28.03.2025

Brake housings for autonomous driving

MAPAL's solution is a technically sophisticated combination

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Combined brake housing unites main brake cylinder, brake booster and ABS/ESP in a single part. This component smooths the way for self-driving cars and saves weight. When it comes to machining complex aluminium workpieces, MAPAL’s solution expertise is very much in demand. 

While self-driving cars are already permitted in various countries, the legal framework for them is still not in place in Europe, where only partial driving automation is permitted. The combined break housing – which unites the main brake cylinder, the brake booster and ABS/ESP in a single part – supports all levels of automated driving. Brake-by-wire is closely related to this, whereby the brake signal is no longer sent hydraulically but rather electrically. 

A requirement for autonomous driving

While the combined brake housing is a prerequisite for automated driving, it also has further advantages. Because they are applied electronically, the brakes can be operated more quickly, which results in considerably shorter braking distances in an emergency. 
MAPAL offers appropriate solutions and suitable tools for the development of combined brake housings.
MAPAL's solution expertise is in demand for the machining of combined brake housings made of aluminum.  ©MAPAL
While the first automotive suppliers have already presented all-electric braking systems, vehicles only use a precursor today – the so-called wet-dry system. This hybrid form uses a hydraulic brake at the front and an all-electric system at the rear axle. This redundancy is made possible by a sophisticated central component that combines both worlds in the tiniest of spaces. 

Defined chip breaking for short aluminium chips

Aluminium with a low silicon content of less than 1% is the material of choice for the combined brake housing. To save costs, extruded profiles are used for the most part. Long chips are created during machining due to the grain flow and the low silicon content. To ensure excellent chip breaking when boring and reaming aluminium with low silicon content using PCD blades, MAPAL makes use of application-specific chip-breaking geometries. Their special topology, which was developed with the help of 3D simulations, ensures defined chip breaking and thus short chips, even at low feed rates and machining allowances. This enables maximum performance and process reliability. 

High demands on surface finishes

With its many bores, the part then looks like Swiss cheese. Each bore has tight tolerance requirements, calling for precision in the IT6 to IT7 range. Because liquid flows through the combined housing, there are high demands on the surface finish. The surface must be free of scoring which can be formed by chips or vibration during machining. Some bores are subsequently anodised to provide more resistance to wear. Rawness of Rz 1 is required to hold this coating. 
The picture shows the chip breakage during machining in detail.
Application-specific chip breaker geometries from MAPAL ensure excellent chip breaking when boring and reaming low-silicon aluminum with PCD cutting edges.  ©MAPAL
MAPAL provides customised tools to machine the combined brake housing. These include a special carbide step drill for pre-machining the motor bore. Afterwards, PCD tools with many cutting edges are usually used to achieve the desired surface quality. The different contours of the valve bores are created with a circular milling cutter featuring very high contour accuracy.

Productive drilling solutions save costs

Various deep bores are also drilled in the aluminium block, which overlap inside the component. Twisted tools with machining depths of up to 30xD ensure chips are removed reliably, so the liquids can later flow unhindered. The deep drilling alone takes up about 20% of the cycle time of approximately 15 minutes. Economical bore machining solutions thus have a considerable effect on overall cost efficiency. 

Up to 5 million of the combined brake housing units are produced each year. They are predominantly produced in multi-spindle machines in two clamping setups. A four-spindle machine is preferred due to its high productivity. As a technology partner, MAPAL works with its customers to develop application-specific machining processes and tool packages for these aluminium parts.

Portrait Ostertag-Mathias

Contact

Mathias Ostertag Public Relations mathias.ostertag@mapal.com Phone: +49 7361 585 3566

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