What is runout accuracy?

Runout accuracy describes how precisely a rotationally symmetric workpiece rotates about its axis without exhibiting lateral deviations. It is crucial for the function and service life of mechanical components. This level of precision is achieved in particular through advanced grinding techniques and high-quality CNC machines. Inaccurate runout causes a component to “wobble.” In practical terms, this means that unwanted forces are applied to bearings and similar components, leading to increased wear.

Runout accuracy in detail

During manufacturing, runout accuracy plays a central role in the functionality and service life of mechanical components and machine elements. It ensures that a rotationally symmetric workpiece does not exhibit lateral deviations or irregularities during rotation. This precision is essential for minimizing vibrations, noise, and excessive wear that can be caused by inaccurate runout.

Good runout accuracy contributes significantly to improving the overall performance and efficiency of machines. For example, in the automotive industry or shipbuilding, crankshafts must be manufactured with high runout accuracy to ensure smooth rotational motion of the engine. Deviations can result in uneven power transmission, increased friction, and ultimately engine damage. Runout accuracy is also of great importance in the manufacture of precision machines such as machine tools or medical devices. It enables exact machining of workpieces and directly influences the quality of the final product. Furthermore, it plays a vital role in the aerospace industry, where components are exposed to extreme loads and the highest levels of precision are required.

How can runout accuracy be measured?

Runout accuracy can be verified using various measurement methods that ensure a workpiece exhibits no lateral deviations during rotation. For example, cylindrical grinding machines are equipped with highly precise measurement systems. High-accuracy probing systems are used for data acquisition, which, in combination with the machine’s linear and rotary encoders, provide precise measurement data. These systems make it possible to measure even very large diameters with an absolute accuracy of ±15 µm and a repeatability of ±5 µm. Using these measurement systems, various geometric characteristics such as runout, roundness, concentricity, and cylindricity can be inspected. In addition, specialized companies have mobile measuring devices that are required for highly precise components.

Another measurement system captures the geometric data of rollers that are necessary for controlling the roller grinding process. It measures the roller with 360 measurement points per revolution with extremely high accuracy and performs measurements both before and during the grinding process. The measuring beam is mounted on the machine bed slide and is equipped with two measuring arms that ensure precise data acquisition. In addition, modern CNC machines are often equipped with integrated measuring systems that continuously monitor runout accuracy during machining. This also makes it possible to apply necessary corrections in real time. However, it is important not to rely on a single method. To ensure precise runout accuracy, manual measurements should also be carried out. If the CNC machine delivers incorrect values, this approach provides a reliable means of verification.

By combining both measurement approaches, it is ensured that the workpiece is machined with high precision and is subsequently capable of performing demanding tasks.

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