Bruce Jenkins, Ora Research
A perennial engineering challenge is designing a part to meet performance requirements while observing design constraints imposed by manufacturing processes. Conventional subtractive machining offers sharply limited ability to cost-effectively produce complex geometries, especially biomorphic shapes and lattice structures. The result of those manufacturing limitations is often components and products with suboptimal functionality and performance.
But today, with advances in 3D printing and especially direct metal printing (DMP) swiftly making these technologies more and more available and effective, many constraints imposed by traditional manufacturing processes are going away. At the same time, software technologies for multidisciplinary design exploration are emerging to help engineering and manufacturing organizations make the most of these new production processes. In particular, rapid advances in topology optimization technology are helping engineers generate the most efficient designs for single-step manufacture by latest-generation DMP systems. With this combination of new technologies, what the engineer designs is essentially what gets manufactured, with very little of the time- and labor-intensive manufacturing engineering that before now was needed to turn engineering intent into machinable reality.
The business value of this confluence of new technologies was dramatically proven in a recent project by software developer Frustum and 3D Systems’ Quickparts on-demand parts service. The project was part of a public challenge to industry by GE Aircraft to reduce the weight of an aircraft bracket while maintaining the strength needed to meet all of its functional requirements, primarily supporting the weight of the cowling while the engine is in service.
Design-critical nature of weight
Since the beginning of motorized travel by land, air and sea, engineers have striven to balance the competing objectives of maximizing strength while minimizing weight. This balancing act has become especially critical in recent years, with swiftly growing and globalizing competition among manufacturers, ever stricter efficiency and emissions mandates, escalating costs and schedule pressures.
Weight is an especially crucial factor in modern aircraft engineering. Although a Boeing 737 weighs some 65 metric tons, shaving just a single pound of weight from the design yields fuel cost savings of hundreds of thousands of dollars per year for each plane. Multiplied by the total number of aircraft currently in operation worldwide, those savings approach $10 million annually, according to a GE Aircraft white paper.
Topology optimization of the design
In the GE Aircraft challenge, Frustum’s Generate topology optimization software provided the first steps in tackling critical weight-versus-strength issues. Topology optimization determines the most efficient material layout to meet the performance requirements of a part design. It takes into consideration the given spatial volume allowed, load conditions on the part, and maximum stresses allowed in the material.
Generate automatically generates optimized geometries from existing CAD files. It models material structure among the design features to generate optimally stiff and lightweight structures. Smooth and blended surfaces reduce weight and minimize stress concentrations.
“Based on an existing conventional part design, our software automatically produces optimized geometry for additive manufacturing, without needing to do any remodeling,” says Frustum CEO Jesse Blankenship.
Unlike parts manufactured by traditional CNC or casting methods, the complexity of the model generated by topology optimization is of no concern, as DMP handles extremely complex models as easily as simplistic ones.
3D printing expertise from 3D Systems On Demand Parts Manufacturing service
Once the initial design was generated, 3D Systems’ expertise came into play. Its On Demand Parts Manufacturing service, available through the company’s Quickparts online portal, is a leading provider of unique, custom-designed parts, offering instant online quoting, expertise in 3D design and printing, and manufacturing services support. The worldwide service is well versed in the most complex aspects of direct metal printing.
“Direct metal printing is much more complex than plastics printing,” says Quickparts business development manager Jonathan Cornelus. “We help our customers to develop parts suitable for DMP, with minimized risks for part distortions or build crashes. We print components using optimized parameters based on our long-term experience in printing parts for customers.”
With the GE Aircraft bracket, Frustum’s Generate imported the original CAD file and performed the topology optimization in one step, delivering an STL file for printing. 3D Systems provided manufacturing advice on the process, material specifications, best build orientation to deliver optimal part properties and achievable tolerances, and identified potential risk for deformations.
The part was printed on a 3D Systems ProX DMP 320 system. Preset build parameters, developed by 3D Systems based on the outcome of nearly half a million builds, provide predictable and repeatable print quality for almost any geometry. An entirely new architecture simplifies job setup and offers the versatility to produce all types of part geometries in titanium, stainless steel or nickel super-alloy. Titanium was chosen for the GE Aircraft bracket, based on its superior strength even when material is thinly applied to lower a part’s weight.
Exchangeable manufacturing modules for the ProX DMP 320 system reduce downtime when changing materials. A controlled vacuum build chamber ensures that every part is printed with proven material properties, density and chemical purity. The small portion of non-printed material can be completely recycled, saving money and providing environmental benefits.
Dramatic weight reduction an eye-opener
The completed part met all the load conditions required by the GE challenge and stayed within the specified geometric envelope, while slashing weight a staggering 70 percent. “This is the kind of project that should be a real eye-opener for automotive and aerospace companies,” says Cornelus, “where reducing weight while providing the same or improved functionality is the lifeblood of their design, engineering and manufacturing operations.”
Beyond the design and performance of the part itself, Cornelus points out that topology optimization teamed with DMP can often consolidate multipart assemblies into a stronger single part, eliminating fasteners and connectors that are often the cause of failures, as well as the time and labor of assembly.
Finally, there is the coveted advantage of speed. Production-grade parts in tough materials such as stainless steel, titanium and nickel super-alloy can be turned around by 3D Systems in as little as two weeks to satisfy the ever-shortening schedule demands of myriad industries.
3D Systems On Demand Manufacturing