Introduction: Mega Prusa I3

Picture of Mega Prusa I3

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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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.


YonathanL1 made it! (author)2017-11-19

Finally i succes build after few weeks and will updte result printing on few day

1. I use 8mm threades rod 2mm pitch
2. I inverse the xy min stop
Without ringing at 100mm/s

jalilo (author)2017-11-04


how configuring build size ? 40*40*40

i made it

work in 150*150*150


cjensen25 (author)2017-05-18

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?


AnttiU (author)2017-04-15

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?

Hatmpatn (author)2016-09-28

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?

stormychel (author)Hatmpatn2016-10-06


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?

Hatmpatn (author)stormychel2017-01-31

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.

Hatmpatn (author)Hatmpatn2017-02-02

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?

Hatmpatn (author)Hatmpatn2017-02-14

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

barbieri.ale99 (author)2017-01-22

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

DanD156 (author)2016-12-22

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?

DirtyThirty (author)2016-12-20

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.

DanD156 (author)2016-12-19

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

JamesE3 (author)2016-12-16

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

SelimM1 (author)2016-12-07

You can use it if you want..

DiegoS8 made it! (author)2016-12-04

Who built this mega prusa, I'm interested in the parts of the x and z axis.
Anyone know anything?

TibiS (author)DiegoS82016-12-06

hi, it's matt.paulson.927. you can find him here on instructables:

stormychel (author)2016-11-25

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 :)

cestb made it! (author)2016-04-27

Thks to Storymichel, my Mega works fine ;)

cestb made it! (author)cestb2016-04-27

More pictures...

carlsandra2005 (author)cestb2016-05-12

so your nema 17 motors holing up? mainly on the Y axis

cestb (author)carlsandra20052016-05-17

With speed less than 50/60 mm/s and acceleration less than 800mm/s², it's ok, but with my big glass plate, i could not go faster without loosing steps...

So i've just bought a Nema 23... It should correct this.

cestb (author)cestb2016-05-28

Works great now with my nema 23 instead of nema 17 for Y carriage...


KirkM11 (author)cestb2016-07-14

Do you have the files on thingiverse for the nema 23 carrier or how did you install it?

SelimM1 (author)KirkM112016-09-08

megaprusa y axis with Nema23

KirkM11 (author)SelimM12016-09-08

I will print this off in the next few days. Now for the x and Z axis.

SelimM1 (author)KirkM112016-09-09

I fix it yesterday and working too good ..

cestb (author)KirkM112016-09-08

I just reuse the original support and add a alu plate (to extend it) to fix the bigger motor.

To help the structure, i add a small part of alu to support the weight of the motor. This small part is between the rod and the structure. it's a kind of "S", one side attached to the rod, and the other side below the motor.

I don't have any picture of that, sorry.

stormychel (author)cestb2016-10-08

You could improve the Y-axis more by eliminating the bottom frame part and using my solution instead:

This is designed for 450x450x3mm aluminium and a 400x400mm silicone heater, so you might be out of luck here with the glass plate, but it works wonderfully well icm kapton tape. My ABS prints are almost impossible to remove after printing, and that is WITHOUT glue, slurry or hairspray.

The print bed is held between 6 printed ABS clamps (tested up to 125 degrees bed temperature), the bottom gets a new Y-belt holder which is a lot sturdier and distributes forces more evenly, reducing hopping of the print bed, and makes the belt perfectly aligned with the stepper and bearing, where the original one puts tension in Z when reaching the last 25% of travel of the Y-axis in both directions.

Finally, the clamps keep the print bed straight and precent it from sagging in the middle.

stormychel (author)cestb2016-10-06


carlsandra2005 (author)cestb2016-09-17

Look great

kozbilek made it! (author)2016-07-11

Hi everyone,

First of all i have to say thanks for all the ideas and suggestions that you share, it was a big help. I also try to design a machine with 40cm3 build volume, very nice to be able to produce big things as a single piece. :)

I've studied both Megaprusa and P3steel designs and come up with the design as you can see in the below. I named it "Daedalus i3".

I have few suggestions for those who want to make a machine of this size;

- We made 2 different versions of this design from 5mm and 3mm ST37 steel and 5mm one come out amazingly rigid but soooo heavy & 3mm one is very light but can't deal with the vibrations enough. So, i think 4mm steel is the right choice. (or if you have time & crazy enough to do it, you can design a machine with monocoque-like chassis from thinner steel, kinda Wanhao style.)

- Silicone heaters with SSRs works great. But if you want to leave the machine on its own or want to print while you are sleeping, you can buy it with built-in thermal fuse and be sure you connect ground wire to Y-axis build plate. I also use power switch with 10A fuse, it feels safer. Mains electricity is not a joke and i don't trust RAMPS board that much. :)

- I use M5 threaded rods for Z-axis with DIY backlash nut design (classic 2x M5 nuts and 1x spring thing.) but M8 rods going to be a better choice, if you could afford use proper 8mm ACME rods for it. It improves the quality noticeably.

- I use KH42KM2B009 model NEMA17 motors with built-in vib. dampers on them and they work OK. No skipping steps @ 60mm/s.

- I use LRS350-12 PSU without any problems but if you want a machine that turns itself off after printing, use modified ATX PSU. It's a nice feature to have.

