Vacuum System Assisted Fused Deposition Modeling To Improve Parts Tensile Strength

• Main Author: Wong, John Huang Ung
• Format: Thesis
• Language: English; English
• Published: UTeM 2017
• Subjects: T Technology (General); TS Manufactures
• Online Access: http://eprints.utem.edu.my/id/eprint/23083/; http://plh.utem.edu.my/cgi-bin/koha/opac-detail.pl?biblionumber=107375; TJ211.42.L64 2017

Additive manufacturing (AM) has come a long way since the days of rapid prototyping began with the capability to produce a complex solid part rapidly. AM has begun to be acknowledged and accepted in numerous industries such as aerospace, automotive, medical, and even art. Fused deposition modeling (FDM), one of the AM technologies, is a popular and most used technology based on polymer extrusion method. FDM generally works by depositing a molten thin polymer filament from the nozzle onto the build platform repeatedly layer by layer up to create a solid part. Despite having the advantages to produce part without any complexity restrictions, the known poor mechanical strength for a functional part produced is the limitation. Literature has found out that one of the main reasons anisotropic behaviour which was the insufficient bonding between layers was found weakest at the z-axis. The layer by layer bonding occurred too fast and was not fully fused together causing weak structural strength and easily shattered through pulling force. It was found that vacuum technology could improve the layer bonding by reducing the convective heat transfer. In a vacuum environment, the reduced amount of air molecules hindered the heat energy to be released from the deposited filament. Simulations were successfully created a vacuum chamber to sustain the vacuum pressure and confirmed the thermal behaviour of heat transfer in the vacuum was similar to the literature study. The pilot test confirmed that the different level of vacuum pressure does affect the tensile strength of the printed parts. Then, a total 20 experiment runs with 60 printed specimens were conducted with two parameters namely layer thickness and vacuum pressure. Results have found out that the highest percentage improvement (16.77 %) were 18.0846 N/mm2 produced by 0.20 mm/21 inHg, while the highest strength measured at 0.25 mm/21 inHg, giving 19.7202 N/mm2. The z-axis produced in vacuum environment was now at 77.67 % of strength produced by x-y axes signifying reduced anisotropic behaviour. It was found out that under scanning electron microscope (SEM), the specimens produced under vacuum pressure had a better bonding formation compared to normal atmospheric ones. Lastly, the ANOVA method had validated the significance of the set of parameters and the optimised parameter was 0.25 mm/21 inHG for recommended tensile strength while 0.22 mm/21 inHg for recommended tensile strain. The vacuum assisted FDM was proven to be feasible and this study had increased the understanding of vacuum technology and FDM to improve the tensile strength of the printed part. Further improvements of vacuum assisted FDM will allow the creation of mechanically stronger complex parts in a wide range of applications.