Prusa i3 Buyers Guide

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Prusa i3 Documentation

Full Kits

All these vendors have an assortment of kits and/or parts specific to the Prusa i3. The list is non-exhaustive and contains both, good and bad quality RepRap-oriented vendors.

To find a shop in your country, click on this little box near "Loc." and you'll find all of them in one spot.

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Developers of ... Reviews and notes NE, USA Borg's i3 Mini mini i3's only MN, USA Printed Parts, SD RAMPS
3Distributed UK Accepts Bitcoin and Ships Worldwide
3D Printer Czar US, HK Acrylic Frame Kits, Worldwide Free Shipping
3D Industries Australia AU Aluhotend hotends (Aluhotend ) various hardware
BCN Dynamics ES DM Frame Box and Aluminum single frame kits.
Bitmovel PT First and only 3d printer parts in Portugal.
Blomker Industries ASIA Aluminum single frame kits.
Charlie's 3D Technologies BE aluminum single frame kits
Createc 3D ES single frame kits
CrunchTech eBay Store USA i3 Printed parts kits in many colors and good quality
eDistri BE Mendel,I3, Icarus Distributor
DIY Tech Shop US <I3x,I3xl,Little Brass Hotend> aluminum single frame kits. Heated beds, All parts are guaranteed and replaced at no cost
eMotion Tech France aluminum single frame kits
Iniciativas 3D ES Full kits[methacrylate and aluminium]
KitPrinter3D ES aluminium & steel (P3Steel) kits]
llama tech 3D printing BE Aluminum single frame kits MakerFarm laser cut frame laser cut wood kits - 6" and 8" heated bed US aluminum & laser cut frame kits HK Prusa i3 kit with aluminum, plexi and iron laser cut frame kits, components, filament. Shipping worldwide. Affordable price.
reprapsource In Beta DE box style frames NL frame kits, fully assembled kits mini i3's, frame kits
RepRap Thailand ASIA Wood and Acrylic single frame kits. India Aluminium Single frame kits, all parts India Frame and Screws are not included. China SZ Aluminium full unassembled Kits. Ukraine Structures made of plywood, all kinds of accessories.

Various kits and plastic parts are also available on eBay. Search for "Prusa i3" for a list. If buying from eBay, make certain to ask the seller which version of the i3 they are for building. There's three flavors: single_plate, box_frame, and mini. single_plate is the aluminum frame (lasercut wood/acrylic alternative available), box_frame is the one where you screw sections of wood together to make a heavy duty box frame, and mini is the 4" x 4" x 4" build volume variant that has an aluminum frame (lasercut wood/acrylic alternative available).


Another option is to attend a build workshop. You can get a group together and ask someone to put on a workshop for you, or you can find a group putting on a build workshop, such as your local Hacker Space.

Here is a list of i3 build workshops:

Sourcing Your Own Parts

Sourcing your own parts allows you to personalize your i3 to fit your needs and budget. The total can range from ~$334 to ~$1,290. If you select the best sourcing options, but find good deals on them, you can expect to pay ~$555.

There are a number of design styles and options for different Prusa i3 parts. This can quickly become confusing, especially for the first time builder. There are only a few resources for building a Prusa, (both box frame and single plate style) and nothing to help would-be adopters across the first big hurdle: what parts to order. An unofficial BOM (Bill Of Materials) was put together in November 2012, but there doesn’t seem to be one for the Beta release.

In order to make things easier, I have tried to bring all the relevant info scattered throughout the internet into one place. If you know of a better alternative part, or have a better or cheaper source for a part, please add it to the list.


The first design choice is between the boxed style frame and the single sheet (also called single plate) style frame. The box style is somewhat more rigid, but also slightly more complex to build and less aesthetically appealing. Single sheet frame is simple, but uses expensive laser cut aluminum parts. (more info here) Note that the two frames require different length rods. For info on the rods, or on using different length rods to increase/decrease your build volume, look here.

