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.
Ability of Additive Manufacturing (AM) to fabricate highly complex geometries from 3D digital models allows us to customize design of life-saving implants and stents for every patient. This project aims to design and optimize patient specific-implants (age, loading conditions, bone density) for large bone defects result from trauma, tumor, large bone resection for different pathologies such infection and treatment methods depending on surgical implications and rehabilitation needs. The deliverables of this study include: (1) Design methodology to developoptimized patient specific AM osseointegration implant, (2) Validated design methodology through the FEA analysis and mechanical testing cadaver specimen, (3) Compare the efficacy of AM implant with commercially available implants during fatigue loading and tissue culture studies.
Sand casting, also known as sand molded casting is one of the oldest manufacturing methods that dates back its origins to thousands of years. Over 70% of all metal castings are produced via sand casting process because of its unparalleled advantages such as low production cost, high production rate and for its simplicity. The process has the capability to produce simple to exceedingly complex castings but under only one condition and that is the manufacturability of the sand mold. Design of sand molds using conventional methods have several geometric limitations, mainly because of the restrictions such as and not limited to necessity of patterns, draft angles and unconventional parting lines.
Such restrictions can be avoided and several other virtues can be attained by fabricating the sand molds in layer-by-layer additive manufacturing (AM) techniques by using a recent novel technique called Binder Jetting. In this process, adhesive is deposited selectively on a layer of powder bed causing the powder to bond at those locations. The bed is then lowered and a new layer of powder is deposited on it and this process is repeated until all part cross sections are formed. By using sand as the working powder, Binder Jetting process can be propitiously applied to print sand molds and such a process is termed as Sand Printing.
Jiayi’s research focuses on redesigning traditionally cast metal parts for casting with 3D printed sand molds. The design process includes two steps: generalization of initial lightweight geometries using Topology Optimization (TO) software (e.g. Abaqus ATOM); post-processing and refinement of the optimized geometries. TO is a well-established design approach to optimize the layout of material and create functional lightweight parts. However, to ensure the manufacturability of the optimized geometries, designers need to know how to take into consideration design and manufacturing constraints during the optimization process. One important goal of Jiayi’s current work is to develop a knowledge based design for sand casting rules based on 3D sand-printing and casting constraints. Such design rules are presented and validated by a case study in which an airplane bearing bracket was redesigned and physically cast with 3D printed sand molds. This research was funded by an America Makes Project – Additive Manufacturing for Metal Casting (AM4MC).
Load through a stiff spherical bearing: 240 lbf (horizontal); 320 lbf (vertical)
Max Von Mises stress: 224.3 MPa (original); 139.2 MPa (optimized)
The competitive edge of fabricating molds using sand printing additive manufacturing techniques is its potential to eliminate the necessity of patterns and cores. But little is known about the advantages and limitations of these opportunities and many such. Most of the casting rules that foundry experts follow are applicable to only traditional sand casting and don’t take advantage of the infinite geometric flexibility that sand printing allows. Santosh’s work focuses on integrating the unlimited geometric flexibility offered by the sand printing process to design and fabricate molds for optimum casting performance such as to eliminate hotspots, tears, gas porosity. Particularly, the project focuses on generating knowledge based design rules in the construction of sand molds for optimal part performance (reduced weight, good mechanical and metallurgical characteristics). The developed design rules are validated using a case study in which a four-cylinder mini-ram exhaust manifold is manufacturing using sand casting where the molds are fabricated using sand printing techniques without the need of a single core which otherwise in traditional manufacturing methods would have needed several cores that would affect both the economics and lead time of the process.
The exhaust Manifold and turbine housing assembly is then redesigned and both are parts are consolidated together to form a turbo-exhaust manifold. The redesigned component was manufactured using the same process and was found to have a 30% lesser weight than the original assembly. The mechanical performance (flow characteristics and pressure drop) are yet to be studied experimentally.
Part Consolidation and Weight Reduction in Exhaust Manifold via 3D Sand Printing:
|Exhaust Manifold and Turbine Housing assembly||Part consolidation of Exhaust Manifold and Turbine Housing|
|Cast parts after rigging removal of Original design (a) and Optimized design (b)|