Construction sites often involve tonnes of steel, heavy machinery and robust structures. It may seem surprising at first that a two-part plastic component, of all things, could fulfil a crucial safety function in such an environment. Yet this is precisely what a recent project by HAMCO demonstrates: spherical polyurethane barrier elements, which are used, for example, as reversing barriers for excavators.
This application impressively demonstrates just how versatile injection-moulded plastic components are today – even in environments that, at first glance, appear to be dominated by heavy-duty vehicles.
A simple task, high standards
The function of the boundary markers is as simple as it is effective: one or more plastic balls are attached to a cord, which is then stretched across the construction site at a specified height. If an excavator reverses and the cab reaches the taut line, the balls come into contact with the cable. This gives the machine operator a clear visual signal that the maximum reverse position has been reached.
The system helps to clearly define work areas, improve safety on the building site and prevent damage to structures, equipment or infrastructure, whether on the ground or at height. .
To ensure that the boundary elements can fulfil this task reliably, they must be able to withstand various, albeit minor, mechanical stresses. They are constantly exposed to the elements, must absorb impacts and, at the same time, retain their shape in order to fulfil their signalling function.
Why polyurethane is the right choice
For this application, Elastolan® C90, a high-quality polyurethane material system, was selected. Polyurethanes are characterised by an exceptional combination of elasticity, abrasion resistance and durability.
Furthermore, polyurethane stands out for its excellent weather resistance. UV radiation, moisture and temperature fluctuations pose no problem for the material – an important prerequisite for long-term outdoor use.
Design for cost-effective manufacturing
The boundary spheres are manufactured using the injection moulding process at HAMCO. Each sphere consists of two precisely fitted half-shells, which are joined together after injection moulding. A central gate ensures an even flow of molten material within the cavity, so that once the half-shells have cooled and been removed from the mould, there is no unplanned shrinkage or warping of the parts – resulting in cost-effective production combined with high dimensional accuracy.
The two-part design also makes installation on site easier. Once the assembly has been fitted, the balls can be easily attached to the suspension cord and installed in the desired position.
This project demonstrates once again just how important close coordination between design, choice of materials and manufacturing technology is. It is only the interplay of these factors that results in a component which is both technically and economically sound.
„What was particularly exciting about this project was how a comparatively simple idea gave rise to a robust safety solution for everyday use on construction sites. At the same time, this application demonstrates just how versatile polyurethane can be – far beyond its original scope of application.“, explains Catherine Durenceau, who oversaw the project at HAMCO.
From the building site to the underground car park
The basic principle behind the application can be utilised well beyond traditional construction site use:
Wherever vehicles need to be positioned precisely, these smaller spherical boundary markers can provide a simple and robust solution. Possible applications include private underground car parks, carports or parking spaces. A sphere suspended vertically from the ceiling reliably signals the optimum parking position to the driver as soon as it touches the windscreen of the vehicle, and prevents the parking space from being occupied by, for example, bicycles, which are still to be parked between the car and the garage wall.
Similar concepts can also be implemented in storage areas, depots or industrial transport routes. The combination of good visibility, mechanical feedback and high robustness opens up numerous possible applications.
