Roaddog Labs Bart Pro 300

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Introduction |Frame Assembly |Y-axis Assembly | X-axis Assembly | Connecting X-axis and Z-axis | Heated Bed Assembly | Extruder Installation | Electronics and Wiring | Validation and Testing | Working with Files and Printing

Bart pro 300 proto 1.jpg

Roaddog Labs Bart 300 Introduction

The Bart 300 is our latest variant of the Prusa i3 Rework. The machine is named for one of our late cats, Bart. It's a mashup of parts from existing i3 Rework designs, mods to those parts and some original parts. This version employs a larger print envelope, 300 mm x 300 mm with precision parts.

Designed for DIY

The intent of the design is so that anyone with access to basic makerspace tools could fairly easily build the design. We opted for a laser cut melamine frame design based on the Graber i3 that eliminates the need for a threaded rod frame. This also adds rigidity that allows the machine to print faster and more accurate than a rod framed based design.

Fewer parts, easier build

The mechanical component requirements have been simplified. The number of parts have been reduced and the assembly simplified. Where possible we have made the parts so they connect in positive fit, one way as to take much of the guess work out of the build. We are reducing the need to square and level parts by integrating the main structure in such a way that it screws together so that no further squaring of the structure is required.

Reducing build complexity also reduces the time and effort required to build the mechanical structure. We’ve cut the volume of plastic required by the printed parts by using the new frame which reduces the time required to print the parts for the machine by about half. That means if you print your own parts you don’t have the tie up the printer at the makerspace for 10-12 hours for a set of parts.

Open means open

The hardware design and is an open platform with editable parts source files. No restrictions, no posturing, open hardware. Source files are available at .

Roaddog Labs Bart 300 Specs

Bart 300
Base and Frame
Full melamine frame, printed parts, latest design for maximum stability and print speeds
Build Envelope
300 mm x 300 mm x 200 mm
Resolution (layer thickness)
low res .3 mm; normal res .2 mm; hi res .1 mm; extra hi res .06 mm
Filament Diameter
Compatable Materials
Any material up to 400* C including PLA, ABS, Laywoo-D, HIPS, carbon fiber reinforced PLA, flexible filament, conductive PLA, polycarbonate, PETG, nylon.
Max Printing Temp
400° C with thermocouple
Heated Bed
300 mm x 300 mm Mic6 precision aluminum bed with 24 volt, 250 watt silicone heater
Bart Direct Drive MK7, low profile, reduced weight and mass or E3D Titan or Bondtech QR
Mini Rambo with Marlin firmware
Power Supply
24 volts, 400 watts compact form factor
X Axis Motion
GT2 belt and pulley; 10 mm precision bearings and chromed, hardened rods
Y Axis Motion
GT2 belt and pulley; 10 mm precision bearings and chromed, hardened rods
Z Axis Motion
TR8x2 (4 lead) precision lead screws; 10 mm precision bearings and chromed, hardened rods
Average Speeds
100 mm/s (stock extruder, perimeters based on average tune)
Machine Footprint
380 mm x 470 mm x 400 mm (610 mm with spool holder)
Control Software
Raspberry Pi equipped Octoprint host for wireless printing, local control, web cam and other features


Frame Parts

  • 2 x side frame
  • 1 x main frame
  • 1 x bottom
  • 1 x bed frame
  • 2 x Y axis belt holder
  • 2 x Y axis idler plates
  • 1 x Y motor mount
  • 1 x front end plate
  • 1 x rear end plate
  • 2 x Z motor mounts
  • 2 x Z motor mount supports
  • 1 x Y end stop mount
  • 1 x Z top

Frame fasteners

  • 60 x 6-32 x 5/8" truss head Phillips
  • 60 x 6-32 square nuts

Printed Parts

  • 4 x Y clips
  • 1 x Y motor bracket
  • 1 x Y belt bracket
  • 1 x Y idler bearing mount
  • 8 x Y bearing mounts (2 per bearing)
  • 1 x X carriage
  • 1 x x end stop block
  • 1 x X end motor
  • 1 x X end idler
  • 1 x X idler
  • 1 x X end stop bracket
  • 1 x Z end stop bracket
  • 1 x extruder body
  • 1 x extruder idler
  • 1 x hot end mounting clip
  • 1 x fan duct
  • 1 x bed probe mount


