VOL. 10 November ISSUE YEAR 2009
in Vol. 10 - November Issue - Year 2009
Innovative Air and Wheel Blast Technology for Shot Peening New Shot Peening Systems Offer More Efficiency and Safety
Due to its modular design the RSA 1400 can be equipped with 6, 8, 10 or 12 rotary satellites. Loading of the satellites with parts can take place manually, semi-automatically or fully automatically, with a positional accuracy of +/- 1.0 mm
Excellent peening effect
With the special double pressure vessel a continuous blast operation without any interruption is possible
Excellent peening effect
Rotary table satellite system RDT 150-S5 with 5 blast chambers
Raw part with unpeened surface
Shot peening improves the surface of different parts and offers many advantages: Higher stress resistance, less wear, higher expected part life with – at the same time – reduced part weights. Because of these positive characteristics shot peening is utilized in many industrial sectors; but it is especially popular in the aerospace and automotive industries. With its innovative peening technologies Roesler not only offers more efficiency but also more safety.
During the shot peening process spherical (round) media is thrown onto a part’s surface at high speed. Each pellet leaves small "dimples" on the part’s surface. This cold-forming process generates an area of intense compressive stress below these "dimples". Overlapping "dimples" create a compressive stress layer that is evenly distributed over the part’s surface exposed to the media. This offers many advantages. For example it prevents cracks, or if cracks already exist, it prevents them from spreading. Further, it improves the fatigue life of parts and prevents corrosion that might be induced by stress or hydrogen embrittlement. The increased part’s strength allows for reduction of the parts weight, which in times of scarce raw material resources, increased cost pressures, increasing energy cost and targeted CO2 reduction, offers an invaluable advantage.
Rösler RSA 1400 - Inducing Compressive Stress with a High Degree of Consistency
The measurement of the induced compressive stress always requires the destruction of the peened components. For this reason the required values of the process parameters like impact angle on the part, blast time, pressure and media quantity thrown, must be kept within a narrow range. Only the precise control of the process parameters guarantees achieving the desired peening results. The Roesler air blast system RSA 1400 incorporates special patented measuring and control features that guarantee the absolute repeatability of the peening process. For example, a special media dosing system for ferritic as well as non-ferritic media allows the precise dosing of the media quantity to be thrown. Air pressure and air volume are set and controlled with special valves. The hose connections are monitored to ensure that the media arrives at the blast nozzles at the correct quantities and at the right pressure. Another important point is the constant control of the size and shape of the media. The RSA 1400 is equipped with a fully automatic, 3-phase media classification system: During the first phase dust and other small particles are removed with an air-wash separator and a cyclone. The second phase consists of running the media over a screen separator, which removes undersize media pellets. The 3rd phase finally consists of a spiral separator, which removes broken media that is no longer perfectly round.
With the acquisition of Baiker AG and Vapor Blast and the development of numerous patents Roesler has become market leader for high-tech shot peening solutions for aerospace as well as automotive applications. These may include the peening of various types of turbine components, gears, drive shafts and crankshafts, springs, etc.
Modular Design Ensures Easy Adaptation to a Wide Range of Technical Requirements
The RSA 1400 offers not only safe and repeatable peening processes but also a high degree of flexibility. For example the modular design of the rotary table permits running the system with 6, 8, 10 or 12 rotating satellite stations. Depending on the parts, these can be directly mounted onto the satellite stations, or in certain cases the satellites must be equipped with special parts fixtures. Placing of the parts onto the satellites can be done either manually, semi-automatically or fully automatically, within an accuracy of +/- 1.0 mm. The parts load/unload area is totally sealed from the blast area so that no blast media can spill into the load/unload area. This helps minimize process times, as the parts loading/unloading step takes place simultaneously with the peening process.
The peening process takes place with different blast nozzles, which are directed at those parts areas that require peening. At a process time of 25 seconds compressive stress levels of up to 1,500 MPa can be induced on the parts surface. The system can easily be adapted to processing different part’s quantities by utilizing one, two or three blast stations at a time. Of course, depending on the parts to be peened or the desired peening results, additional blast nozzles or blast stations can be added.
For a continuous, uninterrupted blast operation Roesler offers special double pressure vessels. A sensor in the lower vessel signals, when the media reaches a minimum level. This causes the upper pressure vessel to send media to the lower vessel. The upper vessel is then replenished with media from the main media hopper.
RDT150-S5 – Compressive Stress Levels of up to 1,200 MPa at High Parts Throughput Rates
In the satellite rotary table RDT 150-S5 blast system various areas of the parts are peened with two high performance Hurricane blast wheels with a power of 15 kW each. The blast wheel location ensures that the media reaches all critical parts areas with the same blast intensity. The compact design of the system allows a very short distance between blast wheels and parts to be peened. This generates exceptionally high blast intensities. Compared to standard wheel shot peening systems, which reach up to 1,000 MPa, the RDT, 150-S5 can easily induce compressive stresses of up to 1,200 MPa.
Another advantage of the Roesler system is the single disk (runner head) design of the blast wheels. Compared to twin disk wheels, this allows a quick change of the throwing blades from the outside without having to dismount impeller and control cage. The total time required to change the throwing blades amounts to about 10 minutes. This keeps idle, non-productive times to a minimum.
More Safety and Less Wear by Utilization of Different Blast Chambers
Another important feature of this blast system is the special design of the rotary table: The table is divided into several blast chambers separated by solid walls. Each chamber contains one satellite workstation, which allows the placement of one or several parts like, for example, gears. The machine can be loaded and unloaded manually or by robot. The blast chambers are made of manganese steel. In the direct blast zone they are additionally lined with tool steel. Furthermore, the chambers are equipped with special magnetic seals. All this ensures that the blast area is properly sealed against the immediate environment. There is no danger of the operator or robot being "shot" at by media, and the turntable can index without any problems.
Like with the RSA series the RDT systems are equipped with all kinds of control features, which guarantee a peening process with high repeatability and an effective media classification. Both peening systems incorporate a blow-off unit. This guarantees that the parts leave the machine without any residual media on their surface.