Process and material behavior modeling for a new design of micro-additive fused deposition

The aim of this paper is to explore the limits and special requirements for additive manufacturing using polymer extrusion with a nozzle diameter much smaller than the conventional one: 0.050 mm diameter. This work is focused on the nozzle design and analyzes the effect of such a reduced diameter on the extrusion process and on the cooling of material while being deposited on the part. The approach is based on experimental and theoretical studies starting from conventional fused deposition modeling technology where the study tested swelling and cooling of filament material during deposition. Experimental work was used to assess the validity of the theoretical model and the first normal stress equation which estimated a swelling factor (diameter) of 1.249 at 0.087 g/h mass rate. The convection coefficient (h) on the plastic part was estimated as7 W/m² K on the first deposited layer; considerably lower than some references show.