## 1 Introduction  
Turbine guide vanes, alongside with turbine blades, are crucial components in the gas turbine system. Due to the complexity of such parts the most reliable process of production is still to cast and machine them in subsequent manufacturing steps. 3D printing of such elements is still under development, especially for parts working in high temperature in the hottest area of the turbine and, therefore, this method is of negligible industrial impact. Proper inspection is of critical importance in the industrial part acceptance process. There are several tests, usually applied simultaneously, like grain etching, non-destructive and destructive tests, and overall part shape inspection. For the purpose of the last of these, the form and profile can be easily inspected by a coordinate measuring machine (CMM). Another method gaining increasing popularity is optical scanning. It has lower accuracy and is still relatively slower, but it is able to deconstruct the overall 3D part shape, which then can be compared with the original CAD (Computer-aided design) model [1; 2]. The trend in modern approaches is to focus on fast-developing 3D scanning techniques, but there is still scope for improvement in existing and commonly used coordinate measurement machines, with strictly-defined rules and standards [3]. Inspection time can vary from a couple of minutes up to several dozens for complex vanes [4]. While CMM is still the most reliable method for part inspection, many researchers point out that is relatively slow and a significant time reduction is needed in order to provide cost effective solutions [5]. Well-written CMM inspection programs can provide reliable and repeatable measure processes for a large set of components and CAD based sampling and point reduction is a very good start for CMM path programming. [PERSON] [6] investigated blade geometry discontinuity, such as small diameter holesor inconsistent depths, demonstrating that a CMM test may not reveal any problems or provide inconsistent results. A possible solution might be non-destructive testing that can identify the occurrence of these flaws before CMM inspection and properly set tolerance boundaries can result in disregard for small, identified flaws. The path for the CMM probe needs to be written in such a way as to avoid collisions between the inspected parts and to include all the shape variations. Good examples of case studies can be found in the work of [PERSON] [7,8] or [PERSON] [9]. Interferences can often occur between the probe and inspected parts. The CMM path should include not only higher shape variations than the desired tolerances, but also rapid curvature changes, and supporting features like handles and stabilizers. [PERSON] [10] discusses path improvement and verification, measurement, and probe radius compensation of shape variations and undesired collisions with components above the desired tolerances. An important conclusion is that the calculated manufacturing tolerances are the desired ideal, but real parts can exhibit high divergences, so the measurement process should adapt to part shape changes greater than the ones that were assumed at the beginning. Parts manufactured outside the desired tolerances can cause CMM probe damage, especially when the set measurement speed is too high. A good prevention strategy is to define safety conditions in the CMM program and operator supervision during the first trials. Path simplification and the required number of inspection points to collect are broadly discussed in literature. Researchers also try to develop their own algorithms e.g., Mansour [11] for overall time reduction of the measurement, or Rui-Song [4] for determination of the reduced number of points and sections to be measured. CAD-based sampling is a good starting strategy, as the nominal shape can be used to determine and improve the measuring path [12]. While designing a simplification process, part variations and possible imperfections should always be considered.