Research on a Novel Method for Measuring Volumetric Error of Coordinate Measuring Machine
CMM (Coordinate Measuring Machine) is used as an accurate measuring instrument in manufacturing and design of products. High accurate CMM is required by the development of super-finish, micro-machinery, micro-electronic mechanical systems (MEMS). The precision of CMM is influenced by its volumetric error and dynamic error. The volumetric error is the major component during slowly probing, but the dynamic error is not omitted during fast probing. Compensating the volumetric error is an effective approach to improve the precision of CMM. The volumetric error in the working space of CMM must be measured and the error model must be set up before compensating. In this paper, a novel method to measure 5 volumetric errors of a guide way at the same time by 3-beam laser interferometer is proposed. The error compensating model is validated by experiment. The method can also be used to measure the dynamical error of CMM and CNC machine in real-time. The research can be referred to design the super higher accurate CMM and the accurate CNC machine.
Quick check error verification of coordinate measuring machines
Abstract Since CMM’s first became available 30 years ago, they have become the dominant measuring instruments in the field of dimensional metrology. Both for manufacturers and users there is a requirement to comprehensively evaluate their performance. These machines must be checked on installation and periodically during their operation. An increasing number of CMM’s are being placed in production line environments where there are potential threats to the machines accuracy such as dust, heat fluctuations, physical contact; hence the requirement for a daily quick check arises. Quick check procedures involve the use of mechanical artifacts, as the use of optical methods (laser interferometry) is not feasible due to the complexity and time of the set-up. There are many general artifacts for CMM checking on the market but for large CMM’s in excess of 1 m3 working volume there are few practical artifacts available for this purpose due to the inevitable trade off between artifact size and accuracy. This paper describes a quick check method in which CMM performance may be evaluated, involving the use of a telescoping ball-bar. This is a development of the principles used ball-bar technologies currently used for checking numerical controlled machines by extending the measuring range of the sensor and applying this to the CMM. The ball-bar system consists of two spheres where the centre distance can be adjusted, where the centre distance is being measured by a transducer or by interferometry. Due to the system consisting of an adjustable artefact, the system is aimed at checking a wider range of machine sizes, from small to medium sized CMMs. The system evaluates errors on the machine from the circular plots that were generated to simulate coordinate points taken on a circular sweep of a telescoping ball-bar. This paper describes methods in which squareness errors are quantified from the circular plot taken from the machine.
Computer-Aided System of Virtual Testing of Gas Turbine Engines
The article describes the concept of a virtual lab that includes subsystem of gas turbine engine simulation, subsystem of experiment planning, subsystem of measurement errors simulation, subsystem of simulator identification and others. The basis for virtual lab development is the computer-aided system of thermogasdynamic research and analysis “ASTRA”. The features of gas turbine engine transient modes simulator are described. The principal difference between the simulators of transient and stationary modes of gas turbine engines is that the energy balance of the compressor and turbine becomes not applicable. The computer-aided system of virtual gas turbine engine testing was created using the developed transient modes simulator. This system solves the tasks of operational (throttling, speed, climatic, altitude) characteristics calculation, analysis of transient dynamics and selection of optimal control laws. Besides, the system of virtual gas turbine engine testing is a clear demonstration of gas turbine engine working process and the regularities of engine elements collaboration. The interface of the system of virtual gas turbine engine testing is described in the article and some screenshots of the interface elements are provided. The developed system of virtual gas turbine engine testing provides means for reducing the laboriousness of gas turbine engines testing. Besides, the implementation of this system in the learning process allows the diversification of lab works and therefore improve the quality of training.