Mega Prusa I3




Introduction: Mega Prusa I3

About: Do not follow the ideas of others, but learn to listen to the voice within yourself. Aldric Negrier aldricnegrier

The Prusa Titan concept was first introduced by the company named on October 8 2014, however to this day the company did not publish the blueprint's for the build of the large Prusa i3 3D printer.

Because i found the concept very interesting i took the liberty of sharing my version called Mega Prusa i3 Rework. The Mega Prusa i3 rework is basically an enlarged version of the Prusa i3 Rework. Is is scaled up from the original design. To be more precise, the Mega Prusa i3 Rewrk is scaled um in order to allow 8 times the build volume of the Prusa i3 Rework, a stunning 400x400x400mm.

Step 1: Photos of Builds and Upgrades

Here are some photos of some builds of the Mega Prusa i3, made by some members of the instructables community.

For more info on upgrades please visit (stormychel designs):

Some very us-full comments/upgrades made by sinstructable user named stormychel:

1 - Do not use the resistors to heat the bed, get a silicone heater here :
2 - You need an extruder :

3 - My version of the frame :

4 - Use my Y-belt holder instead of the original one :

5 - Also print these to shim out the extruder to fit the modified X-carriage :

6 - Use my Z-endstop here with Sainsmart endstops (these might require gentle bending to be able to get to the mounting holes, this also counts for the X and Y ones :

7 - Here's a spool stand I modified to fit the 9mm MDF frame :

Step 2: Open Source RepRap Design

The Mega Prusa i3 Rework by reprapalgarve is just a scaled up version of the Prusa i3 rework 3D printer. Most of the 3d Printed parts where redesigned in order to house the LM12UU Bearings and the 12mm smooth rods.

Because the Mega Prusa i3 is has a big and heavier structure 8mm rods don't work, so for that reason 12mm rods where used.

Use this sketchup file as a guideline for your build.

For more information on the Prusa i3 rework please visit the official reprap source here:

Step 3: Bill of Materials

Here is the list of material needed to build a Mega Prusa i3 Rework, tey are very similar to the Prusa i3 rework.

- Rods

4 Smooth Rod Ø12 740 mm

2 Smooth rod Ø12 540 mm

2 Smooth rod Ø12 600 mm

2 Threaded rod M5 520 mm

4 Threaded rod M10 770 mm

4 Threaded rod M10 430 mm

- Mechanical Parts

14 Linear Bearing LM12UU

1 Bearing 624

4 Bearing 608

1 Belt GT2 1400 mm

1 Belt GT2 1400 mm

2 Coupling 5*5

5 Motor Nema 17

2 Pulley GT2

- Heated bed

1 Aluminium plate 450x450x3mm

1 Glass Plate 450x400x3mm

1 Kapton Tape

8 Binder Clip

1 Thermistor

- Electronics

1 RAMPS Board

1 Arduino Mega 2560

4 Micro stepping Drivers

3 Endstop w/ cables

1 Power supply w/ cables

- Screws, nuts and washers

41 Screw M3 14

3 Screw M3 24

4 Screw M3 50

2 Screw M3 60

6 Screw M4 20

1 Screw M8 30

53 Washer Ø3 mm

6 Washer Ø8 mm

54 Washer Ø10 mm

1 Grub Screw M8 20

5 Grub Screw M3 8

33 Nut M3

6 Nut M4

2 Nut M5

1 Nut M8

54 Nut M10

1 Nylstop Nut M8

Acrylic Frame

1 Single frame with back support
1 Heated bed mount

Step 4: Cutting the Smooth and Threaded Rods

Tools :

- Grinding wheel

- Full Face Mask and gloves

- Grinder

- Pencil and ruler


Using the pencil and ruler mark the cutting lengths on the rods. Using a grinding wheel cut the rods and according to size. After cutting grind the extremities of the rods for a sooth finish.

2 Smooth Rod Ø12 740 mm

2 Smooth rod Ø12 540 mm

2 Smooth rod Ø12 600 mm

2 Threaded rod M5 520 mm

4 Threaded rod M10 760 mm

4 Threaded rod M10 430 mm

Step 5: Acrylic Frame - CNC Mill or Laser Cut


- CNC machine or Laser cutter


- 600x600x10mm acrylic sheet

- Acrylic glue

Instructions: After cutting the acrylic glue the rear part of the frame for extra support.

Step 6: The Y Axis Guide and Transmission System

Mount the Base of the Mega Prusa i3 Rework according to the Skechup design.

Step 7: The X Axis Guide and Transmission System

Mount the Vertical frame of the Mega Prusa i3 Rework according to the Skechup design.

Note that the photos on this step show 8mm smooth rods instead of 12mm, 8mm rods don't work, they do not have enough strength to support the structures in place.

