Hybrid Manufacturing is defined as the integration of dissimilar metal manufacturing processes, i.e. Additive Manufacturing (AM) linked to traditional manufacturing processes, which are planned together such that the final part specifications is fully realized through AM, i.e. geometrical, surface and material property specifications.
Although Additive Manufacturing has unique advantages in processing complex part designs using superalloys, metal AM parts currently do not meet the part tolerance and surface finish requirements for the most mechanical applications. Hence, there is a growing need for integrated metal hybrid manufacturing through both “in-envelope” and “sequential” additive-subtractive manufacturing. AM parts are inherently different from traditionally manufactured parts (e.g., anisotropy, residual stress). So, there is a critical research gap in correlate as-built AM material properties, material characterization, machining parameters on resulting cutting force, specific cutting energy. Our research aims to investigate the influence of AM processes, build orientation, and heat treatment that would lead to varying microstructure along with different machining conditions, which would lead to varying machining behavior in metal AM parts. Current research is focused on building new analytical models to predict machining behavior based on material characterization, and correlation model for AM microstructure and machining behavior, surface finish, and tool wear behavior.
Sand-casting is one of the oldest manufacturing methods, dating back thousands of years. Today, over 70% of all metal castings are produced via sand-casting process due to its unparalleled advantages such as low production cost, high production rate and relative simplicity. This process has the capability to produce a wide range of alloys but are limited in design complexity. Recent innovations in 3D sand-printing (3DSP) offers the ability to produce new mold geometries that were not possible with traditional castings methods. This new technology uses binder jetting to print sand molds with complex design features, while drastically reducing the lead time due the absence of tooling requirements.
A major focus area has been designing 3D novel rigging systems to better control the flow of metal entering the casting. Previous work focused on sprue design and analysis. Using 3DSP to print complex 3D geometries, traditional straight sprues were replaced with parabolic and conical helix sprues. These sprues are only possible via 3DSP and were found to reduce casting defects by 56% and 99.5%, respectively. Currently, research is being conducted to apply the principles used for 3D sprue design to the runner system. The goal of this project is to develop a mathematical model for runner design and other mold components such that critical casting parameters (i.e. desired gate velocity, pressure etc.) can be achieved to produce the ideal runner geometry.
Achieving satisfactory fracture fixation in osteoporotic patients with unstable proximal humerus fractures remains a major clinical challenge. Varus collapse is one of the more prominent complications that may lead to screw cutout. The aim of this study is to achieve improved fixation in fracture implants with novel design concepts that are only feasible through AM when compared to conventional locking plates. In this study, it was shown that the AM manufactured implants with medial strut showed significant reduction of varus displacement during the increasing cyclic loading when compared to conventional designs. AM reversed-engineered locking plates showed similar mechanical behavior to conventional plates with identical geometry. This study demonstrates the feasibility and potential of employing alternative design via AM for fixation of unstable comminuted proximal humerus fractures to reduce fragment displacement.
In this study, a validated design methodology is presented to evaluate AM as an effective fabrication technique for reconstruction of large bone defects after tumor resection in pediatric oncology patients to potentially reduce postoperative complications. It is well-known that implanting off-the-shelf components in pediatric patients is especially challenging because most standard components are sized and shaped for the more common adult cases. The aim of this study is to develop a systematic procedure for the design-biomechanical FEA analysis-AM of patient-specific prosthesis which can achieve required biomechanical strength and anatomical fit for large bone defects following tumor resection.
Porous metallic biomaterials fabricated via additive manufacturing have the potential to improving bone tissue regeneration and tissue-implant interface stability. In this study, bio-mechanical responses of novel metamaterials that exhibit nature-inspired geometries are being evaluated. Specifically, we investigate the morphological, topological, quasi-static mechanical, flexural, and fatigue behavior of the biomimetic metamaterials to evaluate their structure–function relationships as well as success in mimicking different bio-mechanical properties of bone.
Computed tomography (CT) scanning is a commonly used method that permits three-dimensional data to be collected and analyzed. One of the many uses of this technology is the ability to examine internal features of additively manufactured components. Current research project at The SHAPE Lab is focused on characterizing 3D sand-printing (3DSP) samples fabricated via binder-jetting additive manufacturing (AM) technology. High resolution data (~5µm per voxel) is acquired at the Center for Quantitative Imaging (CQI) of Penn State’s Energy and Environmental Sustainability Laboratory (EESL). Image analysis allows for critical 3DSP sand casting mold properties to be examined: total porosity (%), total disconnected porosity (%), pore network connectivity and pore size distribution. Pore network models constructed from this data enables the evaluation of degassing characteristics (e.g., permeability) and mechanical strength of 3DSP molds printed using different manufacturing parameters. Current efforts include real-time imaging of gas flow across 3DSP samples and comparison to numerical models.
Other types of analysis currently being done at the SHAPE Lab include CT scanning of metallic implants fabricated via powder-bed fusion. By examining gas porosity, trapped powder and other types of AM defects, adequate geometries and printing parameters can be setup for optimum implant performance and minimum post-processing.