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3D Printed Automotive Hood Hinge: Over 50% Lighter with Two-Thirds Less Parts

EDAG recently turned to additive manufacturing, specifically a 3D printer from SLM Solutions, to solve a challenge to develop an improved hinge system for a car or truck. The resulting solution is LightHinge+ -- a lighter, stronger, more efficient hood hinge.

EDAG is an independent engineering services provider to the global automotive industry. The company supports clients across the entire value chain -- from the original design idea to product development and prototype construction all the way to the delivery of turnkey production systems.

EDAG overcame obstacles like stringent safety demands and a complex design by 3D printing a hood hinge system that weighed less and was still completely functional.

 

 

As a technology and innovation leader, EDAG also operates established centers of excellence that design landmark technologies for future applications in the automotive industry: lightweight construction, electric mobility, car IT, integral safety and new production technologies.

Voestalpine Additive Manufacturing Center

A business segment of EDAG, voestalpine is a technology and capital goods group with a unique combination of material and processing expertise. In 2016, a new research and development center for 3D printing of metal parts was opened at the voestalpine site in Düsseldorf, Germany.

The voestalpine Additive Manufacturing Center harnesses the manufacturing process for particularly complex and lightweight metal components for use in aviation and aerospace, the automotive industry, tool manufacturing, etc.

Simufact Engineering

simufact engineering is an international software company based in Hamburg, Germany. As a subsidiary of MSC Software and as a part of Hexagon, simufact develops software solutions for the design and optimization of manufacturing processes with the help of process simulation.

Engine hood hinge in additive manufacturing (left) and in sheet-metal design (right)

 

 

simufact simulation solutions form the backbone of development, construction and manufacturing departments of many well-known product development & manufacturing companies. They cover different manufacturing techniques: additive manufacturing processes, welding processes, mechanical joining processes and a variety of forming processes -- including cold and hot massive forming, rolling processes, sheet metal forming and heat treatment.

The Challenge

Stringent safety and functionality demands imposed on active hinge systems for engine hoods mean they are very complex. In the event of an accident with a pedestrian, they extend the distance between the impacting object and any hard engine components by raising the engine hood. A pyrotechnically triggered actuator kicks in within fractions of a second and raises the hood.

These hinge systems can be manufactured by stamping, casting or forging for large-scale production series in excess of 30,000 units per year. The complex kinematics involved require many individual parts (approximately 40 components per vehicle) and high assembly and tooling costs. Active hinges made from sheet metal nowadays weigh around 1500g each and thus generate considerable additional weight in vehicles.

Minimization of the support structures with more than 50% (left) and less than 30% of the material volume.

 

 

However, economic constraints prevent small production runs (80 and 30,000 units per annum) from using large-scale production technologies. Furthermore, design and the lack of assembly space in the front section of sports cars generally prevent sheet-metal methods from being used for active engine hood hinges. Carry-over strategies aiming to minimize investments for small production runs usually cause package and design problems due to the adoption of active hinges from large-scale production.

The collaboration between EDAG, voestalpine Additive Manufacturing and simufact engineering was intended to exploit the potential of additive manufacturing to solve these issues.

The Solution

From the beginning, the requirements for the hood hinge were very high, needing to meet the requirements of strength and rigidity with the largest possible weight savings. In addition, functional integration and the associated reduction in the number of parts was important.

The components were manufactured on an SLM®280 Twin Selective Laser Melting machine.

First, a topology optimization took place. It involved calculating minimum material requirements based on actual loads. The resulting complex geometries are usually only possible through laser beam melting with considerable support structures.

SLM®280 Twin Selective Laser Melting machine

 

 

For the LightHinge+, the share of support structures to be subsequently removed would have comprised around 50 percent of the total melted material volume. In the course of the collaboration, this share was reduced in several iterations, to initially 30 percent and finally to under 18 percent. In other words, eliminating most of the processing steps and achieving considerable material efficiency.

Despite the extensive structural changes, vis-à-vis topology optimization, for reducing post-processing, the final result successfully achieved weight savings of 52 percent compared with the reference sheet metal construction, thanks to applying bionic principles.

Functional Integration

The hinge also comes complete with an automatic hood function. The geometric freedoms of additive manufacturing allowed EDAG engineers to develop complex predetermined breaking point structures.

Furthermore, it was also possible to integrate the connection point for the gas pressure spring and the mounts for the wash-wiper tubing and collar screw into the hinge. This functional integration reduces the number of parts by 68 percent compared to the sheet-metal reference part, eliminating much of the assembly's original weight. This integrated hinge function can be deployed in significantly more compact spaces in sports cars or other high-performance vehicles.

Software -- Simufact Additive

The concentrated input of heat during the additive manufacturing process results in warping and internal stress, due to high rates of heating and cooling. A hinge without warp compensation may thus deviate by between 1 and 2 mm from the CAD model, as measurements showed.

Comparison before and after warp compensation in the lower section: warping versus CAD model (left); warping of the compensated component based on simulation results (right).

 

 

An important interim step when designing and manufacturing additive components is thus to simulate the actual laser melting process. The Simufact Additive Software Solution was created specifically for additive manufacturing and was used for this purpose. This solution allows the simulation of the printing process and subsequent process steps and predicts warping and internal stresses.

Simulating the construction process was crucial in helping improve the design, safety and warp optimization of the additively manufactured hinge. By using the Simufact Additive Software, an overall reduction in engine hood hinge warping of around 80 percent could be reached. It also eliminated the need for costly and time-consuming production experiments, since the components were within the required tolerance from the very first production batch.

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