University of Louisville: Ultrasonic Vibration Improves Layer Adhesion in FDM 3D Printing with ABS2/26/2019
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University of Louisville: Ultrasonic Vibration Improves Layer Adhesion in FDM 3D Printing with ABS https://ift.tt/2BUTcxt In ‘Effect of Ultrasonic Vibration on Interlayer Adhesion in Fused Filament Fabrication 3D Printed ABS,’ by Alireza Tofangchi, Pu Han , Julio Izquierdo, Adithya Iyengar and Keng Hsu, the authors examine the future of FFF (FDM, Material Extrusion) 3D printing, along with how different processes affect performance. They foresee greater potential for FFF printing as a serious tool in manufacturing, as materials, accuracy, finishing, and quality in parts begin to evolve. With the use of 34.4 kHz ultrasonic vibrations during FFF 3D printing, the researchers found up to a 10 percent increase in ABS layer adhesion versus regular FFF processes.
The team explains that there have been several different methods used for strengthening interlayer bonding; for example, adding more heat during or after printing has proven to be effective through elevating the ‘temperature dependent diffusivity.’ Enhancing the surface of filaments also proved to improve strength, along with both infrared and laser heating—added just before deposition of each layer. The researchers also noted that ‘reducing the radius of gyration of polymer chains could also result in similar improvement in inter-layer strength,’ effected through relaxing the polymer chains left in the 3D printed tracks. Ultrasound vibrations permit both relaxation and diffusion of polymers, creating better interfacial adhesion—and possibly resulting in parts bearing isotropic mechanical properties. Testing occurred on a MakerGear M3 that the team customized for the inclusion of the vibrations. Vibrations were created with a 40 kHz-piezoelectric crystal-based bolt-clamped transducer with power rated at 25 W. This was connected to the heater block using a connecting rod and threaded fasteners.
Researchers measured peeling and energy of the inter-related bonds with the ASTM F88 Peel Test, a system well-known for evaluating adhesion between flexible bands that have been sealed. The test is relevant here as the subject matter is also flexible. Results of the study show adhesion forces remaining consistent. When track width-to-nozzle diameter ration varies from .74 to 1.47, however, adhesion increases but then balances out at 1.2 and becomes lower at the larger ratios. Such reactions are caused by shear forces in the flow of the polymer traveling from the nozzle to flow horizontally. The wide increases, so do the flow rate and velocity of the polymer increases.
Diffusivity may be caused by polymer chain disentanglement which also adds to chain relaxation and then counteracts polymer reputation increases.
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