The Development Of CAPP System For Flashless Forging Of Gear Blanks Based On AutoCAD 2005

The CAPP system for flashless forging of gear blanks is developed according to the process of close die forging and the die design, which takes AutoCAD 2005 as platform, VBA embedded in AutoCAD 2005 as objected-oriented development tool. The system can inquire the parameters automatically, fix the parameters interactively and generate the part drawing, the forging drawing, the process card and the die drawing by parameterization. The drawings and the card are created by using AutoCAD ActiveX objects, the databases are managed by Microsoft Access and the user interfaces are designed on the VBA environment.Through four aspects the preforging design of complicate gears is modified and improved. Firstly, a new estimation method whether the complicate gear blanks need preforging or not is put forward—if the upsetting blank can't ensure the finish forging, it needs preforging. Secondly, add a function that the user is allowed to input the value of recess position in the system. It can settle the position fix need of blank or preforging during finish forging. Thirdly, fix the best joint position of complicate gear blanks so that the blanks can be formed by upsetting during finish forging. Fourthly, the form of preforging is modified and the dimension formulas are fixed which can solve the position fix need of blank in preforging impression.The friction press uses the universal die set. The cavity die structure adopts combination die that consists of the cavity die and the prestressed layer that is fixed on the die sets. To design the prestressed layer according to the maximal diameter of the forging's diameter range of each tonnage, thus the dimension of prestressed layer are the same, and the fixation of punch and die set are also the same as for the same tonnage. When different forging in the forging's diameter range of one tonnage are produced, only the dimension of cavity die and free part of the upper die need be designed. In paper three types of upper die and two types of cavity die are designed and the dimension of each type of upper die and cavity die in each tonnage of friction press is given. While the user selects the upper die and the cavity die, the drawings of related upper die and cavity die are generated. Meanwhile, the height of the non-forming part of counter die is fixed and the shut height and the height of cavity die are inputted as parameters, which make the die design more rational.Through the Data Access Objects, we can quote the table's fields in database to realize the inquiry of parameters automatically and quickly. Meanwhile, the forms of modifying the database are designed, which is convenient for adding and modifying data and satisfy the modification need of database.Besides the dwg file type of process chart, an Excel file type of process chart is generated by the communication of AutoCAD and Excel. During the program some useful tip is concluded, which reduces the code.The system has many advantages such as friendly interface, high practicability, the normalization and standardization of die design. The successful development of the system can expand the fine forging process of gear blank, alleviate to the heavy labor of designer and shorten process design time, which has the obvious significance.