06 Folded Sheets

Diploma project

Coming from this experience at my internship, I wanted to work more with steel, especially steel sheet. It intrigued me to shape this material from a flat plane into a 3D body.
Having made this material choice I first went on to research how steel sheet is made.

Origin

Europe is home to several major steel factories, with Germany ranking among the world’s top steel producers. The country has 25 steel manufacturers, 8 of which operate integrated steel mills. One of the largest and most controversial sites is ThyssenKrupp Steel in Duisburg—a historically significant location in Germany’s industrialization that has regained importance due to shifting global supply chains and Germany’s evolving energy policy.

The steel industry is a backbone of the German economy. It supplies key sectors like automotive and mechanical engineering, which together account for two out of three industrial jobs in the country. This explains why the steel industry holds such a vital role, and why job cuts in steel plants are so widely discussed in the media.

But where do the raw materials come from? Germany no longer has any active iron ore mines of its own.

Location of germanys biggest steel mill.

Route

Thyssenkrupp is not very transparent about the origin of its raw materials. However, an official company report from 2008 reveals some insights. According to the report, around two-thirds of the company's iron ore comes from the Carajás mine in Brazil—a massive open-pit mine located in the heart of the Amazon rainforest. The ore is transported by rail to the port of São Luís, then shipped across the Atlantic by large cargo vessels—such as the now-decommissioned MS Berge Stahl. From there, it reaches the port of Rotterdam (Europoort), and is then moved inland by river barges up the Rhine to the port of Duisburg.

Kiruna, a mining town located above the Arctic Circle in Sweden, is home to the largest iron ore mine in Europe. The Kiruna mine played a significant role during World War II and continues to supply large quantities of iron ore, including to blast furnaces in Germany. It currently produces around 26 million tons of raw ore annually—a number expected to rise as new deposits have been discovered. The mine is expanding so extensively that the city above it is being physically relocated to avoid risks from ongoing underground blasting. The ore is transported by rail to the ports of Narvik or Luleå, where it is shipped to markets around the world.

Export route from Kiruna iron ore mine.

MS Berge Stahl

Export route from carajas iron ore mine in Brazil.

Germanys freight transport routes.

Iron ore freight ship seen on Naval tracker.

Iron ore at rotterdam europoort

iron ore at rotterdam europoort

Steel production

To better understand how steel sheet is made I first had to understand how steel is made from iron ore. Therefore I visited the old steel mill in saarbrücken. As a visitor it was only possible to get a indepth tour of the old decomissioned factory, which is right next to the new one. The benefit of this was, we could get real close and see all steps of the production process.

Steel sheet production starts with iron ore and coal. The coal is turned into coke, and the iron ore is heated to remove impurities. In a blast furnace, the coke burns and melts the iron ore into liquid iron. This iron is then refined into steel in an oxygen furnace.

The steel is cast into slabs and rolled while hot to make it thinner. It’s rolled again when cold to achieve the final thickness and smoothness. Finally, the steel sheets are coated to prevent rust and improve durability.

The result is strong, high-quality steel sheets ready for use in construction, cars, and other industries.

Steel slab.

Steel sheet roll.

Cut Steel Sheet formats.

Blast furnace where the iron ore is melted.

Iron ore that was used at Saarstahl.

Hot steel seen at the new factory.

Preservation

Iron materials, except for stainless steel react with moist air to form rust. Rust is a porous layer of yellow to reddish - brown iron hydroxide. Corrosion can weaken the material over time. To protect iron and steel surfaces and enhance their appearance, various surface treatment options have developed.

How was steel preserved before galvanization?

One that has been around for a very long time ist steel blackening.

The process of blackening iron was described as early as the 12th century by the Benedictine monk Theophilus Presbyter. He detailed a method involving the burning of linseed oil onto copper sheets, which were then cleaned and fire-gilded. This technique, known by names like "Braunfirnis," "Firnisbrand," or "oil browning," was sometimes used as an alternative to enamel.

For the rest of the duration of my diploma I contuniously worked on refining this technique. Testing different steel surfaces, like polishing, grinding and sandblasting and how they react to the blackeing technique.

Paper folding

Next to preservation I was looking for a way how to shape steel sheet.

As a child, I rebuilt planes and cars I saw in movies using just folded paper and tape. Unlike store-bought toys like LEGO, paper gave me endless freedom to create any shape I imagined.

