Printability of materials for extrusion 3D printing technologies: a review of material requirements and testin

Abstract

One of the major challenges facing 3D printing for construction is the technological suitability, ‘printability’, of the materials used. These cement-based materials differ from those used in other sectors, which has a series of conditioning factors that are the object of the present analysis. This article first reviews the definition of the term ‘printability’ and its constituent stages. Those stages condition the requirements to be met by cement-based materials, whether designed for other uses or developed ad hoc, and therefore the tests applicable to determine their aptitude for use in additive manufacturing for construction. That is followed by a review of the standardised tests presently in place for mortars and concretes that can be used to verify a material’s compliance with such requirements. The paper concludes with a recommendation on the advisability of developing a standard test or suite of tests to ascertain printability.

Biocompatible Composite Filaments Printable by Fused Deposition Modelling Technique: Selection of Tuning Parameters by Influence of Biogenic Hydroxyapatite and Graphene Nanoplatelets Ratios

“…In terms of using the composite mixtures as feedstock materials for the 3D-printing process, the later observed features may come across as incompatible with the specific requirements for constant filament diameter and surface–volume homogeneity (both essential for the prevention of material clogging in the printer nozzle) [ 6 , 40 , 41 ].…”

“…However, once the loading ratios exceeded these values, the composite filaments presented a mixed morphology that evolved to microfracturing at the highest HA/GNP ratio. In terms of using the composite mixtures as feedstock materials for the 3D-printing process, the later observed features may come across as incompatible with the specific requirements for constant filament diameter and surface-volume homogeneity (both essential for the prevention of material clogging in the printer nozzle) [6,40,41].…”

“…For creating advanced composite filaments, recent biomedical studies have exploited the beneficial interplay between PLA and synthetic spherical HA particles, acquired mainly through chemical surface modification (the addition of binders and/or impact modifiers), but not always with the expected outcomes [ 18 , 34 , 35 , 36 , 37 ]. In addition to the limited incorporation ratios of ceramic material, ranging from 3 to a maximum of 40 wt.%, the reported composites lacked a proper particle distribution in the polymeric matrix, which led to the formation of agglomeration sites [ 6 , 38 , 39 ], as well as the ability to preserve the filaments’ surface uniformity and constant diameter size [ 18 , 38 ], both mandatory requirements for printable materials [ 40 , 41 , 42 ]. As it is well known that the higher the admixed HA amount, the higher the chances for the formation of new bone nucleation sites [ 36 , 38 ], attempts were made to improve it [ 37 ], but they led to the emergence of undesired porosity at the PLA–particle interface, as well as an implicit diminished mechanical resistance [ 18 , 33 , 37 ].…”

Influence of Ceramic Particles Size and Ratio on Surface—Volume Features of the Naturally Derived HA-Reinforced Filaments for Biomedical Applications

“…After adding the larger particles, variable micrometric bumps started to appear on the filaments surface in an irregular manner. Once the HA ratio was increased (>20%), the numerous overlapped bumps formed significant protuberances (clearly seen at 50% HA), which could lead to some issues when printing the filaments (e.g., clogging/accumulation of HA particles or composite mixture in the printer nozzle [ 20 , 22 ]) and lower quality of the final products [ 34 ]. Therefore, for a favorable surface modification of PLA [ 27 , 30 ], the proper filaments dimensions for 3D printing could be achieved by modulating the nozzle diameter, extrusion velocity, temperature, and filling [ 41 ] according to the HA particles size and ratio.…”

“…This translates to the application of AM techniques to a restricted range of polymers. For example, the most popular method used in orthopedics, Fused Deposition Modeling (FDM)/Fused Filler Fabrication (FFF), requires typical materials with thermoplastic properties (e.g., poly(lactic acid) (PLA), poly(ε-caprolactone) (PCL), thermoplastic polyurethane (TPU), and acrylonitrile butadiene styrene (ABS)) necessary for extrusion in the form of filaments at specific temperatures through different-sized nozzles [ 2 , 7 , 22 , 23 , 24 ]. Among them, only PLA is of natural origin (derived from maize, beet, or sugarcane) and is also approved by the Food and Drug Administration as biocompatible, biodegradable, nontoxic, and overall patient-risk-free [ 3 , 8 , 25 ].…”