Thermal Treatment and Particle Size Effects on Coalescence in Extrusion-based Additive Manufacturing

摘要

Transverse and out-of-plane mechanical properties of objects fabricated by fusedfilament fabrication, an additive manufacturing technique, are typically 20-50%lower than bulk properties. A major contributor to this knockdown is poor raster-torasterand interlayer bond strength driven by incomplete polymer coalescence. Thetwo major steps in the coalescence process responsible for bond strengthdevelopment are neck growth and interfacial diffusion. The goal of this work is toexplore the effects of temperature, time, and particle size on coalescence of ABSpolymer in a controlled environment to identify appropriate thermal history to targetduring the printing process for enhanced raster-to-raster and interlayer bond strength.Particle size was found to have a significant impact on neck growth where doublingthe size reduced the normalized neck growth by 58%. Diffusion was qualitativelyassessed by tracking absorbance of red pigment from a red colored ABS particle intothe neighboring white ABS particle at 550 nm. Smaller particle size held at elevatedtemperature for longer time had pigment diffusion across longer distances from theneck region. Results suggest that smaller diameter rasters promote faster and morecomplete coalescence.