Innovations in metal forming

Folding-shearing concept

Folding-shearing. Arising from our work on the mechanics of spinning and our analysis of scrap rates in sheet-metal production, we invented the folding-shearing process to deliver the same geometries as deep-drawing, but without a blank-holder, so leading to much less scrap. 

Cambridge flexible metal spinning machine

Metal spinning. We invented a novel approach to mandrel-free spinning, replacing the conventional solid mandrel with three computer-controlled rollers, and have explored different approaches to tool-path design via  modelling, control and characterising the choices of skilled craftspeople.

Cambridge incremental ring rolling machine

Incremental ring rolling. We have explored various designs for flexible computer-controlled ring rolling processes, invented our own approach with moveable rollers completely surrounding the ring cross-section, and characterised its performance for various applications.

Cambridge incremental sheet forming machine

Incremental sheet forming. We designed and built our own 3-axis CNC machine for this process with a 3D camera to allow feedback control. We discovered that it created through-thickness shearing, that this increases sheet forming limits, and we then invented other processes to exploit this property. 

Hand-formed copper beaker

Novel process design. Drawing inspiration from the history and craft of metal forming, back to earliest times, we have developed several approaches to characterising and automating the design of novel processes.

Cold strip rolling mill and control

Closed-loop control of metal forming. Mainly in collaboration with Professor Stephen Duncan in Oxford, we have developed underlying theory and models and applied closed-loop control to flat metal rolling, incremental sheet forming and spinning processes. 

Variable-section I-beam

Other. We have developed work in contact mechanics related to metal forming processes, and explored several other novel processes including variable section rolling, nested blanking and in-plane transformation of sheet metal blanks.

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Open up the links below for more information and our relevant publications on each topic.

Main contributions:

Motivated by our top-down analysis of global use of steel, in which we identified that half of all sheet steel is cut off during manufacture, we invented the folding-shearing process to form flat sheets into three-dimensional shells, following a first folding-stage. The folded sheet has much more stiffness than the flat sheet, so can be deformed without need of a blankholder.

We have subsequently explored the mechanics and forming limits of the process, and it is the basis of one of our startup companies, DeepForm Ltd.

We subsequently extended the process with new forms of folded shapes, and to produce axisymmetric cups from hexagonal blanks.

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Main contributions:

By examining the contact between the workpiece in metal spinning and the mandrel that defines product geometry, Omer Music showed that the mandrel could be replaced by just three controllable rollers.  He designed a machine to implement this process.

Using this machine, James Polyblank explored the application of closed-loop control to metal spinning, both during operation and for toolpath planning. 

The metal spinning process is highly non-linear which limits the use of closed-loop approaches, however skilled craftspeople are able to control the process and make unfamiliar shapes with high success, even on thier first attempt. Iacopo Russo therefore ran a series of carefully controlled experiments, inviting highly experienced craftspeople to operate our spinning machine via a haptic interface, in order to characterise their understanding of how to design and plan successful tool paths.

Using the flexibility of our machine, Iacopo Russo also explored the value of controlling the process to create asymmetric parts and to emulate the mechanics of the craft process of "raising", in which the outer working roller remains a constant (short) distance away from an adjacent inner support roller.

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Main contributions:

We began working on incremental ring rolling in collaboration with Professor Erman Tekkaya (then at METU in Ankara) and Professor Reiner Kopp (at IBF, Aachen) as a result of which Tim Stanistreet designed a built a highly flexible and controllable model ring-rolling machine working on plasticine rings with which we explored variable wall thickness rolling.

Chris Cleaver went on to develop a full-scale flexible ring-rolling machine, with controllable rollers around all four faces of a single cross-section of the roller, and a cage of support rollers to maintain circularity and flatness.

He used this machine to explore the influence of process design on curvature and, with Johannes Lohmar visiting us from Aachen, temperature distributions during the process.

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Main contributions:

Kathryn Jackson commissioned our custom built machine, applied it to composite sheets, and used a novel experimental approach to reveal that the sliding motion of the tool on one surface of the workpiece in this process leads to a strong through-thickness shearing, contradicting the usual assumptions of sheet-metal forming analysis.

Dan Shouler demonstrated theoretically that this additional shearing enhances sheet metal formability as predicted by forming limit diagrams, invented two novel tests to help characterise the effects of shear, and worked on a novel paddle-forming process aiming specifically to induce as much through-thickness shear as possible to create dramatic new shapes.

We have also explored the use of closed-loop control and novel partial cut-outs in the blanks to improve forming accuracy, and contributed to a number of overview papers in the area.

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Main contributions:

Our interest in novel metal forming processes stems from our first contact with the incremental sheet forming process, which stimulated Julian Allwood to tour the most innovative forming laboratories in Japan with Hiroshi Utsunomiya and survey their inventions.

We have subsequently sought new means to invent processes,  through structured searches (using Zwicky's morphological maps), through exploration of historical craft processes and by exploring the inverse process of "un-forming" a finished part back to its original blank.

As part of this work we have been involved in various international surveys of emerging technologies.

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Main contributions:

Julian Allwood's PhD developed an approximate model of how actuators in rolling mills change the residual stresses in the rollled sheet, allowing application of the theories of "cross-directional control" developed by Professor Stephen Duncan both for on-line control and for actuator setup in commercial flat rolling.

Out of this work, we explored the use of "spatial impulse pulses" created by an incremental motion of a mobile tool in a flexible rolling process - both for designing tool paths and for designing more controllable processes.

We have also contributed to several survey papers around closed-loop control in metal forming.

xxx text on flat metal rolling

xxx text on contact mechanics

Publications on closed-loop control:

Publications on flat metal rolling:

Publications on contact mechanics:

Main contributions:

As part of his work on fast modelling of flat strip rolling, Julian Allwood found a new efficient algorithm to solve a particular class of problems in contact mechanics.

Mark Carruth developed a novel process for rolling variable cross-section I-beams by new control of existing equipment, and also explored the in-plane deformation of flat sheet blanks.

Iain Flint examined the opportunity to reduce sheet metal blanking losses by nesting different parts in the same blanking dies.

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