Using the eRockets Prusa i3 MK3 printer

eRockets recently acquired a Prusa i3 MK3 3D printer. The following contains basic hints for getting started on designing and printing rocket parts.

As you get started, Justin and Mark can provide guidance and advice on proper use of the printer and printing 3D objects.

Getting Started

As a first step, review the new user support information provided by

Good tutorial resources for 3D printing:
* Maker’s Muse, particularly his 3D printing 101 playlist.
* 3D Printing Nerd

The workflow involves three steps:
1. First acquire the .stl file of the design you wish to print or design the 3D object yourself in CAD/CAM software and export the design to a .stl file.
2. Import the .stl file into slicer software to generate a .gcode file.
3. Use the .gcode file to print the object.

Acquiring existing designs

There are many websites devoted to people sharing 3D designs. One of the more popular sites is Thingiverse provides many rocket designs including complete rockets, rocket parts, and rocket accessories. The creators who share their designs may include helpful instructions. All include the .stl files of the 3D objects and some include their original software files (e.g., Fusion 360, SolidWorks) and suggested settings for the slicer software. Just download the .stl files to use them in the slicer software.

Also, there is a shared Google Drive folder Rocketry CAD Folder with designs.

Creating your own designs

There are many good 3D modeling software options each with their advantages and disadvantages. The design software must have an ability to export a .stl format file of the 3D object. All design software come with a learning curve, so expect to spend some time.

Fusion 360: From Autodesk, Fusion 360 is a full featured 3D design software with professional grade features. There is a free version that can be used by hobbyists for non-commercial use.

SolidWorks: SolidWorks is a popular option used by many people.

OpenSCAD: OpenSCAD is freely available software that is “old school.” You write code to create the 3D object. Parameterizing the code allows you to scale the object through a parameter pane. The Rocketry Forum has many OpenSCAD generators for various rocket parts and accessories. 

Slicer Software

The best approach to learning how to use slicer software involves learning the software recommended by the manufacturer. has Prusa i3 MK3 drivers and software. Their current version (2.2.5) includes a customized version of the open source Slic3r software. You’ll probably find just using the Slic3r software easier to start with then their Prusa Control software. 

  • Slic3r software (i3 MK3 software): Prusa Drivers and Apps

  • Settings to start (change/adjust as you gain experience):

    • Printer: select “Original Prusa i3 MK3

    • Print settings: 0.15mm OPTIMAL MK3

    • Filament: PLA (or ABS, PETG, etc)

    • Printer: Original Prusa i3 MK3

    • Fill Density: 20%

    • Support: none (unless your model really calls for it)

    • Brim: None

  • Workflow:

    • Start up Slic3r.

    • In the Plater tab, click the add button to load the .gcode file.

    • Double check basic settings on the right of the window.

    • Only use the Print Settings, Filament Settings, or Printer Settings once you gain some experience and knowledge.

    • Click the Slice Now button on the right of the window.

    • Check the Preview pane (bottom center of window) to review the slicing.

    • Click the Export G-code button on the right of the window to save the .gcode file.


Currently, the MK3 is setup to print from an SD card. Justin and Mark plan to work during Spring 2019 to setup a wi-fi based method of sending .gcode files to the printer and provide basic training on how to use the printer.

* Put SD card into the slot on the left of the printer. Note that the contacts of the SD card should be facing you as you insert the card.
* Power on the printer (right side, the bottom of the power supply).
* Wipe down the PEI spring sheet with 90%+ Isopropyl alcohol.
* Using the menu system, preheat the extruder and bed for the material being used (e.g., PLA, ABS, PETG.)
* Once preheated, load filament if not already loaded.
* Using the menu system, load the .gcode from the SD card.
* The printer steps through a start up sequence and then moves to printing the file.
* Keep an eye on the print, particularly for the first few layers to make sure it is adhering to the bed.
* When the print completes, lift the magnetic PEI sheet off the printer, bend to loosen the print. Remove the print and any extraneous filament on the sheet.

Last Update: 2019.04.21