Welcome dear guest - this is the Trikarus Project homepage!

This is the public documentation space for the Hangprinter machine artwork implementation called "Trikarus". On this space you can find a lot of information about the project and how it is made off.

Trikarus is a custom Hangprinter (large-scale 3d printer), made in FabLab Chemnitz, specially designed for the 4th Saxon State Exhibition at the scene "Machinery Boom" (MaschinenBoom) of Chemnitz Museum of Industry to the anniverary "500 years of industrial heritage in Saxony" in 2020 and later happenings. It was postponed to be exhibited in late 2020 due to global Corona/Covid-19 crisis - i just call it the "coconut crisis" to have a better feeling about that situation. MaschinenBoom happened from 11 July 2020 until 30 December 2021.

Teaser image by https://web.saechsisches-industriemuseum.com/chemnitz.html

Neithertheless we did not give up to plan and build Trikarus. It's a completely non-commercial long-term experiment and project to focus on making Hangprinters more popular and more usable. It's the first Hangprinter implementation which comes with a massive documentation with focus on understanding the core principles (including failed experiments).

It comes with a lot of (experimental) features that "regular" Hangprinters do not have yet like gyro sensor, IMU sensor, Z limit switch, capsulated line guards (felts at the bearings), segmented print platform, a stable mounted hotend, filament feed sensor, IR Z probe, emergency halt, monitoring and other things. Things like parking the effector in position and a filament feeding unit at the bottom are going to be tested out as well (but are no existent yet).

Trikarus is also some "regular" kind of Industry 4.0 project because it utilizes different devices, sensors and actuators by exchanging data the IoT way. A mostly open source utilizing software stack is running 3d printing server, a visual data monitoring and a lot of scripts to automate and stabilize as much as possible. A great palette of things can be done completely remote and with less effort by a well configured client with proper access permissions (security cascade).

The project is called "Trikarus" because the printer's effector is a kind of flying thing. The name also fits to the to former airport "Ikarus" in Chemnitz. The "Tri" stands for the triangle shape of the effector as well as for the print platform and the anchor situation. There's also the old greek story of "Ikarus" where Ikaros, son of Daedalus, installed some wings and flown too near to the sun. His wings melted and he crashed into the ocean. Belonging to this project the sun is the extruder, mounted on the yellow lighted effector, and the ocean is the print bed with blue tape acting as adhesion promotor on it. Sometimes Trikarus comes too far to coordinates it cannot reach and will collide with it's lines.

Trikarus uses a Duet 2 Controller with official RepRapFirmware v3 and runs with Nema 17 stepper motors. It has closed loop control (servo motors) by installed Smart Steppers from MisfitTech, mounted on those Nema 17 motors. It can be set into so called "torque mode" by running commands from Repetier Server or serial console which is running on an Raspberry Pi. The Raspbery Pi is attached to Duet 2 by LAN and USB. To use torque mode the Smart Stepper run a special fork of Smart Stepper firmware which implements it (like Torbjørn did) but without I2C functionality. The Raspberry Pi works as remote multi tool for the complete machine and has to do a lot of important and cool jobs.

Overview of content

Check out the table of content below and start with the What is a Hangprinter and how does it work? to get an orientation.

Click to expand


Because videos help to understand we made a lot of clips for different problems and solutions. We put them on our self-hosted PeerTube instance.

Trikarus @ PeerTube Videos

Live Monitoring of Trikarus

Trikarus is embedded into a network cascade with monitoring system (InfluxDB and Grafana). Using different bash scripts and tools like cURL, as well as things like collectd and Python, we can collect a lot of system metrics to monitor the stability of Trikarus (temperatures, errors, recent controller state, network traffic, ...). The data transmission is established using Freifunk. In case the network operates fine we can show some data on this page. If the following panels do not show data the network is offline or set to another mode (maintenance or testing). Different alerts are configured to push information by mail, like unstable network (dropped packets), high CPU temperatures, system loads, failed watchdog, power states and so on.

