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    Ball Screw

    Ball screw is the most commonly used transmission element in tool machinery and precision machinery. Its main function is to convert rotary motion into linear motion or torque into axial repetitive force, which is characterized by high precision, invertibility and high efficiency.Due to its low friction resistance, ball screw is widely used in various industrial equipment and precision instruments.
    Ball screw is composed of screw, nut, steel ball, prepress sheet, inverter and dust arrester.Its function is to transform the rotary motion into linear motion, which is the further extension and development of ekm screw. The important significance of this development is to change the bearing from sliding motion to rolling motion.

    Phylogeny

    People use screw to do transmission history is not really very long, the traditional screw has been positioning is not good, easy to damage the situation.It was not until 1898 that people first tried to insert steel balls into nuts and screws to replace sliding friction with rolling friction to improve their poor positioning and easy damage.In 1940, more ball screw was placed on the steering device of automobile, which was a great revolution in the application of ball screw and gradually replaced the traditional ACME screw.Until recently, ball screw has become one of the most widely used components in the industry.

    Principle

    1. According to GB/ t17587.3-1998 and the application examples, the ball screw (which has basically replaced the trapezoidal screw, commonly known as the screw rod) is used to convert the rotary motion into linear motion;Or the linear motion into the rotating motion of the actuator, and has a high transmission efficiency, positioning accuracy
    2, when the ball screw as the active body, the nut will be with the screw rotation Angle in accordance with the corresponding specifications of the lead into linear motion, the passive workpiece can be connected through the nut seat and nut, so as to achieve the corresponding linear motion.

    Purpose 

    Ball screw bearings for various purposes, to provide a wide range of standardized products.Widely used in machine tools, ball circulation has circulation pipe type, circulator type, end cover type.Pre – pressure means positioning pre – pressure (double nut mode, position pre – pressure mode), fixed pressure pre – pressure.
    The appropriate type can be selected for use.The screw has precision ball screw with high-precision grinding processing (the precision is divided into 6 grades from co-c7) and cold-rolled ball screw bearing formed by high-precision cold-rolling processing (the precision is divided into 3 grades from c7-c10).In addition, in order to cope with the urgent delivery of users, there are finished products that have been processed on the shaft end, semi-finished products and cold-rolled ball screw bearings that can be processed on the shaft end freely.As the peripheral parts of this bearing, the necessary screw support unit, nut support, locking nut and so on have been standardized for users to choose and use.
    Ball screw bearing is based on the accumulated product technology for many years, from material, heat treatment, manufacturing, inspection to shipment, are to strict quality assurance system to manage, so it has high reliability.

    USE

    High DN value ball screw: high speed tool machine, high speed integrated machining center machine
    End cap ball screw: rapid handling system, general industrial machinery, automatic machinery
    High speed ball screw: CNC machinery, precision tool machine, industrial machinery, electronic machinery, high speed machinery
    Precision grinding grade ball screw: CNC machinery, precision tool machine, industrial machinery, electronic machinery, transport machinery, aerospace industry, other antenna actuators, valve switching devices
    Nut rotary (R1) series ball screw: semiconductor machinery, industrial robots, woodworking machines, laser processing machines, moving and delivering devices
    Rolling grade ball screw: low friction, smooth operation of the advantages of rapid supply and low price
    Heavy-duty ball screw: all-electric injection molding machine, punching machine, semiconductor manufacturing device, heavy-duty brake, industrial machinery, forging machinery

    Type

    There are two common circulation methods: external circulation and internal circulation.Ball in the cycle process and sometimes out of contact with the screw is called the outer cycle;An internal loop is one in which the lead screw is always in contact with the lead screw.Each ball cycle closed circuit is called a column, each ball cycle closed circuit contains the number of lead is called the number of cycles.Each nut of the inner circulation ball screw pair has two columns, three columns, four columns, five columns and so on, each column has only one circle;The outer loop has 1.5, 2.5, and 3.5 cycles per column.

    1) external circulation: the external circulation refers to the re-entry of the ball ball into the circulation between the screw screws and nuts through the spiral groove or intubation on the outer surface of the nut after the end of the circulation process.The return mode of outer circulation ball screw nut pair according to ball circulation mainly includes end cover type, intubation type and spiral groove type.End cover type of common external circulation mode;Intubation type;Spiral groove.End cover type, a longitudinal hole is processed on the nut, as the return channel of the ball, the cover plate at both ends of the nut has the return port of the ball, the ball enters the return pipe, forming a cycle.Tube-type, it USES the elbow as the return pipe, this structure has good workmanship, but because the pipe protrudes the nut outside, the radial size is large.Spiral groove type, it is in the nut outer circle milling out of the spiral groove, groove at both ends of the hole and thread raceway tangent, forming a return channel, this structure than the radial size of the tubular structure, but the manufacture is more complex.External circulation ball screw external circulation structure and manufacturing process is simple, widely used.Its disadvantage is that the raceway joint is difficult to do smooth, affecting the stability of the ball raceway.
    2) inner loop: the inner loop USES a reverser to realize the ball loop. There are two types of reversers.Cylindrical convex key reverser, the cylindrical part of which is embedded in the nut, has a reverse groove 2 at the end.The reverse groove is positioned on the circular surface of the cylinder and the circular key 1 on its upper end to ensure alignment of the thread raceway.The flat circle insert reverse device, the reverse device is a general round head flat key insert, insert into the cutting groove of the nut, its end is open with a reverse groove 3, positioning with the outer contour of the insert.Compared with the two inverters, the latter has a smaller size, which reduces the radial size of the nut and shortens the axial size.However, the precision of the outer contour of the reverser and the groove size on the nut is required.

    Type selection
    Ball screw nuts, according to the ball cycle can be divided into: bent pipe type, circulator type, end cap type.The advantage of these three cycles.
    Bending tube
    (SBN, BNF, BNT, BNFN, BIF and BTK).
    Circulating chip type (HBN type)
    These models are the most typical nuts that allow the ball to circulate through the line by using a bend.The ball is drawn from the groove of the screw shaft into the bend pipe, and then returned to the groove to do infinite cycle motion.
    Circulator type
    (DK, DKN, DIK, JPF and DIR)
    These are the smallest nuts, which change the direction of the ball through a recirculator and return to the original position across the outer diameter of the screw shaft for an infinite cycle.
    The end cover type
    (SBK, SDA, SBKH, WHF, BLK, WGF, BLW, WTF, CNF and BLR type)
    These models are the most suitable nuts for high speed feeding.Using the end cover, the steel ball is scooped out of the groove of the screw shaft into the through hole of the nut. Through the through hole, it returns to the groove and makes infinite circular motion.


    Post time: Nov-27-2018
    
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