Lubrication-free bearing technology and compact energy supply for multi-nozzle 3D printers

The FX-7 Pro multi-nozzle 3D printer from Liqtra GmbH is one of the most productive fused filament fabrication 3D printers currently available (as of 2023). Compared to single-nozzle printing, process times can be reduced by an average of 75% and component strength in the build direction can be increased by up to 37%. Liqtra is currently focussing on orthopaedics: prostheses and orthoses made of polypropylene can be produced quickly and economically as customised products, adapted to the individual needs of the patient, using the 3D printer - even directly on site in the clinic or orthopaedic centre.

The multi-nozzle technology requires a large supply of material. The FX-7 Pro is therefore equipped with a material chamber for eight filament rolls, from which material can be removed simultaneously. Here, the designers saw potential for improvement in the initially used bearing rollers for the filaments, as the design and assembly of the shaft involved a great deal of effort.

For the z-axis of the 3D printer, they were looking for a durable drive technology that could easily withstand the temperatures of around 80°C inside the printer and was as compact as possible to fit into the limited installation space. These requirements must also be met by the cable guides, which ensures that the power supply and data transport function reliably.

With our motion plastics, we at igus had the right solutions ready for use in the 3D printer. The answer to the bearing roller problem are fully assembled xiros conveyor rollers with end caps, which Liqtra can order cost-effectively as injection-moulded parts in special shapes. The conveyor rollers consist of plastic ball bearings and thin-walled tubes, which enable weight savings of up to 48% compared to metal solutions and, in contrast to metal ball bearings, accelerate and decelerate significantly better. This advantage means that no additional brakes need to be used. The practically wear-free bearings also work without lubricants, can withstand temperatures of up to 80°C and are insensitive to dust and dirt.

Liqtra also utilises the advantage of maintenance-free dry operation in the z-axis: dryspin trapezoidal lead screws in a special design with plastic lead screw nuts with flange are used here. Perfectly harmonised in their specifications and geometries, they achieve high levels of efficiency with a low coefficient of friction and low wear rates. The drive system is complemented by a drylin E lead screw stepper motor. It offers high speed, works precisely and is easy to control. Thanks to its compact type, it can be easily integrated into the limited installation space.

FX-7 Pro, series E2.1 for medium loads and E4.1 for higher loads are used. To create sufficient installation space for feeding the eight filaments, the e-chain is installed on the side of the print head in a horizontal installation position. It guides the cable safely and withstands the high forces caused by the large number of supply lines without any problems.