The exact width of the boards is not crucial, so long as the lengths are appropriate to the rods used. (Note that the width of the bottom board limits how far forward the y axis can be placed. This is compensated for by offsetting the linear bearings on the y carriage/bed.) If different board thicknesses are used, the design will have to be modified slightly. The y axis M10 threaded rods should just clear the bottom of the frame in order for the printed attachment points to sit at roughly the right level. The frame width (475mm) should be 5mm longer than the x axis smooth rod length (470mm). The 475mm board is longer so that it can span the whole frame width and overlap two other boards, which are 12mm thick. (450 + 12 + 12 ≈ 475mm)

Box Style Frame
Part Sourcing Options Source
6x 450x100x12mm pieces of wood (If bottom board is more than 13mm thick, it will bow the y axis up.) cut from three boards, each 48x4x1/2"* Home Depot, Lowe’s, etc.
cut from one sheet 24x48x1/2" plywood* Do it Best, Home Depot, Lowe’s, Wickes, etc.
475x100x12mm piece of wood (if using boards that are not 12.5mm thick, adjust length to be 450 plus twice the thickness) cut from one 48x4x1" board* Do it Best, Home Depot, Lowe’s, etc.
cut from one sheet 24x48x19/32" plywood* Home Depot, Lowe’s, etc.
230x230x12mm wooden bed cut from a 10x1" thick board* Home Depot, Lowe’s, etc.
cut from one sheet 24x48x1/2" plywood* Do it Best, Home Depot, Lowe’s, Wickes, etc.
60x 3.5x20mm wood screws #6 x 3/4” wood screws Do it Best, Home Depot, Lowe’s, Wickes, etc.
Glue (optional) Wood glue Local hardware store
Wood Sealant (optional) Assorted shades and colors Local hardware store

*Actual dimensions of lumber are smaller than nominal due to shrinkage during drying. Some given dimensions are actual, and some are nominal.

Wood also warps as humidity changes. To minimize this, select pieces with uniform edge-grain without knots. Oak and poplar are good choices. (More information on wood selection here). Using a wood sealant will minimize changes in moisture content. A thin, light, unsealed wood should be used for the heated bed. A heavy bed will limit print speed and quality, and the heat will break down the sealant. Even paraffin wood sealants designed for saunas wouldn't be able to keep steam from leaving the surface if it gets close to 100°C. It would, however, prevent moisture from returning to that surface after cooldown. Uneven moisture content is what CAUSES warping, so this is a bad idea.

Single Sheet/Plate Style Frame
Part Sourcing Options Source
Single Sheet Frame Parts (6mm thick) Kit with laser cut aluminum parts, Charlie’s 3D Technologies, eBay, NorCal-Reprap, RepRap Source, RepRapteile DE, India
Kit with laser cut plywood parts eBay, TwelvePro, TrickLaser
cut from ¼” Plywood and use gussets for strength Do it Best, Home Depot, Lowe’s, Wickes, etc.


You will need rods to match your frame. Precision ground rods are highly recommended, since bent or uneven rods will directly influence print quality. Bearings may not fit along sections of rod that are too large, and will rattle on smaller sections. Keep in mind that, while precision rod is formulated and tempered for rigidity, rod from welding supply stores is intended to be bent into shape. It is easily marred, and bends easily under any load. For this reason, you may want to buy from a supplier that cuts the rods to length before shipment, since longer rods are more likely to bend during shipping. If sourcing from a local hardware or welding supply store, you may want to roll the rod on the ground or sight down the length to ensure straightness.

Most threaded rod will suffice, provided that it is relatively straight. Precision threaded rod (and precision nuts!) will reduce backlash and improve print precision. For the best quality, any of several varieties of leadscrews can be used (sources listed here), although they require matching nuts. This requires that you modify your printed parts, so they are not listed below. For vertical threaded rods, gravity keeps the nut threads pressed downward against the threads on the rod, and so backlash is less of an issue. A uniform number of threads per inch is still necessary for layer thickness control. M10, M8, and M5 threads have a pitch of 1.5, 1.25, and 0.8 mm per rotation respectively. Although these ISO metric threads are the default, finer threads can also be sourced.

The specific rod diameter used is not crucial, allowing either metric or imperial sizes (although this will create 0.06mm slop in the bearings). Non-precision rods have diameter variations of around ±0.030mm, but too large is worse than too small since the linear bearings won’t fit. Precision bearings are ±0.009 or below. It may also be desirable to use larger rods for i3’s that may have higher loading (many heavy extruders, or a mill and drill head). Different sizes of threaded rods can be used, since they only connect to the i3 via nuts, which can easily be changed slightly. More substantial size changes may require different couplers to connect to the motors. If different smooth rods are used, then appropriately sized bearings must be sourced.

