Ring rolling is an established metal forming process for high strength metal rings used in industrial sectors such as aerospace, electricity generation and oil and gas extraction. Currently it is not possible to produce shaped rings without dedicated tooling for each part, often leading to wasted material, energy and machining cost. Work on Ring Rolling within the Use Less group has focused on ways to produce a wider range of ring shapes with a single 'flexible' tool set.
Flexible Ring Rolling Machine
Chis Cleaver has developed prototype 12-axis machine with a novel tooling arrangement for rolling of shaped rings. Rings of up to 1m diameter are cold rolled in soft aluminium and lead with a variety of inner and outer radial profiles. The project builds on experiments with an earlier flexible ring rolling machine for rolling modelling clay and finite element simulations of the process. (Figure)
In addition, a novel sensing technique has been developed under the closed loop control of metal forming processes project. This has enabled production of rings with variable wall thickness and curvature around the circumference for the first time.
Precision guided flexible forming
This project examines the closed-loop control of geometry and properties for high value metal component manufacture.The aim of the project is to develop world-leading fundamental understanding of flexible metal forming technology, while identifying and demonstrating its commercial value.
Manufacturing involves only three types of processes - adding, changing or removing material. 'Metal Bashing' - changing the shape of metal components without removal or additions - is easily over-looked or even derided as the 'ugly duckling' of manufacturing technology, yet continues to be central to UK manufacturing, and always will be: jet engines, medical scanners, cars, high-rise offices and contemporary industrial equipment all depend on metal forming, both to define component geometries and to create the properties such as strength and toughness which determine product performance.
"Globally we use 25 times more steel than any other metal - in the UK our consumption drives production of 500kg of steel per person per year - and every steel product has been shaped by several metal forming processes."
Despite great excitement over additive processes such as 3D printing, metal forming will never be replaced, because the high-performance properties of steel, wrought aluminium and other key metals can only be developed as a result of careful control of deformation and temperature over time. Globally we use 25 times more steel than any other metal - in the UK our consumption drives production of 500kg of steel per person per year - and every steel product has been shaped by several metal forming processes. Inevitably, metal forming processes are therefore central to the production of a third of all manufactured exports from the UK which are in total worth over £75bn. However, the tools required for forming metal components are custom-made for each application at great cost, so metal forming is often expensive unless used in mass production, yet the drivers for development of future high-value UK manufacturing require increased flexibility and smaller batch sizes without sacrificing either the accuracy or properties of metal parts.
In the past twenty years, several research labs around the world have responded to this challenge and explored the design and development of novel flexible metal forming equipment. However these processes have largely failed to move from the lab into industrial use, due to a lack of precision and a failure to guarantee product microstructure and properties. Recent developments in sensors, actuators, control theory and mathematical modelling suggest that both problems could potentially be overcome by use of closed-loop control, and in work leading to this proposal, we have demonstrated the first online use of a stereo-vision camera in a flexible sheet metal forming process to provide the feedback needed to control the final shape of the sheet precisely. This has shown us that closed-loop control of forming is possible and valuable, but involves a trade-off between product quality, process flexibility and production speed.
This project brings together four disciplines, previously un-connected in the area of flexible forming, to explore this trade-off and develop the key knowledge underpinning future development of commercially valuable flexible metal forming equipment: mechanical design of novel equipment; control-engineering in both time and space; materials science of metal forming; fast mathematical process modelling. We aim to link design, metallurgy and modelling to control engineering, in order to identify and demonstrate the opportunity for developing and applying flexible forming.
Model Flexible Ring Rolling
This machine has 11 degrees of freedom and was, at the time, probably the world’s most flexible ring rolling machine. It deforms plasticene rings of around 120mm diameter through two roll bites, each of which comprises an outer forming roll, and two other rolls which can move with two degrees of freedom each relative to the forming roll. The two forming rolls move outwards together, so the centre of the deforming ring remains stationary. The design of the machine is described here, and it has been built to explore a wide range of machine configurations with the aim of achieving nearer net shape production of low volume high value rings.