The car steering system might look simple. Still, the system is a set of components of different designs, material makeup, and functions that combine to translate a driver’s input into vehicle control.
This guide is a technical overview of the automotive steering system. It focuses on the system, the different types, functions, components, and suitable manufacturing processes.
What is a Car Steering System?
The car steering system combines several components working together to receive input from a driver who wants to control a car’s movement. The system does this by converting the rotational input from the steering wheel into a lateral movement of the wheels.
The main function of the automotive steering system comes from its name: changing the vehicle’s direction. Aside from directional change, the steering system aids stability during turns by ensuring that the wheels follow the correct path. In addition, the steering system gives a car driver tactile feedback on road conditions. As a result, it provides a better driving experience.
Components of the Car Steering System
The car steering system assembles multiple components working together. However, there are many car steering parts depending on the type of steering system.
- Steering Wheel: The steering wheel is the interface for driver input and is typically connected to the steering column.
- Steering Column and Shaft: It connects the steering wheel to the gear mechanism and often has joints that handle misalignment between the steering wheel and the wheel.
- Steering Gear: The gear mechanism converts the rotational motion of the steering wheel into the lateral movement needed to turn the automotive steering wheels.
- Tie Rods: They link the steering gear to the steering knuckles, and they function in maintaining wheel alignment and absorbing shocks during driving.
- Steering Knuckles: Attach the wheels to the suspension system and pivot when the steering input is applied, allowing the wheels to change direction.
The components above are found in all steering systems. Still, in some types, such as the HPS system, we have the power steering pump, which provides the hydraulic pressure to assist with steering, and the electric motor in the EPS system, which provides torque assistance.
How Does Steering Work?
At a fundamental level, the car steering system converts rotational motion (the steering wheel’s turning) into the wheels’ angular displacement. This is achievable through several mechanisms depending on the type of steering system.
Using the rack-and-pinion system, which is popular because of its simplicity, efficiency, and lesser components, as an example, this section will explain the steering mechanism of a car. The car steering wheel, which the driver steers, connects to a shaft and a gear (pinion).
Using teeth, the pinion directly contacts a metal bar called a rack (a linear gear). When a driver turns the steering wheel, the pinion rotates, engages the rack, and moves it left or right based on the driver’s input.
The rack connects to the wheels via tie rods and adjusts the wheel angle relative to the car’s body. When the rack moves left or right, it pushes or pulls the tie rod, leading to the wheel being steered in the desired direction.
Systems that are more complex than the rack and pinion mechanism, such as the power steering or electric power steering (EPS), have additional components to ensure smoother operation. They include hydraulic pumps, electric motors, and sensors.
Using the analogy below, let’s check out the scenario below. Consider a driver making a right turn. He rotates the steering wheel clockwise. The pinion gear will rotate correspondingly, pushing the rack gear to the right. The tie rod will transfer the motion to the steering knuckles, which pivot the front wheel and turn them to the right.
Types of Steering Systems
The car steering system can be classified based on its operational mechanisms, ranging from simple manual to advanced power-assisted systems. Below are the commonly used types:
Rack and Pinion Steering System
The rack and pinion car steering system has a simple, efficient, and compact design that consists of a shaft, pinion, rack, and tie rod, which comes together to ease the control of a car.
The car steering wheel connects to a shaft that rotates a pinion gear. The pinion, in turn, engages a metal bar called a rack. On turning the steering wheel, the pinion rotates and engages the rack. The rack then moves left or right. The rack also connects to the car wheel via tie rods, adjusting the wheel angle relative to the car’s body.
The rack and pinion system is the best for high-performance vehicles because it has minimal backlash and precise gear profiles.
Power Steering System
Power steering systems assist hydraulic or electric mechanisms, reducing the driver’s effort. The two main types are hydraulic power steering (HPS) and electric power steering (EPS).
HPS uses a hydraulic pump driven by the engine, providing pressurized fluid to assist steering. A control valve directs the fluid to either side of a piston attached to the steering rack, helping turn the wheels.
