Principles and techniques for mechanical product design
1 : Mechanical product design principle: Reasonable design should ensure the lowest manufacturing cost under the premise of ensuring the necessary functions of the product. First, the following requirements must be met.
(l) Customer’s requirements for product features and services must be met. The construction machinery provides customers with not only the functions of the products, but also the after-sales services that support these functions. Therefore, in the design process, it is necessary to aim at different functional features of the product, and to make the product have good maintenance convenience.
(2) Comply with the state’s industrial development policies and relevant laws and regulations.
(3) Adhere to the principle of “three-oriented” of standardization, generalization and serialization.
(4) Meet the social requirements for environmental protection.
(5) In line with the laws of technological innovation, attach importance to the protection of intellectual property rights.
(6) From the actual process level and production capacity of the enterprise, emphasize the combination of design, process and production.
2: Product design is not just a pattern design, but also process design and production design. Production design should be studied mainly from the following aspects:
1 Simplify the function or shape of the part;
2 Maximize product standardization, generalization, and serialization;
3 Make the material grades, varieties and specifications specified in the design drawings as consistent as possible with the existing materials;
4 Considering the blank process and the processing process more effectively;
5 Judging the rationality of the process design according to the processing technology, operation rules and related information used in the current normal production of the enterprise;
6 Select the dimensional tolerances and surface roughness that can be guaranteed by mature processing technology;
7 Comprehensive analysis of information related to the production process
3: Adopting the principle of “three transformations”
(l) Parts should be replaced with standard parts or standard parts or purchased parts.
(2) When designing splines and threads, it should be easy to use standard tools and measuring tools for processing and testing. In particular, priority should be given to the existing tools and measuring tools.
(3) For the design of large structural parts and steel castings, use fasteners that do not need to be tapped as much as possible, such as replacing the screw holes with welded nut plates. When designing large workpieces, consider using a well-formed hole as a reference to weld the nutplate.
(4) Try to use existing mature parts or mature structures and process methods to make the products serialized and generalized. With this “building block” method, the design speed can be accelerated, the prototype period of new product prototypes can be shortened, and the market can be occupied as early as possible.
(5) Establish the company’s own “standard parts library” and speed up the design and trial progress. DEYUCNC has now established and gradually improved the “factory standard parts” system and the “factory standard parts library”, and selected the same or similar parts used in more than three main products as factory standard parts.
(6) Select a uniform taper, consistent thickness and size of the steel casting material as much as possible.
4: Improved design from shape and structure
(1) Minimize parts. Combine several parts into one part, for example, change the weldment to a stamped part to reduce the number of parts.
(2) Design the part into a symmetrical structural form.
(3) Designing parts with similar shapes for use in several products to be designed as universal parts.
(4) Simplify the shape of each part, improve the shape of the part, reduce the shape of the bend, and sometimes change the part that is difficult to ensure the dimensional accuracy during the pressing to the welded part.
5: Improve the process plan
(l) Avoid unnecessary cutting, especially the cutting of the clamping reference surface. When welding parts are prepared by welding with a highly automated welding robot, pre-weld processing of the components should be considered to ensure the mutual positional dimensions between the components of the welded parts. Otherwise, the error will be too large and the robot will not be able to automatically track the welding.
(2) Under the premise of ensuring the reasonable use of components, the machining accuracy level requirements such as dimensional tolerance, surface roughness and shape tolerance can be reduced according to actual needs.
(3) Reduce the bending shape and complexity of parts, reduce scrap rate and manufacturing costs.
(4) When the steel is subjected to length cutting, the flame cutting should be changed to the steel cutting and cutting; the flame cutting of the general material is changed to shearing with the shearing machine; the rectangular strip workpiece is changed from the four sides to the cutting. With strip steel, it is only the shearing of the length.
6: Adopting process technology that saves resources and reduces pollution
(l) The steel castings are changed to welded parts. It is difficult for the foundry industry to completely solve the environmental pollution problem and it is easy to produce casting defects, which can be easily solved by welding techniques and welding parts.
(2) Under the premise of ensuring the strength of the parts and optimizing the thickness of the plate, the weight of the parts is minimized. The design of the structural weldment must be such that the rib is stressed and the weld is stressed. The use of thick plates in the construction of structural weldments is often not a requirement for strength, but a need for stiffness, i.e., small deformation of the slab during welding, or small deformation when the weldment is loaded. Some individual slabs can often be replaced by thinner plates with appropriate ribs, which not only reduces the total weight, but also increases the load carrying capacity.
(3) Select reasonable parameters such as weld length and weld angle. A considerable number of designers often confuse “strength welds” with “joint welds”. In design, there is often a tendency for the welds in the weldments to be welded and the weld angles to be better. In fact, the choice of welding penetration or welding is not necessary, the designer should carefully consider the decision.
Principles and techniques for mechanical product design