CASE STUDY: Idneo Improves Mechanical Design Decisions for Tolerancing

One example of where tolerance analysis plays an important role at Idneo is mechanical design of electronic control units (ECU). These units, widely used in automotive markets for powertrains, bodies, comfort, chassis, and active safety, are systems of hardware, software, and extensive mechanics.

Given their importance to the performance and safety of an automobile, an ECU’s mechanical design must robustly meet functional requirements such as for the fit of its printed circuit board (PCB) and housing components during assembly, as well as for gaps between components when subject to field conditions of varying temperatures and forces.

The mechanical design process for an ECU typically starts with the external volume requirements as provided by Idneo’s client. Idneo’s engineers then work from the outside to the inside of the ECU to specify the housing and then how one or more PCBs and any other components will fit within the housing.

As the engineers make Geometric Dimensioning and Tolerancing (GD&T) decisions for stack ups of ECU components, they take into account factors such as mechanical forces, thermal forces, tolerances for pin in hole joints, gap thicknesses, and where to define fixed positioning points.

These decisions are supported by iterative what-if analysis within Concept. After modeling a candidate design with Concept, Idneo’s engineers quickly iterate GD&T values for each stackup to simulate failure rates versus functional requirements. For instance, a lower cost, greater tolerance value within a pin in hole joint might lead to a too high rate of failure during assembly or in operation on a hot day. The result is rapid convergence on values that optimally balance product performance and costs.

Because of Idneo’s experience with Concept and its precise modeling of complex mechanical stackups, their engineers have a high level of confidence in the results.

As a long time user of Enventive Concept for every step in the development of their client’s mechanical designs and during production, Idneo has found the software’s benefits to include:

• Improved knowledge sharing: Once up to speed on Concept, Idneo’s engineers can effectively share the logic behind their GD&T design decisions, speeding up their internal discussions and collective decision making. One of the keys to enabling this is the ability within a Concept model to clearly explain the analysis in a highly visual way. Idneo finds that the sharing of these explanations using tools such as spreadsheets is impractical for designs beyond relatively simple stackups of three or four parts,

• Strengthened trust from clients: Idneo at times shows Concept studies to their clients and find that they have a strong level of comfort and confidence with Concept’s visual and tabular reports.

• Faster decision making with suppliers: Idneo uses their Concept analyses to explain to their parts suppliers why specific dimensional and/or tolerancing values are important to the performance of a design. If the supplier proposes alternatives, Idneo’s engineers can quickly run a Concept analysis to evaluate cost vs. performance tradeoffs. This saves time in collaborating with suppliers in reaching optimal decisions and helps gain their buy in for delivering on agreed to values.

• Enhanced design process: For each of Idneo’s mechanical design projects, there are tests that must be passed to validate design robustness. Their goal is to pass these tests the first time by evaluating robustness throughout the design process. Tolerance analysis is one of the design activities among several, such as prototyping, that lead to robust designs. In particular, Concept’s ability to quickly predict performance failure rates versus GD&T parameters, from the beginning of CAD design to prototyping and then to production, makes it a very strong factor in Idneo’s confidence for designing robustly.

“As a long time user of Enventive Concept, we’ve found it to be an important tool for creating robust designs.”

Kattia Zagastizabal

Mechanical Master
NextMobility at Idneo