To the monitoring dashboard

Hardware Features

  • based on Hangprinter v1-v4 + own ideas and a lot of working and also failed baby experiments, existing knowlegde from the former past, and a lot of stuff from the widy spidy web
  • key phrases
    • frameless printer, hanging printer, Hangprinter, room printer, Freiraumdrucker, Seilwindendrucker, winch printer, rope printer, wire printer, cable-driven parallel 3D printer CDPP, redundantly constrained, line-on-spool, completely restrained positioning mechanism (CPRM), kinematically redundant
  • typical layer heights 0.45 ~ 2.00 mm
  • printable material: PLA (because no heated bed)
  • consumed time: more that you can imagine
  • a lot of lessons learned
    • consumed filament: over 3 kg of wasted filament for failed prints, failed model geometry and better model iterations; around 10kg of filament in total
    • destroyed parts which were replaced while building: rotary encoder, gyro sensor, stepper motor driver and much more
  • Software & remote control → see Network infrastructure and software

    • Duet Web Control (Duet 2 Ethernet/Wifi)
    • Repetier Server & Repetier Server Monitor
    • Monitoring with Grafana, InfluxDB and collectd
    • mjpg_streamer for Webcam
    • UPS powered server infrastructure: Raspberry Pi and Freifunk can be maintained for 4 to 10 hours even after switching off the power in the museum (for neat evaluation of the metrics, saving of configs, etc.)
  • GCode/Firmware: RepRepFirmware with configured HangPrinter kinematics mode and Marlin compatible dialect for slicing
  • 32 Bit Duet 2 Ethernet electronics
  • sensors
    • Infrared sensor for auto leveling in the Z direction
    • limit switch for maximum Z coordinate (not working stable yet because cable collisions can occure) - not integrated in routines yet
    • Filament feed sensor on the extruder realised by generic knob encoder
    • Filament feed sensor on the filament conveyor (double monitoring) - not integrated in routines yet due to hardware issue
    • 3x analogue bubble levels for rough leveling the effector
    • digital gyro MPU 6050 for checking of the surrounding room by measuring and collecting vibration and temperature data (more could be done with this data later) - not integrated in routines yet
    • digital IMU MPU 9250 for precise leveling and measurement of the effector inclination (angle) and vibrations → helpful monitoring for printer calibration (loose / tight tension) or error behavior analysis (e.g. strong floor vibrations) - not integrated in routines yet
  • actuators
    • Aero Titan Extruder with Super Volcano Hotend for 1.75 mm filaments and 1.4 mm nozzle (approx. 10x higher output than normal desktop printers) - PT100 sensor
    • Active filament unwinding device with monitor and integrated load cell (10kg) - under development
    • emergency halt button (this is crucial for printing with safety. It was repeatedly validated to be the best idea you could have building up a large machine with higher forces in extrusion)
    • closed loop servo motors (MisfitTech Smart Stepper)
    • fancy yellow LED stripes at the effector and ceiling module
    • three laser pointers for easy machine calibration (mechanically capsulated by mounting on the top side of the translucent polycarbonate ceiling plate)
  • backup recovery of print (printer can be shutdown and revived later in case the power was not gone (no brake system existent yet)) - experimental
  • different hardware features
    • translucent UV resistant polycarbonate (Macrolon) ceiling plate for a good view of all components (for maintenance, laser pointers and design)
    • more rigid lines (doubled lines for each axis) provide better flex compensation and keeping orientation than single lines
    • fine adjustment of the lines with guitar tuners
    • thumb screws for quick release of messed lines
    • transport rings on the top side and grip handles on both sides for better handling of the ceiling module
    • advanced side carriers at the spools to catch de-spooled lines (prevent lines to get into ball bearings) and for possibly later drive break implementation
    • all parts portable with regular car for various events
    • magnetic adjustable PTFE filament tube guiding from bottom to ceiling module
    • magnetic line winders (reservoirs) for idling lines (bypassing)
    • thick and well isolated main cable for wiring between ceiling module and effector (heavy weight). Acts also as some simulation for Hangprinters which would have more than one extruder or contain more advanced tools
  • frame
    • large frame with support for 3d printed parts up to approx. 2.5 m height x 1 m diameter
    • total frame dimension ~2.8 height x 2.25 m diagonal
    • stable frame parts printed from PETG
    • collapsible frame that can be transported by car
    • can be set up completely by 3 to 4 people
    • can also be used partially (fork corners only)
      • install ceiling module at the room's ceiling with some eyelets / spacers
      • place the three anchors together with the frame corners (tubular steel assemblies) on the floor
      • then it corresponds completely to the actual Hangprinter principle
  • contains a lot of different recycled spare parts from different things like old computers, power supplies and cables
  • black/yellow design
  • low power consumption: max. 200 watts when everything is running (extruders, motors, lighting) - usual operating power is etween 50 and 100 watts

