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Release status: experimental

Delta robot 3D printer with extrusion frame.
CAD Models
External Link

Kossel is a parametric delta robot 3D printer, built in 2012 by Johann in Seattle, USA, based on his Rostock prototype.

It is named after Albrecht Kossel, German biochemist and pioneer in the study of genetics. He was awarded the Nobel Prize for Physiology or Medicine in 1910 for his work in determining the chemical composition of nucleic acids, the genetic substance of biological cells.


There are several printers in the Kossel family.

Legacy Kossel

  • Spectra line instead of timing belt.
  • 623 bearings running directly on vertical 15 x 15 mm aluminum extrusion like OpenBeam, 6 bearings per carriage.
  • PG35L extruder directly on the end effector (moving platform).
  • This design is deprecated but the source files are still available.

OpenBeam Kossel Pro

  • Terence Tam's design for mass manufacturing.
  • Successfully funded on Kickstarter.
  • Stamped and injection molded parts instead of 3D printed.

Mini Kossel

  • This is Johann's latest and stable version.
  • The rest of this page describes the details of Mini Kossel.

Design Goals

  • Zero backlash.
  • Type: Delta printer
  • Speed: 320 mm/s in all 3 directions.
  • Resolution: 100 steps/mm in all 3 directions.
  • Repeatability: better than 0.03 mm (30 micron)
  • Build volume: cylindrical, 170mm diameter, 240mm height.
  • Footprint: triangle, 300 mm width (240mm OpenBeam + printed corners).
  • Frame height: 600 mm.
  • Print surface: unheated round glass, doesn't move.
  • Mass of end effector with hotend: less than 50 grams.
  • Simplicity: fewer than 200 parts.
  • Hardware cost: less than $600 USD.
  • Fully automatic print surface level calibration (autoleveling).

Optionally scale down to a Traveling RepRap that fits within IATA hand luggage size limit (see transportation):

  • Frame height: 550 mm.
  • Footprint: triangle, 270 mm width, 250 mm across (210mm 15 x 15 mm aluminum extrusion like OpenBeam + printed corners).

Bill of Materials

Printed parts

This set of parts weighed in at 271g (without power supply brackets).

All files come from Johann's Kossel repo: https://github.com/jcrocholl/kossel

Recommended print settings:

  • Layer height = 0.2 to 0.3 mm (around 60% of your nozzle size)
  • Perimeters = 3
  • Top/bottom solid layers = 3
  • Infill density = 50%

Note, a PLA End effector may bend or warp if it is not cooled with a fan or insulated. The insulation can be as simple as a loose layer of tin foil to create air pockets between the tin foil and the part. An ABS end effector is less likely to bend. It can also help to insulate parts of the hot end with Kapton tape.

  • Quality machined aluminum parts are available from RobotDigg

A kit with the printed parts is available @ Builda3Ddprinter.eu and think3dprint3d in Europe, or TriDPrinting.com, CrunchTech's eBay store or from Erie 3D Printing in the USA.



  • 100x M3x8mm stainless steel screws (frame and most connections)
  • 100x M3 stainless steel nuts
  • 100x M3 nyloc nuts
  • 6x M3x20mm stainless steel screws (arm attachment to vertical carriage)
  • 12x M3x25mm stainless steel screws (belt idlers and effector-rod attachments)
  • 6x M3x35mm stainless steel screws (tensioners)
  • 50x M3x6mm stainless steel screws (rail attachment to extrusions - 8mm is too long!)
  • 12x M3x16mm stainless steel screws (push rod attachment)
  • 6x M2.5x12mm screws (micro switches)
  • 3x M2.5x16mm (automatic bed leveling probe)

A nuts, bolts and screws kit is available from TriDPrinting.com or Builda3dprinter.eu.

Linear motion

Diagonal push rods

A pre-cut rod kit is available from Builda3dprinter.eu and are 3K woven carbon rods]. Fully assembled carbon rod kit is available at 3dprinteu.eu/shop or TriDPrinting.com or www.UltiBots.com




  • 1x 625 ball bearing (5x16x5)
  • 1x M5-0.8x20 Cap Screw
  • 1x M5 Washer
  • 1x M5-0.8 Hex Nut (Nylock optional)
  • 1x M3-0.5x16 Cap Screw
  • 1x M3 Washer
  • 1x M3-0.5 Hex Nut, Nylock


Automatic Bed Leveling Options - Only need one of the following, depending on which you choose.

 FSR(force sensitive resistor)
  • 3x FSR circular pads
  • 3x mounts for fsr pads
  Bed leveling probe
Z-probe showing safety pin detail.
  • 1x Micro switch (same as for endstops above)
  • 1x Bondhus 1.5mm allen wrench
  • 1x Safety pin with 2.5mm loop
  • 2x Ball point pen spring
  • 1x Euro-style terminal block connector
  • 1x Heat shrink tubing ID=2mm
 Proximity Sensor

Excellent guide to set up proximity leveling can be found on Instructables, search for "auto bed leveling Marlin"

  • 1x PNP Inductive proximity sensor

Several versions are available but the most popular and simple to use is the LJ12A3-4-Z/BY. This model works at 6-36vdc(many other models need at least 12v), and has a sensing distance of 4mm. Can be bought on eBay for <$5

  • 1x mount for your specific effector/carriage



This is not a comprehensive list, but should give you an idea of what tools may be required. Review all build manuals/videos to ensure you have all necessary tools.

