This was designed to look like a pen I made in Jr. High woodshop. Unfortunately, I misplaced it during a Robotics compitison. so when I got a 3D printer I wanted to remake it in the way I remember. After 3 iterations I got it to where I'm happy.
Use a Bic pen that you can easily get and pull the tip and pen ink out as one part, they should come out as one. if you want you can use the cap from the original pen, cut off the clip and it should fit just fine on to the 3D printed pen tip.
print from the large nob at the end of the pen on the print bed.