Rods for Box Style Frame
Part Sourcing Options Source
8mm smooth rods (x axis: 2x 470mm, 1x 20mm; Y: 2x 370mm; Z: 2x 405mm) Precision ground (cut from two 600mm and 2 800mm Precision Drive Shafts) see vendor list
Non-precision rods (BUY THEM AS STRAIGHT AS POSSIBLE and cut from three 36x5/16" rods if necessary) eBay*, Home Depot, Lowes, Tractor Supply, Wickes, etc
2x 400+mm M10 threaded rod (Y axis) cut from 1m long M10 or 3/8” threaded rod Do it Best, Home Depot, Lowe’s, McMaster, Tractor Supply, Wickes, etc
4x 205+mm M8 threaded rods (Y axis) cut from 1m long M8 or 5/16” threaded rod Do it Best, Home Depot, Lowe’s, McMaster, Tractor Supply, Wickes, etc
2x ~370mm M5 threaded rod (Z axis) cut from 1m long M5, 3/16”, or ¼” threaded rod Do it Best, Home Depot, Lowe’s, McMaster, Tractor Supply, Wickes, etc
Pre-cut kits with some or all of the above i3 specific rods Charlie’s 3d Technologies, eBay,MakeMendel, RepRapSource,

3D Acessories Hub]

*There are some precision rods on eBay, but most of them are not. If the seller doesn’t have the tolerances listed, then chances are they aren’t high precision.

Rods for Single Sheet/Plate Style Frame
Part Sourcing Options Source
8mm smooth rods (x axis: 2x 370mm, 1x 20mm; Y: 2x 350mm; Z: 2x 320mm) Precision ground (cut from two 600mm and 2 800mm Precision Drive Shafts) see vendor list
Non-precision rods (BUY THEM AS STREIGHT AS POSSIBLE and cut from three 36x5/16" rods if necessary) eBay*, Home Depot, Lowes, Tractor Supply, Wickes, etc
2x 380mm M10 threaded rods (Y axis) cut from 1m long M10 or 3/8” threaded rod Do it Best, Home Depot, Lowe’s, McMaster, Tractor Supply, Wickes, etc
4x 205mm M8 threaded rods (Y axis) cut from 1m long M8 or 5/16” threaded rod Do it Best, Home Depot, Lowe’s, McMaster, Tractor Supply, Wickes, etc
2x 300+mm M5 threaded rods (Z axis) cut from 1m long M5, 3/16”, or ¼” threaded rod Do it Best, Home Depot, Lowe’s, McMaster, Tractor Supply, Wickes, etc
Kit with all of the above i3 specific rods Charlie’s 3d Technologies, eBay, TwelvePro**

*There are some precision rods on eBay, but most of them are not. If the seller doesn’t have the tolerances listed, then chances are they aren’t high precision.

**TwelvePro rods are intended for their modified frame, not normal i3s.

Basic 3D Printed Parts

Most kits of 3D printed parts will include an extruder of some type, but for simplicity’s sake I will deal with the extruder options separately. There are several types of belts used in RepRap machines, and the GT2 is used for the i3 design. Images of all the printed parts can be found here, and the latest source files are on GitHub. Also, apparently the x carriage is different between the box frame style and the single plate style. This means that an extruder which fits the box style frame may not fit the single plate version, and vice versa. (Is there a discrepancy with other parts to?) Make sure your printed parts match your frame style and extruder type before you buy.

Plastic Parts, excluding extruder
Part Sourcing Options Source
3D Printed parts (for GT2 Belts and Greg's Wades extruder with Jhead) Select based on desired extruder and pulleys/belts. ABS softens at a higher temperature, so is good in proximity to motors. PLA is more wear resistant, and so makes longer lasting gears. eBay, or i3 printed parts vendors

Belts and Pulleys

Timing belts (T2.5, T5, etc.) are highly discouraged in favor of GT2 or GT3 belts. Make sure that the belt holder matches the belt you choose. (The belt holder is one of the 3D printed parts above.)

Sources for Belts and Pulleys
Part Sourcing Options Source
2x 6mm wide GT2 belt pieces (760? And 900? mm long) 1 for x axis, 1 for y cut from 2m circumference belt eBay,or an appropriate vendor
2x 6mm wide GT2 pulleys (should fit 5mm rod) (fox x and y) pulleys with 12 teeth (more is ok) are recommended for minimum positioning error eBay, or an appropriate vendor
package with all of the above cut from 2m circumference belt eBay, or an appropriate vendor

Extruder Cold End

There are a number of extruder cold ends available, but not all will fit the i3 unmodified. To be safe, make sure the extruder you decide on is compatible with your version of the i3 (the single plate and the box frame versions have different carriages). When purchasing extruder parts, be sure that they work with the filament diameter you intend to use (aka, 1.75 or 3mm).

