组合体尺寸标注的渐进式分形建导教学方法

针对工程图学课程教学的重点和难点——组合体尺寸标注，基于尺寸标注的连贯 性和组合体的形体分解，提出采用渐进式分形建导教学方法。通过渐进式教学方法，根据几何 形体的相似性，在每一环节都采用分形建导思想，将复杂形体逐渐分解为简单形体，最终确定 组合体的尺寸标注方案。尺寸标注分形建导方法的迭代规则为“拆、形、位、合”，对应于拆分 形体、确定定形尺寸个数、确定定位尺寸个数、进行尺寸去重复化。明确尺寸去重复化的3 点 原则，并结合不同形体对尺寸标注的分形建导方法进行了应用。将渐进式分形建导教学方法应 用于组合体的尺寸标注，可以充分利用形体的相似性，引导学生循序渐进地完成组合体的尺寸 标注， 以达到组合体尺寸正确、完整的标注效果。

Progressive Fractal Facilitation Teaching Method for Composite Solid Dimensioning

Composite solid dimensioning is of great significance and difficulty in engineering graphics teaching. A progressive fractal facilitation teaching method is proposed based on the coherence of dimensioning and the shape decomposition of composite solid. The fractal facilitation method is employed in each step to decompose the complicated composite solid into simple one, through the progressive teaching method by means of taking into account the similarity of geometric solid. The iteration rule for the fractal facilitation method of dimensioning can be referred to as decomposing, shaping, locating and merging, which is corresponding to steps of decomposing the composite solid, ascertaining the number of shape size, ensuring the number of location size, and merging the repetition sizes. Three principles of dimensioning de-duplication have to be identified, and the fractal facilitation method for dimensioning is applied, in terms of different composite solids. The application of the progressive fractal facilitation method of dimensioning can take full advantage of the similarity of geometric solid, and lead students to accomplish the dimensioning of composite solid gradually, thus attaining a correct and complete dimensioning of composite solid.