Motor core, as the core component in the motor, the iron core is a non-professional term in the electrical industry, and the iron core is the magnetic core. The iron core (magnetic core) plays a pivotal role in the entire motor. It is used to increase the magnetic flux of the inductance coil and achieve the maximum conversion of electromagnetic power. The motor core is usually composed of a stator and a rotor. The stator is usually the non-rotating part, and the rotor is usually embedded in the inner position of the stator.
The application range of motor iron core is very wide, stepper motor, AC and DC motor, geared motor, outer rotor motor, shaded pole motor, synchronous asynchronous motor, etc. are widely used. For the finished motor, the motor core plays a key role in the motor accessories. To improve the overall performance of a motor, it is necessary to improve the performance of the motor core. Usually, this kind of performance can be solved by improving the material of the iron core punch, adjusting the magnetic permeability of the material, and controlling the size of the iron loss.
A good motor iron core needs to be stamped out by a precise metal stamping die, using an automatic riveting process, and then stamped out by a high-precision stamping machine. The advantage of this is that the plane integrity of the product can be guaranteed to the greatest extent, and the accuracy of the product can be guaranteed to the greatest extent.
Usually high-quality motor cores are stamped by this process. High-precision metal continuous stamping dies, high-speed stamping machines, and excellent professional motor core production personnel can maximize the yield of good motor cores.
Modern stamping technology is a high-tech that integrates various technologies such as equipment, molds, materials and processes. High-speed stamping technology is an advanced forming processing technology developed in the past 20 years. The modern stamping technology of motor stator and rotor iron core parts is to use high-precision, high-efficiency, long-life, multi-station progressive die that integrates each process in a pair of molds to automatically punch on a high-speed punch. The punching process is punching. After the strip material comes out of the coil, it is first leveled by a leveling machine, and then automatically fed by an automatic feeding device, and then the strip material enters the mold, which can continuously complete punching, forming, finishing, trimming, and iron core. The punching process of automatic lamination, blanking with skewed lamination, blanking with rotary lamination, etc., to the delivery of the finished iron core parts from the mold, the entire punching process is automatically completed on a high-speed punching machine ( shown in Figure 1) .
With the continuous development of motor manufacturing technology, modern stamping technology is introduced to the process method of manufacturing motor core, which is now more and more accepted by motor manufacturers, and the processing methods for manufacturing motor core are also more and more advanced. In foreign countries, general advanced motor manufacturers use modern stamping technology to punch iron core parts. In China, the processing method of stamping iron core parts with modern stamping technology is being further developed, and this high-tech manufacturing technology is becoming more and more mature. In the motor manufacturing industry, the advantages of this motor manufacturing process have been used by many manufacturers. Pay attention to. Compared with the original use of ordinary molds and equipment to punch iron core parts, the use of modern stamping technology to punch iron core parts has the characteristics of high automation, high dimensional accuracy, and long service life of the mold, which is suitable for punching. mass production of parts. Since the multi-station progressive die is a punching process that integrates many processing techniques on a pair of die, the manufacturing process of the motor is reduced, and the production efficiency of the motor is improved.
1. Modern high-speed stamping equipment
The precision molds of modern high-speed stamping are inseparable from the cooperation of high-speed punching machines. At present, the development trend of modern stamping technology at home and abroad is single-machine automation, mechanization, automatic feeding, automatic unloading, and automatic finished products. High-speed stamping technology has been widely used at home and abroad. develop. The stamping speed of the stator and rotor iron core progressive die of the motor is generally 200 to 400 times /min, and most of them work within the range of medium-speed stamping. The technical requirements of the precision progressive die with automatic lamination for the stator and rotor iron core of the stamping motor for the high-speed precision punch are that the slider of the punch has a higher precision at the bottom dead center, because it affects the automatic lamination of the stator and rotor punches in the die. Quality problems in the core process. Now precision stamping equipment is developing in the direction of high speed, high precision and good stability, especially in recent years, the rapid development of precision high-speed punching machines has played an important role in improving the production efficiency of stamping parts. The high-speed precision punching machine is relatively advanced in design structure and high in manufacturing precision. It is suitable for high-speed stamping of multi-station carbide progressive die, and can greatly improve the service life of progressive die.
