T4F3: temperature for fused filament fabrication

Abstract

Temperature fields and their variations in printed parts are the basis for understanding the physical process of fused filament fabrication (FFF). However, reliable temperature data are still rather limited to date. This article presents a three-dimensional transient-state model to simulate the temporal and spatial temperature variations in FFF printed parts. Model variables range from geometry dimensions and (dynamic) material properties to process parameters, covering all important physical phenomena, including conduction anisotropy and radiant heat transfer. The validation of the model is performed against six sets of experimental temperature data obtained with different geometries, machines, materials, processes, temperature measuring methods, etc. Insights in the thermal process are also reported. For example, the heat penetration depth in printing with poly(lactic acid) is limited to 3 mm, and the Biot number intimately characterises the reheating peaks in temporal profiles. This model shows the potential to become a standardised tool to study the thermal characteristics of FFF printed parts. It is made openly available on website https://iiw.kuleuven.be/onderzoek/aml/technologyoffer. Graphic abstract

Mathematical Model of the Layer-by-Layer FFF/FGF Polymer Extrusion Process for Use in the Algorithm of Numerical Implementation of Real-Time Thermal Cycle Control

“…The conditions are set T| Г2 = 313 K. Initial conditions were set for domains (D1), (D2) and (D3) T| t=0 = T pl = 313 K. T pl is the initial temperature of the platform and the polymer substrate. Based on the results of [67], it was decided to consider the thermophysical properties of PLA as constant, since their dependence on temperature has a negligible effect on the results of numerical simulation; the authors [67] also mention the need to take into account radiative heat transfer in the absence of forced convection. The thermophysical constants of PLA accepted in the model are shown in Table 1.…”

“…There is a significant number of studies [4,30,[62][63][64][65][66][67][68][69][70] devoted to the analysis of the thermal cycle of the FFF printing process and ways to influence it by using the base FFF process parameters, namely the nozzle temperature (extrusion T ext ), temperature of the heated platform T pl , printing speed (or printing time of a layer), ambient temperature in the printing area. All technological parameters of printing except for the nozzle temperature directly affect the temperature of the previous layer.…”

“…The decrease in the welding temperature T w as it moves away from the platform, as well as the unevenness of the temperature field in the volume of the product (along all axes) during the printing process is noted in many studies and is presented as the results of thermography or pyrometry [12,57,63,67,68,72], and the results of electron microscopy of products [7,[13][14][15]25,27,[56][57][58]. This phenomenon is explained by a change in the heat removal conditions during the printing process and cannot be compensated only by a change in the printing speed, temperature T pl or the environment temperature.…”

“…Two-dimensional and three-dimensional mathematical models are described in [31,67,97,98]. Their purpose is to study the thermal cycle of the FFF printing process, as well as the coalescence and intermolecular diffusion of the applied material with the previous layer or bead to determine the printing parameters that ensure the highest quality of the welds.…”

A reheating temperature criterion for adaptive strategy in fused filament fabrication

“…The relative importance of thermal conduction, convection, and radiation in FFF, under different environmental conditions, was also studied by the authors, who could predict that FFF printed parts on the Moon surface might fail due to insufficient cooling, as a result of diminished convection in the Lunar vacuum [3]. In [4], the open accessed T4F 3 model was presented by the authors and adopted to investigate the functional dependence of temperature distribution and variations in printed parts on geometry, material and process settings. Validation was conducted via infrared thermography, by using a previously developed experimental monitoring set up [5].…”