case | sunroof frame

“A roof of light”

WEIGHT, COMPONENT AND TOTAL COST REDUCTION

The sunroof frame is the load-bearing part in automobile panoramic sunroof systems. This structural part forms the connection between the car body and the moving glass, and is typically equipped with a motor, a sliding glass mechanism and sunblind system. Traditionally, this frame is made of metal or a combination of plastic and metal, to cope with the high stiffness demands on the frame: a panoramic sunroof system shall not compromise on safety or driving performance of the vehicle.

The existing commercial sunroof composed of a 30% glass filled SMA frame (XIRAN®), on which two large steel reinforcements were mounted. To reduce weight, components and total costs, it was aimed to make a full plastic redesign, without any concessions to the existing performance.

OUR SOLUTION

Considering the loading conditions and performance targets, as defined in coordination with CIE Automotive, first reference static finite element (FE) simulations were done on the existing design with steel reinforcements. After setting the complete packaging space, topology optimizations were done to identify optimal locations for material placement. 
 
Results of these, in combination with the expertise of Code Product Solutions in plastics, design rules and processing, were used to set up a first surface design. Iteratively, sizing optimizations and consecutive design updates were applied to improve the weaker spots in the initial design and to limit the material usage. More detailed FE analyses done on the final concept, e.g., to verify the impact of fibre alignment (from the injection moulding process) on the final mechanical performance of the part, proved the validity of certain assumptions in the initial design phase. Characterization of material data in here was done with Polyscope.
 
This led to a final concept design, fully made of XIRAN®, saving about 20% of weight and offering great recyclability options. Moreover, integral costs can be reduced compared to the reference.
WHAT WE DID

TOPOLOGY OPTIMISATIONS

To determine the optimal material layout within a design space, this mathematical method, based on the finite element method, is used to evaluate the performance for a set of load cases. Depending on the boundary conditions and constraints set, the design can attain any shape, typically with a high degree of freedom. For this reason, this technique is typically used in the concept phase of a design. However, results of topology optimisation, or also sometimes called: freeform optimisation, typically require further engineering for manufacturability of the parts.

SIZING OPTIMISATION

Following the topology optimisation, our engineers derive a manufacturable plastic design, following design rules and using know-how about materials, processes and costs. To determine the ideal thickness of each plane or rib, fulfilling the mechanical requirements without violating governing manufacturability constraints, sizing optimisations are used. Code Product Solutions has solid experience in using this optimisation technique, which is essential for a solid design process.

MATERIAL SELECTION

Based on the FE-simulation results, the preferred material behaviour was defined. By comparing several proposed materials, the best performing material was selected with respect to stiffness, elastic behaviour and strength.

COUPLED RHEOLOGICAL / STRUCTURAL

Code Product Solutions uses a wide range of CAE techniques to make solutions fit to our customer's needs. By linking the results of rheological simulations towards structural simulations, effects on the part behaviour caused by the injection moulding process, like the orientation of the fibres, can be considered. This way, more detailed insights in the part performance can be gathered. This is used for further optimisation of the design, manufacturing process or the material selection.

OUR RESULTS

  • A full plastic sunroof frame design (virtual demonstrator)
  • 20% weight out compared to plastic/metal reference
  • Equal mechanical performance
  • Less components
 

INQUIRIES?

Interested in meeting to see how we can support you?

CONTACT PAUL HABETS

Code is specialised in product optimisation, with more than 12 years of experience in the light-weight industry. If you require more information about our way of working, feel free to get in touch.

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