A Study On The Automatic System For Measuring Inner And Outer Surfaces Of Rovolving Parts Made Of Special Brittle Materials

A multi-axis CMM for measuring inner and outer surfaces of brittle rotational parts simultaneously is designed and developed in this thesis. The CMM meets the requirement for measuring specified rotational parts made of brittle materials and can be adapted to measuring parts with different forms, in addition, it also can function as a common CMM.The CMM can measure the inner and outer dimensions and forms of the rotational parts automatically; the generics of inner and outer surfaces might be all kinds of complex curves. After the part is mounted, the part can be centered automatically. The whole measuring process is automatic. The machine measures the forms, parameters and their deviations. The measured data are stored and analyzed. A safety protection system is built in the CMM and can prevent accidents effectively.The key technologies needed to be solved include measurement of the inner surface of the parts, centering problem of the parts; collision avoidance issues etc. In order to solve the above mentioned problems, an inverse moving bridge structure for measuring inner surfaces, a mechanism for centering the parts automatically, a set of collision avoidance measures and calibration techniques are creatively developed.Safety is of the most important problems in the design of the machine. Safety and reliability measures are taken from all possible aspects. A vision system is built to monitor the whole process including part loading, centering and measurement. Virtual reality technology is introduced to effectively avoid CMM collision accident occurrence. Multiple limiting and protecting mechanisms are developed. Supplemental measures come into action once any of the protection measures fails. Non-contact probes are used to avoid physical touches of the probes with the workpiece.The calibration, adjustment and performance testing approaches of the measuring machine are studied in detail. A large number of experiments have been carried out to verify the performance of the measuring machine. Errors sources are analyzed and error compensation is introduced to make the measuring machine meet the design requirements.The main creative ideals and innovations of the thesis include the follows.1. A special structure of CMM enabling simultaneous measurement of the inner and outer surfaces for the parts without access from the top for measuring the inner surface and not allowing being mounted horizontally is developed.2. The workpiece is measured by non-contact optical probes in the process of continuous rotation. Key technologies including the unification of three coordinate systems, establishment of unified mathematical model, system parameter calibration have been developed.3. A safety system, including vision system for monitoring the work process, collision avoidance and protection system, has been developed. The CMM is able to detect the foreign bodies during the loading and measuring processes, to check the correctness of the mounting discs, to recognize the types of the workpieces, to avoid the drop of the workpiece, to prevent and protect the part and mechanisms from collision. All these measures ensure high safety and reliability of the machine.