Unique metal products using incremental sheet forming
Sheet metal is needed for various purposes in today’s world and enormous numbers of them are produced in large rolling mills. The sheets are mainly formed using traditional deep drawing and stretch forming techniques. These techniques require expensive equipment and tooling, so large numbers of the same product need to be manufactured in order for the production to be profitable. The production process begins with the design of the tooling and with all the different phases the process can last several months.
But what if a prototype, a unique object or a small batch is needed as quickly as possible? This is where the new incremental sheet forming technology steps in. The technology was originally developed in Japan for the needs of the automotive industry. The Department of Materials Science and Engineering has performed extensive research on the properties and usage possibilities of materials formed using incremental sheet forming. Arto Komulainen studied incremental sheet forming in his master's thesis. One of the objectives of his study was to examine how the method could be applied to manufacturing interior design elements.
“Many Finnish students have probably made a sauna ladle during crafts lessons at school by hammering a round metal plate,” says researcher Tuomas Katajarinne, M.Sc. (Tech.) from the Aalto University Department of Materials Science and Engineering.
“We don’t use a hammer, but an ordinary industrial robot,” he explains and shows how the tool controlled by CAM software slides along the surface of the sheet and moulds it into the desired form, this time into a bowl. In “positive” incremental forming, the form is created above the surface of the sheet and in “negative” incremental forming it is created below the surface of the sheet. Lubrication is used for reducing friction and improving surface quality.
Instead of a forming tool, the robot could use any other tool, such as a ball-point pen, with an accuracy of less than a millimetre. At best, the production process from design to ready product can be performed in less than an hour. The actual forming can be carried out using a blank holder and a simple mould, or in some cases even without a mould, saving time and costs.
Compared to traditional methods, metal formed using incremental sheet forming stretches more without being damaged. It can also be formed in new ways which enables the production of a wider variety of products. The flexibility of the method provides professionals, such as interior designers and artists, with new opportunities to use metal in their work.
“The Department of Materials Science and Engineering is exploring what incremental sheet forming can be used for, but the parties with the financial resources will decide what it will actually be used for,” Katajarinne states realistically.
He sees many opportunities in the method. Hospitals could start using formed copper as wall surfaces and interior design elements since copper has antibacterial properties. Metal façade elements could freshen up the appearance of dreary, suburban concrete blocks of flats. Such elements would also act as insulation and protect buildings from weather conditions.
“Nevertheless, there is a lot of work to do before incremental sheet forming can conquer the world,” Katajarinne says.
He explains that researchers are still not unanimous on the deformation mechanisms that take place during incremental sheet forming. It is particularly important to explore how incrementally formed parts behave in critical environments. If we want incrementally formed components to be used in the wings of aeroplanes we must first prove that their properties are at least as good as those of the components used today.
Researcher Tuomas Katajarinne
School of Chemical Technology
Department of Materials Science and Engineering