Trikarus' core modules, dimensions and weights

See Bills of material and hardware compenent features to get more information about electronics.

effector (mover) assembly

ceiling mount assemblyexhibition frame

  • ~3.9 kg - measured by luggage scale - weight includes ceiling cabling partially
  • ~16 kg - measured by luggage scale
  • ceiling module with homed and fixed effector: dimensions roughly 1.0 m x 0.45 m (height)
  • foldable heavy-weight steel frame
  • max 1.6 m long beam segments

filament feed and sensing unit/system

print platform

Smarty Mac Skydriver
this was not finished yet. Stay tuned

  • height + angle adjustable print platform
  • max 1.3 m long beam segments
  • He watches out for everything

Limitations / missing features / caveats

Targets and demands of Trikarus project

  • not intended to be a high quality machine that ever could or should be mass-produced
  • manufacture large objects. it's strength is in build volume, not speed or precision
  • it's a printer with support for large spaces. Accordingly, an extruder was installed that has significantly more output. This means that the parts to be produced require more material and are therefore much more expensive than conventional 3D prints. Since misprints are priceless, the machine hardware has to be better. Therefore, more costs for closed loop steppers and Co. were estimated here. So it's not a cheap project
  • was built for exhibiting → aims for stable function, quality and optics and is therefore not as inexpensive as regular hardware projects
  • education (showing the procedure and the possibilities of Hangprinters and 3d printing) for visitors and other people
  • learning by doing
  • experimental & further development (open knowledge contribution)
  • self-actualization
  • maybe go mobile from exhibition to exhibition, such as MakerFaires
  • validate, test, improve the Hangprinter working principle
  • modern art / machine art / maker art / hacker art - every machine is also a work of art, an inspiration and an expression of creativity or original ideas or solutions
  • create a good and more complete documentation for Hangprinters, which explains how to operate and maintain the machine. This documentation focuses on the usage of RepRapFirmware but it explains also some differences to Marlin Firmware
  • extension to ceramics printing (postponed)

Contribution and questions

Trikarus is not some kind of fork project to completely rebase on. It is made to contribute as much as possible to the main Hangprinter project. So please do not rely on this as main source and please commit your questions and developments to the ressources provided by the source repositories linked in the bottom section at What is a Hangprinter and how does it work? ("Important web ressources for Hangprinter"). If you have questions and ideas for Trikarus you can drop us an email. If it is related to Hangprinter in general you can drop us too or put it directly into the gitlab repositories of Torbjørn Ludvigsen.

(info) Some different project files were pushed into Gitea → Trikarus @ Gitea


Special thanks to Torbjørn Ludvigsen for all the time for years now investing into so much effort respecting experiments, coding and testing Hangprinter related knowledge. You got a special positions at the tool head.

Trikarus project would not have been possible to make without the FabLab Chemnitz people, machines, tools and knowledge. Thanks to Mathieu for the prototype frame of the printer, to Georg for giving 2 more hands while building up and testing at the museum and to Daniel for organizing and transporting a lot of different stuff. Cheers also to Jens, Steffen, Marcel, Jannis, Stefan, Sven and Tommy.

Another appreciation goes to Freifunk Chemnitz which delivers flexible infrastructure regarding to Wifi. Thanks again to Stefan and Martin helping out with technical stuff.

Thumbs up to the special idea i got from The Case Digital regarding cable guidings.

Finally for giving us the possibilty and space to make that project a huge Hallelujah is going to the Chemnitz Museum of Industry with Jürgen Kabus and Thomas Schmäschke for organizing and spending so much time.

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