Major breakthroughs are mainly reflected in the "bead plate" structure and differential methods. The bead positioning structure is both an improvement in performance and a breakthrough in manufacturing process, and is a technology that both win. Andy Jianqi Group Beijing Sankuo Technology Co., Ltd. (SUNYORK) owns the patent for this technology.
36 indexing devices have experienced 4 years, more than 20 hours per day, accumulated 30,000 hours, hundreds of thousands of times of flip positioning, in high power, high torque, intermittent cutting, accidental broken knife, program error and improper operation The test of various situations, such as collisions, is still as accurate as ever, and the failure rate is zero. Fully demonstrated good characteristics.
To put it simply, the structure is to engage a turntable inlaid with a circle of steel balls and a base that processes a circle of hemispherical grooves. Simple and easy to use, simple and easy to do, simple things can do the most. The combination of the beads and the turntable is like two pieces of jasper, which are matched by the beads of the first and last strings. The convex beads are equipped with grooves, as the saying goes, the yin and yang match, and everything is alive.
At Hall No. 9 of the 2007 Beijing International Machine Tool Show, Ander Jianqi Group Beijing Sankuo Technology Co., Ltd. will display related products of the bead positioning structure.
The characteristics of the bead positioning structure:
1, sub-second indexing accuracy.
Error: Large in the process, small in the results. Process refers to manufacturing and results refer to products.
User: Look at the process, buy the result.
There is no perfection in the world, there are always regrets and defects; for any defect, the accumulation is large, and the solution is small.
Pearl plate positioning structure is to take major issues to minor ones out of the way, even if each processing element there is an error range in degree position three-dimensional space, but with error averaging principle, can make the characterization of the errors to a minimum.
High precision is the basic requirement of the indexing device. In the manufacturing process, the position of the groove is the key to ensure the accuracy. At present, the position tolerance range that guarantees the indexing accuracy and can achieve lower manufacturing cost has been summarized. Due to the principle of error homogenization, the actual indexing error is extremely small and fully meets the general processing requirements.
In the formula:
X: total error
n: total number of steel balls
x i : position error of the i-th steel ball. Since the position error has directionality and belongs to the vector category, the position error of n steel balls with different directions can be obtained by discretizing the error direction by a specific process during processing. If the values ​​of the two errors are the same, the direction of the error is opposite. If the vector sum is equal to zero, the more the number, the closer the sum of the position errors of different directions is to zero. Divided by n, the theoretical error value is extremely small.
At the technical level of the manufacturing process, the bead positioning structure further reflects the advantages that the end facering (the ratchet) does not have. In the process of manufacturing the bead positioning device, it is only necessary to control the hemispherical groove of the inlaid steel ball and In addition, the positional degree of the meshing hemispherical groove controls the quality of the steel ball, and the basic elements affecting the accuracy are all grasped. For example, the bead positioning structure is compared to the end facering (the ratchet):
Tooth shape error: guarantee by steel ball shape error and quality of spherical milling cutter,
Tooth direction error: Due to the symmetry of the spherical structure, the bead structure does not have this error at all.
Pitch error: guaranteed by the position of the groove.
and many more.
The groove position degree refers to the positional accuracy of the X, Y, and Z three-dimensional space, and the Z-direction depth is particularly important, but it can be easily achieved by using a high-precision CNC machine tool.
Give it a little self-healing ability; wear is always a bad thing in people's eyes, in fact, a small amount of wear may be a good thing in certain occasions. If we reduce the wear difference in all directions (not to control the amount of wear, but to control the amount of wear in every direction), the process of using a small amount of wear is also a process of more uniform position and higher precision.
Therefore, if the faceted toothed disc (rat tooth plate) is a successful application of the principle of error homogenization, the bead disk positioning device is another successful example of the application error homogenization principle. The latter is inferior to the former in terms of positioning accuracy, repeat positioning accuracy, and longevity, that is, precision retention. It is superior in impact resistance.
2, the large stiffness reflects the anti-vibration and impact resistance
The large stiffness and impact resistance is the outstanding feature of the positioning mechanism of the bead disc. The bearing contact area reaches several tens of square centimeters, which can withstand large impact loads. After a period of use, the steel ball and the groove are more consistent, and the contact stiffness is greater than the initial. Stiffness when in use. The indexing rotary fixture made by the positioning of the bead disc exhibits excellent characteristics under heavy-duty cutting conditions with large cutting amount and interrupted cutting for 4 years.
In the four years of participation in performance and life verification, there is also a conventional device for positioning the face gear (rat tooth plate). The accuracy and maintainability of the two are not sensible. The obvious difference lies in the face gear plate ( The rigidity of the ratchet is far less than the positioning of the bead. The reason is that due to the limitation of the manufacturing process, the end facering (the ratchet) is fixed to the base and the turntable by screws. The two positioning pins are circumferentially positioned. When the impact force is encountered, the positioning pin is sheared and deformed, and the movement between the toothed disc and the base or the turntable is generated, and the bead manufacturing process can be conveniently performed directly on the body of the turntable or the base. . Therefore, there is no such displacement deformation.
Different sizes of bead positioning devices have different contact areas. The 36 sets of devices involved in the verification have a contact area of ​​tens of square centimeters. The unique structure can increase the contact area as needed and improve the impact strength. When necessary, the same number of 1 or 2 turns of steel balls and grooves can be added to different diameters, and the impact strength will be multiplied. When space is limited, it is difficult to increase the number of steel balls. Since the steel ball needs a certain adjacent space for riveting, the grooves can be closer, so one steel ball can be placed at every interval. It can also play a reinforcing role.
