Process parameter determination for small recycling plants for the production of filament for FFF printing using the Taguchi method

With the increasing use of the filament fabrication process, the in-house production of filament and the recycling of PLA waste is becoming more and more important. Small desktop filament extruders with associated peripherals enable small businesses and private users to carry out these recycling processes. Determing the right process parameters is of crucial importance here. These are usually only issued by the polymer manufacturer and the machine manufacturer. However, the development of own process parameters is important for new polymer compounds, as well as polymers with unknown manufacturers, as is typical in recycling. The common Taguchi method, which is used for process optimisation within the FFF process, was also used in this article to produce improved parameter sets for the production of filament using a single screw extruder (3devo Precision) with four heating zones. In this experimental field, the Taguchi method did not prove promising. Due to the small dimensions and compact design of such desktop filament extrusion machines, it was found that the setting parameters cannot be considered independently. The main parameters influencing the process were identified as the extruder screw speed, the cooling capacity and the temperature of the heating coil at the hopper. Nevertheless, parameter sets for PLA pellets and recycled PLA could be developed which have a better performance in terms of homogeneity of the diameter over time compared to the previously available parameter sets.