Influence of Flowability on the Processability of Thermoplastics in Additive Manufacturing: Comparison of Fused Layer Modeling ( FLM ) and Fused Granulate Fabrication ( FGF Niclas Norman Henrichs, Jan T. Sehrt, Thomas Brinkmann, Luca P. M. Bürgel, Daniel Michael Berger

ABSTRACT

This study investigates the influence of melt flowability and rheological behavior on the processability of thermoplastics in fused layer modeling (FLM) and fused granulate fabrication (FGF). Four PP grades, two ABS grades, and two SAN grades were analyzed using rotational and capillary rheometry. The results were correlated with stringing behavior, surface quality and extrusion stability in both processes. Amorphous ABS and SAN exhibit consistently higher processing stability in the FGF process than semi‐crystalline PP grades. At the process‐relevant shear rate (), the amorphous polymer viscosities ranged from 520 to 700 Pa s, compared to 80 to 290 Pa s for PP. Higher PP viscosities correlated with irregular extrusion, surface defects, and melt fracture. For Sabic 505P, melt fracture onset was observed (feed rate 75 mm/min). Only the highest‐flowability PP grade (Sabic 579S, MFR: 47 g/10 min) enabled satisfactory component quality in the FGF process. Due to differing test conditions in the material data sheets, no direct correlation could be established between MFR or MVR and the FGF processability. The results highlight dynamic viscosity—and possibly molecular weight distribution—as decisive factors for granule processability, providing guidance for the pre‐selection of suitable polymers.