Karl Rabofsky GmbH

Inside Rabofsky – Principles of UV based 3D printing

PLEATMASTER © Rabofsky

Karl Rabofsky GmbH is a special purpose machine manufacturing company with a historical background of more than 120 years. Rabofsky designs and manufactures so called pleating machines for the production of pleated material in the automotive and pharmaceutical industry as well as for other branches as heating ventilation and air-conditioning (HVAC) or sunlight protection. Rabofsky’s machines are highly automated and comply with a high quality standard. More than 75% of the production is exported to the European Community, North America and Asia. Typical pleating lines are around 8 meters long, 3 meters wide and 2 meters high.

3D printer 'PYOT One' © Rabofsky

Since 2016 Rabofsky also designs and manufactures modern 3D printers following the “fused deposition modelling” (FDM) method. Those 3D printers process exclusively thermoplastic polymers like for instance acrylonitrile-butadiene-styrene, impact resisting polyamide or polypropylene. They are equipped with a special print head – the extruder – melting wound plastic strings of an e. g. 1,75mm diameter and placing thin tracks of flowing hot plastics with a diameter of 0.1 to 0.4 mm layer by layer on a heated printer table. As for the pleating machines already practiced for many decades Rabofsky’s 3D printers are designed for industrial purposes coming with a well-proved set of tools for each type of plastic to obtain high quality printouts with an excellent degree of reproducibility.

Fused Deposition modelling 3D printers have some major advantages but also some important disadvantages. One of the disadvantages is, that the more resistant thermoplastic polymers dedicated for industrial applications tend to warp, that means, they can more or less change their shape when they cool down resulting in printouts, which are outside the necessary tolerances of the dedicated operation purpose. Appropriate countermeasures are a 3D compliant CAD modelling, accurate slicing and strict process control procedures. Another disadvantage is the limited resistance of thermoplastic polymers against mechanical and thermal strain.

These disadvantages and the limited process speed of the FDM method form the main reasons for exploring new 3D printing techniques using advanced duromers (thermosets) instead of thermoplastic polymers. In contrast to the FDM method duromers are not melted by an extruder, but have to be applied by a precise dispenser and cured instantly by a field of UV LEDs emitting two different specific wavelengths, one wavelength for the surface of the track and the other for the interior. Rabofsky is one partner of the joint research project “BUERMA” with Fraunhofer Gesellschaft and Technical University of Wildau together with other industrial partners located in the area of Berlin. This consortium explores new ways of UV-based 3D printing breaking the current limits of FDM 3D printing.

Rabofsky offers an interesting factory tour presenting, explaining and practical testing the triple of machines and devices on visitors demand explained above by a team of experienced engineers. The tour will be concluded by a technical discussion and a “questions and answer” session for the visitors. The printouts will be handed over to the visitors as giveaways.


Address

Karl Rabofsky GmbH
Motzener Str. 10a
12277 Berlin, Germany

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