Step 8: The Z Axis Guide and Transmission System

Mount the Z axis of the Mega Prusa i3 Rework according to the Skechup design.

Step 9: The Electronics

Wire the electronics according to the wires on the schematic, with the exception of the heat bed.

Step 10: The Aluminium Heat Bed

Fist i tried to connect 4 heat-beds together but eventually found a more cost efficient way to do it using resistors.

The Heat bed is made from a 450x450x3mm aluminum plate. It has 4 10W resistors 4.7 Ohm in parallel connected to the Ramps D8 connector.

Each resistor has 2 holes for fixating on the plate using screws.


- Tap 4mm threaded screw holes in the aluminum plate (for fixating the resistors)

- Fixate the resistors in place using M4 bolts

- Connect all 4 resistors in Parallel

Step 11: Mega Prusa I3 Rework Vs Normal Prusa I3 Rework

Prusa i3 rework

- Build volume 200x200x200mm

Mega Prusa i3 rework

- Build volume 400x400x400mm

Step 12: The Final Results

The Mega Prusa i3 Rework is a excellent machine to have in your arsenal of 3D printers :) because of its large build volume and because it is easy to build.

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1,223 Discussions


9 months ago


how configuring build size ? 40*40*40

i made it

work in 150*150*150


Thanks for the great article! I'm planning on building this with an aluminum frame 2020.

Any pointers on where I can find the printable motor mounts for this frame?



1 year ago

I'm at the stage of ordering parts. Was checking out those ball bearings and noticed that I can only place 2 x 608's baset on the scetchup model on belt idlers. Where do the left over 2 x 608 and 1 x 624 go?

Hello all Mega Prusers!

I'd like to start seeing some pictures of your Mega Prusa prints. I'm honestly starting to doubt the whole construction of the Mega Prusa since I really can't get rid of the small waves in the walls of prints which probably are caused by vibration in the construction(probably in the Y-bed). I would like to see some proofs of successful prints so that I know that good prints are actually achievable!

I run acceleration in Y=250mm/s2 X=250mm/s2 XYjerk=10, what are you running?

4 replies


the vibrations originate from the Y-axis, the large bed in general, and the Z-axis. You can improve quality by fixing the top of the vertical frame to the back of the horizontal frame by threaded rods. Also, this is not THE printer to make gorgeous prints, it is a printer to make large prints, especially those where strength and size are more important than visual appeal. Can post a photo of what you consider to be 'bad' quality so we can compare?

After hundreds of hours I am now nearing completion of the printer. There are countless of upgrades on my mega prusa. But at last I have been able to print the first ABS part I am genuinely happy with.


But I still have some minor ringing problems, which pretty much points to the Y-axis being too unstable.
I'm running the Stormychel version of the Y-bed and I have also 10mm rods going diagonally from the bottom of the plate the printer stands on to the X-pillars. Should generate a real stiff frame, but I'm imagining the 2mm alu sheet vibrating when changing direction quickly. Help me brainstorm how to stabilize the Y-axis even further! Maybe carbon rods running in a cross under the aluminium sheet?

After some additional settings and stiffening up the frame I made the 3DBenchy in ABS.


can anyone print the plastic parts of the printer and shipping by corrier? naturally I pay for it!

Does anyone know where i can get the frame laser cut? is there a servese on the web that has decent prices for this kinda of thing?

Maybe I am looking in the wrong area but I cannot find the files to cut the frame in MDF. I have a CNC (not laser cutter) and would like to get the frame cut. Thanks.

Hey just currious.. About how much does this thing cost to put tohether?

why are 2 of the smooth rods 540 and 2 are 600?

You can use it if you want..

I have published my evolution of the Mega Prusa i3 on Thingiverse. It features a stronger frame (also in case of MDF), support for 2 Chimera hotends, and all my improvements I made to the Mega Prusa i3, including the alternative Y-carriage. Enjoy :)

my mega prusa is working charm with %30 acceleration .. its too slow but working .. I take of 2 rod from middle so it work much better but still slow .. and now I will try it with nema23

Does anybody have the STL files to convert the frame to run nema 23 on the x y and z axis?

hi everybody, i'm new here and i own a prusa i3, the one from zchek republic.

do you tink it would be a good idea to scale up this design to 100cm^3 ?

and if not, why

1 reply

Hi there,

I mentioned some of my problems in the below. Moving Y-axis design is practical for building and designing but moving a large mass lowers the quality (at high speeds), makes big problems for fine-adjusting and it's going to cost much more than what u can imagine. (bigger motors, different drivers, etc.)

So i think bridge type cnc machines (like Shapeoko) are more suitable for 40+cm3 usage. At the end, it will cost a lot less than prusa design with more satisfactory results and reliability.