High speed milling (HSM) is currently one of the most important technologies used in the aviation industry, especially concerning aluminium alloys. The difference between HSM and other milling techniques is the ability to select cutting parameters – depth of the cut layer, feed rate, and cutting speed, in order to simultaneously ensure high quality, precision of the machined surface, and high machining efficiency, all of which shorten the manufacturing process of the integral components. By implementing the HSM technology, it is possible to manufacture very complex integral thin-walled aerial parts from the full quantity of the raw material. At present, aircraft structures are designed to mainly consist of integral elements which have been produced by welding or riveting of component parts in technologies utilized earlier in the production process. Parts such as ribs, longitudinals, girders, frames, coverages of fuselage and wings can all be categorized as integral elements. These parts are assembled into larger assemblies after milling. The main aim of the utilized treatments, besides ensuring the functional criterion, is obtaining the best ratio of strength to construction weight. Using high milling speeds enables economical manufacturing of integral components by reducing machining time, but it also improves the quality of the machined surface. It is caused by the fact that cutting forces are significantly lower for high cutting speeds than for standard machining techniques.

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Subtracting manufacturing technologies have entered that realm of production possibilities which, even a few years ago, could not be directly adapted to direct production conditions. The current machines, i.e. heavy, rigid cutting machines using high spindle speed and high feed speed, allow for manufacturing very thin and relatively long parts for use in the automotive or aerospace industry. In addition, the introduction and implementation of new 70XX aluminium alloys with high strength parameters, as well as monolithic diamond cutting tools for special machining, have had a significant impact on the introduction of high-speed machining (HSM) technologies. The main advantage of the applied manufacturing method is obtaining a very good smoothness and surface roughness, reaching even Sz = 6–10 μm and Sa <3 μm, and about four times faster and more efficient machining compared to conventional machining (for the beam part). Moreover, fixed and repeatable milling process of the HSM method, reduction of operational control, easy assembly of components and increase in the finishing efficiency compared to other methods of plastic processing (forming) are other benefits. The authors present a method using HSM for the manufacturing of aircraft parts, such as the chassis beam at the front of a commuter aircraft. The chassis beam assembly is made of two parts, front and rear, which – through a bolted connection – form a complete element replacing the previous part made using traditional technology, i.e., cavity machining, bending and plastic forming. The implementation of HSM technology eliminates many operations related to the construction of components, assembling the components (riveting) and additional controls during construction and assembly.

) -Szel-Tech Szeliga Grzegorz; dr inż. Edward Rejman (erejman@prz.edu.pl), dr inż. Robert Smusz (robsmusz@prz.edu.pl) - Politechnika Rzeszowska im. Ignacego Łuka-siewicza Przedstawiono strategię obróbki przedmiotów cienkościen-nych, która stwarza szereg problemów technologicznych związanych ze zmianą kształtów i wymiarów przedmiotu obrabianego, oraz sposoby przeciwdziałania drganiom podczas obróbki skrawaniem, aby nie następowało pogorszenie struktury geometrycznej powierzchni obrabianej -chropowatość powierzchni. Z kolei odkształcenia plastyczne mogą być przyczyną błędów kształtu oraz źródłem naprężeń własnych w warstwie wierzchniej, trudnych do usunięcia, powodujących deformację przedmiotu po obróbce. Podnosi to koszty wytwarzania, zwłaszcza przedmiotów cienkościennych, z uwagi na powstawanie braków i wydłużanie czasu produkcji. W celu poprawy jakości wykonania przedmiotów cienkościennych zastosowano kilka sposobów minimalizacji odchyłek kształtu i chropowatości powierzchni, takich jak: optymalizacja strategii obróbki, podwyższanie prędkości skrawania v c , optymalizacja parametrów skrawania, zwłaszcza posuwu na ostrze f z oraz promieniowej głębokości skrawania a p i szerokości warstwy skrawanej a e ze względu na minimalizację składowej siły skrawania prostopadłej do powierzchni frezowanej ścianki. SŁOWA KLUCZOWE: obróbka z wysokimi prędkościami skrawania, frezowanie, konstrukcje cienkościenne Machining operations of thin-walled elements generate a lot of production process issues related to deformations and elastic and plastic displacements of the workpiece. Due to displacements of the milled workpiece, vibrations can occur, and thus, geometric errors may occur on surface in the structure of the workpiece. Furthermore, plastic deformation can also cause shape problems and be a source of internal stresses in the surface layer, which are highly difficult to remove and lead to deformation of the workpiece after machining. Consequently, this leads to an increase in the manufacturing costs of machining operations, especially of thin-walled elements, due to shortages and increased manufacturing time. It is recommended that multiple methods for minimizing machining errors be utilized to improve the quality of thin walled elements, such as: optimization of the machining strategy, increase of the cutting speed v c , optimization of cutting parameters, especially feed per blade f z , the radial depth of cut a e due to the minimization of the cutting force component perpendicular to the surface of the milled wall. KEYWORDS: high speed machining, milling, thin-walled constructionsFrezowanie z dużą prędkością skrawania HSM (high speed machining) jest stosowane w przemyśle lotniczym, zwłaszcza podczas obróbki stopów aluminium [6]. Czynnikiem odróżniającym HSM od innych technik frezowania jest taki dobór parametrów -szerokości frezowania, głębokości skrawania, posuwu oraz prędkości skrawania - który zapewnia dobrą jakość oraz dokładność wymiaru i kształtów przedmiotu obrabianego, a równocześnie wysoką wydajność, aby skrócić...

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The high level of durability and reliability is a strict requirement for today's aircraft constructions. The most important aspect is the mass of the structure which has a decisive influence on both the volatile and technical properties of an aircraft as well as its economical operation. Modern aircraft structures, or more precisely their load-bearing structures, are almost exclusively manufactured as thin-walled ones which meet the requirement to minimize the mass of the structure. While the local loss of coverage stability is permissible under operating load conditions, exceeding critical load levels of the structural skeleton elements (e.g. frames, stringers) is practically synonymous with some destruction of the structure. It results in a necessity for the continual improvement of both design methods and the improvement of structural solutions of aviation structures. By reducing the thickness of the cover and, at the same time, introducing densely spaced stiffening longitudinal elements, a structure with considerably higher critical loads can be obtained and, consequently, a more favorable distribution of gradients and stress levels which directly contributes to an increase in fatigue life. This paper attempts to analyze the above-mentioned problem more closely, using the example of a densely ribbed rectangular plate.