Thermal and facture characterization of welding zones produced by polymer

extrusion 3D printingJonathan E. Seppala, Kaitlyn E. Hillgartner, Chelsea S. Davis, and Kalman B. Migler

Polymer & Complex Fluids GroupNational Institute of Standards and Technology (NIST)

Polymers & Complex Fluids GroupNIST Adhesion Soc.

Feb 23rd, 2016

reprap.org

FDM/FFF Process

Fused deposition modeling (FDM)™aka Fused filament fabrication (FFF)aka Material extrusion

Weld Zone

Nozzle

Printing Layer LP

First Sub-Layer LP-1

Polymers & Complex Fluids GroupNIST Adhesion Soc.

Feb 23rd, 2016

Outline

II. Rheology

I. Thermography III. Fracture Strength

𝜎𝜎 =2𝐹𝐹𝐻𝐻

III. Comparison to Classical Weld Theory

Wool Poly. Eng. And Sci. 1988 28

Polymers & Complex Fluids GroupNIST Adhesion Soc.

Feb 23rd, 2016

Materials

ButadieneSpheres

TEM micrograph ABS

Styrene Acrylonitrile Matrix

J. Mater. Sci. Lett. 19 (2000) 73-75

Acrylonitrile butadiene styrene (ABS)Butadiene-g-Styrene Acrylonitrile/Styrene Acrylonitrile (BgSAN/SAN)

Polymers & Complex Fluids GroupNIST Adhesion Soc.

Feb 23rd, 2016

Process Characterization: Thermography

Extruder

Polymers & Complex Fluids GroupNIST Adhesion Soc.

Feb 23rd, 2016

IR Intensity Profiles

Reflection + Emission Intensity

LP

LP-1

LP-2

Polymers & Complex Fluids GroupNIST Adhesion Soc.

Feb 23rd, 2016

Temperature Profiles

Weld zone:Average of layer above and below.

Polymers & Complex Fluids GroupNIST Adhesion Soc.

Feb 23rd, 2016

Weld Temperature

Print Speed Extrusion Temperature

To be published in Additive Manufacturing

Polymers & Complex Fluids GroupNIST Adhesion Soc.

Feb 23rd, 2016

ABS Rheology

• Shift factors from time-temperature superposition• Provides comparison in molecular mobility between

different temperatures

1 s at 230 °C

1200 s at 150 °C

Polymers & Complex Fluids GroupNIST Adhesion Soc.

Feb 23rd, 2016

Spectroscopic Monitoring of Fused Deposition Modeling

acrylonitrile peak (A) butadiene peak (B) styrene peak (S)

Blue: Crystalline ABS in starting strand

Red: Molten ABS just below nozzle

Raman Spectrometer

Light Source

Fiber optics

v

Polymers & Complex Fluids GroupNIST Adhesion Soc.

Feb 23rd, 2016

Conclusion

Temperature measurement / thermal imaging is 1st step towards development of physics based model of FDM.

Weld formation in material extrusion occurs over ~1 s; most of the interdiffusion occurs over time scale much less that 1s.

Temperature kinetics, rheology and weld theory provide foundation for understanding fracture strength as a function of temperature and feed rate.

In-situ monitoring is achievable. Linking back to real time control is a challenge.

Polymers & Complex Fluids GroupNIST Adhesion Soc.

Feb 23rd, 2016

Contact info:

Seppala:http://www.nist.gov/mml/msed/polymers/jonathan-e-seppala.cfm

Migler:http://www.nist.gov/mml/msed/polymers/kalman-migler.cfm