The material punched by the progressive die is in the form of coil, so modern stamping equipment is equipped with auxiliary devices such as uncoiler and leveler. Structural forms such as level-adjustable feeder, etc., are respectively used with the corresponding modern stamping equipment. Due to the high degree of automatic punching and high speed of modern stamping equipment, in order to fully ensure the safety of the die during the punching process, modern punching equipment is equipped with an electrical control system in the event of errors, such as the die during the punching process. If a fault occurs in the middle, the error signal will be immediately transmitted to the electrical control system, and the electrical control system will send a signal to stop the press immediately. At present, the modern stamping equipment used for stamping stator and rotor core parts of motors mainly includes: Germany: SCHULER , Japan: AIDA high-speed punch, DOBBY high-speed punch, ISIS high-speed punch, the United States has: MINSTER high-speed punch, Taiwan has : Yingyu high-speed punch, etc. These precision high-speed punches have high feeding accuracy, punching accuracy and machine rigidity, and reliable machine safety system. The punching speed is generally in the range of 200 to 600 times /min , which is suitable for punching the automatic stacking of the stator and rotor cores of the motor. Sheets and structural parts with skewed, rotary automatic stacking sheets.
2. Modern die technology of motor stator and rotor core
2.1 Overview of the progressive die of the stator and rotor core of the motorIn the motor industry, the stator and rotor cores are one of the important components of the motor, and its quality directly affects the technical performance of the motor. The traditional method of making iron cores is to punch out stator and rotor punching pieces ( loose pieces ) with ordinary ordinary molds , and then use rivet riveting, buckle or argon arc welding and other processes to make iron cores. The iron core also needs to be manually twisted out of the inclined slot. The stepper motor requires the stator and rotor cores to have uniform magnetic properties and thickness directions, and the stator core and rotor core punching pieces are required to rotate at a certain angle, such as using traditional methods. Production, low efficiency, precision is difficult to meet the technical requirements. Now with the rapid development of high-speed stamping technology, high-speed stamping multi-station progressive dies have been widely used in the fields of motors and electrical appliances to manufacture automatic laminated structural iron cores. The stator and rotor iron cores can also be twisted and stacked. Compared with ordinary punching die, multi-station progressive die has the advantages of high punching precision, high production efficiency, long service life, and consistent dimensional accuracy of punched iron cores. Good, easy to automate, suitable for mass production and other advantages, is the direction of the development of precision molds in the motor industry. Stator and rotor automatic stacking riveting progressive die has high manufacturing precision, advanced structure, with high technical requirements of rotary mechanism, counting separation mechanism and safety mechanism, etc. The punching steps of stacking riveting are all completed on the blanking station of stator and rotor. The main parts of the progressive die, the punch and the concave die, are made of cemented carbide materials, which can be punched more than 1.5 million times each time the cutting edge is sharpened, and the total life of the die is more than 120 million times.
2.2 Automatic riveting technology of motor stator and rotor coreThe automatic stacking riveting technology on the progressive die is to put the original traditional process of making iron cores (punch out the loose pieces – align the pieces – riveting) in a pair of molds to complete, that is, on the basis of the progressive die The new stamping technology, in addition to the punching shape requirements of the stator, the shaft hole on the rotor, the slot hole, etc., adds the stacking riveting points required for the stacking riveting of the stator and rotor cores and the counting holes that separate the stacking riveting points. Stamping station, and change the original blanking station of stator and rotor to a stacking riveting station that plays the role of blanking first, and then makes each punching sheet form the stacking riveting process and the stacking counting separation process (to ensure the thickness of the iron core). For example, if the stator and rotor cores need to have torsion and rotary stacking riveting functions, the lower die of the progressive die rotor or stator blanking station should have a twisting mechanism or a rotary mechanism, and the stacking riveting point is constantly changing on the punching piece. Or rotate the position to achieve this function, so as to meet the technical requirements of automatically completing the stacking riveting and rotary stacking riveting of punching in a pair of molds.
2.2.1 The process of automatic lamination formation of the iron core is as follows: Punch out riveting points of a certain geometric shape on the appropriate parts of the stator and rotor punching pieces. The form of the riveting points is shown in Figure 2 . It is convex, and then when the convex part of the previous punch of the same nominal size is embedded into the concave hole of the next punch, an “interference” is naturally formed in the tightening ring of the blanking die in the die to achieve tightness. The purpose of the fixed connection is shown in Figure 3 . The process of forming the iron core in the mold is to make the convex part of the stacking riveting point of the upper sheet When the blanking punch pressure acts, the lower one uses the reaction force generated by the friction between its shape and the die wall to make the two pieces overlap. In this way, through the continuous punching of the high-speed automatic punching machine, a neat iron core can be obtained which is arranged one by one, the burrs are in the same direction and have a certain stack thickness.
