Research On STEP Based Key Technology Of CNC Manufacturing For Special-Shaped Screw

Screw parts are widely used in various fields, such as war industry, petroleum, chemical industry, rubber industry, injection molding and sewage disposal. In recent years, more and more researches focus on the design and process of screw parts. According to different application backgrounds and device required parameters, screw parts have distinct design parameters, such as length, inner diameter, outer diameter, spiral flute, number of leads and pitch. So the expression of these parts is not uniform in mathematical model and NC machining planning.In order to achieve seamless connection between design and manufacturing, screw parts' information is expressed in STEP standard in this thesis. As a international standard which was established by International Standards Organization (ISO), it is used for exchange of industrial product data, and the product's model could be expressed completely. Based on the research about structure and grammar of EXPRESS language, STEP information is extracted for screw parts model in Java program. Then the mapping between STEP file and screw parts' model is build.The screw parts' models not only cold express geometry information, but also combine the matter of NC machine and manufacturing method. Aim at whirlwind milling method, this thesis establishes the model of axial cross section, and classify them by set theory. Considering that the model of flute spiral is a key part, curve of this part is interpolated and fitted. The model in this thesis combines with whirlwind milling's characteristics, and it provides support of mathematical basis and computational methods for CNC interpolation.CNC machining is based on EtherMAC motion control platform, which is researched and developed independently. CNC interpolation, acceleration and deceleration control are executed on host computer with the help of screw parts' model. After calculating coordinate positions of every interpolation period, data packages should be rated and set up according to EtherMAC protocol. Communication between host computer and EtherMAC is achieved in JNA method, and the delay time is tested In program.In the last section of this paper, a prototype machine system is developed to verify the whole research content of this issue, including STEP information extraction, manual input information and 3D model display. Prototype system also could establish communication between host computer and EtherMAC platform, and calculate interpolation for CNC manufacturing of screw parts.