Due to the rise in versatility and competitiveness of 3D printers the popularity also rises, resulting in a lot of research into the different aspects of the 3D printer. One of these aspects is the extruder. The 3D printers make an object by layering a filament, which is done using an open-loop stepper motor. When printing, the filament is heated and becomes liquid, next to be extruded to form the desired layered object.
An open-loop extruder works fine when it comes to a continuous process, where you just keep on printing. However, problems arise when the printing is dynamic and has to stop and start very often, or when changing velocity, as with corners. Due to a pressure build-up in the nozzle, the fluid keeps coming out. This ”oozing” results in possible problems for the desired product. Because of the open-loop system all the settings to prevent oozing has to be done manually. E.g. such a system can retract the filament at a certain preset distance. But this distance is not always enough or it can be more than it should be. Because of this, it is necessary to improve this method.
This research focuses on a closed-loop extruder. This should make it possible to control the nozzle pressure more accurately by controlling the torque produced by the motors, i.e. by controlling the current through the motor. To be able to make such a controller it is necessary to first determine the plant of the system. This plant basically describes the system, the extruder, and nozzle, which has a torque as input and a fluid flow as output, given material properties such as viscosity, compressibility, and others. For this research, an initial hypothesis can be formed, namely: with closed-loop control of the extruder the torque can be related to the pressure in the nozzle to improve the oozing behavior of the nozzle. The biggest challenges will be to determine the plant of the system and to invert the plant relations in order to make a good controller. Research needs to be done to understand the controller, plant, and the extruder and nozzle.