The impact of process parameters on mechanical properties of parts fabricated in PLA with an open-source 3-D printer

Abstract

Purpose - This study aims to quantify the ultimate tensile strength and the nominal strain at break (f) of printed parts made from polylactic acid (PLA) with a Replicating Rapid prototyper (Rep-Rap) 3D printer, by varying three important process parameters: layer thickness, infill orientation and the number of shell perimeters. Little information is currently available about mechanical properties of parts printed using open-source, low-cost 3D printers. Design/methodology/approach - A computer-aided design model of a tensile test specimen was created, conforming to the ASTM:D638. Experiments were designed, based on a central composite design. A set of 60 specimens, obtained from combinations of selected paramers, was printed on a Rep-Rap Prusa I3 in PLA. Testing was performed using a JJ Instruments - T5002-type tensile testing machine and the load was measured using a load cell of 1,100 N. Findings - This study investigated the main impact of each process parameter on mechanical properties and the effects of interactions. The use of a response surface methodology allowed the proposition of an empirical model which connects process parameters and mechanical properties. Even though results showed a high variability, additional ideas on how to understand the impact of process parameters are suggested in this paper. Originality/value - On the basis of experimental results, it is possible to obtain practical suggestions to set common process parameters in relation to mechanical properties. Experiments discussed in the present paper provide a variety of data and insight regarding the relationship among the main process parameters and the stiffness and strength of fused deposition modeling-printed parts made from PLA. In particular, this paper underlines the shortage in existing literature concerning the impact of process parameters on the elastic modulus and the strain to failure for the PLA. The experimental data produced show a good degree of compliance with analytical formulations and other data found in literature

An investigation into 3D printing of fibre reinforced thermoplastic composites

“…The average tensile strength and stiffness are 33.5 MPa ( ± 2.7%) and 1.85 GPa ( ± 6.1%) respectively. The properties are lower than the bulk properties of Nylon [44], showing that the fibres do not reach their ultimate strengths. The flexural strength and stiffness were found to be 55.3 MPa ( ± 3.4%) and 3.0 GPa ( ± 4.1%) respectively.…”

“…The addition of fillers to the printing filament reduces die swell, as reported in three different studies [19,26,28]. The addition of fibres may be used to alter the thermal energy transfer between printed beads during deposition and the flow and the swelling behaviour of the material when leaving the nozzle.…”

“…Therefore, the heat conductivity and capacity are important, as they affect how heat is distributed and the temperature profiles of the printed tracks. Qualitatively, the main sintering process is understood and several studies focused on the effect of some of these parameters [19][20][21]. Of further interest is how the addition of fibre reinforcement to the feedstock will affect these parameters, this is discussed below.…”

“…Bellini [19] found numerically that a high thermal conductivity of the filled material (roughly a factor of 7 higher than unfilled material) improves heat transfer from the liquefier to the printed material, improving overall flow. The addition of fillers to the printing filament reduces die swell, as reported in three different studies [19,26,28].…”

Open Source Multi-Head 3D Printer for Polymer-Metal Composite Component Manufacturing

“…Printable polymer material characterization has increased the knowledge available to engineers for common PLA and ABS materials [6][7][8][9] along with an increasing list of thermoplastics [10,11], polymer metal composite materials [12][13][14] and polymer ceramic composite materials [15][16][17][18] for a number of novel applications, including medical and health-related components [19][20][21][22][23]. Subsequently, advancements in material understanding has led to the development of more sophisticated RepRap machines.…”