Press
Neunkirchen, 16 July 2025. Powerful lifting capacities, a long telescopic boom and global mobility – this is what characterises the LTM 1110-5.1 mobile heavy-duty crane from Liebherr. As a supplier to the automotive and commercial vehicle industry, SCHÄFER Perforated Metal developed a protective sheet in collaboration with the crane manufacturer, which encloses the front of the air filter on the 544 hp diesel engine and also serves as a maintenance access point. The requirements: The ventilation grille must fulfil the required air flow rate and retain its shape and appearance for at least 20 years if handled properly. Weight also plays a decisive role even on a small scale. The corrosion resistance of the component was confirmed by means of a salt spray test. The air filter protection plates are manufactured in Neunkirchen, North Rhine-Westphalia. The Liebherr factory in Ehingen receives the component just-in-time, ready for installation and use.
A perforated sheet may appear simple at first glance. However, each hole type fulfils specific requirements and offers unique advantages. Added to this are the choice of material, sheet thickness, processing and surface finishing. On closer inspection, it becomes clear that its manufacture requires the highest precision and customised solutions for the respective area of application. This is the only way to optimally utilise the critical properties such as functionality, durability, appearance, stability and lightness in practice.
High-quality perforated sheets are the basis for durable solutions. The base material comes from within the SCHÄFER WERKE Group, from the EMW Steel Service Centre, one of the largest plant-independent steel service centres in Europe. With an average stock of over 300,000 tonnes of thin sheet in thicknesses from 0.25 to 16 millimetres and in almost all marketable grades, EMW guarantees a reliable supply of materials. The perforated sheets business area also benefits from this.
Perforated sheets, for example in the form of protective and ventilation grilles for engines, are used in particular for commercial vehicles, such as construction and agricultural machinery, which have to function in corrosive conditions with exposure to chemicals, moisture, dirt and mechanical influences.
A machined perforated plate with a hexagonal honeycomb structure is used as an air filter grille for modern Liebherr diesel engines. The component is visibly mounted on the undercarriage of the LTM 1110-5.1 mobile heavy-duty crane. The task is to enclose the air filter at the front of the 544 hp diesel engine, which drives both the undercarriage and uppercarriage of the crane.
The LTM 1110-5.1 crane is being gradually revised and redesigned as part of a model facelift. Thanks to the collaboration, a multi-part sandwich construction consisting of aluminium sheet – manufactured by the metre with unfavourable edge areas and bonded in a special frame – was replaced by a monolithic component made of DC06 steel. An unperforated edge enables injury-free handling during installation and removal, and emphasises the function of the component as maintenance access to the air filter.
The sheet steel plate that was developed is just one millimetre thick and measures 355 by 900 mm. The result? Less assembly work, reduced material consumption, lower risk of contact corrosion, easier handling, minimised risk of injury and, all in all, significant cost savings. In addition, the weight has been reduced from 2.0 kg with a material thickness of 1.5 mm to 1.2 kg. Because, even with a 60-tonne mobile crane, every component is subject to strict weight optimisation.
The LTM 1110-5.1 is a single-engine crane, which is why one air filter panel is installed per crane. The lead time to the start of series production of the facelift is two years on average. Several dozen cranes of this model are produced every year. Small quantities of this size are a particular challenge for many suppliers. Over time, the changeover will extend to all Liebherr mobile crane types, which are produced in quantities ranging from 5 to over 100 units per year.
“The visit to Blechexpo in Stuttgart paid off for us. This is where we first became aware of SCHÄFER Perforated Metal. A perforated sheet on display was the eye-catcher. After getting to know each other for the first time, things went from strength to strength. The collaboration was highly professional. Within a few months, we had developed a new solution in dialogue and had the test samples on the premises. We knew our requirements and SCHÄFER Perforated Metal knew in detail what was possible and practical. We now have an ideally flat component without cracks, i.e. free of stresses and deformations, whose durability we have tested,” says Frank Reinhard, Design and Development Undercarriage, Liebherr-Werk Ehingen.
A diamond-shaped perforation, for example, allows for a free cross-section of around 75 per cent. This means that one square metre of perforated sheet consists of 25 percent metal and 75 percent open areas (holes).
