Investigating the effect of cooling rate on strength of Fused Filament Fabrication parts using differential scanning calorimetry technique

Abstract

Fused Filament Fabrication (FFF) is an extrusion based AM technique. Among the various AM processes, FFF manufactured parts offers lower strength. In FFF process, the primary concern of strength is bonding between strands and it is greatly influenced by the heat transfer during the manufacturing process. The extent of bonding not only influences the strength, but also the structural integrity of the part. To study the bonding between extruded polymer strands of FFF process, investigation has to be done to understand the influence of rate of cooling during FFF process. This study focuses on investigation of cooling rate affects on FFF-ABS (Acrylonitrile Butadiene Styrene) parts over its tensile strength. Differential Scanning Calorimetry (DSC) experimentation technique records the thermal history of the polymer and hence this test is applied to estimate the glass transition temperature of the polymer at different cooling rate. To support the DSC graphs, tensile testing of FFF made parts is done on the parts manufactured at two extreme extruder temperatures namely 230⁰ C and 250⁰ C. Further to the extent of bond formation, neck growth is estimated by capturing the scanning electron microscope graphs and neck growths are estimated. The outcomes indicate that the part extruded at higher temperature shows better strength. This establishes the fact that higher neck growth is due to higher or proper cooling process. The results also show that the parts cooled at higher cooling rate have better bonding in terms of neck growth which proves a good agreement among the cooling rate, strength and neck growth.