Development Of Graphics System Of Four Coordinate Measuring Machine

With the development of modern aviation industry, the requirement of the engine technology becomes higher and higher, and the performance and lifetime of engine are directly affected by the geometry and manufacture quality. The methods of vane examination include profile modeling method, contact measuring method and non-contact measuring method. Low efficiency, low precision and high cost of examination are the characteristics of profile modeling method. The precision and efficiency of contact measuring method are higher than that of profile modeling method, but the probe may be harmful to the vane surface, which affects the vane surface quality. Especially, when the vane is small and thin, the deformation of vane can arise from the contact stress.Comparing with contact measuring method, non-contact measuring method has the characteristics of zero-contact, higher resolution and great range of measurement. Non-contact measuring method has no measuring stresses and frictions on the surface of vane, so it can measure soft and susceptively distorted object surface. The measuring speed and sampling frequencies of the method are high and it can collect the points on the object surface densely to form data cloud.The principle of three coordinate measuring machine is summarized as follows: Firstly, measured object is placed on the position of three coordinate measuring machine; Secondly, the object surface coordinate values are obtained; Thirdly, the geometry, shape and location of the vane are calculated by mathematic operation.The non-contact measuring machine is developed to examine the vane surface of engine presser, which is high accurate and efficient. The new technology such as laser measurement, precise mechanism and surface reconstruction based on NURBS are applied on it.The main research contents and results are summarized as follows.1. The data of the vane surface is measured and the path planning is optimized.2. The original data are dealt with. Gross error and redundant data are eliminated by statistical means, and fragmentary data is mended.3. The technology of vane surface reconstruction based on NURBS is applied. The theoretical curve of vane section is plotted, and tolerance curve of vane section is plotted too. The error of the point on the vane surface is calculated and the model of vane is reconstructed. The precision of surface reconstruction is improved by applyingthe technology of NURBS.4. The parameters of vane are identified, which is adopted to judge whether the vane is beyond the range.5. The varieties and causes of error are analysed, pseudo-rigid-body model is built and structure error is compensated.The machine is successfully developed to measure the vane of engine presser by no-contact method. As a result, it is proved to be useful to guide the non-contact measurement.