With the hexagonal perforation Hv 6.0–6.7, the free cross-section can even be increased to over 80 per cent. The weight is reduced to the same extent, while the air flow rate increases proportionally. At the same time, the hole pattern ensures sufficient stiffness and provides reliable protection against mechanical impact from objects with a diameter of more than 6 mm. Leaves, for example, have no point of attack to clog the air filter.
The production of the standardised hole pattern Hv 6.0-6.7 is particularly demanding, as the ratio of hole size (6 mm), material thickness (1.0 mm) and web width (0.7 mm) must be precisely matched. The webs, which are just 0.7 mm thick, must not crack or lose stability during production and must be able to withstand external influences even under harsh operating conditions. This high-precision manufacturing process requires not only comprehensive expertise, but also first-class punching tools, which SCHÄFER Perforated Metal produces in its own tool shop.
In the production of perforated sheets using punching, metal punches are mechanically pressed into the smooth sheet surface under pressure, creating the desired hole patterns. After perforating, it is advisable to break the edges, depending on the application. This procedure is a suitable preparation for the next finishing steps, as implemented by SCHÄFER in production. Following mechanical finishing, chemical or electrochemical processes, among others, can provide permanent corrosion protection for perforated sheets.
A high-quality finishing option that is frequently used in the automotive and commercial vehicle sector is cathodic dip coating (CDC). It is also used for the air filter plates. After this work step, the surface coating is not yet UV-resistant. In order to achieve permanent corrosion protection and a high resistance to ultraviolet radiation, powder coating is a particularly good option alongside other processes such as painting.
But even with the coating, the challenges are not obvious at first glance. The more perforations there are per unit area, the more demanding the coating process becomes. In concrete terms, this means that measures are required to prevent the perforations from clogging during the coating process. At the same time, the amount of material applied must not be too small, especially at the edges of the holes.
Edge coverage plays a decisive role here: For permanent corrosion protection of perforated components, it must be sufficiently present without impairing the function. The perforations must remain completely open so as not to distort the free cross-section.
“The perforated sheet project for Liebherr cranes involved numerous parameters that influenced each other and had to be precisely coordinated. Function, design, weight, assembly effort and durability had to be harmonised. The customer requirements were clearly defined from the outset and communicated transparently. Thanks to our many years of experience from projects in the automotive and commercial vehicle industry, we were able to work together to develop an optimum solution and quickly achieve the ideal result,” explains Torsten Schoew, automotive expert for engine protection and cooling at SCHÄFER Perforated Metal.
Corrosion is an ongoing issue for anyone who works with steel or processes metal parts. Estimates put the damage caused by corrosion at EUR 100 billion per year in Germany alone. By complying with a series of standards, statements can be made about the corrosion behaviour of metallic components.
The long-term corrosion resistance has been tested and certified by independent test laboratories using the standardised salt spray test. Nevertheless, as part of the extensive quality assurance measures, Liebherr Cranes also exposed perforated sheets delivered ready for installation to the harsh conditions of the salt spray in the factory’s own test chamber and confirmed the laboratory results.
Even after 1,008 hours in the salt spray test, the perforated sheets remained both visually flawless and corrosion-free. There was no detectable edge alignment of the surface finish. One of Liebherr’s key quality criteria is the flawless appearance of the heavy-duty cranes for at least two decades – provided there is no external influence.
Low-corrosion perforated sheets are a proven construction and design element with versatile functions in the commercial vehicle industry. They take a wide variety of forms, have to be integrated into complex environments and reliably fulfil their purpose for many years.
The product variety of SCHÄFER Perforated Metal comprises over 400 different hole patterns, including round, square, diamond, slotted and hexagonal perforations. A wide range of materials such as steel, stainless steel, aluminium, as well as copper, zinc, brass and plastic are used in production. An in-house design department with experienced application experts develops customised patterns and optimises even highly complex projects. This means that almost all conceivable applications and individual design requirements can be realised.
In addition to the wide range of perforations, the company offers a broad spectrum of processing services, including laser cutting, folding, notching, punching and degreasing. In addition, the perforated sheets can be finished in the factory with common RAL colours. This enables the company to provide just-in-time delivery of ready-to-install assemblies.
Perforated sheet design for maximum performance on mobile heavy-duty cranes.zip