Lesson 31 Dimensional tolerances and surface roughness尺寸公差与表面粗糙度 机械专业专业英语教学用书.pptVIP

Lesson 31 Dimensional tolerances and surface roughness尺寸公差与表面粗糙度 Because of the highly competitive nature of most manufacturing business, the question of finding ways to reduce cost is ever present. A good starting point for cost reduction is in the design of the product. The design engineer should always keep in mind the possible alternatives available to him in making his design. It is often impossible to determine the best alternatives without a careful analysis of the probable production cost. Designing for function, interchangeability, quality, and economy requires a careful study of tolerances, surface finishes, processes（加工方法）, materials, and equipment. Lesson 31 Dimensional tolerances and surface roughness尺寸公差与表面粗糙度 To assure sound and economical design from a producibility standpoint, careful consideration of the following general design rules—both separately and together—is of paramount（至高无上的）importance. The order of importance may vary according to design requirements, or factors, but the overall importance（总体重要性）always remains the same. Lesson 31 Dimensional tolerances and surface roughness尺寸公差与表面粗糙度 Seek simplicity. Design for maximum simplicity in functional and physical characteristics(功能特性和结构特性）. Determine the best production method. Seek the help of a production engineer to design for the most economical production methods. Analyze materials. Select materials that will lend themselves to low-cost production as well as to design requirements. (选择既能满足设计要求,成本又低的材料） Lesson 31 Dimensional tolerances and surface roughness尺寸公差与表面粗糙度 Eliminate fixturing（固定） and handling（装卸）problems. Design for ease of locating (定位), setting up, and holding （定位、夹持与装卸）parts. Employ maximum acceptable tolerances and finishes. Specify surface roughness and accuracy no greater than that which is commensurate with（相称的）the type of part or mechanism being designed, and the production method or methods contemplated（深思的）. Lesson 31 Dimensional tolerances and surface roughnes