Manufacturing power steering rack housing in Aluminium alloy via high-precision CNC machining:

Among the first to be specialized in Titanium and special alloys CNC processing, CRP Meccanica consolidated its position as unique point of reference for manufacturing parts with complex geometry and tight tolerances. An example of complex application to be manufactured via high-precision CNC machining is the power steering rack housing in Aluminium alloy

Among the first to be specialized in Titanium and special alloys CNC processing, CRP Meccanica consolidated its position as unique point of reference for manufacturing parts with complex geometry and tight tolerances


2020 marks the 50th anniversary of CRP Meccanica, leading company in the field of High Precision CNC machining for prototype batches, pre-series and small production runs.
It was the year 1970 when Roberto Cevolini, after gained experience in several mechanical and High Precision areas, established his own company for High Precision CNC machining.
With an entrepreneurial vanguard heritage in Motorsport and F1, CRP Meccanica became the creator of innovative and avant-garde solution for the most complex and demanding sectors.
CRP Meccanica is still inspired by Roberto Cevolini's founding principles and skills: entrepreneurship, independence, forward-looking management. This allows to anticipate the market needs and provide innovative solutions.

Nowadays the CNC Department at CRP Meccanica is equipped with the latest 5-axis machining centers (including several pallet centers), live-tooling lathes, wire and sinker EDM machines and a quality control department.
Indeed the CNC center at CRP Meccanica maintains the latest CNC technologies and practices in the industry, shown by the fact that CRP Meccanica has successfully passed the audit for Quality Management System standard ISO 9001:2015. The certificate is valid for the production of High Precision CNC machining components in various exotic alloy including titanium, specialized in prototype batches and small production runs, based on client's specifications.

An example of CRP Meccanica expertise to manufacture parts with complex geometries and strict tolerances comes from Motorsport: the power steering rack housing for racing cars.
Engineer Franco Cevolini, CEO and CTO CRP Meccanica, comments: " The Motorsport industry has always been a primary adopter of innovative technology, we are very proud to have been one of their High-Tech supplier and partner for over 50 years. On the other hand, we are very pleased to be a technological point of reference also for other demanding sector such as Aerospace, Defense, Robotics, Medical."
The power steering rack housing manufactured by CRP Meccanica
Power steering system is a device designed to decrease the force the driver has to apply to the steering wheel to steer the wheels. If not present, maneuvering the steering wheel can become difficult for the driver due to the considerable strength he has to exert. It is an advancement of the steering system.
"Power steering has literally revolutionized the way the automotive population drives, especially in next-generation high-performance cars" adds Engineer Franco Cevolini.

As safety-critical component of the power steering system, the power steering rack housing is a very complex part: it contains not only the rack but also channels for the passage of pressurized oil and hydraulic actuators that help the movement on the horizontal axis.

CRP Meccanica started manufacturing this component many years ago for the most important F1 teams, that is when it was known as "steering housing", not yet "power steering housing".
"At that time - Engineer Franco Cevolini states - steering housings were quite simple: the steering column meshed directly on the rack and that's it.

"In today's steering rack housing, on the other hand, manufacturers have to deal with the power steering system. So the more complex the part became, the more complicated was machine it, especially the creation of the cylinder bores and the satisfaction of the tolerances required."

The image above represents a 2016 power steering rack housing for racing car, CNC machined by CRP Meccanica in Aluminum 2014. Nowadays more performance-oriented alloys are used such as Aluminum-Lithium alloys that offer superior mechanical characteristics.

It is an extremely complicated part to create that requires expertise and ability along with the acquaintance of the material. Moreover, it needs very complicated manufacturing processes, that is the combination of different types of processes: 5-axis continuous milling machining and advanced lathe machining.
"Investing in technological renewal has always been our priority - Engineer Franco Cevolini states - and this kind of application is a clear example of the high level of expertise achieved by every unit of our CNC Machining Department."
"In fact - Cevolini adds - once the power steering rack housing is CNC machined, it demands special surface preparations and treatments (pre- and post- hard anodizing) final honing, deburring and the removal of sharp edges, before proceeding with final testing."
Surface preparations and treatments
To better understand the complexity of the application, we must consider that inside the power steering rack housing there is a hydraulic actuator assisting the driver to steer the vehicle. Actuator is a hydraulic cylinder with a sliding piston.
Aluminum is a quite soft metal; after a while the mechanism of the actuator would tend to "eat" aluminum (that is, to enlarge the diameter) and the hydraulic seal would no longer work properly, causing oil leakage. The consequence would be - at best - the decrease of the power steering effect, but at worst, it could cause a dangerous blocking.
To avoid this issue, a hard anodizing treatment between 5 and 6 hundredths of a millimeter is done on the CNC machined application.
This process produces a hard wear and an abrasion-resistant coating on the surface of aluminum part. The purpose of hard anodizing is to increase hardness and wear resistance of the part. To complete the surface finish, final-honing process follows.

Aluminium power steering rack housing presents a lot of bores that intersect each other, that's because the system has been designed in such a way that, pursuant to solenoid valves that open and close, it is possible to intervene on the power steering system to make it work at its best. Pressurized oil goes through the bores.

During the manufacturing of the Aluminium power steering rack housing, sharp edges with burrs are created at the intersections between the bores. Burrs themselves are not an issue but, since oil will be flowing inside the bores, if burrs are not removed, they could be torn away by oil, with the risk to "go around" and cause seizure.
It is therefore important to use suitable treatments that guarantee an accurate deburring of bores intersections in order to avoid any issue of detachment of material.
"CRP Meccanica can rely on workers - Cevolini adds - highly specialized, also in these type of preparations and treatments. The results have always been of the highest level, as the finished part shows".

Crpmeccanica.com

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