Research And Application On Key Technologies Of A CAD System For Plastic Profile Extrusion Die

Plastic profile is widely used in building materials industry because of its unique processing property.As the basic equipment for production of plastic profile,the profile extrusion die has an important impact on the quality and production efficiency.At present,there are many problems in the design of profile extrusion die,such as repetitive work and poor standardization.In this paper,combined with the specific needs of a large extrusion die manufacturing enterprises,the key technologies of CAD system for profile extrusion die are studied.The parametric technology,feature recognition technology,top-down design method and knowledge-based rapid design method are applied to the design of extrusion die,and the CAD system based on UG for plastic profile extrusion die is established.The main research contents and work of this paper is as follows:(1)As to the variety of surface shape and the complexity of modeling,the concept of surface design based on closed loop is put forward.The theory and method of feature recognition are analyzed and applied to the design of flow channel surface.Firstly,the method of sketch inspection based on feature recognition is proposed,which can realize the fast removal of the disconnected and overlap curves curve in the sketch;Secondly,the method of closed loop identification is proposed,which realizes the automatic recognition of closed loops in a sketch;Finally,the method of surface design based on closed loop is presented,which realizes the rapid design of flow channel surfaces.(2)As to complex structures and low correlations between modules in extrusion die set,the integral design method is put forward for extrusion die based on the analysis of the theory and method of top-down design.And the parametric technologies are analyzed and applied in extrusion die set design.Firstly,combined with the reference set and expression technology,the die set standard parts library and databases are established,also the integral die set standard parts group is established based on assembly constraints;Secondly,the integral die set configuration method is proposed,and the plates detailed design is implemented through the application of WAVE Technology;Finally,The method of interference check based on PSO is put forward,which makes the interference assembly components modify intelligently.(3)As to the complicated waste lines and dimensions in the engineering drawing,through analysis of the concepts and methods of knowledge engineering,the automatic dimensioning method based on knowledge for extrusion die is studied.And the automatic dimensioning model based on knowledge for extrusion die is put forward.According to the structural characteristics of the extrusion die,the knowledge base of dimensioning features and the feature search method are established,which realizes the rapid identification of plate dimensioning features.According to the dimensioning process of extrusion die,the rule model of redundant line elimination,positioning dimension and size dimension is put forward,which achieves automatic dimensioning of the specification,location,tolerance and text.(4)The requirement and overall framework of the CAD system for plastic profile extrusion die are studied,and the CAD system for plastic profile extrusion die based on UG is established.Also taking the design of an extrusion die for flat frame product as an example,the proposed system key technologies are verified,which shows that the research results have good practical value.