Conversely, the EPS system replaces the hydraulic pump with an electric motor controlled by sensors and an electronic control unit (ECU). As a result, the electric motor provides precise torque assistance. Additionally, it is adaptable to driving conditions and speed.
Recirculating Ball Car Steering System
The recirculating ball car steering system is common in heavy-duty vehicles, trucks, and SUVs because of its robustness. It uses a worm gear that rotates within a housing filled with ball bearings. Turning the steering wheel rotates the worm gear, moving the ball bearings. These bearings engage the sector gear, causing the pitman arm to turn the car’s wheels.
Manufacturing Processes for Auto Steering Components
The manufacturing processes depend highly on the components and the material makeup of the car steering system. Common manufacturing processes include CNC machining, die casting, and injection molding. Additionally, the components are subjected to finishing processes depending on the design and material. However, a common thing to note is the need for precision and accuracy irrespective of the choice of manufacturing process.
CNC Machining
In car steering system manufacturing, CNC machining is a manufacturing and finishing process suitable for several components, including steering gears, shafts, and tie rods. The machining process is highly precise since CNC machines are programmed to cut these profiles to tolerances within micrometers.
Common CNC machining techniques used in manufacturing automotive steering parts are CNC milling and turning. Both processes can achieve the precision required to adhere to the needed dimensions.
Metal Casting
Metal casting and other metal fabrication methods are suitable for making metallic steering system components like blanks for gears, knuckles, and housings. Die casting and sand casting are the most common examples, with advantages such as precision and support for mass production.
These casting techniques produce durable parts with compatible materials like cast iron and aluminum alloy. Additionally, the parts can be subjected to heat treatment to improve their mechanical properties.
Injection Molding
Injection molding is like die casting but for plastic components. It is integral in manufacturing automotive steering components like housings and motor covers. The process involves injecting molten plastic into a CNC-machined mold made from aluminum or steel to create predetermined shapes.
Injection molding processes work with high-strength thermoplastics, their corrosion resistance ensures car steering components function optimally even in harsh conditions.
Using thermoplastics in manufacturing car steering parts is cost-effective. They are also important in modern car steering systems because they reduce noise and vibrations, enhancing the driving experience.
3D Printing
3D printing is more of a prototyping process for developing automotive steering products, and it is used by many automotive manufacturers to verify their ideas.
Additive manufacturing is the ideal option for low-volume prototyping and manufacturing of complex steering components. It offers flexibility in design and can create difficult geometries with traditional methods like CNC machining.
Steering gear prototypes are often 3D printed in nylon or resin to test fit and function before mass production. The rapid turnaround allows for design iterations and functional testing without expensive tooling.
Common Car Steering System Parts and Their Manufacturing Process
To fully understand and apply the manufacturing process in different accessories, this section will introduce the different components, their material makeup, and the suitable manufacturing process.
Steering Wheel
The steering wheel has a metal core, usually steel or aluminum, and an outer covering made of polyurethane, leather, or wood for comfort and aesthetics. There are two manufacturing processes for the components. Die casting and forging for the metal core and injection molding for the outer covering. Moreover, for leather or wood, you can consider manual wrapping
Steering Column and Shaft
The steering shaft is made of high-strength steel, often with a hardened or chrome-plated surface, and the steering column is made of steel or aluminum. The manufacturing process for the steering shaft is CNC machining (turning). Additionally, heat treatment can improve the durability of the part before machining. Roll forming or extrusion (for aluminum) and machining are used for the final shaping of the steering column.
Steering Gear
The steering gear is made of high-strength steel, often carburized for wear resistance, with cast iron or aluminum housing. The manufacturing process includes CNC machining (gear hobbing or shaping) and heat treatment (carburizing). The housings are often made using die casting (for aluminum) or sand casting (for cast iron), followed by machining.
Tie Rods
The tie rod is a steel alloy often coated with zinc or chrome for corrosion resistance. The ball joint is hardened steel and has a plastic or rubber bushing. Manufacturing processes for the components include forging and subsequent machining for the tie rod and steel ball joints and injection molding for the bushings.
