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P3Steel Logo 12 wiki.png


Introduction | Bill of materials | Proteins | Vitamins | Painting the steel frame parts | Main steel frame assembly | Y-axis assembly | X-axis assembly | Connecting X-axis and Z-axis | Motor assembly | X and Y-axis motions | Heated bed assembly | Extruder assembly | Electronics and wiring | Extras

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Release status: working

Remix of Twelvepro's redesign of Josef Prusa's i3
CAD Models
External Link


The P3Steel is a remix of Twelvepro's redesign of Josef Prusa's i3.

Leonardo - the prototype P3Steel printer - was designed and built by Irobri in April 2013, after attending a local Maker show in Zaragoza, Spain.

The main frame structure, built from laser-cut 3mm steel, is extremely strong and simple to assemble, and eliminates the need for several printed parts due to the use of steel parts instead of threaded rods for the "Y" subframe (as in the original Prusa i3 and many of its variants).

P3Steel V1.2 Renderization
Steel as a building material has several advantages over e.g. aluminum
Steel is one of the least expensive building materials available - structural steel is 10 times cheaper than aluminum.
Laser cutting steel is easier and cheaper than cutting aluminum.
Steel is stronger than aluminum.
Steel is 3 times heavier than aluminum, although this could be considered both an advantage and a disadvantage, in the sense that a heavier frame does not tend to vibrate as much as a lighter frame. Also, if we consider the total weight of the printer, the difference between an aluminum frame and a comparable steel frame is not that much (around 2.5kg extra).
Structural (carbon) steel requires painting or galvanizing for protection against corrosion. Stainless steel, of course, does not require painting.

The P3Steel design is for 3mm thick steel and with lots of carvings to reduce weight. All square holes and tabs have special rounded corners for accommodating corresponding parts and give a very good fit between parts.

The design has slots for M3 nuts in the places where the screws fit so no threading is required.

Improvements over the standard Prusa i3

  • Stronger frame due to the use of structural steel.
  • Solves the frame flexing thanks to its reinforcement squares.
  • Simplifies the construction, eliminating the complex subframe of threaded rods in the Y-axis.
  • Once assembled, everything is in place, no adjustments needed.
  • Eliminates the need for several printed parts.
  • The steel mounts for motors and rods are much stronger than their plastic counterparts.
  • The only two threaded rods needed are the ones for the Z-axis (5mm).
  • Uses shorter smooth rods lowering the build costs.
  • Once assembled, it forms a compact, solid structural unit that can be transported as a block.

Main dimensions (frame version 2.0)

P3Steel main measures

Enlarge image

Frame versions

The P3Steel frame design has evolved since it release. Here are the various versions and how they differ:

Version 1.2: Leonardo, original printer, the one I made.

Version 2.0: After some requests from a Spanish group building around 30 printers, I have modified the bed, now it holds with 4 LM8UU instead of 3 and it has also a system to level with 3 points instead of the original 4, it should be easier with this new design. I kept the original 4 points also just in case someone still wants to use them. I included in the gallery some 3D renders of the new bed. The rest of the printer is exactly the same as version 1.2

Everything snaps together and holds with M3x12 screws (mainly), I also used nylon self locking nuts to prevent future problems due to vibration.

The printer uses 8mm chromed smooth rods (Z axis: 2 x 320mm, Y axis: 2 x 341mm and X axis: 2 x 375mm) and only two M5 threaded rods (295mm approx. each since depends on motor coupling and if you want some to stick out through the top) for the Z axis, printed parts required came from a standard Prusa i3, you only need the parts for the X axis assembly and the extruder.

The printer structure is assembled quite fast and needs no adjustments. The electronics are installed on either side of the frame, horizontally, holes provided are for an Arduino mega and RAMPS 1.4. Motors are NEMA 17, GT2 pulleys, LM8UU and 608zz bearings. Hotend is budas type, but depending on the extruder plastic parts, will also accommodate J-head and E3D hotends. The hotbed is the standard MK2B.

Version 2.01 (by AndrewBCN): this is exactly the same as version 2.0 except for the changes listed below.

  • The interference between the Y stepper and the M3 nyloc nut holding the Y stepper support has been solved by stretching the support by 2mm (see the P3Steel Y axis assembly page for details).
  • The frame has been stretched by 9mm, meaning the Y-axis 8mm smooth rods should now be 350mm long (same as the original Prusa i3), and not 341mm long anymore (4mm have been added to the front and 5mm to the back).
  • Two 3mm holes have been added along the sides of the front Y-axis subframe, one on each side, to attach optional accessories / cable ties to the frame.
  • The practically useless part that could eventually be used as a Y belt holder has been deleted (there are much better designs that can simply be printed).

