In addition to process efficiency and material development, design is a key factor for industrializing additive manufacturing. A simulation-driven design approach has become indispensable and only the comprehensive consideration of manufacturing constraints assures a successful product development. Therefore, software company Altair has as its main goal to make performance and cost saving potential accessible in the early stages of the decision-making process.
Together with APWORKS, M&H CNC Technik and RSC Engineering, Altair (Nasdaq: ALTR) presented several solutions for Additive Manufacturing at Formnext 2018, such as the Sogeclair Optimdoor, a hybrid-lattice hip implant (made in collaboration with EOS), Stephan Henrich’s BushBot Chair, an optimized packaging line component by elmec3D, a 3D printed support arm (M&H) as well as an optimized foot rest and the housing of an e-drive (RSC).
Altair transforms design and decision-making by applying simulation, machine learning and optimization throughout product lifecycles, offering a broad portfolio of simulation technology and its patented software licensing model for Simulation-Driven Innovation™. With more than 2,000 employees, Altair is headquartered in Troy, Michigan, operates 71 offices throughout 24 countries and serves more than 5,000 customers across broad industry segments.
As presented by Mirko Bromberger, Altair GmbH ‘s Marketing Director, the “Altair Inspire platform enables to identify system requirements, create structural innovation, and assure manufacturability within a single simulation-driven design environment further than identifying performance and cost saving potentials in the early stages of a development process.”
The Altair space at Formnext also featured a dedicated demo theatre illustrating the creative application of simulation technologies for various manufacturing methods, including product demos of Altair Inspire and SIMSOLID. Focusing on the growing importance of AM process simulation, in fact, Altair acquired SIMSOLID in October 2018. SIMSOLID works on full-fidelity CAD assemblies to provide fast, accurate and robust structural simulation without requiring geometry simplification, cleanup or meshing.
The SIMSOLID computational engine is a commercial implementation of novel and unpublished mathematics based on extensions to the theory of external approximations. SIMSOLID controls solution accuracy using multi-pass adaptive analysis, making it extremely fast and memory efficient. Large and complex assemblies can be solved rapidly even on laptop computers.
The robotic and “psychological” BushBot Chair
Stephan Henrich is a German based architect focusing on designs for 3D printing and robotic applications. The BushBot Chair is a kinetic robotic furniture-design referring to the concept of the Bush-Robot, a hypothetical fractal branching grasping machine, with the four feet of the chair supporting four articulated branching-systems of three sub-branchings, ending in 24 contact-stars.
The chair consists of selective laser-sintered PA12 and flexible TPU parts. The ends of the branches, touching the body, are realized as a segmented bendable surface, supported by multiple flexing cantilevers to adjust to the human body. The contact surface is topped by a lamella system to add anti-skid properties.
Structural optimization has been used to both minimize material usage and to implement zones of adapted flexibility at the main joints (performed by integrated quasi-flat-springs) to control the kinematics of the trees. In addition, the chair is also a psychological machine: the user has to first take a risk in order to profit from the relaxation it provides. He needs to overcome his fear to release the body in a repulsive-looking, spiky bush.
Altair and successful health applications
The number of joint replacement surgeries in the U.S. is experiencing a tremendous development: not only are joints being replaced due to fractures and severe pain, but also to facilitate the continuation of an active lifestyle.
According to the National Hospital Discharge Survey (NCHS), the number of total hip replacement surgeries of patients 45 years or older in the United States more than doubled between 2000 and 2010 and the total number of hip replacement surgeries for people between the ages of 45-64 has almost tripled during that same time: a dramatic change since many implants used for hip replacements haven’t been designed for active lifestyles. Additionally, much of the data indicating some prostheses should last more than 20 years is based on patients leading a more sedentary lifestyle.
While total hip replacement surgeries are seeing an increase in demand, 10-20% of the patients may require a revision surgery because of a failure or wearing-out of the prosthesis, most commonly due to loosening of the implant stem. This loosening can be caused by bone resorption or loss of bone mass, while revision surgeries can be more complex, especially for elderly patients, and bone resorption can increase the risk of bone fracture.
These risks can be avoided—or at least reduces—by applying optimization and simulation technologies to a hip implant, therefore improving the longevity and how it performs. Two ways of doing this are to include more dynamic load cases when designing the hip implant stem and focusing on reducing stress-shielding in the bone surrounding the implant. When analyzing a design using computer simulation, it is important to include all the various load cases a product might see during its life cycle. The current load cases considered when designing hip implant stems might only involve daily activities such as standing, sitting, walking and climbing stairs. However, with an increasing number of younger patients having total hip replacement surgeries and older patients staying active later in life, additional load cases should be considered.
With this in mind, Altair included jogging in addition to other standard daily activities, but biking, swimming, and other activities could be included during the design process. Adding these load cases could increase the longevity and performance of hip implant stems.
In terms of materials, most hip implant stems are made of titanium due to its biocompatibility, but titanium is roughly 6.5 times stiffer than the cortical bone of the human femur. When a solid titanium stem is implanted in the femur the load distribution will change in the remaining bone. Often the load into the bone will be reduced because the titanium stem is so much stiffer than the natural bone.
With the recent advances in additive manufacturing capacities, Altair has introduced lattice optimization which generates structural lattice and can be incorporated in areas where the solid structure is not necessary. Each beam diameter of the lattice can be fine-tuned to achieve the design constraints and objectives. These technologies have been applied to the geometry of a general hip implant stem and the results were very promising.
In the end, the stress-shielding caused by the implant was reduced by 57% when comparing the generic design and the optimized design. Furthermore customized design could be printed and in the surgeon’s hands the following week.