in Vol. 5 - July Issue - Year 2004
Rösler helping to reduce Production Cost and increase the Quality of Aero Engine Blades
This shot blasting system (Roboblaster) with robo
The transport belt and nozzles of the SBI 1200.
Forged turbine blades are surface finished by different vibratory centrifugal and shotblasting processes.
A robot plays the role of production assistant in its handling the components. A special sealing system made of abrasion-proof manganese steel provides safe sealing of the steel space.
As a complete supplier, Rösler Oberflächentechnik GmbH is the international market leader for the manufacture of vibratory and shot blasting equipment and consumables for the efficient finishing of metal and many other surfaces such as synthetics, wood and stone. Due to the continuous expansion, permanent extension and flexible design of the equipment range as well as the increasing globalisation of distribution and sales Rösler now has 12 branch offices and 970 employees worldwide, the family- owned business is in its third generation and, under the management of Mr. Stephan Rösler, Dipl.-Kfm., has gained an excellent reputation in the surface finishing sector.
If an aerospace engineer were to show even a small finished aero engine blade to a person outside the industry and ask them to estimate its production cost, it is unlikely they could do so, because it is difficult for an “outsider” to appreciate the skill and time required to produce it.
Multi Axis machining centres are now widely used in the industry and have played a Significant part in the quality/ cost factor. Surface finishing however is still an expensive and time consuming part of aero engine blade production, and it is in this area that Rösler have and are playing a major role in the design and supply of finishing equipment to the Worlds engine builders and repair centres.
In recent years many have invested in Rösler finishing machines for new factories. Forged blades require De-Scaling between forging stages and a popular choice for this process has been the Rösler Multi Nozzle Thru- Feed Blast Machine (seen below) The SBI 1200 SI10 is a 10 nozzle air system that cleans and descales the surface of the blades after the heating and forging processes as they are gently tumbled and transported through the cabinet by means of a unique polyurethane cam belt. Components are loaded by conveyor. They exit onto a motorized circular table to avoid damage, having been exposed to the aluminium oxide shot for several minutes. The surface at this stage will be clean from the work carried out in the SBI.
The aerofoil and platform surfaces are barrelled using a process that Rosler developed using special ceramic abrasive medias to vibratory finish the parts. A more up to date and modern method of blade finishing, and now chosen by many engine builders is the Rösler FKS35.1 A2 high energy centrifugal force finishing machine with belt dryer and process water circulation system. The FKS is able to cut down the surface of a component up to twenty times faster than a conventional vibrator or barrel. The movement of the abrasive mass in the working chamber is activated by a spinner plate located in its base, centrifuging it, and creating a vortex. Although cutting rates are high, surface protection is also high, the blades being completely encapsulated in the special ceramic abrasive media that is produced by Rösler, and traveling through it all at the same speed, in the same direction. The FKS is a double batch finishing system, meaning that one batch of work is being processed whilst another is being separated from the abrasive chip. The batch in separation will be washed on the screen area before feeding into a Rösler through feed hot air dryer. The systems programmes are controlled and monitored by a PLC. Process times will sometimes vary a little to take into account the surface start condition across blade families. It is however around two hours, and in this time a surface reading of 20 micro inches (0.5 micro-metres ) Ra or less can be achieved.
The aerospace industries of the world probably more than any other use the technique of shot peening to re-introduce compressive stress into their components after forming and machining. Rösler are rightly proud that over the past few years to have played a major role in the development of peening machines and processes now used in the aerospace industries. Many have elected to purchase Rösler equipment, and an increasing number to invest in the robotic options that are also part of their build programme.
The main advantage of a robotized system is that once all the critical times and settings of the components in the blast stream have been determined and set, such as, angles, distances, coverage velocity etc then the process is infinity repeatable. A further important advantage is that many aero engine components require masking in certain areas during peening or blast cleaning. It is possible with a robot system to sometimes design the tooling to mask these critical areas.
Shot peening is an indispensable process used in the manufacture and maintenance of engine and airframe parts to increase the resistance against material fatigue. Shot peening requires exactness and repeatability. Both are decisive features, in order to comply with the regulations implemented by the manufacturers of aircraft to achieve the highest level of safety and profitability. A universal hardening shotblasting robot system by Rösler for manufacture, repair and maintenance work ensure absolute precision and repeatability through a special fully automated process control. During the process, the shotblasting media undergoes an integrated classification system, it is sorted according to size and shape, processed continuously and brought back into the cycle, thus ensuring the highest possible integrity of the peening process in all operations of the process. The weight of the used shotblasting media is measured continuously, and sensors monitor the flow of shotblasting media. Twenty sensor readings per second make it possible to guarantee an even (+/- 2%) flow of shotblasting media. To ensure constant quality results this system has an electronic Almen-reading which constantly monitors the intensity of the shotblasting stream. The system with a 6-axle robot for jet manipulation and a rotary table can be used to process a wide range of engine parts, improving and/or restoring their endurance limit.
The Rösler group over the past few years has developed and introduced into the aerospace market many machines and processes that have not only helped to reduce costs, but at the same time have contributed to improve quality and consistency of finish.