Steering Knuckles
Steering knuckles are made from cast iron (for strength and durability) or forged aluminum (for lightweight applications). The manufacturing process for the component depends on the material. For cast iron steering knuckles, it is sand casting. On the other hand, aluminum knuckles undergo forging for an increased strength-to-weight ratio. Both processes then undergo precision machining.
Below is a table summarizing the auto steering components, their material makeup, manufacturing process, and post-processing techniques.
| Auto Steering System | Material | Manufacturing Process |
| Steering Wheel | Steel/Aluminum core, Polyurethane/Leather/Wood | Die casting/forging (core), Injection molding/wrapping (cover) |
| Steering Shaft & Column | High-strength Steel, Aluminum | Roll forming, CNC machining |
| Steering Gear | Steel (teeth), Cast Iron/Aluminum (housing) | Gear hobbing/shaping, Die/sand casting |
| Tie Rods | Steel alloy, Zinc/Chrome coating | Forging, Machining |
| Steering Knuckles | Cast Iron, Forged Aluminum | Sand casting, Forging |
| Power Steering Pump | Cast Aluminum/Iron | Die/sand casting, Machining |
| Electric Motor (EPS) | Aluminum (housing), Copper (windings) | Die casting, Wire winding |
| Control Units & Sensors | Silicon (sensors), PCB with copper, Plastic | Semiconductor fabrication, PCB etching |
| Rack | Steel alloy | Forging, CNC machining |
| Idler Arms | Cast Iron, Forged Steel | Forging, Sand casting |
| Pitman Arm | Forged Steel, Cast Iron | Forging, Machining |
| Drag/Center Link | Steel alloy | Forging, CNC machining |
Considerations for Car Steering System Manufacturing
The steering system plays an important role in vehicle safety and handling. Hence, there is a need for stringent adherence to standards to ensure every component meets the strict dimensional, material, and performance standards.
Dimensional Inspection
Steering system components, like gears, tie rods, and shafts, need tight dimensional tolerances for proper fit and smoother operation. A minor deviation from the intended dimension can result in inadequate or excessive binding, compromising the driving experience.
Common dimensional inspection tools include coordinate measuring machines (CMM), optical comparators, and laser scanning. These tools provide precise measurements of the complex geometries of each part so that they align with its design specifications. For example, you can inspect the profile and spacing of each tooth of gear in a rack-and-pinion system using CMM tools.
Material Testing
The materials used to manufacture a steering component must exhibit the required properties. These depend on the components with gears requiring materials with high tensile strength, hardness, and wear resistance. To ensure this, material testing is needed.
Material testing can be destructive and non-destructive, with common tests being tensile testing, hardness testing, and metallurgical analysis. Tests like the tensile tests can verify the ability of the component to withstand the loads encountered during vehicle operation. Additionally, hardness tests will ensure the component’s surface has the necessary wear and impact resistance.
Fatigue Testing
The car steering system is subjected to continuous stress. Hence, they must be durable to perform optimally throughout the vehicle’s lifespan. To ensure this, fatigue testing is needed, i.e., repeated application of loads to components to simulate real-world conditions and identify potential failure points.
Fatigue testing is applicable in evaluating the wear and tear of the component. Furthermore, it can reveal issues like insulation breakdown, leading to component failure over time.
Functional Testing
Before a steering system is approved for production, it undergoes functional testing to simulate its performance in a vehicle. This testing typically includes steering effort measurements, road simulations, and noise, vibration, and harshness (NVH) evaluations.
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Conclusion
The car steering system combines several components to translate a driver’s input into precise vehicle control and plays a major role in vehicle safety and control. Manufacturing the different components of the system requires considering the design, material choice, and manufacturing process to ensure quality.
What are the three types of steering systems?
The three basic types of car steering systems are rack and pinion, power steering, and recirculating ball steering systems.
What are the requirements of a good steering system?
A good steering system should have an ergonomic interface for the driver. Additionally, it should be precise, smooth, light, and compact.
What factors influence the material selection for steering system components?
Material selection depends on the steering system component and then factors like strength, weight, corrosion resistance, and manufacturing costs.
