Open source

Dr. Joshua Pearce’s new open-source ‘Cerberus’ can 3D print PEKK for sub-$1000

A team led by Michigan Technological University’s Joshua Pearce, known for his work in open-source 3D printing, have released the design plans for a low-cost, high-temperature open-source FDM printer.

Dubbed the ‘Cerberus’, the three-headed machine can be built for less than $1000 and is capable of printing a number of high-performance materials such as PEKK and Ultem/PEI. As it stands, the self-replicating system is compatible with just one 500°C hotend, with the other two options set to be released soon.

The frame of the Cerberus. Image via Joshua Pearce.
The frame of the Cerberus. Image via Joshua Pearce.

3D printing reusable PPE

For the majority of 2020, makers from around the world have been putting their 3D printers to use by producing PPE to combat global shortages. The issue is: these PPE parts are often only used once before being discarded. Thermal, oven-based sterilization is generally not feasible for FDM-printed components due to low deformation and melting temperatures, so there is indeed a need for low-cost, high-temperature materials (and machines capable of extruding these materials).

While there are several high-performance printers on the market, the high costs associated with them make them inaccessible to the average hobbyist. In fact, NASA has previously modified a commercially-available Lulzbot Taz to fill this very gap, designing a delta-style high temperature extrusion machine. Pearce now aims to build on this work with the newly developed cartesian-style Cerberus.

The Cerberus 3D printing a PEKK face mask. Photo via Joshua Pearce.
The Cerberus 3D printing a PEKK face mask. Photo via Joshua Pearce.

The open-source Cerberus 3D printer

Running down the reported capabilities of the machine, it certainly delivers in the value-for-money department. An E3D heated bed capable of 200°C, coupled with a V6 all-metal hotend packing an impressive 500°C, enables printing with even the most notoriously-difficult engineering filaments. The closed-off printing chamber features a 1kW space heater core running on mains voltage for a rapid start-up.

The frame is cleverly designed so that all of the low operating temperature electronics – such as the motors – are placed outside of the heated chamber, also eliminating the need for an abundance of individual cooling fans. Furthermore, there is the potential for dual extrusion modifications and automatic bed leveling through the integration of a probe.

Having performed tensile tests on parts printed on the machine, Pearce reports an average tensile strength of 77.5MPa for the PEKK (390°C) and 80.5MPa for the Ultem/PEI (380°C). As a proof of concept, an open-source face mask was then printed in PEKK and placed in an oven at 120°C for 30 minutes.

The test piece was successful and showed no observable deformation, with the specification sheet stating it should be operational until 150°C. The material can also be annealed to increase the maximum operational temperature to 260°C – more than hot enough to achieve full sterilization.

The 3D printed PEKK mask after oven sterilization. Photo via Joshua Pearce.
The 3D printed PEKK mask after oven sterilization. Photo via Joshua Pearce.

The open-source files for the Cerberus can be downloaded here. Further details of the printer and its setup can be found in the paper titled ‘Open source high-temperature RepRap for 3-D printing heat-sterilizable PPE and other applications’. It is co-authored by Noah Skrzypczak, Nagendra Tanikella, and Joshua Pearce.

Pearce, often regarded as an ‘open-source champion’, has a number of similar projects under his belt. Just this summer, he developed an open source, computer vision-based software algorithm capable of print failure detection and correction. Leveraging just a single camera pointed at the build plate, the code tracks – layer by layer – any printing errors that appear on the printed part. Last year, Pearce also made his open-source 3D printing course available online for free, stating that his one goal is for it to “become legendary”.

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Featured image shows the frame of the Cerberus. Image via Joshua Pearce.

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