Research On Slicing Algorithm Of Ice Mold Rapid Prototyping Based On STL Model

Investment casting based on the ice mold is a kind of investment casting process using ice mold instead of expendable casting process such as wax mold and white mold.This process has the characteristics of high precision,low cost,pollution-free and low control requirements.The traditional method of obtaining ice mold requires the production of silicone rubber mold.But the production process of silicone rubber mold is complex,long production cycle and high cost,which is suitable for the needs of large and medium volume casting production.In order to quickly produce high-precision ice molds and meet the needs of small batch as well as personalized casting production,our research group uses RPM technology to produce ice mold—the rapid prototyping technology of ice mold,which is essentially FDM technology.The difference of technology is the use of different materials and prototyping conditions.Although there are many methods of rapid prototyping,the two-dimensional contour data of the model is still the first step in rapid prototyping.Therefore,the study of slice processing technology is an important task.In order to complete the STL model data processing software which is used in the ice model rapid prototyping experiment system,this paper proposes a slice algorithm based on dynamic spatial index and develops a slice software prototype system.The main contents of this paper are as follows:(1)The basic research on the rapid prototyping of ice molds is carried out.This paper analyzes the three types of existing STL model based on the slice algorithm.The principle,implementation steps,advantages and disadvantages of each type of algorithm are also given.According to the characteristics of ice mold forming,the requirements of rapid prototyping algorithm are analyzed.(2)A group slicing algorithm based on dynamic spatial index is proposed.The vertex index of STL model is constructed by K-d tree to realize the removal of the vertex redundancy.The global topology reconstruction of STL model is reconstructed based on the half-edge structure.The half-edge structure,representing the adjacency relation of STL model triangles is integrated into the vertex index.Based on the position characteristics of the triangular patches in the slice direction,the spatial indices of the K-d tree and the half-edge structure are used to quickly calculate the ordered triangular faces of each group.By constructing the global topological relation of the model,the algorithm can not only reduce the time of constructing the local topological structure of each set of triangular patches,but also improve the efficiency of the slices processing by using the K-d tree's high efficient query performance and the topological relation stored in the half-structure.(3)A rapid prototyping software prototype system of ice mold is developed.The overall software design scheme is determined through the functional analysis of the slicing software prototype system.The modular design method is used to classify the software and clarify the functions of each module.Based on the slicing algorithm as the core algorithm,the chip software prototype system is realized by using the graphical development application framework Qt and OpenGL technology.The main purpose of this paper is to develop a prototype software system which is suitable for the ice-model rapid prototyping experiment system built with our project group.By absorbing the advantages of existing slicing algorithm,this paper proposes a group slicing algorithm based on dynamic spatial index and realizes the slicing software prototype system based on Qt and OpenGL.The slicing algorithm and the slicing software prototype system proposed in this paper are respectively verified.The results show that the slicing algorithm is stable and feasible,which can slice the STL model efficiently.The slicing software prototype system realizes the expected function.It can carry on the auxiliary transformation to the model,the multi-angle observation to the model and the function of displaying each slice contour.