Multi Jet Fusion Technology Research Articles

Investigation of stiffness and energy absorption of variable dimension helical springs fabricated using multijet fusion technology

Recent advances in additive manufacturing (AM) have made the direct manufacturing of intricate shapes such as metamaterials and complex geometries easier, more efficient, faster, and optimally functional, as compared with the manufacturing of simple solid blocks. In this study, the authors conducted experimental investigations and simulations on the energy absorption, stiffness, and deflection of various variable dimension helical springs fabricated by a recently developed high-speed AM technology, namely, the multijet fusion (MJF) system. The variable dimension helical springs were designed by defining various parameters such as the pitch, diameter of the spring wire and spring coil, and total height of the spring. For comparison, the total masses, bounding boxes, and total heights of all samples were kept constant. The results show that the variable parameters (e.g., shape) significantly affect the properties of helical springs; therefore, the stiffness and deformation can be controlled by varying them for a particular application. Furthermore, in designing variable dimension helical springs, nonlinear force–displacement behaviors and stiffness, along with reductions in weight and maximum stresses, can be obtained. Finally, it was concluded that by optimally defining the above parameters, a spring with an ideal geometry can be designed, thereby realizing comfort, stability, and reliability, along with other application-specific benefits (e.g., lightweight).

Effect of Orientation Angle on Surface Quality and Dimensional Accuracy of Functional Parts Manufactured by Multi Jet Fusion Technology

Multi Jet Fusion (MJF) is one the new Additive Manufacturing (AM) method which belongs to powder bed fusion technology class and used for additive manufacturing of polymer based parts. There are restricted number of research about this developing technology. In this study, it is aimed to investigate the effect of build orientation angle on surface quality and dimensional accuracy of the printed bolts as functional parts. Samples were manufactured in two different build orientation such as 90 and 45 degrees. Surface quality and dimensional properties of the bolt tooth such as tooth height, tooth angle and distance between two teeth were inspected by optical and tactile precision measurement systems. The results were evaluated by comparing the measurement data with each other for two different sample groups and also with nominal design data. For determining the significance of the difference between two sample groups and nominal data the results were also evaluated by Student’s t-test statistical analysis. The results revealed that, orientation angle had significant effect on surface roughness, tooth height and tooth angle but it didn’t affect the distance between two teeth.

Dynamic Performance of a 3D Re-entrant Structure

In this study, the mechanical performance of a three-dimensional (3D) re-entrant structure subjected to dynamic compression was experimentally investigated using a high-speed Instron machine. Quasi-static tests were conducted for comparison. All samples were fabricated by multi-jet fusion technology. A finite element (FE) model was developed using ABAQUS/Explicit and validated against the dynamic test results in terms of deformation mode, plateau stress, and Poisson's ratio. The validated FE model was subsequently employed to study the effects of the number of unit cells, geometrical parameters (aspect ratio, H/L, and re-entrant angle, θ) of the re-entrant unit cell, and compressive velocity. The results showed that the structure with H/L = 1 and θ = 45° had the highest specific energy absorption (SEA) when compressed in the Z direction and the structure with H/L = 1.1 and θ = 75° had the highest SEA when compressed in the X direction. Moreover, the performance of the 3D re-entrant structure was compared with that of a 2D re-entrant structure with the same geometrical parameters. The energy absorption of the 3D re-entrant structure was also compared with other popular cellular structures using an Ashby chart.

Modelling of the capillarity effect in Multi Jet Fusion technology

Multi Jet Fusion is a powder-based Additive Manufacturing technology patented by Hewlett-Packard Inc. It is characterised by the use of lamps instead of lasers to heat and melt polymers and by fusing and detailing agents that are jetted on the polymeric particles to modify and to control their heat absorption and thus selectively melt them. The high production rate and excellent mechanical properties of the manufactured parts, even in comparison with Laser Sintering, together with the overall product quality make this technology effective for a production of small series of end-parts rather than functional prototypes.In the present paper, the so-called capillarity effect is investigated. Capillarity derives from the interaction between the detailing and the fusing agents during the layer-based part building and it determines a deviation of the upper planar geometries when close to the border edges between the molten material and the powder bed.A model for the estimation of the capillarity effect is here proposed by adopting the free liquid meniscus theory. A benchmark geometry was designed to be affected by the capillarity effect and then manufactured by the MJF process. Values of the contact angle and of the characteristic length of the capillary, which are necessary to implement the analytical model, were obtained by experimental measurements made on the benchmark geometry.As a result the capillarity effect showed a dependence on the border edge orientation. The comparison between calculated shapes of the plane affected by the capillarity effect through the analytical model was in accordance with the experimental measurements thus allowing a reliable prediction to be made.

Assessment of 3-D Printing Technologies for Millimeter-Wave Reflectors

Three different 3-D printing technologies—stereolithography, fused deposition modeling, and HP Multi Jet Fusion technology—are compared to build a parabolic reflector operating at 100 GHz. Fabrication tolerance and surface roughness before and after metallization are accurately measured. The performance of the reflectors is measured in the near field, and it is compared against an optical grade reflector. In this way, the performance of the final product is thoroughly assessed.

Multi Jet Fusion PA12 Manufacturing Parameters for Watertightness, Strength and Tolerances.

The aim of this paper is to explore the watertightness behaviour for high pressure applications using Multi Jet Fusion technology and polyamide 12 as a material. We report an efficient solution for manufacturing functional prototypes and final parts for water pressure applications and provide manufacturing rules for engineers in the pressurized product development process for up to 10 MPa of nominal pressure. The research findings show manufacturers the possibility of using additive manufacturing as an alternative to traditional manufacturing. Water leakage was studied using different printing orientations and wall thicknesses for a range of pressure values. An industrial ball valve was printed and validated with the ISO 9393 standard as also meeting tolerance requirements. This paper is a pioneering approach to the additive manufacturing of high-performance fluid handling components. This approach solves the problem of leakage caused by porosity in additive manufacturing technologies.

Fabrication of polymeric lattice structures for optimum energy absorption using Multi Jet Fusion technology

Unlike stochastic foams, 3D printed lattice structures can be created with a tailored microstructure to achieve the desired global mechanical properties. In this study, quasi-static energy absorption of six polymeric lattice structures of different unit cell topologies and deformation behaviours but with identical relative density are investigated. For the first time, a recently developed powerful 3D printing technology, namely Multi Jet Fusion (MJF), is utilized to produce high quality and performance lattices. Nonlinear finite element analysis (FEA) is used to analyse their compressive response and energy-absorbing characteristics. To validate the FEA results, experimental compression tests are performed on two types of lattices. The results of this investigation showed that the global energy absorption of lattices can be improved through controlling and manipulating their micro-topology. It is found that the lattice structures with bending-dominated deformation have low stiffness and strength but provide good energy absorption capability. The stretch and buckling dominated structures are shown to be stiffer and stronger but have low energy absorption performance. The findings of this research identify high performing unit cell geometries that can be used for energy absorption application of lattice structures in the development of advanced 3D printed structures that are superior to stochastic foams.