The influence of laser parameters and scanning strategies on the mechanical properties of a stochastic porous material

Abstract

Additive manufacturing enables architectured porous material design, but 3D-CAD modelling of these materials is prohibitively computationally expensive. This bottleneck can be removed using a line-based representation of porous materials instead, with strut thickness controlled by the supplied laser energy. This study investigated how laser energy and scan strategy affects strut thickness and mechanical strength of porous materials. Specimens were manufactured using varying laser parameters, 3 scan strategies (Contour, Points, Pulsing), 2 porous architectures and 2 materials (Titanium, Stainless Steel), with strut thickness, density, modulus, mechanical strength and build time measured. Struts could be built successfully as low as 15° with a minimum diameter of 0.13 mm. Strut thickness was linearly related to the specific enthalpy delivered by the laser to the melt-pool. For a given stiffness, Titanium specimens built at low power/slow speed had a 10% higher strength than those built at high power/fast speed. The opposite was found in Stainless Steel. As specimen stiffness increased, the Contour Strategy produced samples with the highest strength:stiffness and strength:weight ratio. The Points strategy offered the fastest build time, 20% and 100% faster than the Contour and Pulsing strategies, respectively. This work highlights the importance of optimising build parameters to maximize mechanical performance

Micromotion and Push‐Out Evaluation of an Additive Manufactured Implant for Above‐the‐Knee Amputees

“…Metal additive manufacture (AM) is currently used to manufacture orthopedic implants such as the 4Web spinal fusion cages and the distal portion of the Stryker triathlon tibial component . One advantage of AM is the ability to manufacture with lattice structures, which enable structures from stainless steel, titanium alloys, and tantalum with stiffness gradients from 0.5 to 20 GPa, well in the range of human bone . We hypothesize that we can use AM technology to produce a cortical bone stiffness‐matched end bearing implant with a minimal fixation feature for above‐knee amputees.…”

“…21,22 One advantage of AM is the ability to manufacture with lattice structures, which enable structures from stainless steel, titanium alloys, and tantalum with stiffness gradients from 0.5 to 20 GPa, well in the range of human bone. [23][24][25] We hypothesize that we can use AM technology to produce a cortical bone stiffness-matched end bearing implant with a minimal fixation feature for above-knee amputees. This would allow for easy installation during surgery, would generate physiological stresses in the femur, would potentially allow a sub ischial socket to be worn and could be more easily revised should it become necessary.…”

3D Architecture of Trabecular Bone in the Pig Mandible and Femur: Inter-Trabecular Angle Distributions

“…The stochastic lattice (here referred to as the S-lattice) was also manufactured in a cylindrical shape of 15 mm in diameter and 15 mm in height, but contained a higher number (around 20,000) of fine connected elements of 150-250-µm thick. In the stochastic lattice, the nodes were randomly positioned in 3D and were stochastically interconnected to form a partially connected network with the average number of neighbors given as 4, as described by Ghouse et al (2017).…”

Additive manufactured push‐fit implant fixation with screw‐strength pull out

“…Porous pegs were designed to be a stochastic (randomized) porous lattice structure. 22 The effective elastic modulus of a peg could influence its fixation mechanics as it determines the ratio of implant/bone deformation following push in. Therefore, the pegs were manufactured with two target moduli spanning the range of trabecular bone: A low effective modulus structure of 600 MPa representing lower end of cancellous bone, 37 and a high modulus structure of 2.6 GPa representing the modulus achieved by modern porous arthroplasty designs 25,38,39 and the higher end of subchondral cancellous bone.…”

“…21 For implant fixation, a big draw of AM technology is the ability to create porous structures that bone can grow into, allowing improvement in long-term fixation; consequently porous structures have been extensively researched. [22][23][24][25][26][27][28][29][30][31][32] Recent research has also suggested that AM fixation features could improve the initial stability of implants. 14,15 This area has been much less researched but is of equal importance as initial implant stability is a prerequisite for long-term fixation.…”