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Siemens Power Generation is one of the world’s leading manufacturers of power generation equipment. Its facility at Newcastle upon Tyne is dedicated to providing service support to power utilities worldwide. This includes the supply of new spare and replacement blades not only for machines to its own family of designs (KWU, Westinghouse & Parsons), but also for other manufacturers plant. The non OEM business requires the reverse engineering of design data from samples of original blades to either manufacture direct copies or for the re-engineering and manufacture of blades which will provide improved performance compared to the original design intent.
The reverse engineering of the blade root and any blade tip details is relatively straightforward, but to reverse engineer the sometimes complex form of the blade aerofoil is more difficult. This requires the measurement of a large number of points over the blade aerofoil surface. The Blade Shop at Newcastle has a number of Brown and Sharpe coordinate measuring machines fitted with Renishaw touch trigger probes. Whilst this is appropriate for the in process verification and final inspection of
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manufactured blades, it is too slow for the reverse engineering of non OEM blades. When reverse engineering, it is necessary to measure many more points over the surface of the blade aerofoil.
To address this, SPG decided to investigate the feasibility of fitting a laser scanning head to one of their coordinate measuring machines. Although relatively new, laser scanning techniques are now widely used by the automotive, aerospace and energy industries and even the entertainment industry. The laser scanner is used to quickly generate a 3D pointcloud of the scanned item. This pointcloud can be further processed to create a 3D model which can be used to reverse engineer the item.
With the need for accurate and rapid data collection, SPG decided to fit a Metris LC50 high speed laser scanner to one of their Brown and Sharpe coordinate measuring machines (CMM). As it is mounted on the Renishaw PH10 indexing head, it can still be quickly interchanged with a traditional touch trigger probing if necessary. The lightweight Metris scanner is a laser stripe sensor which works by projecting a line of laser light onto the blade while a small charge coupled device (CCD) camera views the line as it appears on the surface. The CMM moves along the blade in different orientations capturing the data rapidly and with high accuracy and repeatability typically within 10 microns. The path the laser scanner follows is fully programmable by teach-in or visual basic macros, allowing the automation of multiple scans of different blades. As it lays down a 50 mm band 768 points wide, it is possible to scan a blade in a very short time (at up to 20,000 points per second). This is approx 30 times faster at gathering data than continuous touch trigger probing we have also used.
The engineer then uses the dedicated Metris software to generate and manipulate the pointcloud which can also be filtered to optimise the number of points from the different overlapping scans and thus reducing file size. A high density of points is preserved at the edges and over sharp contour changes, while fewer points are kept in the planar areas of the blade surface.
To align and integrate all related software, SPG chose to use a Class A surfacing tool optimised for complex freeform design to rapidly create surfaces from the point cloud data. Verification tools such as color maps deviation charts indicate where the pointclouds differ form the surfaces. The surfaces are then imported into their ProEngineer CAD/CAM system in order to create a 3D solid model. In the case of re-engineered blades, the model can be used for engineering analysis.
The resulting model is then used to create part programs for the machining of the new blades. The same model can also be imported into the Brown & Sharpe PC-DMIS software for the creation of CMM programs for the in process inspection of the machined blade features. All the software packages are fully integrated allowing rapid error free exchange of data.
Siemens have successfully reverse engineered and manufactured generator rotor fan blades for a contract in Sudan. The blades were produced as copies from a sample, in less than 12 days with a considerable time saving during the scanning of the blade.
Reverse engineering of other manufactures blades and components forms an important part of our business growth plan for the restructured business.
Aside from the company’s core business of turbine manufacture, Siemens has recently provided scan data for a sub-contractor of a leading car manufacturer. The part was a chassis component and was to long to fit onto the CMM. The part was therefore scanned in two halves then the Metris software was used to match the two point clouds back together. A comparison of the scan data to the original model was carried out and an error map of the part given to the customer. The customer has since placed an order 100 hours of scanning time at our facility.
Metris provides total solutions for 3D digitizing, 3D inspection and reverse engineering to the design and manufacturing community. It was founded as a software company with a new and challenging paradigm for computer aided verification and inspection. Today Metris is unique in being able to offer a total solution including both the digitizing hardware and software. The software solutions comprise applications for optimized digitization, quality inspection and reverse engineering with a focus on ease of use, accuracy and productivity. These capabilities enable users in sectors as diverse as automotive, aerospace, power generation and consumer products to optimize their processes resulting in strategic competitive advantages such as shorter lead times, higher quality levels and lower production costs. Examples of applications where these technologies are already common practice are inspection and reverse engineering of sheet metals, turbine blades, mobile phones, sporting goods, toys and many more.
Download: Siemens PG uses LC50 for reverse engineering of turbine blades (PDF file)
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