Included are the printable STL files (start with "Open3D fountain pen") for:

1. standard size barrel/body which can accommodate 2 short international ink cartridges or a standard converter (1 in use, 1 for spare),

2. mini size barrel/body which can contain 1 short international ink cartridge (for those that like short pens),

3. mini size barrel/body with threads on the back to screw the cap firmly on when posting cap,

4. the cap itself.

5. for convenience, I'm also including Zoidberg38's pen section. I'm sure Hargo's Kaweco section variation (https://www.thingiverse.com/thing:2769490) would also fit; but I've not tried it.

Files starting with "working" were my working files used to create the shapes and joining the shapes together. Feel free to use them to make your own pen variation. The Openscad files were used to create the elliptical streamlined shapes. The threads were cut out from Zoidberg38 (https://www.thingiverse.com/thing:2026499) designs and pasted onto the shapes using Microsoft's 3D builder.

With Microsoft's 3D Builder, it was quite easy to load an object and "stick it" to the pen. Then just merge the objects together and print it.

For the business end of the writing components, I used what I previously bought; the Lamy nib/feed from Aliexpress, about SGD $5 for a set of 5 feeds and nibs. I feel that the straw is required as an ink barrier, as PLA seems to be a bit porous. When ink touches it, it soaks through and stains the material.

Feed:
https://www.aliexpress.com/item/32823667546.html?spm=2114.12010615.8148356.24.d3837930JmXAAy

Nib:
https://www.aliexpress.com/item/32817000287.html?spm=a2g0o.detail.1000023.8.5affaf475hOh1v

Things to improve:

1. adding a pen clip: plastic (is it strong enuf)? screw on metal clip (where to buy)?
2. personalise it with a name?
3. make it thinner?
4. etc, pls share your designs :-)