Real-time measurement of ring-rolling geometry using low-cost hardware

Abstract

Ring-rolling is an industrial forming process to produce high-strength metal rings up to 6m diameter. Thickwalled cylindrical workpieces of material, typically metallic alloys, are compressed between two or more internal and external rollers and rotated until a target geometry, often outer diameter, is achieved. The process is inherently unstable and the process is often constrained and/or controlled to improve its stability. This paper presents an image processing algorithm for the measurement of ring geometry through photogrammetry in real-time. These measurements will form part of the feedback control system for a ring-rolling process. An off-the-shelf USB webcam is used to capture images of the ring during forming and the scene is controlled to maximise contrast and minimise occlusions of the ring. The image processing tasks include object identification, edge detection, outlier rejection and distortion rectification. The process has been implemented on a desktopscale forming machine and has been shown to work at rates suitable for control the ring-rolling process using feedback.

Control of ring rolling with variable thickness and curvature

“…In addition to measuring the overall shape of the ring, it is also necessary to track the movement of the ring material relative to the tools. The relative speed of the forming roll Experimental setup for clay rolling trials, including video camera for recording the top surface of the ring [6] and the ring material are difficult to determine accurately due to changing contact conditions that lead to variable amounts of slipping. Therefore, an optical tracking strategy has been adopted.…”

“…The use of a camera measurement system in this work enables the control of ring curvature and radial thickness along its circumference. Recent developments in sensing in ring rolling using photogrammetry have shown that it is a practical observation technique [4,6,15,16]. [6] showed that the function of the guide rolls could be replaced by controlling the relative driving speeds of the axial and forming rolls to keep the ring centred.…”

“…Such an increase in production flexibility significantly extends the applicability of ring rolling for products, which are produced in small batches. The current work aims at extending the flexibility of ring rolling processes, through simultaneous control of variable radial thickness [6] and variable curvature [5]. It will be shown that creating rings with both variable radial thickness and variable curvature is possible using conventional rolling hardware with additional sensing and control.…”

Ring rolling with variable wall thickness

“…Measurement is achieved by a calibrated optical camera mounted above the ring, as described in [12]. It measures thickness around the circumference by standard edge detection techniques and infers the location of the current ring centre and midline in the camera's frame of reference.…”

Establishment of cellular automata image model and its application in image dimension measurement

“…In the last 20 years, the image measurement technology has developed rapidly at home and abroad and has been widely used in the measurement of geometric parameters of parts [26][27][28][29][30]. The micro-size measurement and appearance detection of precision parts used are aerial remote sensing image, light wave interferogram, and the analysis of stress and strain field state distribution map, and so on.…”