Reddit user 5ilver posted his no cost 3d printer project. He made it from parts and scrap from his workshop. It uses hot glue pistol sticks. It looks rough and it prints rough but the cost is zero :-)
Full thread and more information on Reddit:
https://www.reddit.com/r/3Dprinting/comments/3auec9/my_zero_buck_hot_glue_printer/
Full thread and more information on Reddit:
https://www.reddit.com/r/3Dprinting/comments/3auec9/my_zero_buck_hot_glue_printer/