03/05/2021
By David Kazmer
The Inaugural Webinar for the National Science Foundation SHAP3D Industry-University Research Center will be Tuesday, March 9 at 2 p.m. ET. This free webinar is for practitioners and researchers interested in 3D printing of multiple materials.
TITLE: Pressure Sensing and Compressibility Characterization/Control in Material Extrusion
SPEAKER: David Kazmer, University of Massachusetts Lowell
ABSTRACT: An instrumented hot end is presented including on-board melt pressure and acceleration sensors. The role of compressibility is explored by modeling the mass flow rate and transient fluid capacitance given in-line observation of the melt pressure. The underlying theory and implementation are described for the compressible flow simulation inspired by injection molding simulation. The simulation results are presented for the validation part and #3DBenchy. The simulation is then used for control purposes including a popular all-in-one benchmark. In the second part of the talk, both compressibility and viscosity behaviors are characterized. Several faults are diagnosed by analysis including
- limited melting capacity of the hot end,
- skipping (grinding) of the extruder drive gears,
- low initial nozzle temperature,
- varying flow rates associated with the intermeshing gear tooth velocity profile, and
- delays and reduced melt pressures due to drool prior to extrusion.