High-quality 3D printer processes plastic particles from toner

In a joint research project, TH Köln and the company mz Toner Technologies have developed a 3D printing process that uses plastic particles from a toner for printing.

Compared to conventional methods, this alternative achieves better quality and higher throughput. A further development should now make it possible to print with metals and ceramics as well. In the long term, an application in space travel is conceivable. The 3D printing of plastic products is already widely used in prototype construction, for customized individual parts, and partly also in small series production, as the project partners say. In mass production, additive manufacturing has not yet been used, among other reasons, because of the relatively slow processes and uncertainties regarding component quality. Both aspects are expected to change through the project.

Many 2D layers are stamped into a 3D part using a stamping machine.

The approach developed in the project is based on electrophotographic printing, which is widely used in laser printers. It uses a photosensitive drum in the dark, which is fully electrostatically charged. The laser beam then selectively erases the charges. When the plastic particles from the toner come into contact with the drum, they adhere to the still charged areas and can be transferred to a substrate.

The plastic particles used in the toner of the project partner at TH Köln are between 10 and 100 micrometers in size. Accordingly, the 2D layers produced per pass are very thin. However, this very small resolution achieves good mechanical properties and a good surface quality. To transform the printed two-dimensional layers into a three-dimensional component, the individual layers are stacked on top of each other in a stamping machine and fused at 200 to 220 degrees Celsius.

3D component quality close to that of injection-molded parts

Tests with sample bodies made from the technical plastic ABS show that their properties are comparable to those of conventional manufacturing processes and other additive methods, as the protagonists emphasize. In tensile tests, the parts reached a tensile strength of 1,904 megapascals (MPa). In the literature, for example, values of 1,627 MPa are reported for the fused deposition modeling process, and 2,300 MPa for the injection molding process. Currently, the prototype can print up to five square meters per minute in two dimensions, as we learn further. The number of workpieces produced depends only on the number of transfer units working in parallel.