motor casing
The manufacture of motor shell is a very important part in motor production. The materials of motor shell are generally cast iron, cast aluminum alloy, section steel (steel pipe), steel plate and so on. Low-power motors in China generally use cast iron, cast aluminum alloy and steel (steel pipe) shells, which have a large amount of workpiece processing, many processing procedures and long production cycle. The working environment of operators is poor and the labor intensity is high; Energy waste is great, and materials waste fire.
Internationally, developed countries such as Germany, Belgium, Japan and other countries have adopted a large number of steel shells as early as the middle of this century. This new processing technology of casing is a kind of processing technology with little cutting. Some domestic motor manufacturers began to study the manufacture of steel plate casings in the early 1970s, and a certain batch was formed in the mid-1980s. However, due to the use of cutting machine-pressing "U" type (or "W" type)-pressing "O" type, welding (manual or CO2 shielded welding)-polishing-once turning 1 18 pieces (referred to as bottomless chassis for short), there are many types of equipment used, and the proportion of human factors affecting the quality is large, so it is difficult to guarantee the quality.
At present, some developed countries generally use advanced special processing equipment for processing, which has high mechanization and automation and good quality. In the motor market of developed countries, low-power motors are generally steel plate shell motors. 1989, domestic trial-production processing equipment of steel plate bushing such as steel plate bushing winder and motor steel plate bushing welding machine has been started. In recent years, materials are expensive and the domestic motor market is weak. In order to reduce the manufacturing cost of motor, improve the quality of steel plate shell, enter and occupy the motor market in developed countries, it is necessary to study the new manufacturing technology of motor steel plate shell.
Comparison between old and new process schemes
The so-called old process scheme refers to the extrusion process scheme before the advent of special processing equipment for steel plate casing manufacturing.
Blanking under the shearing machine (length× width)-punching with a punch-pressing "U" (or "W")-pressing "O"-welding-grinding-lathe length-shaping, and the roundness (inner circle of the casing) is large, so it is generally necessary to arrange the processing at both ends, which will bring certain influence to the process of stator external pressing.
The so-called new process scheme refers to the rolling process scheme of special processing equipment for manufacturing steel plate shells:
Blanking of shearing machine (sleeve unfolding width)-punching length of punching machine-rounding by rounding machine-argon arc welding by special welder-total length of lathe.
As can be seen from the above two schemes, the former needs eight processes and the latter needs six processes. Even if a shaping process is added, there is still one less process than the former. It can be seen that the accuracy of inner circle dimension, inner roundness and welding appearance quality of the former motor steel plate shell are influenced by more factors than the latter.
Process flow and inspection after molding
(1) calculation formula
The formula for calculating the expanded length of casing is
The process adopts micro-radial expansion method, and the plastic correction coefficient K is 0.999-0.9999.
(2) Process flow
2. 1 Shell blanking with unfolded geometry
Because it is difficult to ensure the dimensional accuracy when cutting under the shearing machine, the shearing machine cuts according to the width (the width of the unfolded geometry of the casing), and the common punching machine cuts according to the length (the length of the unfolded geometry of the casing), as shown in figure 1, that is, cutting is combined with punching.
2.2 The shell is round.
The new two-roll rounding machine can be formed at one time, and the straight line section A of the welded seam after rounding is about 3 ~ 5 times the thickness of the plate. Because of the existence of the straight line section at the joint, there is a slight sharp corner here after welding, as shown in Figure 2. In fig. 2b, the rounded shell opening is less than10mm.
2.3 Chassis welding
The shell is welded by butt welding argon arc welding. The sleeve is sleeved on the mandrel and clamped by two bricklayers to ensure that the welding butt welding is neat and flat. The welding equipment is equipped with a programmable controller, and the welding gun adopts a motor steel plate shell welding machine with a speed stabilizing device. The welding surface is flat and smooth, as shown in Figure 3. After welding, there is a dust angle at the shell weld, as shown in Figure 3b.
2.4 shell molding
Generally, the roundness grade of steel plate sleeve after rolling and welding is less than or equal to 0.50 mm, and the sleeve shaping process can be cancelled if the finish turning and double stopping process is adopted. In order to cancel the finishing process of double notches and ensure the consistency of the inner hole size of the casing, that is, to ensure the consistency of the notch size, the micro-radial expansion method is used to finish the casing.
(3) Accuracy of detection methods and measuring tools
3. 1 detection method
Because there is a straight line at the joint of the casing after rounding, it is not completely eliminated after welding, so the three-point detection method is adopted. This detection method can be used to detect the inner hole of the casing after welding and shaping, and also suitable for detecting the stop part of the stator (or stator core) after press-fitting.
3.2 detect the inclination of measuring tools
The measuring tool is used to detect the formed casing, and its accuracy is as follows
200mm vernier caliper with accuracy of 0.02mm; 500mm vernier caliper with accuracy of 0.05mm; 500mm vernier caliper with accuracy of 0.02mm; Internal micrometer, accuracy 0. 1 mm
A the roundness of both ends of the stator stop is not greater than 0.40mm;
B stator adopts turning double stop process, which can cancel the casing forming process;
Improve processing quality and reduce labor intensity;
D the external press-fitting process is adopted without flanging, and the end cover has two sizes to choose from. If one size is adopted, the shell can be shaped with a slight spindle.