Injection moulding: The key to protecting the tunnels of Norway?

KraussMaffei are working with Norwegian company Oldroyd to waterproof the country’s vast tunnel networks through injection moulding practices, using recycled sea plastics.

Tunnels are an everyday phenomenon in Scandinavia due to the structure of the fjords. Norway alone has over 900 tunnels, and the world's longest road tunnel is also located there. The enclosures for the traffic are complex because of sophisticated membrane system lies behind the pipes visible to the driver. This system prevents water penetrating the soil causing damage to the concrete.

Oldroyd is a company that specialises in the area of waterproofing against rain, according to the company it holds over 90% of the market share in the Nordic countries. 

Originally concentrating on film extrusion, founder John Oldroyd Cheetham also accessed the injection moulding technology with the help of KraussMaffei and now operates three hydraulic CX 160-750 with a clamping force of 1600 kN.  

So-called spacers, curved products with grid structure, which create a distance between rock and membrane, are produced on these machines in a cycle time of roughly 15 seconds. They weigh approximately 150 grams, whereby there are around 20 different models, varying in diameter and height.

100% sea plastics

300,000 to 400,000 of the spacers are required for one tunnel alone. For these quantities, the company claims it pays off ecologically to use recycled materials. Oldroyd claims it uses 100% sea plastics, consisting of roughly half PP and half PE. The remnants of broken fishing nets and plastic ropes are collected on the coast of Norway by specialist companies and crushed, washed, and regranulated. 

Kraussaffei claims the APCplus machine feature is very helpful for the changing material compositions and resulting viscosity fluctuations. It ensures a very constant shot weight by adapting the switchover point and the pressure level from shot to shot.

Safe "ghost shifts" at the weekend

Efficient automation is required in order to be able to produce plastic products competitively in Europe. All Oldroyd machines are therefore equipped with oversized LRX robots from KraussMaffei. With their very long vertical axle, these large quantities of manufactured products can be stacked up – starting with a ground-level pallet up to a height of two meters. In the case of the tunnel spacers, according to the company this volume covers the production of one (unmanned) weekend.

2-component project with TPE 

A new CX with two-component equipment will soon go into operation at Oldroyd: a 2-component platen, called RoadStar, which is secured on the steel rods that connect the concrete wall and the rock layer. Up to now these platens were made of metal and corroded accordingly, which is why maintenance is required and a replacement after roughly 50 years. Whereas the RoadStars were estimated to have a service life of 120 years according to special aging tests. 

The RoadStar has been tested by Oldroyd customers and according to Kraussmaffei has also widely accepted because the integrated TPE layer has a sealing effect, while the other side (made of PE) is impact resistant.