2.2.2 The control method for the thickness of the laminations of the iron core is to punch through the riveting points on the last punching piece when the number of iron cores is predetermined, so that the iron cores are separated according to the predetermined number of pieces, as shown in Figure 4 . An automatic stacking counting and separating device is arranged on the mold structure, as shown in FIG. 5 .
There is a plate-pulling mechanism on the counter punch, the plate-pulling is driven by a cylinder, the action of the cylinder is controlled by a solenoid valve, and the solenoid valve acts according to the instructions issued by the control box. The signal of each stroke of the punch is input into the control box. When the set number of pieces is punched, the control box will send a signal, through the solenoid valve and the air cylinder, the pumping plate will move, so that the counting punch can achieve the purpose of counting separation. That is, the purpose of punching the metering hole and not punching the metering hole is achieved on the stacking riveting point of the punching piece. The lamination thickness of the iron core can be set by yourself. In addition, the shaft hole of some rotor cores is required to be punched into 2 -stage or 3 -stage shoulder countersunk holes due to the needs of the support structure.As shown in Figure 6 , the progressive die should simultaneously complete the punching of the iron core with the requirements of the shoulder hole process. The above-mentioned similar structure principle can be used. The die structure is shown in Figure 7 .
2.2.3 There are two types of core stacking riveting structures: the first is the close stacking type, that is, the core stacking riveting group does not need to be pressurized outside the mold, and the bonding force of the core stacking riveting can be achieved by ejecting the mold. . The second type is the semi-close stacking type. There is a gap between the riveted iron core punches when the die is released, and additional pressure is required to ensure the bonding force.
2.2.4 Determination of the setting and quantity of the iron core stacking riveting: The selection of the iron core stacking riveting point should be determined according to the geometry of the punching piece. At the same time, considering the electromagnetic performance and use requirements of the motor, the mold should consider the stacking riveting point. Whether there is interference in the position of the punch and the die insert, and the strength of the distance between the position of the stacking riveting ejector pin and the edge of the blanking punch. The distribution of stacked riveting points on the iron core should be symmetrical and uniform. The number and size of stacked riveting points should be determined according to the required bonding force between the iron core punches, and the manufacturing process of the mold must be considered. For example, if there is a large-angle rotary stacking riveting between the iron core punches, the equal division requirements of the stacking riveting points should also be considered. As shown in Figure 8 .
2.2.5 The geometry of the core stack riveting point is: ( a ) Cylindrical riveting point, suitable for the close-stacked structure of the iron core;( b ) V -shaped stacked riveting point, which is characterized by high connection strength between the iron core punches, and is suitable for the close-stacked structure and semi-close-stacked structure of the iron core;( c ) L -shaped stacking riveting point, the shape of which is generally used for skew stacking riveting of the rotor core of an AC motor, and is suitable for the close-stacked structure of the core;( d ) Trapezoidal stacking riveting point, the stacking riveting point is divided into a round trapezoidal and a long trapezoidal stacking riveting point structure, both of which are suitable for the close-stacked structure of the iron core, as shown in Figure 9 .
2.2.6 Interference of stacking riveting point: The bonding force of the core stacking riveting is related to the interference of stacking riveting point. As shown in Figure 10 , the difference between the outer diameter D of the stacking riveting point boss and the size of the inner diameter d (that is, the amount of interference), which is determined by the edge gap between the punch and the die at the punching riveting point, so selecting the appropriate gap is an important part of ensuring the strength of the core stacking riveting and the difficulty of stacking riveting.
2.3 Assembly method of automatic riveting of stator and rotor cores of motors3.3.1 Direct stacking riveting: in the rotor blanking or stator blanking step of a pair of progressive dies, punch the punching piece directly into the blanking die, when the punching piece is stacked under the die and the die When inside the tightening ring, the punching pieces are fixed together by the protruding parts of the stacking riveting on each punching piece. 3.3.2 Stacked riveting with skew: rotate a small angle between each punching piece on the iron core and then stack the riveting. This stacking riveting method is generally used on the rotor core of the AC motor. The punching process is that after each punch of the punching machine (that is, after the punching piece is punched into the blanking die), on the rotor blanking step of the progressive die, the rotor blanks the die, tightens the ring and rotates. The rotary device composed of the sleeve rotates a small angle, and the rotation amount can be changed and adjusted, that is, after the punching piece is punched, it is stacked and riveted on the iron core, and then the iron core in the rotary device is rotated by a small angle. The iron core punched in this way has both riveting and twisting, as shown in Figure 11 .