- I use 3mm 6061 aluminum plate for Y-axis and for the frog plate but you can't make it perfectly flat. So you have to use inductive sensor and auto bed-leveling feature for trouble-free big size prints. (Use NPN type with long detection distance - 8mm or more, like LJ18A3-8-Z/BX)

- I use LM12UU type bearings with cable ties but i don't think they are good enough. For the new design im drawing, i will go for SCE...UU (also called SC...UU) type bearings with proper mounting solutions.

- If you can, make connection points for them and use cable chains for wiring along Z and X axis. Spiral cable wraps are not good enough.

- Also i got some ringing problem at high speeds along the Y-axis and couldn't get rid of them by changing the belt tension and acceleration & jerk settings. I think its because of the spring based Y build plate & general problem with prusa design. What do you think about this?

You know what they say, "a chain is only as strong as its weakest link.". I hope I'll be back with new updates, so stay tuned. :)

stormychel (author)kozbilek2016-10-06

That looks too good. Designed something like that too; never made one though...

kozbilek (author)stormychel2016-10-08

Thank you stormychel. I know that feeling, sometimes it's very hard to get money & free time together in the same place. :)

stormychel (author)kozbilek2016-10-08

True :) Working to finally get that Chimera hotend that's gathering dust here for almost a year to work because the Wade extruder is wearing out... At first I was planning to use a Diamond hotend instead but in the end I'll go with the Chimera, since a) I already have it and b) I think it allows for more precise control over which color goes where, when there is no leaking off cause. The leaking is no big concern because I always use the same brand of ABS, HIPS and PETG, and have gotten a feel for how they flow.

This conversion will also make my X-carriage a lot lighter, which in turn allows for higher speeds. I can comfortably print 100mm/s now, just set and forget. Speeds up to 200mm/s are handled well by the machine, but this gave me some issues with a) infill not sticking well, and b) the Y-axis losing steps on larger (heavier) prints. I tackled issue a by lowering my default layer height from 300 micron to 250, this has worked wonders. Issue b is still a hard one, as it is very unpredictable, but I've seen that some people went to a Nema-23 with good results so that might be next. My idea was to use 2 Nema-17's, one on the front of the Y-carriage and one on the back, but then wiring could become an issue. I might solve this in the firmware, but I'm not so keen on branching the Marlin firmware, because then I need to keep up with it's development cycle as well, and I have a lot of other stuff on my hands... but it probably would work and would not be so hard to implement... This solution has the advantage of reducing latency in belt travel, because we do not depend on the bearing in the back to distribute the forces...

If I keep the wooden frame (which is 99% sure as it performs well and is the cheaper option), I will make it a complete triangle to the back of the bottom frame by an adjustable threaded rod. There's a little too much flex on the top end, so this is something that I should have been doing for a lont time, but what kept me back is that the printer performs well as is. This will all change when I introduce forces by putting the bowden extruders on top...

kozbilek (author)stormychel2016-10-12

We are using locally made Sigma 3D hotend in here. I think the point is, as you said, printer works well and i dont want to get in trouble with it for now. :)

You are talking about amazing print speeds and chimera plan sounds great. I've never seen one in working condition but excited to see the results. Please share some photos after you build it.

MladenT3 (author)2016-09-18

I want share my remixes.

Nema 23 parts for X and Z axis. I did NOT tested.

Maybe this for Y motor mount is better option because is smaller and you need less material. I have this on my Prusa i3 Rework and all axis runs on Nema23. Works very good and fast.

SelimM1 (author)2016-09-08

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

ElSaico made it! (author)2016-08-08

My red/black Mega is well underway! The only things left are:

- Finishing the wiring on the right (tomorrow!)

- Power supply (delayed buying it until the time of assembly, then lacked $)

- Silicone heater (stuck in customs for God knows how much more)

- Relay (only necessary with the heater anyway)

- The plastic itself, of course. The first run is going to be in PLA for technical reasons (see "heater in customs limbo", above)

With all that I expect my first print in a couple weeks, tops. About time, since I started to slowly import its components about five months ago...

ElSaico (author)ElSaico2016-08-08

Next up: an equally king-sized, aluminum-framed CoreXY (probably a Vulcanus Max). But this is for much further.

KirkM11 (author)2016-08-02

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

PedroI9 (author)2016-07-23

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

kozbilek (author)PedroI92016-07-30

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.

EireannA (author)2016-07-09

What power supply and bed are you guys running?

Ivan_D made it! (author)EireannA2016-07-20

Im running 12V/280W Silicone Heated Bed Plate 300x300 over relay and 50A power supply. It is enough to heat the aluminum plate 450x450x6mm

EireannA (author)Ivan_D2016-07-20

thats great info, thanks

TibiS (author)EireannA2016-07-11

mine was a 12V, 29 amp, 240W... never had a problem with it

EireannA (author)TibiS2016-07-11

sounds good, what bed you running?

TibiS (author)EireannA2016-07-11

it was a 400x400 silicone rubber heated bed. 600watt/220V controlled by a relay
check this out:

they make custom heated beds also, you ask, they send, very good products

About This Instructable




Bio: Do not follow the ideas of others, but learn to listen to the voice within yourself. Aldric Negrier aldricnegrier
More by aldricnegrier:BIGLID - Big LED Interactive DisplayConverting CNC Electronics to ArduinoRooBee One - SLA DLP Aluminum Frame 3D Printer
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