in Vol. 4 - November Issue - Year 2003
CNC Shot Peening Machine for Aircraft Engine Parts
Author: Bernd Marsche, Project Engineer at Baiker AG
Multipurpose CNC Machine for all kinds of Aircraft Engine Parts
Equipped with 2 hydraulically driven Loading Stations
Rotation Head for Internal Peening
Shot peening is nowadays a standard process for the overhauling and manufacturing of aircraft engines. Worldwide, there are not much more than a half a dozen manufacturers of large aircraft engines. They basically deliver all the engines for the airliners. Naturally this is a huge industry. The Swiss company Baiker AG, developed a concept for shot peening equipment, which can process almost all the engine parts, which require this surface treatment.
A shot peening machine which can peen all kinds of engine parts must be able to treat hubs, disks, blisks, fan blades, compressor blades, airfoils, engine shafts, etc.. So the equipment shall not just be able to deal with parts of various sizes, there are also external as well as internal peening applications involved. This huge complexity of different parts combined with the need to use several shot sizes are the real challenge for the machine builder. Furthermore, the complete process must be recorded, either on paper or on hard disk.
Specification of the Machine
In order to cope with all the geometrical shapes of the parts, the CNC nozzle movement unit has a total of 4 axis, which can interpolate to each other. The CNC turntable has the ability to either index to any given position or to simply rotate. If a very long engine shaft has to be treated, an optional vertical turntable can be installed. All axis can be programmed with the help of a remote control, which can be hand carried into the cabin by the operator. Using a "Teach-in" programming style, the writing of a program becomes rather simple because the operator just has to follow the geometry of the work-piece and "teach in" the coordinates of a particular location by the push of a button.
The nozzle movement unit can either be connected to an external peening nozzle or an internal peening rotation head.
The parts are loaded with the help of two hydraulically driven loading stations. The advantage of having two loading stations is that the operator can do the loading of a work-piece while the machine is in operation. Or on request, the machine will first receive the work-piece from the first loading station and then, without any action from the operator, get the second work-piece. So depending on the part, it could be possible that the machine is in operation for a couple of hours, without direct supervision of an operator.
Of course that is only possible since the equipment will automatically turn off if one of the important peening parameters, such as flow rate, air pressure and nozzle movements are exceeding the given tolerances.
Besides the standard process visualization system, such modern machines are on request equipped with a number of software packages. That can be a SPC system (statistical process control), a tool to calculate the Almen saturation curve and to determine certain process data or simply a maintenance coordination program.
Equally important is the media preparation system, which is included in the machine concept. It is very important for uniform peening results that the media is and stays within the quality parameters required. This particular machine can chose from 3 different shot sizes and continuously recycles the shot. For each working cycle the shot is sieved for size classification. Furthermore either continuously or periodically the shot is lead through a band shape classification system to sort out the broken or uneven shot.
In order to make this equipment as user friendly as possible, all maintenance areas are easy to reach and the noise emission is not larger than 70 dBA.