There are two types of structures that drive the rotary device in the mold to rotate; one is the rotational structure driven by a stepping motor, as shown in Figure 12 .
3.3.3 Folding riveting with rotary: Each punching piece on the iron core should be rotated at a specified angle (usually a large angle) and then stacked riveting. The rotation angle between punching pieces is generally 45 °, 60°, 72° °, 90°, 120°, 180° and other large-angle rotation forms, this stacking riveting method can compensate for the stack accumulation error caused by the uneven thickness of the punched material and improve the magnetic properties of the motor. The punching process is that after each punch of the punching machine (that is, after the punching piece is punched into the blanking die), on the blanking step of the progressive die, it is composed of a blanking die, a tightening ring and a rotary sleeve. The rotary device rotates a specified angle, and the specified angle of each rotation should be accurate. That is, after the punching piece is punched out, it is stacked and riveted on the iron core, and then the iron core in the rotary device is rotated by a predetermined angle. The rotation here is a punching process based on the number of riveting points per punching piece. There are two structural forms to drive the rotary device in the mold to rotate; one is the rotation conveyed by the crankshaft movement of the high-speed punch, which drives the rotary drive device through universal joints, connecting flanges and couplings, and then the rotary drive device drives the mold. The rotary device inside rotates. As shown in Figure 14 .
The second is the rotation driven by the servo motor (special electrical controller is required), as shown in Figure 15 . The belt rotation form on a pair of progressive die can be single-turn form, double-turn form, or even multi-turn form, and the angle of rotation between them can be the same or different.
2.3.4 Stacked riveting with rotary twist: Each punching piece on the iron core needs to be rotated by a specified angle plus a small twisted angle (generally a large angle + a small angle) and then stacked riveting. The riveting method is used for the shape of the iron core blanking is circular, the large rotation is used to compensate the stacking error caused by the uneven thickness of the punched material, and the small torsion angle is the rotation required for the performance of the AC motor iron core. The punching process is the same as the previous punching process, except that the rotation angle is large and not an integer. At present, the common structural form to drive the rotation of the rotary device in the mold is driven by a servo motor (requires a special electrical controller).
3.4 The realization process of torsional and rotary motionIn the process of high-speed punching of the progressive die, when the slider of the punch press is at the bottom dead center, rotation between the punch and the die is not allowed, so the rotating action of the torsion mechanism and the rotary mechanism must be intermittent motion, and it must be Coordinate with the up and down movement of the punch slider. The specific requirements to realize the rotation process are: in each stroke of the punch slider, the slider rotates within the range of 240º to 60º of the crankshaft , the slewing mechanism rotates, and it is in a static state in other angular ranges, as shown in Figure 16 . The method of setting the rotation range: if the rotation driven by the rotary drive device is used, the adjustment range is set on the device; if the rotation driven by the motor is used, it is set on the electrical controller or through the induction contactor. Adjust the contact range; if mechanically driven rotation is used, adjust the range of the lever rotation.
3.5 Rotation safety mechanismSince the progressive die is punched on a high-speed punching machine, for the structure of the rotating die with a large angle, if the blanking shape of the stator and rotor is not a circle, but a square or a special shape with a tooth shape, in order to ensure that each The position where the secondary blanking die rotates and stays is correct to ensure the safety of the blanking punch and the die parts. A rotary safety mechanism must be provided on the progressive die. The forms of slewing safety mechanisms are: mechanical safety mechanism and electrical safety mechanism.
