Analysis of a centerless control scheme for profiles of large-sized shells in the process of their shaping

Shilin A.N., Atamaniuk R.G., Besedin E.Yu., Pastukhov M.R. Analysis of a centerless control scheme for profiles of large-sized shells in the process of their shaping. Scientific and Technical Journal of Information Technologies, Mechanics and Optics, 2026, vol. 26, no. 2, pp. 436–441 (in Russian). doi: 10.17586/2226-1494-2026-26-2-436-441

Control of the geometric parameters of large-sized shells — the basic parts of energy and oil and gas equipment — is a critically important task that determines the quality and productivity of their assembly. Existing methods based on measuring the elements of a circle have significant methodological errors and require precise centering, which is difficult for large parts with deviations from the round shape, primarily ovality. Development and metrological analysis of a centerless method for monitoring diameter and deviation from roundness, free from methodological errors and allowing improving the accuracy and efficiency of measurements in production conditions has been proposed. The method is based on the fundamental geometric property of a circle, according to which its diameter is equal to the maximum distance between two points on the inner surface. The method is implemented in the form of an optoelectronic device containing a laser rangefinder mounted on a carriage moving along the contour of the shell. The rangefinder performs an angular scan of the opposite section of the inner surface, and the control unit captures an array of distances and determines the diameter as the maximum value in the section. The design of the device ensures compliance with the principles of Abbe and inversion which makes the measurement scheme invariant to positioning errors. To verify the method, a computer simulation of the measurement process was performed for shells with an oval cross-section shape. It is established that the instrumental error of the laser rangefinder (± 1 mm) is the main one and does not exceed the established technological tolerance of 1 % of the nominal diameter. Metrological analysis on oval cross-section models has shown that the error in determining the diameter functionally depends on the amount of ovality, however, within the permissible values of ovality, the requirements of the technological process are met. The developed method and device make it possible to directly control, with high accuracy and without the requirement of centering, the diameter and deviation from the roundness of the inner surface of large shells. The main advantages of the proposed solution are invariance, autonomy, and simplicity of technical implementation. The device can be used for postoperative and acceptance control in nuclear, energy, and oil and gas engineering as well as in other industries to reduce the complexity of assembly and ensure the quality of parts joining.

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