The rotor is one of the important parts of the motor, its quality has a direct impact on the motor aluminum consumption and stray loss, improve the quality of the die-cast rotor, reduce motor aluminum consumption and stray loss, is to improve motor efficiency and reduce the motor temperature Measures. The quality of die-cast cast aluminum rotor, not only requires its size should meet the requirements of the drawings, but also should not have holes, shrinkage, cold isolation, cracks and inadequate casting defects such as the existence of, in particular, not more bars, And porosity defects. In addition, the aluminum content of impurities, especially carbon content, but also shall not exceed the technical requirements to ensure that the rotor of aluminum conductivity.
By compressor rotor tester WIND-RT-1 mostly of the aluminum die-casting problem can be detected
Below are the main problem happened during production, and the prevention and solution,
1. Porosity
Porosity is characterized by smooth surface, the shape of irregular holes, generally occurs in the broken wall thicker and in the vicinity, for the dispersion of small holes. The main reason for the formation of stomata is the lack of fullness of the pressure chamber, resulting in gas in the pressure chamber occupies a certain space, in the injection of gas and aluminum liquid into the die-casting mold cavity simultaneously. The general solution is as follows
1.1 Improve the chamber fullness, as far as possible the choice of smaller pressure chamber. Aluminum liquid to the pressure chamber, the pressure can not be too fast that the flow can not be too fast, so that the pressure chamber of the gas through the pressure chamber discharge port. For full-vertical rotor die-casting machine, it should be a reasonable choice slow shot trip.
1.2 If the gate speed is too fast, so that when the liquid aluminum in the filling turbulence, but also prone to pores. The general solution is to meet the good shape of the state, increase the cross-sectional area of the gate to reduce the gate speed.
1.3 Filling too fast, so that the die casting mold cavity gas discharge is difficult, the same will produce pores. In the molding has been guaranteed under the premise should be appropriate to reduce the filling speed.
1.4 The final filling die casting parts of the exhaust channel should have sufficient cross-sectional area to make the gas discharge smooth, if blocked should be promptly ruled out.
1.5 pressure chamber and die-casting mold cavity surface coating should not be too much, too much paint will fill the process of aluminum liquid produce more gas, the gas is difficult to discharge in a short time.
1.6 Should de-oil before the die-casting rotor to the film processing, otherwise, in the die-casting combustion due to heat will produce a lot of gas, and can not all discharge from the cavity
2. Bubble
Bubble is characterized by the die-cast rotor in the epidermis, gathered in the gas expansion of the bulging bubble. The cause of the bubble is generally die casting mold temperature is too high, so that aluminum liquid in the filling process involved in excessive gas caused, such as coating too much, will make the volatile gas is wrapped in the rotor end ring surface. In addition, with die-casting mold exhaust poor, open mold and other factors related to premature. This bubble is not obvious in the surface of the die-cast rotor, in the shaftless rotor heating sleeve shaft, the performance was more prominent.
To solve the bubble is to control the work of die-casting mold temperature and filling rate of aluminum, that is not too high filling speed, the appropriate increase in the gate area, in general should not be large; And retention time.
3. Shrinkage
The shrinkage is characterized by irregular shape, dark, rough surface with holes. Shrinkage is usually caused by the internal failure of the aluminum liquid in the condensation process in a timely manner. Such as aluminum smelting process and the heating specification is not reasonable, the pressure is too low, the time is too short.
The measures to solve the shrinkage cavity are to control the temperature of the aluminum liquid, raise the pressure of the injection pressure, and prolong the time of holding pressure.
The die cast aluminum rotor, porosity, bubble, shrinkage hole and shrinkage of the three defects are rare, the bubble is generally in the rotor is re heating performance obviously, pores are often exist. The stomatal distribution of the rotor is not uniform, and the end ring is more than that of the air hole, and the upper end ring (finger) is more than the lower end of the ring (Jing Moduan). For die casting rotor, air hole is difficult to eradicate, only through the selection of die casting parameters and reasonable design of die casting die, so that the pores to a minimum degree. Generally speaking, the reduction of the injection rate is favorable to the reduction of porosity, and the pressure shooting speed has little effect on the porosity of the rotor in the range of m/s 0.7~1.5. The effect of pressure on the porosity of the rotor is more obvious, the higher the pressure, the lower the porosity. Some experiments show that when the pressure is increased from 20 MPa to 30 40%~70%, the porosity is reduced by about MPa. Therefore, the reduction of the porosity of the rotor in the selection of process parameters is mainly to improve the compression ratio of pressure, of course, the choice of compression ratio pressure according to the specifications of the die casting rotor and the performance of the equipment used to determine. The holding time, stay time, die cast temperature, die structure, coating type and daub uniformity and pressure chamber filling degree and other factors are crucial, so in the actual production can not be ignored.
