In a project for the Advanced Research Projects Agency—Energy (ARPA-E), Ricardo, Inc. partnered with United Technologies Research Center (UTRC) to develop a detailed cost model for 10 key automotive components (chassis, powertrain, controls, etc.). The project, titled Reducing Automotive CAPEX Entry Barriers through Design, Manufacturing and Materials, analyzed the investment barriers for lower-volume production. Amongst various findings were opportunities to use 3D printing to reduce the necessary investment in tooling.

Passenger vehicles and commercial trucks incorporate several metal components, often requiring enormous capital investment in tooling. The cost of a die set can vary from a few thousand to more than $1 million, depending on die size, part complexity, and required die durability and life.

Companies trying to customize their products or bring new technology to market typically lack sufficient opportunities to achieve economies of scale. Low-volume demand for aftermarket parts also suffers from the same limitations.

To study these challenges, Ricardo developed a manufacturing-cost model and database that enables users to estimate production costs and required investments for a large variety of components at different production volumes. The cost model determines bottom-up costs for forming of individual parts, as well as their assembly into components. It can analyze key business drivers such as tooling investment, equipment cost, process time, materials, scrap, automation, labor, supply-chain impact and factory overhead.

Leveraging its expertise and the manufacturing-cost model, Ricardo studied the costs associated with the conventional manufacture of 10 subassemblies for the Toyota Corolla, representative of a traditional high-volume passenger vehicle. The cost analysis shows that, for all of the analyzed components, production costs start to become prohibitive below an annual volume of 50,000 units. The root cause is the relatively large capital investment needed for dies, fixtures and other tooling.

Traditionally, stamping or drawing dies for high-volume production are expensive. As Ricardo and UTRC collaborated to explore the economic feasibility of innovative production techniques, they took a look at the use of additive manufacturing (AM) to fabricate stamping dies. Among the AM techniques considered were laser and electron-beam powder-bed processes, which tend to provide the best geometric accuracy; and lower-cost welding processes that can more-rapidly deposit material, but do so with limited geometric accuracy. Researchers ultimately decided that wire-arc additive manufacturing (WAAM) offered the ideal solution for developing stamping dies that do not require fine features.

WAAM builds components layer by layer by depositing molten metal delivered by weld wire. The process uses six-axis robots in conjunction with a specialized cold-metal-transfer (CMT) welding system to produce a fully dense deposit.

To develop a cost-effective and rapid process to print dies, the Ricardo-UTRC team opted to use preforms—starting plates or extrusions—and then apply the WAAM process to 3D-print all of the necessary features onto the preforms. This saves significant time and money compared to 3D printing a die from scratch. To meet the required die dimensional tolerances, excess weld metal is deposited and then finish-machined.

Table showing manufacturing costs and cycle times for three die sets, excluding costs for engineering, design, launch and markup. (Source: 3D Metal Printing Magazine)

>>Read more detail by Piyush Bubna and Michael P. Humbert, 3D Metal Printing, October 20, 2016

3D Metal Printing of Automotive Stamping Dies