Mechanic Technician Handbook

Author: Chief Editor: Huang Xiangcheng et al
Publisher:
Publish Date: 2000-07-01
Features:
Section: 3. Mechanical Design Requirements
(1) Design Factors A characteristic that affects the design of a part or the entire system is called a design factor. Typically, in any given design task, there are many design factors to consider. For example, strength, reliability, thermal factors, corrosion, wear, friction, utilization, cost, safety, quality, noise, shape, flexibility, control, stiffness, surface roughness, lubrication, maintenance, and volume. Under certain conditions, a design solution may only consider important design factors. Once a major design factor meets the requirements, other factors may no longer need to be considered. Some of the aforementioned factors are related to the size, material, and processing technology of parts in the system, while others affect the overall structure of the system.
(2) Adhering to National Standards Design must follow relevant codes and adopt standardized principles. China's relevant authorities have formulated many standards and specifications. When designing products or components, it is essential to strictly comply with all the provisions in the standards and specifications. For example, drawings must conform to national drafting standards. In various types and specifications of machinery, a significant number of components are identical. By standardizing these components and serializing them based on different dimensions, designers can avoid redundant design work and directly refer to relevant materials. For instance, using standard parts in threaded connections is very convenient, eliminating the need for redesign. Adopting standardized dimensions is an important measure to reduce product costs. Material selection should be as economical and practical as possible. Materials that are rarely used, expensive, or difficult to obtain in the market should preferably be avoided. Recommended material varieties in the material catalog should be prioritized. For externally purchased components, such as motors, pumps, bearings, and fasteners, it is advisable to select those that are easily available. In design, legal metrological units must be used to implement metrology laws.
(3) Economic Considerations in Design During the design decision-making process, cost factors play a very important role. To reduce product costs, efforts must be made in the following four aspects:
(1) Further simplify the design, reduce the number of parts, and improve standardization and generalization.
(2) Use cheaper materials.
(3) Improve the processability of blanks, parts, and assembly, and reasonably select accuracy, tolerances, fits, and other technical requirements.
(4) Improve production and management systems. Among these four aspects, simplifying the design is the most important.