Ms. Shen's friend Xiao L engaged in motor product inspection work, and talked about small and medium-sized L. In the actual inspection process, when the casting wall was too thin, the deformation was particularly serious after the completion of the processing. The more common ones are small machine numbers such as Y2-112~132. The elliptical problem of the base seat and inner bore is particularly serious, and the base may even be cracked during the press of the stator into the base.
Many problems occur due to castings
The design of the wall is too thin and the design defects are insufficient. The actual deformation is not only easy to deform, but also the fatality is that the geometrical tolerances of the structural parts such as the base and the end cover are not effectively controlled, and the assembly accuracy of the motor is greatly reduced. Defects in mechanical properties such as noise and vibration have naturally become a problem that cannot be avoided or avoided.
The design of the motor castings is very particular. The problem of ventilation and heat dissipation during the operation of the motor, adapting to the processability of the actual production process equipment, whether the overall structure of the motor is aesthetically pleasing, and a series of problems involving the performance of all aspects of the motor must not be underestimated, and must be carefully calculated and simulated carefully.
Among the many problems related to casting design, the technical problems are often the most difficult to consider in the design process. The situation is more complicated. It has often been cast into casting blanks and processed to find that there are still many details not considered. Today, Ms. participated in the motor castings to share and share some knowledge and experience related to casting.
Problems in the design of castings
In casting production, due to many factors affecting the quality of castings, casting defects caused by design are more deadly, so they must be highly valued and treated with care.
1 Design principles
First of all, it is necessary to consider the two functional requirements of strength and heat dissipation; secondly, the shape is novel and beautiful, and the processing technology is good; and the third is to reasonably set the reinforcing ribs and the process ribs on the structure of the specific casting.
2 Reasonable wall thickness of castings
Each cast alloy has its proper wall thickness when cast using a casting method. If the wall thickness is selected reasonably, it can not only ensure the mechanical properties of the casting, but also prevent the occurrence of certain casting defects. Since the fluidity of the cast alloys is different, the "minimum wall thickness" of the castings that can be cast by different cast alloys is different under the same sand casting conditions. If the wall thickness of the designed casting is smaller than the "minimum wall thickness", defects such as insufficient pouring and cold insulation are likely to occur. The "minimum wall thickness" of the casting depends mainly on the type of alloy and the size of the casting. In order to avoid similar problems, the new castings should be fully technically exchanged with the casting manufacturer to prevent the incompatibility of the cast parts.
3 Casting wall thickness to strive for uniformity
If the wall thickness difference of each part of the casting is too large, a hot joint of metal accumulation is formed at the thick wall, so that defects such as shrinkage cavities and shrinkage are easily generated in the thick wall. At the same time, due to the large difference in the cooling rates of the various parts of the casting, thermal stresses are also formed, which sometimes cause cracks in the thin joints of the casting.
The uniformity of the wall thickness of the casting is such that the cooling rates of the walls of the casting are similar, and not all wall thicknesses are required to be identical. For example, the inner wall of the casting should be thinner than the outer wall due to slow heat dissipation, and the thickness of the rib should be thinner. When checking the uniformity of the wall thickness of the casting, the machining allowance of the casting must be considered.
4 Characteristics of gray iron castings
Due to the different casting properties of various alloys, their structures also have their own characteristics. Because of the small shrinkage, shrinkage and hot cracking tendency of gray cast iron, the requirements for the uniformity of the wall thickness of the casting and the transition between the walls are relatively low, but the wall thickness is sensitive to the mechanical properties, so The thin-walled structure is most suitable. But also to prevent extremely thin sections, in order to prevent the appearance of hard and brittle white mouth tissue.
5 castings intellectual development
The requirements of surface quality, short delivery time and environmental protection have led to continuous renewal and changes in casting processes and methods. The original extensive soil sand casting was completely eliminated, and new processes and new methods such as resin sand casting, lost foam casting and vertical line casting came into being, gradually developed towards the direction of intellectual development, which had a profound impact on the motor manufacturing process and promoted the motor design concept. Further move towards precise design and rapid update.