  • 2 x Chromed, hardened precision steel shaft M10 x 511 mm Y axis
  • 2 x Chromed, hardened precision steel shaft M10 x 430 mm X axis
  • 2 x Chromed, hardened precision steel shaft M10 x 310 mm Z axis



  • 20 x M3 x 10 mm socket head cap screws
  • 40 x M3 x 12 mm socket head cap screws
  • 5 x M3 x 14 mm socket head cap screws
  • 5 x M3 x 16 mm socket head cap screws
  • 8 x M3 x 25 mm socket head cap screws
  • 6 x M3 x 30 mm socket head cap screws
  • 2 x M3 x 35 mm socket head cap screws
  • 2 x M3 x 50 mm socket head cap screws
  • 30 x M3 hex nut
  • 12 x M3 nyloc nut
  • 55 x M3 washer

  • 7 x M4 x 30 mm socket head cap screws
  • 6 x M4 hex nut
  • 3 x M4 nyloc nut
  • 10 x M4 washer
  • 1 x M8 x 30 mm socket head cap screw
  • 1 x M8 nyloc nut
  • 6 x M8 flat washer

Mechanical Parts

  • 12 x LM10UU linear bearings
  • 2 x 624zz bearings
  • 1 x 608zz bearing
  • 3 m GT2 belt
  • 2 x GT2 Pulley, 20 tooth
  • 1 x MK7 filament drive gear
  • 2 x extruder springs

Other Parts You'll Need

Basically everything but the frame but here's a general list to get you started. Remember, if it's not listed in the kit you have to provide it. If you are converting from an existing Rework or i3 you may be able to use your existing parts.

  • Z lead screws and nuts TR8-2 x 300 mm recommend
  • print bed and heater
  • motors
  • hot end
  • any fans you may need
  • power supply
  • electronics package

Where to Source Parts Not Included

I only recommend vendors and parts that I have used with good results. These are some of the vendors I used when I was selling full kits. You can use most any of the parts used on other i3 builds but this is what I use.

Electronics and Motors

Ultimachine Mini Rambo control board

Kysan motors

Power Supply

24 volt, 400 watt (can be less if using relay powered heat bed)

I use Arlen and Alice in Shenzhen

TRC has name brand Meanwell units but considerably more expensive.

Hot End

E3D hot ends from Filastruder

For lower temp material (max 245*C) the v6 Lite is a good choice

For higher temps (max 400* C with thermocouple) the v6 is a good choice

Be sure and specify the 24 volt option when you order the hot end

Heat Bed

I use a precision steel tooling plate called Mic6, 1/4" precision cast aluminum from Online Metals as the bed.

For the heater I use a vinyl heater from Alirubber in Shenzhen. The size is 300 x 300, 360 watts, 24 volts

Ebay or Amazon also have PCB style 300 x 300 heaters.

For a print surface I use either blue painters tape or PEI sheet. The PEI is available from McMaster Carr.

Lead Screws

Aliexpress or Amazon or ebay all have plenty of TR8 lead screws. You'll need 300 mm with a four screw nut.

What You Need to Bring

Most importantly, a maker's spirit. This frame only kit will require you to source all the parts not included in the kit. This kit is intended for an intermediate or advanced builder. It is suggested you have prior experience building and using DIY/Reprap style 3D printers.



Material specific to the Bart components and documentation that are not derived from other sources are released under the Creative Commons Attribution 4.0 International license.

Where applicable, the license of any derived work will be posted as well.

The original Prusa i3 single plate files ( from Josef Prusa licensed under GPL v3.

The original i3 Rework ( printed parts files from eMotion-Tech are released under GPL 2.0.

The original i3 Hephestos files ( from bq Department of Innovation and Robotics are licensed under Creative Commons Attribution 4.0 Sharealike International.

The Graber i3( is licensed under GPL v3.0.

The original modified i3 X idler with adjustable belt tensioner from ramkam ( licensed under Creative Commons Atribution-Sharealike, no version stated.

Marlin firmware ( from Erik van der Zalm licensed under GPL, no version stated.

The original direct drive extruder for Wilson/i3 ( from mrice licensed under Creative Commons Attribution- Share Alike license, no version stated.

Introduction |Frame Assembly |Y-axis Assembly | X-axis Assembly | Connecting X-axis and Z-axis | Heated Bed Assembly | Extruder Installation | Electronics and Wiring | Validation and Testing | Working with Files and Printing