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

Abstract

Desired mechanical properties are major area of interest within the field of Additive Manufacturing (AM) technologies. Fused Filament Fabrication (FFF) is an extrusion-based AM technique. 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 the extruded polymer strands of FFF process, investigation must be done to understand the influence of rate of cooling during FFF process. The present study focuses on investigation of cooling rate effects on FFF-ABS (Acrylonitrile Butadiene Styrene) parts over their tensile strength. Since glass transition temperature plays a key role in understanding the history of the thermal behavior, it is hence important to estimate its value for various extrusion temperatures. To understand this, glass transition temperature is estimated through Differential Scanning Calorimetry (DSC) experimentation technique as it records the thermal history of the polymer and hence this test is applied at different cooling rate. Additionally, to support the DSC graphs, tensile testing of FFF made parts is done on the parts manufactured at two extreme extruder temperatures namely 230° C and 250° C. Better bond formation between the strands contributes to higher strength and hence neck growth is estimated by capturing the scanning electron microscope graphs. The higher strength (as obtained for 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. The novelty of this work lies in polymer characterization to provide more insights in FFF layer deposition process (effect of different cooling rate on FFF process) using DSC and mechanical testing/analysis.