There are no files for an extruder among the official STL files (either box or single plate), so there is no official extruder. There is a version of Greg’s Wade Extruder, as well as a Bowden extruder (both dual and quad versions!), which have been modified to fit the single plate version of the i3. Greg’s Wade Extruder seems to be most common, although the compact/dual extruders appear to work to some degree (Seems to be still under development, as of 2013-8-15). (Note: A compact extruder is essentially half of a dual-extruder, with a few small design changes.)

Direct drive extruders push filament through the hot end quickly, and can retract it just as quickly to reduce oozing. Higher gearing ratios give more precision (good for smaller nozzle apertures and layer heights) at the cost of slower speed. The lowered motor torque allows smaller, lighter motors.

Greg’s Wade Extruder
Part Sourcing Options Source
Printed parts (this was likely included in the Basic 3D Printed Parts section above) eBay, USA,
Hobbed bolt, M8 x 60mm (make sure the bolt is hobbed at the desired location. If using 1.75mm filament, be sure the cuts are shallow enough to catch) Precut hobbes eBay,
Local hardware store (cut hobbes yourself, if you have the equipment) Ace Hardware, Do it Best, Home Depot, Lowe’s, Wickes, etc.
3x 608zz bearings for bulk discount, purchase with 608 bearings from the hardware section below eBay, or any of these suppliers
Smooth 8mmx20mm bar (axle for idler) cut from the excess left over from making the rods. eBay*, Home Depot, Lowes, Tractor Supply, Wickes, etc
4x M4 springs (optional) Some people prefer rubber matt or lock washers eBay
Other miscellaneous hardware assorted nuts and bolts, in accordance with which design you choose Local hardware store
Full kit with all of the above eBay

Note: Nuts, bolts, etc may vary slightly depending on exact extruder design. If you can’t find what hardware to get, go with the above plus a couple M3 screws 30-40mm long some M4 screws 20mm long, and nuts/bolts/washers to fit (including locking nuts). Get a bunch of washers for the M8 bolt in case you need to use them as spacers.

Raldrich Geared Stepper Extruder

This extruder that was listed in an early i3 Bill of Materials. Is it the official i3 extruder?

Compact Dual Extruder (experimental)

Both the Compact and the Dual Compact Extruder require 42BYG48HJ50 geared motors instead of standard NEMA 17 motors. The motors used in development were sourced from 2engineers, which has since changed their design. A PG35L might be adapted, and could be sourced from NMB Minebea. Two sets of drive-gears, 608 bearings, bar axles, springs, and assorted nuts and bolts are also required for the extruder. Details surrounding the compact dual extruder are scarce. Several people appear to have “working” hardware, but so far the software is still under development.

Applications include dissolvable support material, printed electronics (using off the shelf conductive filament), faster high-detail printing, composite materials (living hinges, etc.), as well as multi-color prints. Full color printers would be better served by dyeing the filament or by using a mixer extruder or RichRap extruder.

I3ext by SGraber

Machined drive gear and geared drive from stepper to filament driver. This is a derivative of the one Josef Prusa uses in his build workshops. It has been reworked to accept a Jhead-compatible hotend and use a standard MK7 hobbed pulley. Github repository is here:

Extruder Hot End

First of all, the hotend must fit to your extruder cold end.

You also have a couple options when it comes to the extruder hot end. The J-head extruder was designed so that it could be machined all in one piece. This makes it cheaper and more reliable, but means you need a J-head for each nozzle diameter you want to print with. (They do have exchangeable PTFE liners for different filament diameters.) Having a separate nozzle, heater block, barrel, and PTFE sleeve allows the user to mix and match filament size and nozzle diameters on a whim.

J Head Nozzle
Widely used hotend, fine for ABS and PLA.
MG Plus
Magma Hot End
From Trinity Lab. Appears to work with i3 Rework only.
Same mount as Jhead.
All Metal hotend.

a semi complete list of other hotends can be found here Hot_End


About any RapRap electronics can be used. If a dual extruder is used, an electronics supporting this is required, of course. See the Comparison of Electronics, Alternative Electronics and List of electronics pages for more info.