3, 0.1 degree small index is easy to manufacture
Three-piece faceted toothed disc (rat tooth plate) indexing positioning structure If the difficulty of different teeth in the inner and outer ring gears is well known, the structure limits the overtravel groove. However, whether the number of the outer ring grooves in the bead positioning structure is equal, there is no difference in the processing cost, and only the relevant parameters of the machining program can be set. The manufacturing process is no different from the ordinary bead positioning structure. If the cost of achieving a certain gear ratio is not considered, the cost of the small angle index is the same as the cost of the common index. Therefore, with the differential principle, the bead positioning structure can easily achieve a small angular division of 0.2 or 0.1 degrees.
For example, in the application of 0.2 degree small indexing, the bead plate is made into a separate rotating body, and the bead plate is inlaid with 72 steel balls on the side of the base, which matches the 72 grooves of the base, and the minimum indexing unit 5 degrees. The bead plate is inlaid with 75 steel balls on one side of the turntable, which is consistent with the 75 grooves of the turntable, and the minimum indexing unit is 4.8 degrees. as the picture shows:
Thus, when the bead disk in the middle rotates 5 degrees with respect to the frame, the steel ball on the other side of the bead disk is replaced by the steel ball in the latter position, and is displaced forward by 0.2 degrees (5-4.8= 0.2). Because 0.2:5=1:25, a 1:25 transmission between the bead and the turntable can achieve a convenient and fast 0.2 degree small division operation. See below:
The bead positioning structure can be easily realized for other minimum indexing units. 144 steel balls are 150 pieces of steel balls, and the indexing units are 2.5 degrees and 2.4 degrees respectively. After differential rotation, the minimum division of 0.1 degrees can be obtained. .
In practical applications, the 0.1 degree small-division-structured bead plate still uses a 0.2-degree indexing device, with 72 steel balls on one side and 75 steel balls on one side, which is different from the 0.2-degree indexing device. : The number of hemispherical grooves processed on the base is 144, and the number of hemispherical grooves machined on the turntable is 150, so that one steel ball is inserted in each groove to achieve a minimum division of 0.1 degrees. unit. The currently developed product, the 0.1 degree small angle indexing device is a 0.2 degree bead plate and other parts, only the number of the turntable and the base groove is different from 0.2 degrees.
According to the same principle, 72 steel balls are more than 80 steel balls, and the indexing units are 5 degrees and 4.5 degrees respectively. After differential rotation, a minimum index of 0.5 degrees can be obtained. 36 steel balls are 40 pieces of steel balls, and the division units are 10 degrees and 9 degrees respectively. After differential rotation, the minimum division of 1 degree can be obtained, and so on. The above 0.5 degree and 1 degree indexing devices can also share the same bead disk, and so on.
If the base side steel ball and the groove are set to 80 pieces, the number of the ball side groove and the groove number of the turntable is set to 81 pieces, and the division units of the two are 4 degrees 30 minutes and 4 degrees 26 minutes 40 seconds, respectively. The difference is 3 minutes and 20 seconds (200 seconds); the gear ratio is 81:1, so the differential indexing can be obtained with a small indexing unit with a minimum indexing unit of 200 seconds.
There are few angles used in some applications, such as some large floor boring machines, only 0, 90, 180, 270 degrees, but the contact stiffness is higher, in this case, increase the number of balls and the diameter of the ball The bead plate can be made into a horizontal and vertical steel ball matrix, the contact area of ​​the steel ball can reach hundreds or even thousands of square centimeters, and the carrying capacity can reach several tens of tons or hundreds of tons.
The schematic diagram of the small indexing device that has been developed and has been put into production is as follows:
The structure is one of the products already produced. It is to embed all the steel balls on one side of the bead plate, and the 72:75 is evenly distributed in two circles. The steel balls in the inner ring are matched with the grooves on the turntable, and the steel balls on the outer ring Consistent with the groove on the base, the bead disk is axially displaced and loosened, and is angularly displaced with the turntable by 25:1, so that the turntable has no axial displacement and the minimum indexing unit is 0.2 degrees. Rotate the positioning.
4, long life
The set of 36 sets of bead disc indexing devices has been verified for 30,000 hours in 4 years. There is no sign of wear and tear, and the external force of the bead positioning structure is small when positioning and rotating. When there is no wear and tear after positioning, Together with the hardness of the steel balls and the heat treatment of the grooves, the wear is minimal. Because the structure is not point, line contact, but surface contact, because the contact area is several tens of square centimeters (equivalent to several times the contact area of ​​the same volume heavy-duty rolling bearing), the contact area is large, the contact pressure is small, the frequency of stress change is low, and the material is Fatigue failure, the probability of pitting occurs is almost zero. Since the life test takes time, the life expectancy should exceed 100,000 hours based on the results of the existing tests. Therefore, the structure itself is destined for a long life.
5, low cost
The most notable feature of the bead positioning mechanism is the low manufacturing cost. In the manufacture of the bead disc positioning device, there is a significant cost difference between the manufacture of the end face toothed disc (the rat toothed disc). On the numerically controlled machine tool that achieves the required precision, n pieces are machined on the base and the turntable respectively by the spherical milling cutter. The groove, the groove on one side of the inlaid steel ball has a depth exceeding the radius of the steel ball, and the other side is smaller than the radius of the steel ball, and then the selected steel ball is riveted to the turntable using a special riveting device. The cost of processing a pair of bead disks is less than a fraction of the structure of the face gear plate (rat tooth plate). The process is suitable for production in the pipeline.
The structural features also reduce the number of manufacturing steps, shorten the manufacturing cycle, simplify the production method, facilitate inspection and measurement, and improve quality controllability.
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