Research On 2D Automatic Dimensioning Based On Design Feature

As for manufacturing status, using 2D drawings instruct processing is still the main form of factory processing, and it often takes half of the designer's time to finish the dimensioning, so, the speed of engineering drawing dimensioning will greatly affect the efficiency of design and manufacture. At present the mainstream 3D software have the function of automatic dimensioning in the design of engineering drawing, the method them adopt is display the sketch dimensioning and constraints directly in the engineering drawing, the result of dimensioning have big difference with actual situation at most time, on the contrary, it will reduce the efficiency of dimensioning, this paper proposed a way of engineering drawing auxiliary automatic dimensioning base on design feature for the situation. First of all, recognizing basic feature and combination feature from model, finally finishing those feature's shape and position dimensioning in engineering drawing. This paper's Concrete study content as follows:First, establishing all kinds of basic feature's sketch library, then extracting stretch and revolve feature's sketch. Using edge data of every loop in sketch to create our own edge object, then combining edges in loop. Finally, using the method of pattern matching to match the sketch of feature need to recognize and sketch of basic feature, then recognized basic stretch feature and basic revolve feature(hole, shaft, cube, etc.).Mechanical parts not only have basic feature, but also have combination feature consist of hole or shaft(array holes, step hole, step shaft, etc.). First of all, according to the same axis and the same normal vector direction to classify the basic hole and basic shaft,then, designing different search recognition algorithm for each combination feature, the algorithm effectively recognized combination feature in 3d model.This paper designed the data structure to save different kinds of features, and added special properties to data structure for feature recognition and preventing repeat dimensioning. Finally using automatic dimensioning technology achieved automatic dimensioning for recognized features in the engineering drawing. Through this method, we effectively achieved auxiliary automatic dimensioning on engineering drawing, and got the purpose of raising the speed of dimensioning.