We have developed this kit to expand the Y axis  of your Prusa i31 which increases the printing area to 20 x 30 cm. What´s more, the Y axis is now more robust and easier and faster to assemble. You can check all the changes on the GitHub project repository.

To expand it simply follow these steps:

  1. Print off the new parts that you will need. Download them here.
  2. Assemble the new Y axis following the steps in the diagrams. Pay attention as you will need to reuse some of your printed and non-printed parts.
  3. Upgrade the firmware for the new printing area. Instructions at the end of this post.

Attention! Do not dismantle your printer until you have printed the new parts.

Base_larga_03n Base_larga_04n
 Base_larga_bottom Base_larga_top


Bill of Materials

In this diagram you will find all the parts of the expansion kit. The parts marked with a blue circle are included in the kit. The parts with an orange circle need to be printed. The parts with a grey circle are to be reused from your current printer.






Acrylic bed and glass printing surface

metacrilato (3)

Acrylic bed

The acrylic bed holds the glass printing surface. At the same time it is fixed to your aluminium Y axis using screws and springs. The springs allow the height of the printing surface to be adjusted, while absorbing unexpected inferences with the hot-end. The acrylic based is designed for 8mm material. The corners have been rounded to avoid mechanical stress. Thanks to this we guarantee long term performance by avoiding cracking of the acrylic.


Voids have been made in the acrylic bed, removing 36% of the material of the solid part and reducing the weight considerably. The voids are made to match the aluminium Y carriage in order to achieve aesthetic equilibrium of the whole axis. aluAluminium Y axis carriage (not included in the kit)
Cristal A4Glass printing surface The glass is 5 mm thick to strengthen it while maintaining a perfect flat surface.





The rods have been internally drilled with M4 threads. This enables them to be screwed in directly to the front and rear aluminium mounting plates. Consequently the assembly is made easier, the rods are shorter and the printed corners are not required anymore. The nylon washers serve to eliminate structural tension caused by variations (or tolerances) in the length of the rods, and also to absorb vibrations (and noise).





Front and rear aluminium mounting plates

These parts are a derivation of the PowerCode 3 and GalaCC 4  equivalent parts. They have been modified in order to screw in the rods (previous versions used printed parts for assembly). These plates have been designed for 4 mm aluminium.

Aluminium Front PlateAluminium Front Plate

Aluminium Rear Plate

 Aluminium Rear Plate


Printable Parts

End-stopY axis Endstop Holder This part is derived from the corresponding Prusa i3 Hephestos part. It has been made larger in order to fit the new length of the rods.
This part has been derived from the PowerCode Y axis belt tensioner. An M3 screw has been used to facilitate its acquisition. A guiding appendix has been added to avoid the part to rotate around the screw, solving this problem that was present in the PowerCode Pieza fijadora 1Y axis belt tensioner
Pieza fijadora 2Y-Axis motor holder This part is derived from PowerCode and GalaCC printer. It’s used to secure the Y axis motor to the rear mounting plate.


Your current firmware may be configured to limit the Y axis length to 200 mm. You  will need to upgrade the firmware in order to be able to print on the full 300 mm of your new bed.

  • You can upload the firmware using Cura 3D5. This video explains how to do it.


  • If you prefer, you can configure and compile your own Marlin6 for Hephestos please follow this link to the GitHub repository or download the source code.

  • If you have a customised Marlin version and want to keep on using it, just modify these parameters on the Marlin Configuration.h file.


  1.  Prusa i3 3D printer
  2.  Hephestos 3D printer
  3.  PowerCode 3D printer
  4.  GalaCC 3D printer
  5.  Cura 3D 3D printer
  6.  Firmware for Marlin 3D printer

17 thoughts

  1. Dear
    the Print Bed Expansion Kit is also suitable to a i3 rework or to a p3steel?
    Thank You

  2. Hi,

    Just purchased the Print Bed Expansion Kit from a local supplier.

    Any advice on adding a heated bed?



  3. Alberto Valero

    Hello, adding a heated bed can be complex due to the big surface, as you would need a power supply with at least 600 Watt and a controller board able to handle currents up to 30-40 Amperes, which is not usual. I would not advise to use heated bet for such a big printing surface.

  4. Hi Alberto,
    just a short question. I cant find a hex file in the Download. Can you say me the correct name, maybe i find it anywhere else.
    Thanks from Okoterfestcity 😀

    1. Solved! Hard stuff doing this for the first time… hate the programs with their different versions NOT working together with the current OS or Windows :(


      1. Hi Karl,

        You are right, there is a problem downloading the HephestosXL_1.3.1.hex file at least with some browsers, we will fix it soon.

        Thanks por your patient, and also for reporting.

        1. Hey Pablo,
          thanks for your answer. Just cant download the Version anywhere. No 10.10 Mac, No 2x Win7 PC with all Browsers. Can you send me the data?
          werner.werner ät
          Would be very nice, because the current version i downloaded (dont know which one exactly) sucks. Fails in Filament Loading, Heating and so on…
          Thank you!!!

          1. Hi Karl,

            I have send you an email with the file.

            Thanks for your patience.

  5. Hi Pablo Lozano,

    Can you send me the HephestosXL_1.3.1.hex file too?
    Thank you.

    1. Hi Hung,

      I have sent it to you.

      Thank you for your patience.

  6. Hello,
    Can you send me the firmware update to?
    Thank you,

    1. Hi Antonie,

      I have sent it to you.

      Thank you for your patience.

  7. Hi there,

    can you send me the correct file as well?
    Thanks in advance!


  8. how many mm should the frame be from the back plate?  I can’t find any instructions that mention this.

Comments are closed.