CADs and "How do I get/make a file to print?"

I want to print! What is the basic process?
And that is basically it. The gcode file is generally one instruction to the printer per line. A circle that seems to be a smooth circle might be broken into hundreds of individual moves. While gcode allows for the movement of the print head through an arc, most slicer software does not use that capability and some firmware does not support movement through curves. All movement is in straight lines.
 * 1) You either create or download a file that describes a 3D thing.  The most commonly used file format is a type called an stl file.  In this sort of file, your 3d model is represented by triangles.  The triangles are "dimensionless".  The file could be in inches or millimeters but almost always is in millimeters, but this is not specified anywhere in the file.  ".stl" files are the common format for 3d models in the 3d printing world.
 * 2) You slice the file. A slicer is a program that understands the physics of how your printer works, how fast it can run, how hot the bed and how large the print bed is, and what shape the bed is and how hot the  extruder should be, how big the nozzle is, and so forth.  It then renders that 3D object  from the .stl file and takes horizontal slices through the object.  It figures out how to move the print head, how fast to move the print head, how much filament to feed to the print head and when. The best slicers think ahead at least some, in some areas. And the same STL file, sliced by different slicers, will print very differently.  In some cases this is because the people who wrote one slicer were planning on using it with different hardware, or had different opinions about what was important.  You might consider using several different slicers and figuring out which one you like.  You might like more than one for different things.  Many are free to use.
 * 3) You transmit the file produced by the slicer to the printer.  You can write the gcode file to an SD chip, and the printer can read it, or you can drive the printer via USB (or for some printers, not the He3D printers, Wi-Fi).

One thing you should understand is that the gcode process generally has no feedback..There are a very few cases where you wait for something to happen, like for something to heat up or cool down. And there is an implied wait when you tell the printer to move - the printer attempts to complete the move before it goes to get the next instruction. But if an instruction fails, (like something

This page is a stub. Intend to include:
 * Use of CAD programs and how to export to a 3D printer file format.
 * References for pre-built models
 * http://www.thingiverse.com/