VOL. 25 March ISSUE YEAR 2024

Standards Forum

in Vol. 25 - March Issue - Year 2024
Robots and Their Relationship with Shot Peening, Coverage, and Intensity Curves
Christian Tyroll

Christian Tyroll

The integration of robotics into the process of shot peening represents a significant advancement in the field of material engineering and manufacturing. The introduction of robotics has greatly enhanced the precision, efficiency, and repeatability of this process, particularly in achieving specific coverage requirements and managing intensity curves. Not only is the reliable application of this safety-critical process enhanced in terms of repeatability and accuracy, but evidence of the process in terms of parameter, media, and movement control is available for download on the completion of the process. This then can be included in the quality records for the manufacture of that part by order, batch and even serial number identification. In other words, watertight traceability, combined with an accurate process record.

Robots, with their high degree Robots, with their high degree of flexibility and precision, have become indispensable in modern shot peening operations. They can be programmed to control the shot peening nozzle or lance, ensuring uniform coverage and consistent application of shot peening intensity across the surface of the part being treated. The use of robots allows for the automation of the shot peening process, which can significantly reduce human error, increase production rates, and produce a higher quality surface finish. Increased production capacity with no deterioration in the quality of the process is a significant development in improving production rates. This is an invaluable development to meet the ever-increasing aircraft build rates planned for the next few years.

This development is made possible by precise control of the process, especially in terms of ‘coverage’. Coverage refers to the percentage of the surface that has been impacted by the shot peening process. It is a critical parameter in shot peening, as inadequate coverage can lead to uneven stress distribution and potentially premature failure of the part. Achieving 100% coverage or more ensures that the entire surface is uniformly treated, which is essential for the effectiveness of the process. Anything more than the specified coverage will result in a loss of production efficiency, even if the coverage is within an allowed range as per the specification. In most cases, exceeding the specified coverage will result in a non-conforming part.  

Robots excel in achieving precise coverage requirements due to their ability to follow complex paths with high repeatability. By programming the robot to move the shot peening nozzle in predefined patterns, processors can ensure that every part of the surface receives the correct amount of shot peening, regardless of the complexity of the component geometry. This is particularly beneficial for components with irregular shapes or hard-to-reach areas, where manual shot peening would be difficult and less reliable.

The intensity of shot peening is measured by the Almen intensity, which quantifies the kinetic energy of the shots impacting the surface. The intensity is a crucial factor in determining the depth and distribution of residual compressive stresses induced by the peening process. It is typically represented by intensity curves, which plot the Almen intensity against the coverage percentage. Here, robots again play a pivotal role in managing the intensity curves during the shot peening process. Through precise control of the nozzle speed, distance from the surface, and the angle of impact, robots can adjust the intensity of shot peening to match the specific requirements of each part. This level of control is vital for achieving the desired material properties, as different applications may require different intensity levels and stress profiles. Robots can be equipped with sensors and feedback systems that monitor the intensity in real time and adjust the peening parameters accordingly. This capability ensures that the intensity remains within the desired range throughout the process, resulting in more consistent and predictable outcomes.

The integration of robotics into shot peening operations offers several advantages over traditional manual methods, some of which are listed below.

Precision and Repeatability: Robots can maintain the shot peening intensity and coverage, which is crucial for achieving the specified residual compressive stresses in the surface of the treated parts.

Flexibility: Robots can maintain a program library, allowing a variety of parts to pass through the shot peening shop without having to redevelope the process. Also, Almen shot peening programs can be linked to the production program, making them highly adaptable to various manufacturing situations.

Efficiency: Automation of the shot peening process can significantly increase throughput and reduce the time required for peening operations.

Safety: Using robots for shot peening minimizes the exposure of human workers to potentially hazardous conditions, such as exposure to high-velocity shots and noise.


The relationship between shot peening and robotics is a testament to the continuous evolution of manufacturing technologies. Robots have not only increased the efficiency and precision of the shot peening process but have also made it possible to achieve specific coverage requirements and manage intensity curves with unprecedented control. As robotic technology continues to advance, we can expect further enhancements in the shot peening process.

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MFN Contributing Editor

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