my Bambu X1C with the following settings:

• 0.4 mm nozzle, 0.28 mm layer height, structured build plate (though build plate adhesion is not a problem).
• No supports required.
• Cage: 2 bottom layers, 2 peripherals (print sequence: first inner, then outer), 2 top layers, 15% infill.
• Cover: 2 bottom layers, 2 peripherals (print sequence: first inner, then outer), 2 top layers, 15% infill.
• Rollers: 2 bottom layers, 2 peripherals (print sequence: first outer, then inner), 2 top layers, 15% infill.
• Spiral: zero bottom layers, one peripheral, zero top layers, 100% concentric infill. In Bambu Studio, the layers of the spiral should look like the enclosed picture (all layers' nozzle paths steering smoothly around corners and along spiral arms). This seems a bit odd, but it provides maximum strength.

IMPORTANT:

• Do not remove the spiral from a hot build plate, but wait until the build plate has cooled down. Otherwise, the spiral arms may become permanently deformed. The spiral and its axles appear to be fragile. However, the working load will act from the cap's perimeter via the rollers to the inner flank of the cage.
• To ensure that the opener will work properly, the three rollers must rotate smoothly on the axles. For this purpose, there is a deliberate gap between the rollers' bores and the axles. Make sure (e.g. with a suitable drill if necessary) that the rollers' bores are smooth and that the spiral's axles are free of stringing and blobs (e.g. cutting them off with a knife). Print the spiral and the rollers individually. Print the parts individually. If you choose to print the parts in one go, then print them object by object,

Assembly:

• Press the triangular bore of the spiral over the triangular axle of the cover. You can glue the triangle (not the arms!), but press-fitting should be enough, as there will be no loosening forces during use, and if you don't glue it, you can replace the spiral without reprinting the cover. The triangle guarantees the correct angular position of the spiral relative to the cage.
• Push the rollers over the axles of the spiral. They should turn on the axles without noticeable friction.
• Put the cage over the cover/spiral/rollers combo.
• Screw-on cover version: Secure the cover to the cage with three 2.2 x 9.5 mm or (preferably) 2.2 x 6.5 mm or 0.1 inch sheet metal screws. This will maintain repairability (although my openers have never broken so far after using the above print parameters).
• Glue-on cover version: As an alternative, you can glue the cover to the cage. The three stubs help maintain its position during drying.

I am providing an .stl file and OpenSCAD source code to print test caps for testing and demonstrating the opener's function and diameter range.

The source file can be engineered for almost any cap diameter range. However, the outer diameter of the opener will increase with (a) the maximum cap diameter and (b) the diameter range. An opener with a range of, say, 28 to 42 mm using my design will have an outer diameter of approximately (42 + 1) + 2 * (42 - 28 + 7) + some mm for the walls = about 90 to 100 mm, which may be more difficult to handle with small hands. Furthermore, the height of the tapered section of the rollers will have to be increased, increasing the

As always, I include the OpenSCAD source file for you to adapt and/or improve:

• Download and install OpenSCAD fromhttps://www.openscad.org
• Launch OpenSCAD and open the enclosed OpenSCAD source file (/File/Open).
• Amend the parameters at the top of the file or even amend the code.
• Save your changes (/File/Save).
• Render the design (/Design/Render).
• Export the rendered design, for example, as an .stl file (/File/Export/Export as STL).
• Cut and print.

See my other designs at
https://www.thingiverse.com/thinger13/designs

History (TL;DR):

• During the Corona lockdown in winter 2020, I discovered asimomagic's ingenious bottle opener athttps://www.thingiverse.com/thing:3971787. In retrospect, it seems to be an implementation of the expired patent.https://worldwide.espacenet.com/patent/search/family/029390693/publication/JP2003300597A?q=pn%3DJP2003300597.
• At that time, I designed (but did not publish) a double-diameter remix for 30 and 40 mm caps. It worked very well for caps of exactly these two diameters, but failed on even slightly deviating caps.
• I then started designing about 10 variations of adaptive openers printed in PLA. These designs either failed to work (e.g. due to insufficient adaptive range, insufficient or excessive friction) or worked well but were unintuitive to use. A colleague praised one of my most complex designs (implementing a planetary gear) as "only for Nobel Prize winners". Traumatized by such encouraging feedback, I put the project on hold for several years.
• A few weeks ago, I suffered another frustration when I offered one of my initial, easy-to-use Asimomagic-Remix openers to an occupational therapist for his patients. It failed on her bottle because its cap had a slightly narrower diameter than 30 mm.
• Ashamed, I silently vowed to make a fresh start and to nail down a working solution. It took me another week of work, but I now have the satisfaction that it's actually working, even when printed in materials as hard as PLA. It uses the mechanical principle of a freewheel. Any friction problems are solved by toothed rollers and a cage.
• Looking back, my current implementation seems to be a variation of the expired patent.https://worldwide.espacenet.com/patent/search/family/017962367/publication/JPH10147398A?q=pn%3DJPH10147398and possibly the patent that has not yet expiredhttps://worldwide.espacenet.com/patent/search/family/051577454/publication/JP2014156278A?q=pn%3DJP2014156278, but I didn't research it further.