  • 1x metric caliper
  • 1x M4 Tap Drill bit
  • 1x M5 Tap Drill bit
  • 1x 1.5 mm allen wrench
  • 1x slow-set epoxy

Assembly instructions

Step By Step Instructions

For a video tutorial and step by step instructions see the following website: Kossel mini & Kossel XL build instruction or go to the YouTube channel

Instructions for Kossel Mini kits from Blomker Industries

IPFS link to Instructions

Detailed build manual from Think3dPrint3d with pictures for every step is available here:

Think3dPrint3d Kossel mini build manual

This is a GERMAN translation of Think3dPrint3d's manual:

HKBay.com Mini Kossel Detaillierte Bauanleitung in PDF Format

HKBay.com Mini Kossel Detaillierte Bauanleitung auf Instructables.com

Wiring and commissioning instructions for Mini Kossel using 32-bit Duet electronics:

https://miscsolutions.wordpress.com/2015/01/04/upgrading-the-mini-kossel-to-duet-electronics-part-1-hardware/ and the other articles in that series

Video assembly from the perspective of someone new to the Kosssel:

YouTube Playlist by engineglue

Autolevel probe

X_MAX, Y_MAX, Z_MAX top endstops: NC (Normally Connected). M119 for these should show:

  • TRIGGERED when the carriage touches the endstop.
  • open during normal operation.

Z_MIN autolevel probe: NO (Normally Open). M119 for Z_MIN should show:

  • TRIGGERED when the autolevel probe is retracted (up).
  • open when the autolevel probe is deployed (down).
  • TRIGGERED when the autolevel probe touches the print surface.

Make sure that M119 does NOT show X_MIN or Y_MIN, if it does you must change them to -1 in Marlin/pins.h.

Although the parts list suggests that a small allen wrench be used, in reality, a short piece of wire might work slightly better since it can rotate more easily.

FSR Autolevel


Mini Kossel FSR Auto Leveling Setup Guide

Viki LCD with Azteeg X3


Connect Viki J2 to Azteeg EXP3 port like this:

  • +5V to +5V (red)
  • GND to GND (black)
  • SDA to SDA (blue)
  • SCL to SCL (green)
  • ENC_A to D22 (white)
  • ENC_B to D7 (yellow)

Connect Viki J3 to Azteeg ICSP port like this:

  • CS to CHIP SELECT (D53) (red)
  • BTN to D32 on EXP2 (optional) (black)
  • DI to MOSI (blue)
  • CLK to SCK (green)
  • DO to MISO (white)
  • CD to CARD DETECT (D49)(yellow)

CS (D53) and CD (D49) are directly next to the ICSP port, slightly under the expansion shield, but the connectors still work fine if you push them in slightly angled.

BTN is for the pause/stop/resume LCD button (kill switch). We recommend not connecting it and using a power switch for emergency stop instead. If you do want to use it, it should be connected to the Arduino BTN_ENC pin. Otherwise set BTN_ENC to -1 if not used.

This uses the LiquidTWI2 library v1.2.3 or later. Copy the LiquidTWI2 directory into the Arduino libraries subdirectory (something like /Applications/Arduino.app/Contents/Resources/Java/libraries/LiquidTWI2, just next to the existing LiquidCrystal folder). If you end up with a directory named "LiquidTWI2-master" then remove the "-master" part. We tested this successfully with Johann's latest Marlin version (as of 2014-03-21) and Arduino 1.0.5.

In Marlin/Configuration.h uncomment or adjust the following lines:

  • #define MOTHERBOARD 33 // Azteeg X3
  • #define LCD_I2C_VIKI

In Marlin/pins.h under MOTHERBOARD == 33 adjust the following lines:

  • #define SDSS 53
  • #define SDCARDDETECT 49
  • #define BTN_EN1 22
  • #define BTN_EN2 7
  • #define BTN_ENC 31

Disconnect solder jumper JP12 at bottom of Azteeg X3 to disable onboard SD slot and use pins for external SD reader (Viki LCD SD slot).

Where to buy

Shop Stock Location
3dprinterkart.com - Kossel/Delta Lowest Prices India based - ships worldwide
3dprintersbay.com - Kossel/Delta Printers US based - Ships Worldwide
Build A 3D Printer.eu Kossel Mini & XL - Highest quality parts EU/Netherlands based - ships worldwide
Think3dPrint3d Complete DIY Kit Components UK based - ships worldwide
www.HKBay.com Komplettes DIY Kit mit Deutscher Anleitung HK/Switzerland based - ships worldwide
www.UltiBots.com Kossel Mini & 250 V-Slot DIY Kits USA Based - ships worldwide
3DMarkt.at Complete DIY SET, E3D Extruder, Large Austria based - shipping to EU
reprap.cn full metal extruder,four wheels design bigger size China based - shipping to worldwide
reprapworld.com Kossel mini Netherlands Based - ships worldwide
RepRap PT Printer Parts Portugal Based - Ships to Portugal and Spain
FunReprap France Kit Kossel Mini et Maxi en Français Site Français - Mode d'emploi en Français
Replikeo Kit or Assembled Kossel Hong Kong based - Worldwide shipping
DIYKits.eu Improved Kossel Mini Kit EU/Croatia - Ships to EU


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