What is the best free source for generating g-code Ok so i have built a 3d printer from old cd rom drives. Before installing the 3d pen(extruder/hotend) i used www.makercam.com to export i file containing a star. With a marker attached the machone successfully drew a star. Now i have the 3d pen but using makercam i am not having any luck. Is there a better way to generate files for my new toy?
Try using TinkerCAD!

I'm not advertising here - I have used TinkerCAD in the past for 3D printing.
TinkerCAD allows you to easily build and create simple shapes by the press of a button. (I assume this is what you mean by generation)

It is great for testing if your homebrew 3D printer works.

Link: https://www.tinkercad.com/