The build surface is chosen so that the printed filament adheres to it. Various tapes can be used, and have the advantage of being easy to remove from both the piece and the bed underneath. Glass provides poor adhesion, however hairspray or a glue-stick can be used to make a good bond.

The bed doesn’t necessarily have to be heated. If the first few layers of a print cool non uniformly, they have a tendency to curl up like a potato chip. Heating the bed greatly minimizes this problem.

Printed Circuit Boards are the most common type of heated bed. They must be etched from 35µm copper clad silicon, NOT plated. Non-uniform copper will not heat evenly. For especially tall/thin parts, a heated build chamber can be used to reduce warping. If using an aluminum frame, you may want to insulate the bottom to improve heating rate and max bed temperature. See for more information on bed construction.

Bed Parts
Part Sourcing Options Source
(Optional, but highly recommended) Heated bed (generally 214x214mm) PCB Heated Bed (Most uniform heating. May require LEDs and wires) eBay, or see vendor list
Stripboard PCB heating element (cheap, but effective) VeroBoard
Repurposed heaters (hot-plate, motorcycle grip heater, Silicone heating mat, polyimide film heater, clothes iron, etc.) eBay
Heat bed with Aluminum clad resistors (TO220 Resistors fail eventually) eBay
Heat bed by taping down uninsulated wire with Kapton tape (nichrome wire or other) eBay
Bed Material/build surface (if using glass/ceramic/metal without tape, you may want to coat with strong hairspray, PVAc glue or a glue-stick to promote adhesion.) Glass plate/mirror (you can buy precut, or cut it yourself) eBay
Metal (heats evenly, but thin metal warps) Ace Hardware, Do it Best, Home Depot, Lowe’s, etc.
Ceramic tile (Easier to cut/drill than glass, but heats up slowly) Home Depot, Lowe’s, Wickes, etc.
Tape (kapton or masking tape) eBay, or pretty much anywhere
4x binder clips Something to hold the build surface in place (if needed ) Amazon, eBay, Staples, etc
Thermistor (required for heated bed) You may want to purchase this from the same source as your hot end thermistor eBay


I could only find two sources for this. One is an [outdated, unofficial, and untested bill of materials]. The other is the BOM for the i3 Rework. I have noted the discrepancies below. Once I build my I3, I will try to update this list with any additions/changes.

Mechanical Parts
Part Sourcing Options Source
10x linear bearings/bushings (7 for x axis, 3 for y) LM8UU linear bearings eBay, or see vendor list
3D Printed PLA bushings, or commercial bushings (quiet, but lowers positioning precision. You will need a way of attaching them) Print own, or see vendor list
2x ball bearings (608 or 624 for x and y belts, depending on design. Cold end will require additional bearings) ZZ are the most common, although 2RS or VV may be preferable for a milling and drilling head. eBay, or see vendor list
2x couplers (z-axis) 5x5mm steel couplers eBay, or somewhere with RepRap parts
3d printed couplers (Easy Reliable Coupler, auto-centering coupler, etc)  ???
Stretch 4?mm ID plastic tubing over 5mm rod and motor shaft
Nuts and Bolts
Part Sourcing Options Source
18x M3x10mm bolt (12 for motors, 6 for endstops)
14x M3x30mm bolt (10 for linear bearings, 4x for heated bed
28x M3 nuts (10 for linear bearings, 12 for heated bed, 6 for endstops) non-locking
54x M3 washers (optional, 20 for linear bearings, 16 for heated bed, 12 for motors, 6 for endstops)
5x M4x20mm bolt (2 for x/y-axis tensioners, 3 for endstops) preferably thumb screw for easy tightening
2x M4x25mm bolt (x/y-axis tensioners)
7x M4 nuts (4 for x/y-axis tensioners, 3 for endstops) 2x must be non-locking
5x can be nyloc
10x M4 washers (optional, 4 for x/y-axis tensioners, 6 for endstops)
2x M5 nuts (x/z-axis) must be non-locking
22x M8 nuts (y-axis threaded rods) non-locking
22x M8 Washers (optional, for y-axis threaded rods)
12x M10 nuts (y-axis threaded rods) non-locking
12x M10 washers (optional, for y-axis threaded rods)
4x Zip Ties (optional, for belts) small