In recent years, Ms. Shen has been puzzled, and started to deal with several motor appearance problems, without exception, not related to steel plate welding parts. The reason is that there are a lot of special motors using weldments, there are many exposed welds and the treatment of welding slag is not complete, which can not be compared with a large number of castings using EPC process. Therefore, the quality inspection department does not release due to apparent problems, and the production department does not deal with it on the grounds that it is both time-consuming and hard to start. Ms. took part in the coordination with orders, and finally persuaded them to polish again. After all, the delivery of the contract could not be delayed and the quality problems could not be ignored.
Looking back, isn't this the battle between castings and welded steel? In today's increasingly prominent environmental protection problems, two factors will cause the motor manufacturers to use welding parts irregularly: first, the supply of castings is in short supply; second, the existing castings of motors used in specific occasions do not meet the requirements or one-time small batch special orders.
Castings and welded steel parts have their own advantages. Generally, the main structural parts of the motor are castings, which are mainly based on the following considerations: 1) complex modeling; 2) suitable for mass production in professional foundry; 3) good cutting performance and short manufacturing cycle; 4) low cost; 5) easy to guarantee the apparent quality. However, for the motor with uncertain market prospect and high risk, the cost of casting mould invested in advance is difficult to be digested or shared equally, so it is not suitable to adopt casting structure scheme in motor design.
The production of welded steel parts includes a series of complex processes, such as cutting and blanking, welding, annealing, sandblasting or shot blasting, which involves many types of work and long cycle, and is suitable for special motors with small quantity and complex types. However, some applications do not allow the use of cast iron, special structure motors such as water jacket cooling can only be welded with steel plates, and even some customers have specified that the motor shell must be made of steel. Therefore, although the apparent quality of welded steel parts is difficult to control and the process is cumbersome, it can effectively avoid risks when used in the verification stage of the new scheme, but it can greatly shorten the cycle when dealing with the special structure or single specification motor. The environmental protection problems brought by the production process are not as serious as the casting production.
Casting or welded steel plate is not only a simple design option, but also two completely different design ideas and styles. Designers need to carefully figure out the characteristics of casting and welded steel plate in material, mechanical properties, process methods, etc., and make the most of their advantages to design a motor with novel modeling and excellent mechanical properties.
As for the casting, it is a part formed by the casting method in terms of the forming method. The casting method is to inject liquid metal into the mold cavity, solidify and cool to obtain parts. The design of castings must consider the rationality of process and structure, and follow the following design principles:
1) In order to facilitate the separation of casting blank and metal mold when taking out the mold from the sand mold or EPC process, a 0.5 ° - 4 ° lifting angle shall be made on the surface perpendicular to the parting surface.
2) Machining allowance machining allowance shall be reserved on the surface of castings to be machined, and its size shall vary according to the type of casting alloy, machining accuracy, shape and size of castings. For steel castings, large castings and castings with complex shapes, the rest are relatively large.
3) Fillet in order to facilitate the molding and avoid the crack at the sharp corner of the casting during the cold shrinkage and the defects such as sand sticking during the sand casting process, the intersection angle between the inner cavity walls shall be made into fillet.
4) Try to replace the thick wall with stiffener or reticular structural reinforcement and enhance the rigidity and strength of the structure.
5) The single side closed cavity should be designed deep enough for the withdrawal hole of CNC lathe to avoid hitting the cutter when it is deep.
From the point of view of design, the structure of welded steel members is very particular. It is necessary to carefully and carefully plan the lapping of members with various layout, thickness and shape. The design principle is:
1) The welding properties of materials weigh the mechanical properties and welding properties of materials, and avoid using high carbon steel or heterogeneous materials for welding.
2) The actual material consumption is small, it is better to select standard section steel, and try to use the same specification or common thickness specification steel plate.
3) The construction scheme is simple and the welding process is simplified to the greatest extent, and it is easy to achieve the level of accuracy between the finished parts and the design requirements.
4) The welding finished product has high strength, complete function and perfect shape.
5) The welds can avoid the parts that affect the appearance as much as possible. Through the design of the joint between the components, the stress of the welds can be reduced, the number of surface welds can be reduced, and the appearance quality can be improved by means of design.
6) Highlight the design style of the whole machine, make full use of the flexible and random multi-dimensional structure of the weldment, put an end to the elements inconsistent with the structure and shape of the motor, and highlight the design concept of originality and lean manufacturing.