The CATIA Knowledge Advisor module embeds implicit design practices into the entire design process and translates them into clear knowledge, expressing all the knowledge units in the product with parameters, relationships, and behaviors, and forming products in the form of DesignTables. knowledge base. Using the knowledge of the knowledge base, define all the engineering parameters that affect the performance of the product, form the engineering rules expressed in the form of mathematical formulas and function relations, and then establish the design guiding process of these engineering rules according to the product design needs, thus realizing the engineering parameters to geometric parameters. Drive process.
The CATIA knowledge consultant organically combines the knowledge units in the product knowledge table, defines the knowledge rules of the products in the form of formulas, rules and inspections, and establishes a self-learning algorithm for product parametric design, and sets corresponding error information and recommendation suggestions. Object-oriented knowledge engineering languages ​​connect these design rules.
Parametric modeling of helical gears in CATIA environment Three-dimensional parametric modeling of helical gears is carried out in the context of CATIAV5. Given the basic characteristic parameters of the inclined gear: tooth number = 25; normal modulus m = 4; helix angle β = 15 °; normal pressure angle n = 20 ° normal tooth height coefficient h * a = 1; The headspace coefficient C*=0.25; the tooth width B=50 mm.
Obtain the involute rectangular coordinate equation: x=rbsint-rbtcosty=rbcost+rbtsint In the CATIA environment, use f(x) to define the characteristic parameter type and formula of the helical gear to be modeled: Z=25, m=3, r= Mz/2, a=20degrb=rcos(a),ra=r+mh*a,rf=r-m(h*a+C*) where: is the number of teeth, m is the modulus, r is the radius of the division circle, rb is the base The radius of the circle, ra is the radius of the tip circle, rf is the radius of the root circle, β is the helix angle, a is the normal pressure angle, B is the tooth width; s is the tooth thickness on the index circle, and e is the root transition circle Corner radius.
Establish the involute parameter equation in fog: x=rb*sin(t*PI*1rad)-rb*t*PI*cos(t*PI*1rad)y=rb*cos(t*PI*lrad) +rb*t*PI*sin(t*PI*1rad) gets the involute as shown in 2: 2 Involute. On this basis, we can easily get the gear contour, as shown in 3: 3 tooth profile basic parameters Then, a single helical tooth is obtained by scanning on the β=15° spiral line, and finally a complete helical gear is obtained by the circular array, as shown in 4: 4β=15° helical gear establishing design knowledge table (DesignTable), here we give The main parameters of the helical gear, as shown in 5: 5 change the parameter in the DesignTable β = 20deg, you can generate a new gear, as shown in 6: 6β = 20 ° helical gear yk (x, y) rbtx work research Open line.
Conclusion The parametric modeling method discussed in this paper combines advanced knowledge engineering principles, and the product design knowledge is used throughout the design process. By establishing a product knowledge base, using knowledge and acquiring knowledge, knowledge-driven product parametric design is realized. And through the introduction of parametric 3D modeling of helical gears, it embodies an important feature of modern computer-aided design, and provides accurate and reliable 3D solid type for CAE/CAM.
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