Cnc Worm Wheel Gear Grinding Machine Automatic Knife Technology Research

The requirement of gear accuracy is becoming higher and higher in industry equipment manufacturing. The traditional method of gear grinding machining can not meet this need. The high precision gear grinding machine emerges as that requirement and extends continuously. The method of worm wheel grinding manufacture is very important for gear finishing.In the process of worm wheel gear grinding, the tool preset is an important factor which affects machining accuracy and machining efficiency. The traditional tool preset is finished by workers, which results in low efficiency, low accuracy for tool setting and poor consistency. The workpiece accuracy only achieved GB-7level precision, so the development of high accurate automatic tool preset technique is very important. To solve this problem, a new automatic tool preset method with the use of AE(acoustic emission) for contact detection is implemented, which can realize automatic tool preset in high efficiency and accuracy.The main work and achievements are as follows:(1) To determine the tool’s target position in process of tool positioning, a geometric model of grinding process was established. The target position of tool positioning was determined by analysis and computation of clamping situation and meshing relative position actually. This conclusion provides positioning target for worm wheel. By analysing the difficulty of realization in real process, middle position of cogging was determined as target position and the feasibility is proved by computation.(2)In order to confirm the tool’s offset in automatic tool preset, an automatic tool preset system was constructed which uses AE technique for contact detection and AE signal as feedback signal for CNC system through signal analysis. The offset and the target position was confirmed by contact detection between worm wheel with cogging surface and coordinates recording of tool holder along axis Y. The feasibility of the project is proved by gear grinding testing. The optimal voltage threshold of contact detection was confirmed by analysing machining accuracy, which provides reliable judgment for contact detection.(3)To realize the linkage controlling and positioning of the machine spindle, the secondary development of SIEMENS840D CNC system was finished and control program for motion flow was programmed. Firstly, operation interface in process of automatic tool preset was developed, the interface was programmed with VB programming and the DLL files were programmed with VC. Monitoring and setting of process parameters was realized. Secondly, the program of machine motion control was programmed with SIEMENS advanced programming language. At last, the controlling of spindle motion and tool accurate positioning were realized.