Polymer Injection Forming Breakthrough from Corus

15 April 2004

Corus has made a major step in making steel products that are formed and bonded with polymers in a single process.

The technical breakthrough, known as Polymer Injection Forming (PIF) is expected to lead to a new era of innovative consumer and other products.

The breakthrough will be licensed to designers and manufacturers for the production of products as diverse as mobile phones, consumer electronics, light switches, IT equipment, kitchen appliances, cutlery, automotive components and garden furniture.

Steel coated with a thin layer of polymer is not new, but Polymer Injection Forming (PIF) shapes the two materials in one step and bonds a thicker layer of polymer to steel, thus reducing several production and assembly stages to just one. As existing plastic injection moulding equipment can be used, investment in new machinery is not necessary.

Corus’ technology centre in the Netherlands has spent three years developing the technology. The result is products with the strength of metal but with the flexibility and freedom of form of plastic. The technology is expected to appeal to manufacturers of, say, electronics consumer goods requiring the electromagnetic properties and the look and feel of steel, but also the flowing curves of plastic. It therefore has the potential to add value to the product and to increase market share while at the same time reducing overall manufacturing costs.

The polymer can protect the steel’s sharp edges and is strong enough to be used as a hinge, spring, slide or lock. The polymer also aids corrosion prevention and product safety.

Polymer Injection Forming allows the use of conventional injection moulding machines with minimal extra investment. A metal sheet is inserted between the two mould halves. When the mould closes, the metal sheet is carefully cut to the desired blank size. During the same operation the blank is shaped. This can be done by deep drawing or by bending the steel into the basic product shape. When the mould is completely closed, the polymer is injected into the remaining cavity under high pressure. When the molten polymer makes contact with the metal sheet the two materials are permanently bonded. The pressure of the injected polymer can also be used to carry out a second deformation step, such as embossing a logo or a texture. When the mould opens, the finished product can be ejected from the mould and the cycle is repeated.
Sink marks - due to the properties of the metal sheet, annoying sink marks are no longer visible. With Polymer Injection Forming, less attention needs to be paid to preventing the visual disturbances caused by variations in polymer thickness.
Product safety - with the right design, the injected polymer flows smoothly around the sharp edges of the metal sheet, making the product safe to use, and easy to handle.

Polymer Injection Forming is claimed to lead to considerable cost reduction, because of the integrated production and assembly stages. Due to the intrinsic stiffness of the metal sheet, less polymer volume is needed. For example, PIF comprising 1.0mm of polymer and 0.2mm of metal equates in cost to 1.8mm of polymer; in weight, it equates to 2.6mm of polymer and in strength, to 3.8mm of polymer.

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