From this experience, I tried to draw inspiration—not limiting myself to what can be done in a
CAD computer program but experimenting hands-on with how a sheet of paper behaves when
folded in various ways.

To avoid using heavy industrial machines to form steel sheets, I explored different paper-folding techniques. My goal was to develop a kind of folding language I could later apply to steel, allowing me to work intuitively and efficiently.

After testing many shapes, I focused on a few that worked well and refined them further, building 1:10 scale models to better understand and improve the designs.

By using only rectangular sheets, I could reduce material waste and improve recyclability. Folded and bent shapes often result in surprisingly strong and stable objects.

Making the paper models was fun, and soon my workspace was full of small 1:10 models. I discarded the ones I didnt liked and continued to make improvements on the ones that I liked. The goal was to create interesting shaped, not specific objects.
Certain shapes had their own properties, and sometimes the shape made way for a usecase.

There was one folding technique that stood out to me. When a slid is cut into a sheet, two surfaces are created next to each other. When sliding these over each other, the rest of the surface tensions into a soft round shape.
This technique results in very interesting concave shapes. reminding of shells, bowls and seats.

Here are the objects which intrigued me the most. These objects are shown in the exhibition therefore I will only show you the paper models, the steel sheet objects are shown later at ZKM Pavillion.

Pendant Lamp

Pendant Lamp uses inward folds to tension the flat sheet into a convex shape. The inward folds hold tight a steel wire, used to hang the obejct into the air. Recessed LEDs light the inside of the Lamp, showcasing the volume created by tension.

Couch Table

The couch table visualizes the technique from “Shell” in a bigger scale. Four folds create feet for the table to stand on. The folds also create a flat tensioned plane on top.

Shell

This sculptural object playfully uses the act of cutting into the sheet and moving the resulting flaps over each other. A tensioned 3D Volume creates. Combining round and rectangular lines.

Folded Chair

The folded Chair uses tension to wrap sheet steel around a steel frame. The resulting curvature creates a comftable seating shell. While being ridgid enough to hold the persons weight it also gives enough stretchability to lean back.
The seat is not permanently attached to the frame, it relies on tension to hold together.

Bench

The bench is a blend of two steel sheet folding techniques. The top surface is expertly brake-formed, creating three distinct folds that not only ensure a comfortable seating area but also allow the rectangular seating surface to curve gracefully towards the ground. This design is further enhanced by a strategic cut and slide method, which introduces tension to the bench's feet and contributes to its rounded base.

A central crease in the seating surface adds stability and serves as a water drainage channel on both sides. The rounded shape allows the bench to rest on the ground only at its two sides, with the front and back elegantly curving upwards. This design lends the entire structure a lighter, more dynamic feel, making it both functional and aesthetically pleasing.

Plate

The "Frosch" is a phenomenon in sheet metal processing where tension is created in the material through deformation. By applying force against this tension, the sheet metal "springs" back with an audible snap into an opposite shape. The plate series utilizes this effect to create a concave form that serves as a plate or bowl.

After creating 1:10 scale models, the next logical step was to build 1:1 cardboard models. At this stage, it became clear that the tension created by the folds made the shapes surprisingly stable.

In fact, the bench prototype was so sturdy that someone could sit on it.
Based on this success, I decided to use thinner steel sheet for the final objects than I initially calculated.

All of these objects were translated into 2D cut drawings.

But surely the steel sheet would be way harder to fold. Therefore clear tests had to be made where to apply force and where to pull exactly to create the shape I was looking for.
With the bigger objects, sometimes it was enough to bend it with hands and clamp it down to weld and secure it in place.
bigger surfaces to bend also means more leverage which makes ropes and wrenches unnecessary. For the smaller objects like the pendant lamp it was necessary to use steel wire and wrenches to archieve the final shape.

Therefore each object needed its own steps for manufacturing.

A videotaped process of the bending can also be seen later in the exhibition.

Cardboard model with rope tensioning.

Steel sheet execution of the prevoius test.

The last step was ordering the 2D drawings.
I lasercutted all the objects onto 1mm raw steel sheet.

Bending was not easy, and while I had tools, ratchets, clamps and the hfg workshop, there was always need for helping hands.

Therefore before heading over to the exhibition to see the results I want to thank my amazing friends, helpers and family for supporting me during this time!