Investigation And Realization Of Computer Aided Design System For Flat-knitted Fabric

Computer aided design(CAD) refers to the design process that the designers are engaged in using the computer and graphics devices. It is the core of the techniques to innovate the traditional design methods. How this technique is combined with the production facilities is an important metric of the grade of the production techniques. The computerized flat knitting machine is a highly intelligent electromechanical device that has substituted for the manua lly operated flat knitting machine. The flat knitting CAD software is the major medium of interaction between the designers and the computerized flat knitting machine. However, this technique in China are greatly interior to the foreign counterparts. There are several issues, which exist in the domestic flat knitting CAD system, such as simplex view, low intellige nce program and the separation of forming and pattern designing module.Hence, in order to shorten the product the development cycle, reduce the production costs, accelerate the digitalizat io n, and make the Chinese equipment and products more competitive around the globe, it is necessary to develop a set of multifunctional, intuitive and intelligent flat knitting CAD applications.This work carried out the research on the data structure, image representation, fabric designing method and forming techniques, meanwhile constructed the mathematical model of flat knitted fabric.The flat knitting fabric data was classified into two categories: pattern data and parameter data. The two classes of data were analyzed in the form of knitting point and knitting line, respectively. The knitting points include the information about knitting movements of the two needle bed, raw material and sinking depth, while the knitting lines contain the parameters of machine speed, take down, feeders and the system. A matrix-based mathematical model was constructed, where the process line was the vertical dimension, the pattern width was the horizontal dimension in the pattern type data, and the number of parameters was the horizontal dimension in the parameter data. Based on the constructed mathematical model of the fabric, the flat knitting CAD data structure was defined, where the pattern type data was defined to be the 2-D array which took the point-wise data structure as the element, and the parameter data was defined to be the general 2-D array. In addition, the compressed numbered symbols, pattern color and module index for pattern notation, the needle location information for knitting techniques graphics, the knit loop unit number, brightness and temporary point information for knit loop structure are added to the point-wise data structure. The information of Pattern line, periodic knitting and knitting techniques line are added to line information. The augment of data is the foundation of multi-view representation meanwhile reduces the computation of the program.This work adopted the knitting techniques, pattern notation and loop structure view to represent the knitted fabric. And analyzed the data information included in the knitting techniques graphic unit, in which took the knitting loop as an example, discussed the variatio n of symbols at different conditions and designed the judgment flow of the graphic symbols, then achieved the drawing of the knitting techniques graphic through layered maps method. The pattern notation graphic contains ground structure layer and forming layer. The paper designed the symbols in these layers for each category and the graphic unit in it adopt the combinat io n of rectangle and symbol, in addition, in order to enrich the graphical display approaches, provide various choices for the display color of rectangle and symbol. Loop is the graphic unit of loop structure image, in order to generate frequent, real, flexible loop graphic unit, this work proposed a loop center line model based on the interlacing point and simulated the regular and deformation of knit loop and tuck loop respectively, meanwhile constructed the loop center line model which adapts to different deformation by cubic Bezier curve. Texture mapping was done with the loop center line as the baseline. Adding texture interpolation and brightness variatio n can make loop more lifelike. The loop simulation program was developed with VC++. For the purpose of displaying the solid intermeshing relationship of the 2D loop graphic, the paper proposed a layered mapping method which segments the loop longitudinally and set the different layers with different partial graphics, then combine the layers to represent the blanking relationship of the loop. As wel, presented a rule of mapping sequence to solve the issue of overlapping relationship in the same layer. Through this method, it can achieve the loop structure representation of regular stitch and cable stitch and fabric design by loop unit.In terms of structure variations, the automatic loop transfer and stitch coverage methods were studied. The implementation of automatic loop transfer improves the safety of operation and the efficiency of design, and accelerates the operational speed of the software. The flood fill algorithm was used for selection of irregular regions and coverage of non-flat stitches. Jacquard classification was defined in the jacquard pattern algorithm. The different types of jacquard were decompose graphically. The steps for achieving flat and non-flat jacquard were proposed to simplify jacquard editing. As for the fabric shaping algorithm, this dissertation took the V-collar raglan sweater of women as an example to discuss the calculation, editing and fabric shaping of the shaping technique. The style-based parametric calculating method and the layered data structure were proposed. The procedures of the automatic gathering algorithm were devised to edit the shaping technique. The curve of the round collar technique was fitted using the parabola. The fabric shaping was partitioned into the stages of shaping informa t io n conversion and technical point integration. It realized the transformation of forming techniques line information to point information, and the forming techniques is completed after combining with the techniques point in the ground structure, in general, the method simplified the operation flow of forming product design.The three aspects above were studied closely around the point of flatting knit fabric CAD system. After researching the computerized flat knitting principles and shaping methods, this dissertation developed the system in order to display the fabric structure as intuitively as possible and simplify operational procedures. The proposed system will be helpful for intuit i ve and efficient design of the flatting knit fabric and forms the foundation for customizing flatting knit products.