Closed Loop Control
Fused Deposition Modeling (FDM), also known as fused filament fabrication (FFF), is a 3D printing process that successively builds 3D parts through the deposition and fusing of 1D filaments to consecutively define 2D layers. While FDM is a widely used process, the 3D printed part properties are governed by the complex relationships between the transient temperature, dynamic material flow, and resulting molecular diffusion. The proposed research connects expertise in rheological modeling and plastics machinery design to investigate the use of low cost instrumentation to perform on-line rheological analysis and process control. The main tasks include:
- on-line characterization of the melt viscosity through the use of an FDM extruder equipped with a closed loop stepper motor drive that provides the motor torque and rotation,
- modeling of the FDM process with respect to die swell and drawdown as well as welding and solidification based on a unified axisymmetric finite element analysis that operates in near real-time given FDM process feedback,
- off-line and on-line validation of the rheological, dimensional, and structural properties.
In parallel with this research, educational outreach is being performed through integration with the PIs’ process control and materials science courses, teacher training through the UTeach program, and Maker Faire conferences.
Block diagram of closed loop control structure for 3D printing
A protocol has been developed to broaden the portfolio of materials and processes for fused deposition modeling. A four step process is initially proposed consisting of the following:
- Material Characterization: To verify the material composition and thermal stability while also characterizing the material viscosity to guide processing in extrusion and subsequent fused deposition modeling (1 day);
- Filament Production: To produce filament to a target diameter of 1.75 mm with minimal variation using an extruder with process instrumentation including a laser micrometer that ensures filament alignment and consistency (1-2 days);
- Test Specimen Production: To produce tensile test specimens printed with longitudinal and transverse filament orientations according to an efficient design of experiments that investigates environment temperature, nozzle temperature, deposition rate, and layer thickness (1-2 days).
- Protocol Verification: To test the printed specimens to verify the capability of the procured filament and implemented process including quantification of the void fraction, bond strength, and anisotropic properties of components manufactured by fused deposition modeling (1-2 days).