3.6 Structural characteristics of modern die for motor stator and rotor coresThe main structural features of the progressive die for the stator and rotor core of the motor are:
1. The mold adopts a double guide structure, that is, the upper and lower mold bases are guided by more than four large ball-type guide posts, and each discharge device and the upper and lower mold bases are guided by four small guide posts to ensure reliable guide accuracy of the mold;
2. From the technical considerations of convenient manufacturing, testing, maintenance and assembly, the mold sheet adopts more block and combined structures;
3. In addition to the common structures of progressive die, such as step guide system, discharge system (consisting of stripper main body and split type stripper), material guide system and safety system (misfeed detection device), there are The special structure of the progressive die of the motor iron core: such as the counting and separating device for the automatic lamination of the iron core (that is, the pulling plate structure device), the riveting point structure of the punched iron core, the ejector pin structure of the iron core blanking and riveting point, the punching piece Tightening structure, twisting or turning device, safety device for large turning, etc. for blanking and riveting;
4. Since the main parts of the progressive die are commonly used hard alloys for the punch and the die, considering the processing characteristics and the price of the material, the punch adopts a plate-type fixed structure, and the cavity adopts a mosaic structure, which is convenient for assembly. and replacement.
3. Status and development of modern die technology for motor stator and rotor cores
The automatic lamination technology of motor stator and rotor iron core was first proposed and successfully developed by the United States and Japan in the 1970s , which made a breakthrough in the manufacturing technology of motor iron core and opened up a new way for the automatic production of high-precision iron core. The development of this progressive die technology in China started in the mid-1980s. It was first through the digestion and absorption of the imported die technology, and the practical experience gained by absorbing the technology of the imported die . The localization has achieved gratifying results. From the original introduction of such molds to the fact that we can develop such high-grade precision molds by ourselves, the technical level of precision molds in the motor industry has been improved. Especially in the past 10 years, with the rapid development of China’s precision mold manufacturing industry, modern stamping dies, as special technological equipment, are becoming more and more important in modern manufacturing. The modern die technology for the stator and rotor core of the motor has also been developed comprehensively and rapidly. At the earliest, it could only be designed and manufactured in a few state-owned enterprises. Now, there are many enterprises that can design and manufacture such molds, and they have developed such precision molds. The technical level of the die is becoming more and more mature, and it has begun to be exported to foreign countries, which has accelerated the development of my country’s modern high-speed stamping technology.
At present, the modern stamping technology of the stator and rotor core of my country’s motor is mainly reflected in the following aspects, and its design and manufacturing level is close to the technical level of similar foreign molds:
1. The overall structure of the motor stator and rotor iron core progressive die (including double guide device, unloading device, material guide device, step guide device, limit device, safety detection device, etc.);
2. Structural form of iron core stacking riveting point;
3. The progressive die is equipped with automatic stacking riveting technology, skewing and rotating technology;
4. The dimensional accuracy and core fastness of the punched iron core;
5. The manufacturing precision and inlay precision of the main parts on the progressive die;
6. The degree of selection of standard parts on the mold;
7. Selection of materials for main parts on the mold;
8. Processing equipment for the main parts of the mold.
With the continuous development of motor varieties, innovation and the update of assembly process, the requirements for the accuracy of the motor iron core are getting higher and higher, which puts forward higher technical requirements for the progressive die of the motor iron core. The development trend is:
1. The innovation of die structure should become the main theme of the development of modern die technology for motor stator and rotor cores;
2. The overall level of the mold is developing in the direction of ultra-high precision and higher technology;
3. The innovation and development of the motor stator and rotor iron core with large slewing and twisted oblique riveting technology;
4. The stamping die for the stator and rotor core of the motor develops in the direction of stamping technology with multiple layouts, no overlapping edges, and less overlapping edges;
5. With the continuous development of high-speed precision punching technology, the mold should be suitable for the needs of higher punching speed.
The use of modern stamping technology to manufacture the stator and rotor cores of the motor can greatly improve the level of motor manufacturing technology, especially in automotive motors, precision stepping motors, small precision DC motors and AC motors, which not only guarantees these The high-tech performance of the motor, but also suitable for the needs of mass production. Now, domestic manufacturers of progressive dies for motor stator and rotor iron cores have gradually developed, and the level of their design and manufacturing technology is constantly improving. In order to improve the competitiveness of Chinese molds in the international market, we must pay attention to and face this gap.
In addition, it must also be seen that in addition to modern die manufacturing equipment, that is, precision machining machine tools, modern stamping dies for designing and manufacturing motor stator and rotor cores must also have a group of practically experienced design and manufacturing personnel. This is the manufacturing of precision dies. the key. With the internationalization of the manufacturing industry, my country’s mold industry is rapidly in line with international standards, and improving the specialization of mold products is an inevitable trend in the development of the mold manufacturing industry, especially in today’s rapid development of modern stamping technology, the modernization of motor stator and rotor core parts Stamping technology will be widely used.
Post time: Aug-10-2022