Control of ring rolling with variable thickness and curvature

Abstract

Radial-Axial Ring Rolling (RARR) is an industrial forging process for making strong, seamless metal rings. Conventionally, rings are made circular with constant cross-section. In this work we demonstrate a sensing and control strategy to create rings with variable radial wall thickness and variable curvature using standard RARR hardware. This has a number of potentially useful applications but also provides an understanding of how to control these properties for conventional RARR. The sensing uses a calibrated video camera to take a series of images of the ring top surface. Image processing is employed to measure and track the ring material in-situ. The complete state of the ring is represented by the ring thickness and curvature as a function of its volume fraction, which is computed by combining the measurements from the unoccluded areas with estimates of the ring shape elsewhere. Additionally, we present a marking technique for tracking of material as it rotates through the rolling machine, even after significant deformation of the ring has occurred. We show that rings with a wide range of variation in local thickness and curvature can be formed using conventional RARR hardware and a photogrammetric state measurement technique, combined with open-loop scheduling and feedback control of thickness and curvature. Rings with both variable thickness and non-circular shapes have been produced virtually using numerical simulations and in reality using modelling clay as a material to simulate metals at forging temperatures. We demonstrate that this technique extends the range of shapes achievable with standard RARR hardware.

Rolling Eccentric Steel Rings on an Industrial Radial–Axial Ring Rolling Mill

“…The dynamic feed of the mandrel thus creates a ring with a circumferentially variable wall thickness. A method for producing rings with circumferential variable wall thickness was already discussed by Cleaver et al [9] using a model ring rolling mill and model materials like plasticine at room temperature [10]. There were two differences between the used test bench and an industrial ring rolling mill.…”

“…Furthermore, the mandrel and main roll were moved together along the Xaxis to keep the ring in the center of the rolling mill [9]. However, in industrial radialaxial ring rolling mills, there is a notable obstruction in viewing the ring caused by the A method for producing rings with circumferential variable wall thickness was already discussed by Cleaver et al [9] using a model ring rolling mill and model materials like plasticine at room temperature [10]. There were two differences between the used test bench and an industrial ring rolling mill.…”