Abstract: In computer aided numerical control (NC) lathe turning automatic programming system,
fast and accurate parts graphic input is the primary link of realizing CNC automatic programming.
Based on the feature of DXF shaft parts graphic information, through in-depth analysis of DXF file
structure, data structure was set up based on the data of shaft parts (including geometry information
and process information). Graphic element intersection algorithm was adopted to extract and put in
the feature information of each figure, and users could click on the feature of graphic element on the
screen and enter the corresponding process information, and then data processed will be stored in the
database by using dynamic binding technology. Different feature of the graphic element will produce
different types of table. It can input part graphics through the way of opening the database, and finally
it outputs data structure required by the system. Results show that the developed application system
can rapidly and accurately input DXF shaft parts graphics, and data structure generated meets the
demands of calculating tool locus, which is able to provide technical supports for virtual NC
machining simulation.

Key words: NC lathe turning, DXF, shaft parts, data structure, graphic element intersection, database