On the build orientation effect in as-printed and as-sintered bending properties of 17-4PH alloy fabricated by metal fused filament fabrication

Purpose The purpose of this paper is to systematically investigate the influence of build orientation on the anisotropic as-printed and as-sintered bending properties of 17-4PH stainless steel fabricated by metal fused filament fabrication (MFFF). Design/methodology/approach The bending properties of 17-4PH alloy fabricated by low-cost additive manufacturing (MFFF) using three build orientations (the Flat, On-edge and Upright orientations) are examined at both as-printed and as-sintered states. Findings Unlike tensile testing where the Flat and On-edge orientations provide similar as-sintered tensile properties, the On-edge orientation produces a significantly higher bending strain with a lower bending strength than the Flat orientation. This arises from the printed layer sliding due to the Poisson's effect, which is only observed in the On-edge orientation together with the alternated layers of highly deformed and shifted voids. The bending properties show that the Upright orientation exhibits the lowest bending properties and limited plasticity due to the layer delamination. Originality/value This study is the first work to study the effect of build orientation on the flexural properties for MFFF. This work gives insight information into anisotropy in flexural mode for MFFF part design.

Chloride Diffusion by Build Orientation of Cementitious Material-Based Binder Jetting 3D Printing Mortar

Binder jetting 3D printing (BJ3DP) is used to create geometrical and topology-optimized building structures via architectural geometric design owing to its high degree of freedom in geometry implementation. However, building structures require high mechanical and durability performance. Because of the recent trend of using 3D printing concrete as a structural component in reinforcing bars, its durability with respect to chloride penetration needs to be reviewed. Therefore, in this study, the compressive strength and durability of the chloride diffusion of cement-based 3D-printed output were evaluated. In addition, to confirm the performance difference based on the build orientation, the compressive strength and chloride diffusion were evaluated with respect to the build direction and transverse direction. The experimental results show that the compressive strength was approximately 22.1–26.5% lower in the transverse direction than in the build direction and that the chloride diffusion coefficient was approximately 186.1–407.1% higher in the transverse direction. Consequently, when a structure that requires long-term durability is produced using BJ3DP, it is necessary to examine the design and manufacturing methods in relation to the build orientation in advance.

Creep Behavior of Polyamide 12, Produced By Selective Laser Sintering With Different Build Orientations

The successful use of components, produced by selective laser sintering as a rapid manufacturing process, requires a comprehensive understanding of the material. In this study, the effect of specimen build orientation on the mechanical properties of selective laser sintered polyamide 12 was investigated in detail. Samples were printed with an orientation of 0°, 15°, 45° and 90° to the build platform. Additionally to quasi-static tensile tests, Creep tests under different loads (5 MPa, 10 MPa, 15 MPa and 20 MPa) and for different times (10 hours and 1,000 hours) with and without relaxation were performed. Creep behavior was analyzed using the Burgers model. Therefore, the elastic strain, the relaxant strain, the viscous strain and the total deformation were determined. Results show that the build orientation has no significant influence on the long-term creep behavior, at small stresses. Short-term creep and relaxation tests show, that the elastic and viscous strain are only slightly influenced by the build orientation. However, the viscoelastic strain is affected by the build orientation. Furthermore, the deformations resulting from creep and relaxation have no significant influence on the mechanical behavior as shown by tensile tests.

Predicting the effect of build orientation and process temperatures on the performance of parts made by fused filament fabrication

Purpose The performance of the parts obtained by fused filament fabrication (FFF) is strongly dependent on the extent of bonding between adjacent filaments developing during the deposition stage. Bonding depends on the properties of the polymer material and is controlled by the temperature of the filaments when they come into contact, as well as by the time required for molecular diffusion. In turn, the temperature of the filaments is influenced by the set of operating conditions being used for printing. This paper aims at predicting the degree of bonding of realistic 3D printed parts, taking into consideration the various contacts arising during its fabrication, and the printing conditions selected. Design/methodology/approach A computational thermal model of filament cooling and bonding that was previously developed by the authors is extended here, to be able to predict the influence of the build orientation of 3D printed parts on bonding. The quality of a part taken as a case study is then assessed in terms of the degree of bonding, i.e. the percentage of volume exhibiting satisfactory bonding between contiguous filaments. Findings The complexity of the heat transfer arising from the changes in the thermal boundary conditions during deposition and cooling is well demonstrated for a case study involving a realistic 3D part. Both extrusion and build chamber temperature are major process parameters. Originality/value The results obtained can be used as practical guidance towards defining printing strategies for 3D printing using FFF. Also, the model developed could be directly applied for the selection of adequate printing conditions.