Manufacturing Continuous Fiber-Reinforced Printing Filaments: Development of a Post-Consolidation Unit

Abstract

A novel, temperature-controlled post-consolidation unit is developed to test its potential to improve the melt impregnation process used to manufacture continuous fiber-reinforced filaments for additive manufacturing of high-performance thermoplastics. Preliminary laboratory characterizations have identified Hexcel HexTow AS7 and Arkema Kepstan 6004 as suitable dry carbon-fiber roving and thermoplastic matrix material, respectively. Filaments are processed by melt impregnation with varying parameters (e.g., different temperatures), as well as with and without the post-consolidation unit. A thermographic camera is used to monitor the process and observe the temperature distribution of the filament during post-consolidation. The filament quality is determined by a 3-axis measurement device (filament diameter), micrographs, and X-ray microscopy. The test results show that the temperature of the filament drops below the glass transition temperature over a production length of less than 100 mm when cooled by air. Using the post-consolidation unit keeps the filament above the glass transition temperature of the matrix (160 °C) for a production length of 550 mm, allowing compaction by the integrated grooved rollers. The test results show that post-consolidation reduces defects, improves the roundness of the filament cross-section, and minimizes diameter variation.