LUMENIUM LLC IS A VIRGINIA-BASED COMPANY developing an innovative family of internal combustion engines. The Inverse Displacement Asymmetrical Rotational (IDAR) engine is a novel and totally singular design for producing powerful, efficient, internal combustion. Its unique geometry permits dramatic yet efficient work output from a small, light engine consuming less fuel and producing lower emissions.
For Lumenium, the ability to iterate quickly has a direct impact on time-to-market and engine performance. Currently, they use an in-house CNC machine and wire electrical discharge machining (EDM) to make prototype parts, but the process is relatively time consuming and costly. Lumenium is seeking a faster, more costeffective approach to prototyping parts within the engine assembly.
Parts within the IDAR engine must withstand the extreme heat and stress inherent to internal combustion engine operation. Each component must adhere to specific requirements—including high dimensional accuracy, strength under dynamic loads, and low thermal expansion. The weight of each part is an important consideration for overall power density and efficiency. Additive manufacturing allows Lumenium to meet these requirements and tackle complex part geometries—like internal cooling channels to improve engine performance. With the Studio System, Lumenium can bring this technology into their existing workspace for faster design iteration and functional prototyping.
Internal combustion engines represent a $350 billion market with three categories of engines: the traditional piston engine, novel opposed piston engines, and rotary engines. Lumenium’s IDAR engine technology adds a fourth category, representing a paradigm shift in the power production. The engines operate under substantial heat and stress so engine components must withstand dynamic loading conditions, combustion forces of 1500 psi, and combustion temperatures of 1500 °C.
Designing a complex product with extremely high performance requirements has led to multiple generations of engine designs, each with a long conceptual phase of designing, prototyping, and iterating. The ability to perform frequent design iteration has a significantly beneficial impact on final engine performance. The full engine development cycle for each generation of the IDAR engine takes between three to five years. Identifying a faster, more cost–effective approach to prototyping is critical to IDAR engine development, and the ability to lightweight parts while adhering to other mechanical property requirements directly impacts engine performance.
Printing vs Machining
Lumenium makes approximately 20 prototype parts per month. The majority (about 95%) are manufactured in-house using five-axis CNC machining and wire EDM. Machining complex geometries with CNC involves many complicated tool paths and sometimes more than 80 different machining operations. Each operation requires re-programming, which often involves custom fixturing and an operator to realign the part. Even if post machining is required on the printed part, the number of overall machining operations is significantly less. Programming the CNC machine requires a trained, dedicated operator and can take weeks for a single, more complex job—from design to creating the CNC tool path to fixturing to machining. Some parts require post processing by outside vendors adding up to three weeks to the fabrication.
The remaining 5% of prototype parts—typically conventional, round parts—are sent to an outside machine shop where lead times average about three weeks. The long lead time limits Lumenium’s ability to iterate on the design, thus having a direct impact on engine performance.
In addition to extended lead time and high costs, machining offers only limited options for light-weighting parts. Weight is critical to engine performance where a 50% reduction in engine weight can potentially double the rated engine speed (RPM) and power output. To reduce weight with machining methods, engineers can do little beyond selecting a lightweight material. Without changing material, reducing weight via machining typically requires altering the part geometry—adding time and complexity—which can result in weak points within the part structure. Early versions of the engine used parts machined from solid blocks of aluminum, a lightweight alloy. However, aluminum expands as temperatures increase which is an unfavorable property for engine components that operate at high temperatures. Steel has a coefficient of thermal expansion that is 68% less than aluminum.
The Studio System prints parts with closed-cell infill—an internal lattice structure printed throughout the part. Users can adjust infill spacing to meet strength and weight requirements. Parts printed with infill will have significantly lower thermal transfer. This reduces part weight while maintaining strength, which enables Lumenium to pursue steel as part of their solution.
For Lumenium, rapid prototyping is essential to product development and maturation as the IDAR engine approaches commercialization. The design and function of each part within the assembly is critical, so the ability to refine and iterate quickly has a direct impact on the overall engine performance. Previous methods of machining each prototype part—either in-house or by an outside machine shop—are time–consuming and costly. The printed saddle, swing arm, and connecting rod demonstrate the time and cost savings that the system delivers.
Considering the time associated with programming CNC machines, labor costs, and design limitations, the Studio System would cut Lumenium’s design iteration time in half. With a full development cycle of 3 to 5 years, the time savings has significant impact on the product development cycle and the revenue model.
Part 2 of this case study will focus on functional testing of the printed engine components, exploring trade-offs between light-weighting and strength for different infill settings.
About Desktop Metal
Desktop Metal, Inc., based in Burlington, Massachusetts, is accelerating the transformation of manufacturing with end-to-end metal 3D printing solutions. Founded in 2015 by leaders in advanced manufacturing, metallurgy, and robotics, the company is addressing the unmet challenges of speed, cost, and quality to make metal 3D printing an essential tool for engineers and manufacturers around the world. In 2017, the company was selected as one of the world’s 30 most promising Technology Pioneers by World Economic Forum, and was recently named to MIT Technology Review’s list of 50 Smartest Companies.
Lumenium is a Virginia-based, advanced engine technology company and inventor/ developer of a highly innovative family of internal combustion engines (IDAR engines), the engineering of which represents a paradigm shift in power production. Lumenium has been financed entirely by private capital, provided by a loyal array of investors with broad and diverse industry expertise, since its inception in 2004. For more information, visit their website.