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The deep drawing process for perforated metal components

The production of perforated metal components for the front of commercial vehicles is a challenge in terms of manufacturing technology: it is necessary to reconcile technical requirements for air permeability, filter effect, stability and weight with modern design specifications.

For example, in order to optimise the air passage through the perforated plate and thus enable maximum engine performance, the webs must be made extremely thin. At the same time, the filter effect of the bonnet must not be lost despite the increasing free cross-section. In addition, it must be ensured that the perforated component with its filigree webs meets the stability requirements of the bonnet and withstands the adverse environmental conditions of agriculture.

From the point of view of manufacturing companies, these challenges raise the question of the technically best and most economically attractive manufacturing process. Deep drawing has proven to be a guarantee of success for the implementation of design requirements. The prerequisite is that the manufacturing company has experience, know-how and the necessary intuition in deep drawing.

Deep drawn metal sheet

Know-how and experience as key factors in deep drawing

Deep drawing perforated metal components is one of the most demanding forming tasks – in addition to specialised deep-drawing tools, it requires experience, practical knowledge and a sure instinct. The production challenges lie above all in the flow behaviour of perforated sheet: this differs significantly from solid sheet and does not allow for reliable computer simulations. If the forming process is carried out incorrectly, there is a risk of deformation in the perforation, and in the worst case, the filigree webs may even break. Deformations in the perforated sheeting in turn harbour the risk that the subsequent coating will be impaired and the air permeability of the component will remain below the requirements.

Despite all the production challenges: Deep drawing perforated metal components also offers far-reaching opportunities. Because those who master the “challenge of deep drawing” in the production of perforated sheets are rewarded with optimal results: no other forming process offers such far-reaching design and optimisation possibilities to combine the versatile requirements for design, stability and air permeability.

Deep drawing press

The development of deep drawing tools

Deep drawing tools are expensive to purchase. In the development phase, the readiness of the thermoforming tool for series production is particularly important, because changes lead to extreme additional costs: to ensure this, early coordination and close cooperation between OEM and manufacturer is crucial.

In tool development, it is advisable to carry out tests on air passage and installation with the help of prototypes for which a finished thermoforming tool is not yet necessary. One of the methods used is the classic rapping mould. The rapping moulds can be cheaply milled from steel or aluminium, then a usually soft-annealed perforated sheet is rapped into shape on a negative mould. This makes it possible to create a rapping pattern that is very close to the final product. The customer thus gains valuable insights into the feasibility of the vehicle without having to use cost-intensive deep drawing tools. This approach allows tool developers to easily respond to design changes and develop a tool with high production readiness.

From the selection of the right material to the deep drawing parameters

Even the selection of the raw material can have a decisive influence on the quality of the perforated component. For deep-drawing, for example, steel grades such as DC04-DC07, which have different deep-drawing qualities, can be used as basic materials. The choice of material has an influence on the flow behaviour, among other things – and is thus also decisive for the occurrence of rejects. A more expensive base material can lead to cost advantages in production thanks to its more precise flow behaviour. Therefore, the first step is to decide which raw material is best suited for the individual requirements.
In the deep-drawing process, it must be taken into account that perforated sheet behaves completely differently from solid material. The thin webs of perforated metal components react sensitively to minimal changes. Therefore, practical experience and intuition are required to control the forces in deep drawing and to avoid cracks and deformations.

Furthermore, the quality of the perforation is also crucial, because important component requirements such as design, stability, corrosion protection and filter effect depend significantly on the hole pitch, hole width and web width. Furthermore, the choice of the right hole geometry – hexagonal perforation or round perforation – is decisive for the air passage.

Practical example: 71 % free cross-section for perfect air passage

This practical example underlines the importance of pronounced, collaborative consultation and development work in the production of perforated metal components for modern commercial vehicles: Working closely together, deep-drawing specialist Solvaro has succeeded in achieving a free cross-section of 71% for the front and side grilles of the Massey Ferguson® 7S Series. This ensures optimum airflow to the engine and allows the vehicle to deliver full power at all times.

To achieve this cross-section, the engineers opted for Hv 2.1-2.5 perforation of the grilles. This poses a challenge in terms of production technology, as the webs are even thinner here than with the more common hexagonal perforations. When deep-drawing the complex geometry, it was therefore particularly important to prevent web cracks and deformations. It was crucial to optimally determine the relevant deep-drawing parameters on the basis of empirical values. During the subsequent coating process, the focus was on corrosion protection; a cathodic dip coating process with optimised layer thickness was used to control the influences of edge alignment.

Information on the expert

Martin Schneider

Martin Schneider
SOLVARO GMBH, Head of Engineering
Expert Engineering

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