Rheological properties and machinability in dry turning of neat PLA and PLA reinforced with hemp fibers

Abstract

Society still overuses polymers without fully considering their environmental impact. However, attention is increasingly shifting towards biocomposites, which already have practical applications in various fields. Despite progress, finding alternatives for complex, precise parts remain challenging. This is why we are focusing on hybrid manufacturing, which combines the benefits of 3D printing and machining. 3D printing allows us to produce parts with complex geometries, while machining ensures the precision required to meet the highest technical standards. However, this combination of processes can present challenges. Lubricants cannot be used in cutting to prevent affecting the printed layers and hydrophilic fibers. Without lubrication, localized heating occurs during machining, and since polymers are thermally insulating, this can cause material melting, degrading the surface and quality of the part. Therefore, it is essential to first study the dry machinability of these materials to prevent such issues. This study is part of a broader approach aimed at exploring the combination of Pellets Additive Manufacturing (PAM) and milling, particularly on a biocomposite composed of 80% PLA and 20% hemp fibers. However, this aspect is not directly addressed here. Instead, this paper focuses on understanding the cutting behavior of PLA, both pure and reinforced, by analyzing the influence of cutting parameters through turning operations on injection-molded parts. The objective is to assess their impact on surface integrity and cutting forces. This approach facilitates the study of fundamental cutting parameters. Optimal cutting parameters for these materials are identified by analyzing cutting forces and assessing surface quality.