Working with File Types

This introductory tutorial will help you understand how different file types are used in Simplify3D.  There are several different files used for 3D printing (.stl, .fff, .gcode, .factory, etc.), so we’ll start at the beginning of your workflow and explain when each file type is used.  You will also learn how to export and save these different file types.

STL and OBJ Files: Output from CAD Software

statue of liberty meshThe first step in the Simplify3D workflow is to import an STL or OBJ file.  STL (STereoLithography) and OBJ files can be exported from a CAD program or downloaded from a website that provides 3D design files such as Thingiverse, YouMagine, or MyMiniFactory.

At Simplify3D, we refer to these files as a “mesh” or “triangle soup” because they describe the three-dimensional surface of a model through thousands and thousands of tiny triangles.

FFF Files: How Your Model Will Be Printed

After you import an STL or OBJ file, the next step in the workflow is to add a “Process.”   Your Process contains all the information that defines how a specific part will be sliced and printed on your 3D printer, including settings for your extruder, layers, infill, temperature, supports, etc. When you save or export your Process, a FFF file is created. A FFF file is actually saved in plain-text format and can be opened with a text-editor if you are curious about what is being saved.

During the initial software setup, Simplify3D will automatically add and configure your first Process based on the printer you have selected (typically called “Process1”).  In most cases, you will only need one Process to print all of the models on your build platform. However, there are some advanced printing modes that may require more than one Process (see Printing with Multiple Extruders or Using Different Settings for Different Regions of a Model).

Screen Shot 2014-07-01 at 2.03.12 PMThere are many times when you will want to modify the Process settings. For example, if you want to use a custom layer height, printing speed, or infill percentage. To make changes to your process, click the “Edit Process Settings” button. After you have made your modifications, choose OK to save your changes. The Simplify3D Software will automatically remember your last saved Process settings, so you can quickly make changes without worrying about saving lots of files.

There are some examples where you may need to export your Process settings. For example, if you have multiple printers, you can export the best settings for each machine so that you can easily switch between the different configurations.

To save your FFF Process Settings:

  • Open the FFF Settings window (by clicking “Edit Process Settings”)
  • Enter a new Process name, if desired, and click Export (as circled below)
  • After you export the file, it will automatically be added to the “Select Profile” drop down list so that you can easily reload these settings at a later date

Export Circled

G-Code/X3G Files: Instructions for Your Printer (Toolpaths)

G-Code (or X3G) is created when Simplify3D “slices” a 3D model into precise instructions for the printer.  G-Code tells computerized machines where to move to, how fast to move, and through what path to move, which is also known as the 3D printing toolpath. G-Code uses a plain-text format whereas X3G is written in binary. The X3G format is used by machines with the MakerBot or Sailfish firmwares (such as the MakerBot Replicators, FlashForge, Wanhao, MBot, etc.).

When you click Prepare to Print!, your 3D model will be automatically converted into the 3D printing toolpaths for your machine. You will be able to inspect a very realistic preview of each line and layer of your toolpath. When you are satisfied with the preview, you have two options: 1) Begin printing over USB, or 2) Save Toolpaths to Disk. If you choose to print over USB, there is no need to save a copy of your G-Code or X3G file, as you will be streaming this information directly to the printer.

To save a G-Code or X3G file: select the “Save Toolpaths to Disk” option.  You will be prompted to identify a location where you want to save your files (if your printer uses the X3G format, the software will also create the corresponding .x3g file in the same location).

Factory Files: A Combined File to Retain Your Simplify3D Project

Saving a Factory File picSimplify3D offers a unique way to save all the information about your project into one comprehensive file, known as a “Factory File”. The Factory File includes a copy of the 3D models that have been imported, their positions on the bed, your Process settings, and any custom support material that has been created.

Whenever you exit the Simplify3D Software, the state of the application is automatically saved so that you can easily resume where you left off the next time you open the program. There is no need to save a Factory File each time you close and reopen the program. However, there are other times you may want to save this file such as sharing your project with a friend or creating a back-up for personal use.

To save a Factory File: in the top menu bar, click File > Save Factory File As.

Creating File Associations for a Speedy Workflow

If you “associate” certain file types with the Simplify3D Software, a double-click will automatically open that file type within the Simplify3D Software. For example, if you double-click on a G-Code file (after establishing the file association), the toolpath will automatically be loaded into the Simplify3D animated preview window.

Simplify3D Software can be associated with the following file types:  .STL, .OBJ, .GCODE and .FACTORY files.  The instructions below will help you establish file associations using your specific operating system.


  • Right Click on the specific file; Select “Open With…”
  • Browse and select Simplify3D; Enable “always use this program”


Mac OS X

  • Control + Click on the specific file; Select “Open With…”
  • Click “Other”; Browse and select Simplify3D; Select “Always Open With”



  • Right Click on the specific file; Select “Open With…”
  • Select “Other”; Browse and select Simplify3D


Now that you understand the different file types and processes associated with using Simplify3D, you’re ready to get started!