How to use the Prusa i3 MK3

This is intended to be a general purpose guide to the Prusa i3 MK3 3D printers at the Construct. If you are unsure about anything presented here or have any questions, be sure to seek out help from a maker mentor or other qualified staff member.


Read ALL parts of this tutorial before starting your print!


Step 0: Should I print this?

  • Take a look at these considerations to answer this. If you’re confident that 3D printing is the way to go, then carry on!

Step 1: Model your parts

  • How you go about doing this will vary depending on what type of part you are making. Any software will do as long as it can export to the .STL format. Please see our designing for 3D printing page to determine what sort of software is the best type to use, and how to design your part to print well. Alternatively, you can use an online model sharing site like Thingiverse to locate and download a model for printing.

Step 2: Printing preparation

  • In order to get your files into a printable form, they must be exported from the modeling software in .STL  or .obj.  STL files do not encode units, so in order to make the part print at the correct scale, export from your CAD software in millimeters (mm).
  • The Construct uses a custom version of Cura to prepare and slice parts. The icon looks like this:
Cura logo
  • Open Cura from the computer’s desktop.  Before continuing, check the printer profile, found towards the top left of the screen, and make sure that it is set to Prusa i3 MK3.
the printer profile option, set to the prusa i3 mk3
  • Click the load model from file button, Load model from file icon and browse for your part. When the part loads, it may not be in the orientation you desired, though it should be the correct scale if you exported it correctly.  Click on the part, and Use the scale button scale icon to adjust this if necessary. You can use the output dimensions to scale your part to match the size you expected.
  • Use the move button move icon and rotate button rotate icon to orient your part so that it fits in the print area, and so that support is minimized. A good general rule of thumb is to make your part a pyramid: put the widest flat face at the bottom, and have the smallest region pointing up. Also factor in the orientation of the layers, and the fact that a low, flat print will be faster than a tall, skinny print.
  • Once your orientation is set, Cura will pre-slice your part. Wait for this to finish; take note of the print time and weight of material in the lower right.
the print time and material weight of a part as displayed in Cura
  • You also can click the print preview button preview icon to see the print with support and raft generated. Use this opportunity to check it for any unexpected support regions and as a last sanity check before printing.
  • Once you are satisfied with the time and weight, find a printer that is not in use. Remove the SD card from the printer and plug it in to the PC.
  • Cura will now allow you to save the file to the SD card by clicking the save to disk button, below your print time and material weight.
  • Before continuing, fill out the Construct 3D Printing Form (which will appear on Cura once you save). This log allows us to gauge the printers’ usage level and filament consumption, as well as charge you for your print, so it is mandatory for every print job run.
the print export screen for the prusa

Step 3: Printing

  • Click the eject button in Cura, then take the SD card out of the computer and plug it into the printer.
  • Ensure that the surface on the bed is flat, smooth, not ripped, and free of any material. Check the filament spool and make sure there is enough filament to produce your part. If the printer does not have sufficient plastic, speak to a staff member. Do not attempt to change rolls yourself.
  • On the printer, navigate to your part file (usually at the end of the list) and select it to begin the print.
  • The printer will home, heat, and print the part automatically. Please observe the printer until it has printed several layers (~10 min), as most print failures happen within the first 10 layers.
  • Once it appears to be printing well, it may be left alone to complete. Construct staff will not restart prints that fail due to user error. It is your responsibility to follow all of the above steps and make sure your prints run as they should.

Step 4: Finishing

  • To remove the part, carefully insert the round-edged scraper underneath the part and slide in. Gently apply force to one side of the part until it separates. If you are worried about damaging the printer or the part, ask a staff member for help.

As always, if anything is unclear or you have further questions, ask someone experienced with 3D printing in the lab.

Happy printing!