4. Crack
Die-casting rotor crack is divided into two kinds of cold crack and hot crack. Cold crack is characterized by the rotor end ring surface or the guide bar has penetrated or not penetrate the crack elongated slit, the crack is not oxidized. As the rotor temperature decreases or under external force, the crack will expand. Hot crack is characterized by the rotor end surface of the ring has penetrated or not penetrate the slit groove, the crack has been oxidized, under the action of external forces have trends, especially the rotor cooling to room temperature, the crack depth, width And length are increased
Cause:
(1) the rotor structure design is unreasonable, especially the structure of the end ring unreasonable,
that is, when the thickness of the end ring and width ratio is less than or equal to 0.4, easy to crack.
(2) the original aluminum ingot Fe / Si content exceeds the technical requirements.
Practice has proved that when Fe / Si ≥ 2.5, fewer cracks.
Solution:
(1) Fan, the balance column and the end ring should have a large sleek angle, in order to reduce the stress concentration, increase its strength.
(2) Aluminum melt process, it is necessary to strictly follow the melting aluminum standard operation to reduce the aluminum liquid oxidation and inspiration.
(3) Reasonable control of mold temperature and aluminum pouring temperature.
(4) Control of pressure and mold retention time, so that casting the rotor has enough
5. End ring inner ring off
The inner ring of the end ring is one of the common quality problems of the die-casting rotor. The main reason is that the packing time is too short, or the aluminum liquid is not completely solidified due to the aluminum temperature is too high, or because the end ring is thin and wide, Gate and thick, in the open mode premature situation, can cause the inner ring off.
The inner ring off will cause serious quality problems. As the inner ring off can lead to broken rotor, so such problems should be reasonable control of dwell time and mold retention time, and appropriate to reduce the aluminum pouring temperature.
6. Slot quality
6.1 Slot recess
Notch depression is mainly due to the rotor core is too high stacking factor that the core is too long, in the mold when the rotor core punching force in the clamping force under the deformation caused by notch depression. Therefore, the rotor core laminating coefficient should be reasonable, that is, after the rotor core length of the rotor to meet the technical requirements, but if the core length is too short, rapid filling in the aluminum liquid, prone to aluminum and difficult to retreat axis.
6.2 Notches are missing
Notch slot for more reasons, mainly due to the rotor punching the keyway and cast aluminum axis on the oblique key with the gap is too large, resulting in a piece of film positioning are not allowed, the displacement is too large, resulting in notches. In the die-casting, the rotor core is not smooth, which affects the apparent quality of the rotor. On the other hand, the effective area of the rotor bar is reduced, which affects the motor performance, such as high motor temperature and low efficiency.
7. Aluminum mis positioning
The main reason is channeling between aluminum rotor punching burr is too large, the lamination pressure coefficient is too low; in the process of a foreign body in the rotor loading pad into the film; liquid aluminum casting temperature is too high; the filling speed is too high. The increase of the stray loss of the motor will affect the performance of the motor. When there is a piece of aluminum, it should find out the reason and take the corresponding measures to solve it.
8. Inclusion, cold isolation, broken sticky mode
8.1 Inclusion is characterized by the end of the ring, balance column, fan blades and guide bars in the formation of irregular holes in the hole filled with debris. The main reason for the aluminum liquid purification is not complete; aluminum liquid impurities, scoop aluminum liquid into the impurity and oxide; die-casting mold is not clean; paint painted too much or impurity foreign body. When the full-vertical die-casting machine from the fan side into the aluminum, the majority of manufacturers in the pressure chamber into the asbestos paper cap, asbestos paper cap easily pressed into the rotor end of the ring and the wind caused by inclusions.
The above-mentioned circumstances as long as careful operation, strengthen the liquid aluminum purification, a reasonable choice of paper cap length, inclusion is completely avoidable.
8.2 Cold compartment
Cold compartment is characterized by a few aluminum liquid docking or lap each other, not completely integration of the gap, the junction of the edge was rounded shape, similar reasons and inclusions. Such as poor mobility of aluminum liquid, low temperature die-casting mold, the gate speed is low, low temperature aluminum liquid filling and other forms of aluminum is not good. In addition, the die-casting mold of the exhaust channel is poor, can also cause cold isolation.
8.3 Broken bars
Broken bar is characterized by discontinuity of the guide bar of the squirrel-cage rotor. The reason for the breakage of the guide bar is similar to that of the cold compartment and the inclusions. However, depending on the specifications of the rotor, the shape of the rotor groove and the width and area Of the size. The main measures to solve the broken bars are: adjust the pouring temperature of aluminum liquid, injection speed (gate speed), injection pressure ratio, melting aluminum specifications and die casting parameters.
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