Stereolithography, or STL, is a 3D file protocol developed in 1986 by Chuck Hull of 3D Systems. Typically employed as the output model of a CAD system, STL is, in short, a means of describing a 3D object in mathematical terms.
These descriptions store and transfer data about the file model in the form of tiny geometric shapes, which join together to form the subject’s surface, much like in the image above. And while STL has become the defacto standard file format for 3D printing, few 3D printers actually interpret STL directly. Instead, the STL file must first be sliced into G-code layers.
This is the job of a slicer.
To understand the need for slicing, one must first understand the 3D printing process. Once a concept model is defined in the chosen CAD program, it is prepped for manufacture by being sliced into layers.
Model layers are defined bottom to top. Each layer is a 2D definition of the model’s geometry in the X-Y plane at a particular height in the model. Slicers define these layers in G-code, the positioning language of all CNC machines.
Each layer’s thickness is up to the user’s discretion, but typically runs 0.2 to 0.4 millimeters. Each layer then is built onto the 3D printer’s build surface, one atop the other. At the end of this, you get your model printed in 3D.
Slicers are the software that analyze the concept model and break it down into the proper machine code. While there are several popular slicers on the market, they all share some common features:
The purpose of the model will play a part in defining these parameters. If you’re drafting, you may consider the ‘draft mode’ to save on material and time. If you’re printing a piece to show off, you may consider a slower print speed and smaller layer height to have a nicer finish. All of these factors are under control of the slicer, all becoming part of the final G-code.
So, with all the slicers that are available, how do you choose the best one for you? As a rule of thumb, start with the one that comes with (or is recommended for) your 3D printer. These ‘standard issue’ slicers will come with good support and a wide user base, making it a great place to start.
But don’t get locked in. There are many slicers out there, most of which are free. Once you’re familiar with the general way a slicer works, consider branching out to one that might give you different options and capabilities.
All slicers have a similar user interface. All offer mostly the same parametric adjustment capability. However, the efficiency of the actual G-code, the way details are transported from conceptual to actual, and the overall ease of use varies greatly from program to program.
All will have a learning curve so don’t give up on the first failure! Practice on a few different slicers, then go with the one you develop the best taste for.
Lastly, you may want to join a user group for your 3D printer. If you outgrow the default slicer, or your prints tend to lean more toward the exotic, find out what others are doing to meet similar challenges.
Once you’ve designed your model in CAD and saved it as an STL, slicing is the finishing process to convert your STL to G-code.
Select the parameters that suit your needs, adjust scale and desired quality, hit “Slice” and viola, a custom G-code file ushers your new baby into the world. You just have to be ready with the cigars.
Feature image source: Bill Porter / All3DP
License: The text of "STL to G-Code: How to Convert STL Files to G-Code" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.