CAD file for version 2.01: File:PRUSA i3 steel 3mm lasercut 2.01d irobri.dwg (generated with DraftSight 2014, use a recent version of DraftSight or SolidWorks to open)

(see the Discussion tab for justification of these changes)

Version 2.5 (by AndrewBCN): this is a dual Bowden extruder capable, slightly enlarged P3Steel variant derived from my earlier P3Steel 2.01 variant. In keeping with the KISS philosophy of the original P3Steel and avoiding changing something that works, as few changes as possible were made in relation to version 2.01:

  • The frame is 10mm wider. This is achieved by making the central plate and the two Y-axis end plates 10mm wider. Note that the distance between the Y-axis smooth rods remains the same..
  • The frame is 10mm taller. This is achieved by making the central plate and the two side panels 10mm taller.
  • The holes to mount the Arduino Mega 2560 + RAMPS board are 10mm higher, increasing the clearance for the USB cable.
  • There is an added cutout in each of the side panels to keep the frame weight in the same range as the original P3Steel 2.01.
  • There are two stepper motor cutouts, one on each side panel, for mounting two optional Bowden extruders.
  • All screw holes now have the same diameter, 3.2mm (the holes for the electronics on the side panels were previously specified at 2.6mm diameter for later tapping with M3 threads, this is now deprecated).

Apart from the minor changes above, nothing else is changed.

Note that making the printer 10mm wider and 10mm taller does not really result in an increase in the print envelope, rather it makes it easier to achieve the original print envelope of the Prusa i3 (200 x 200 x 200mm or 8l).

Also note that use of the Bowden extruder stepper mounts is optional. Basically the P3Steel 2.5 DXL can still be built exactly like the original P3Steel, with a single Greg's Wade's Geared Extruder on the X-carriage, or one can use a single Bowden extruder mounted on either sidepanel, or two Bowden extruders mounted on both sidepanels.

CAD file for version 2.5 (zipped): File:PRUSA i3 steel 3mm lasercut 2.5DXL e irobri.dwg.zip (generated with DraftSight 2014, use a recent version of DraftSight or SolidWorks to open)

(see the Discussion tab for justification of these changes)

Also note that versions 3.0 and 4.0 mentioned below are not derived from either versions 2.01 or 2.5, they are independent developments by their respective authors.

Version 4.0 (By Alvaro Rey and Daniel Torres) From Version 3.0 (By Ghosthawk) with the listed changes

  • The extruder no longer hits the Z axis top bracket
  • Y axis belt tensioner ( that may be placed printed or metallic )
  • Weight reduction cutting as much material as possible
  • Holes to bolt to the PSU
  • Electronics as high as possible so that the cables are well hidden LCD
  • Holes in the top bracket of the Z axis to position bearing
  • Holes in the top bracket of the Z axis to place spool holder
  • Axis movable to lose the least footprint
  • Y axis bed it's suitable to install 20x20 heated beds or 20x30 heated beds
  • The hole for the motor connector has been enlarged , allowing install engines below 70 OZ
  • Bed with option for 3 or 4 bearings
  • Bed with choice of 4 or 3 leveling points
  • Holes for Zip ties was added to the main frame

The Y-Axis rods have been changed, now uses 10mm rods ans LM10UU lineal Bearing We recomended use aluminum beds for y axis.

We test aluminum frame too in 3mm. It works just the same

20x30 Frame - the Y-axis 10mm smooth rods should now be 510mm long

This version use aluminum beds, in orther to reduce weight in Y-Axis

20x30 Frame


Assembly animation


On YouTube: https://www.youtube.com/watch?v=In_Q6NkX3fs

Assembly manual

Modification to use Spindles

To use 10mm diameter spindles we need to separate the smooth rod and the spindle, leaving room for the nut and bearing parts in the X axis. Therefore some adaptation is required. We have designed a few pieces for use them in the original structure, so the changes were minimal.

This file File:Adaptacion Husillos.zip contains the OpenSCAD design files along with some other files to support for visualizing the set.

Where to buy


Proyecto Clone Wars


  • The P3Steel is not to be confused with the 3Done P3.