The business unit Hydraulic Brake Systems (HBS) within the business area Autonomous Mobility and Safety is a part of the Continental Automotive Technologies group. It develops, produces and integrates active and passive safety technologies as brake systems for passenger cars and controls vehicle dynamics. In 2017, the product group started a special initiative with the goal of guaranteeing the feasibility of casting designs while striving for a “first time right” strategy. This article describes the motivation for introducing MAGMASOFT®at Continental, the subsequent implementation process and achievements up to today.
As casting components play a key role in the development of a brake caliper, Continental decided in 2018 to set up a Casting Competence Center (CCC) team to take care of all casting-related topics in R&D. To achieve the aim of “first time right”, it becomes necessary to understand the castability of the designs; for this purpose, Continental HBS implemented MAGMASOFT®. The team was soon joined by colleagues to support CCC with respect to design and supplier quality management (SQM) topics.
The main activity concerns ductile iron castings, accounting for approximately 60% of the brake caliper weight. A typical front axle caliper consists of anchor, housing, piston, brake pads and spring elements, Figure 1.
The cast parts are designed individually for each customer project within the available design space in the wheel house to fulfill the specific customer requirements, such as mass and stiffness. The consideration of castability of a part design in an early design phase avoids comparatively late rejections by suppliers and end customers.
With regard to the complex design and critical castability, Continental decided to choose housings as pilot project for the evaluation of internal simulation activities, Figure 1 (center). The main function of a housing is to apply the clamping force for pressing the brake pads onto the rotor, which then creates the frictional forces for the brake torque for decelerating the car.
A hydraulic pressure of 160 bar is applied which deflects the cast component and leads to an increased hydraulic volume between cylinder bottom and piston. This additional volume of brake fluid is called "volume consumption" and is a key criterion for the stiffness of a brake caliper, Figure 1 (right).
As the brake system is part of the unsprung weights of a car, the development target is to achieve the best compromise between stiffness and weight of the housing at the lowest possible costs. The fact that the clamping force is applied by hydraulic pressure implies a special requirement regarding the soundness of the cast housing. To eliminate the risk of leakage, the cylinder area has to be free from casting defects, e.g. porosities.
A functional failure at a late stage of the R&D process may lead to weeks of delay and causes unplanned costs through additional loops. This relates to cast part redesign, simulation, production and inspection of samples. Often costly tool modifications up to a completely new tool in the worst case are needed if an adaption may not be +possible. After demonstrating the importance for Continental to guarantee housings that are free from casting defects, the next consequential step was to build up internal casting simulation expertise.
The concept of the Casting Competence Center and the internal application of MAGMASOFT® are as follows:
› Investigation of draft versions regarding castability at the earliest possible phase to avoid/reduce late design changes due to feasibility problems
› Building up our own casting simulation expertise
› Better understanding of solidification process and resulting defects, e.g. shrinkage porosity
› Predicting the potential quality range of worldwide supplier base to develop efficient countermeasures and avoid localized designs
› Development of robust casting designs for global platforms
The full access to all simulation output variables enables a deep investigation of root causes. Findings can be shared with all involved teams, such as Design/FEA simulation, to define countermeasures that meet requirements from more than one perspective – e.g. less additional weight without change to the exterior shape.
The implementation process of MAGMASOFT® at Continental HBS started in October 2017 and was intensively supported by MAGMA. Major milestones, shown in Figure 2, were:
› Basic and complementary training for cast iron by MAGMAacademy
› Development of a 1st standard simulation model adapted to Continental’s requirements
› Sourcing and adaption of necessary data
› Visiting worldwide key suppliers to openly communicate Conti activities and set up co-operations
Due to the lack of detailed casting process data, the set-up of a standardized simulation model and simulation procedure is essential. Supported by MAGMA, the multiple cavity tool normally used for the series production of housings was converted into a simplified single-cavity standard simulation model. Using MAGMASOFT®´s integrated geometry database, the runner and feeder system of the standard layout can be changed through parametric set-up and thus be easily adapted to different application projects, Figure 3.
As a first success of all these activities and major step towards reliable internal feasibility studies, thanks to the support of the supplier base and Conti labs, the Casting Competence Center was very quickly able to predict the supplier simulation results quite accurately, shown in Figure 4.
Pursuing the strategy of a “first time right” casting component design, a key indicator for measuring the success is the average number of casting-related design loops per product. Figure 6 clearly demonstrates that, since the introduction of simulation with MAGMASOFT® in 2018, the targeted number of loops for 2019 were reduced significantly. Consequently, the target for 2020 has been set towards the “first time right” goal.
Figure 5: Key performance indicator (KPI) confirming the benefit of integrating MAGMASOFT® in the development process at Continental
Based on the successful implementation at Continental HBS in Frankfurt and the positive feedback of key suppliers, a global roll-out of casting simulation with MAGMASOFT® was started. More and more colleagues in Europe, US, Mexico, China and Japan are gradually integrated into the CCC and casting simulation activities.
A continuous improvement of the prediction quality of casting simulation results is achieved by a close collaboration between Continental, MAGMA and casting suppliers. In the last three years, Continental shared their simulation models and the corresponding lab data with MAGMA and their suppliers to implement reasonable findings into ongoing development activities of MAGMASOFT®.
Figure 6 illustrates one example of this collaboration in which all participants provided all necessary data to validate and guarantee an excellent correlation using new enhanced feeding capabilities in MAGMAiron.
Continental is committed to further implement the new methodology and make it available to all site globally that are involved with design, robustness and supply chain of advanced braking systems.
Founded in 1871, Continental AG is a technology company that offers safe, efficient, intelligent and affordable solutions for vehicles, machines, traffic and transportation. With more than 240,000 employees in the business units Automotive, Powertrain and Rubber Technologies at 595 locations in 59 countries, Continental is one of the largest automotive suppliers in the world.
Therefore, Continental is also one of the major casting users worldwide, especially in the business units Automotive and Powertrain Technologies.