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Introduction and application of ball screw part.1
Updatetime: 2021-07-13 11:42View:

CNC machine Ball screw:

Ball screw is an ideal product for converting rotary motion into linear motion or linear motion into rotary motion.

Ball screw is the most commonly used transmission element in tool machinery and precision machinery. Its main function is to convert the rotary motion into linear motion, or to convert the torque into the axial repetitive force. It has the characteristics of high precision, reversibility and high efficiency at the same time.Because of its small frictional resistance, ball screw is widely used in various industrial equipment and precision instruments.

 


Composition:

Ball screw is composed of screw, nut, steel ball, prepress plate, inverter and dustproof device.Its function is to transform the rotary motion into the linear motion, which is the further extension and development of the ekham screw. The important significance of this development is to change the bearing from the sliding motion to the rolling motion.

1) use

Ball screw bearings offer a wide range of standardized products for a variety of purposes.Widely used in machine tools, the ball circulation method has the circulation tube type, the circulator type, the end cover type.Preloading methods include positioning preloading (double nut, bit preloading) and constant preloading.The appropriate type can be selected according to the purpose.The screw rod has the precision ball screw with high precision grinding and the cold rolling ball screw bearing with high precision cold rolling processing.As the peripheral parts of this bearing, the necessary screw support units, nut bearings and lock nuts have also been standardized for users to choose.

Ball screw bearing based on the accumulated product technology over the years, from material, heat treatment, manufacturing, inspection to shipment, are managed by strict quality assurance system, so it has high reliability.

Application:

Ultra high DN value ball screw: high speed tool machine, high speed integrated machining center machine

End cover ball screw: quick handling system, general industrial machinery, automatic machinery

High speed ball screw: CNC machinery, precision tool machine, industrial machinery, electronic machinery, high speed machinery

Precision abrasive ball screw: CNC machinery, precision tool machine, industrial machinery, electronic machinery, transport machinery, aerospace industry, other antenna used actuator, valve switch device

Rotary (R1) series ball screw: semiconductor machinery, industrial robots, woodworking machines, laser processing machines, conveyors, etc

Rolling grade ball screw: low friction, smooth operation, and fast delivery and low price

Heavy load ball screw: full electric injection forming machine, punching machine, semiconductor manufacturing device, heavy load brake, industrial machinery, forging machinery

How to select servo motor and stepping motor correctly?

1, mainly depending on the specific application, simply to determine: the nature of the load (such as horizontal or vertical load, etc.), torque, moment of inertia, rotational speed, accuracy and deceleration, this ball screw has been quick easy collection, upper control requirements (such as requirement for port interface and communication), main control mode is position, torque, or speed.Power supply is dc or ac, or battery power, voltage range.Determine the type of motor and driver or controller.

2. How to match the stepper motor driver

Depending on the current of the motor, a driver greater than or equal to this current is provided.If low vibration or high precision is required, subdivision actuators can be used.For large torque motors, use high voltage actuators as much as possible to achieve good high speed performance.

What is the difference between 3,2 and 5 phase stepping motor? How to choose?

The cost of 2-phase motor is low, but the vibration is large at low speed, and the torque decreases quickly at high speed.The 5-phase motor has smaller vibration and better high-speed performance, which is 30~50% higher than the 2-phase motor. It can replace the servo motor in some occasions.

4. I want to directly control the servo motor by means of communication, is that ok?

Can, also more convenient, just the speed problem, for the response speed requirements are not too high application.If fast response control parameters are required, it is better to use the servo motion control card, which usually has a DSP and a high-speed logic processing circuit to achieve high-speed and high-precision motion control.Such as S acceleration, multi-axis interpolation, etc.

2) type:

There are two common types of circulation: external circulation and internal circulation.The ball in the process of the cycle is sometimes out of contact with the screw called the outer cycle;Always in contact with the lead screw is called the inner loop.Each loop of the ball is called a column, and the number of leads contained in each loop of the ball is called the winding number.Each nut of the inner circulating ball screw pair has 2 columns, 3 columns, 4 columns, 5 columns, etc., each column has only one circle;There are several types of outer loops in each column, such as 1.5, 2.5 and 3.5 cycles.

(1) external circulation: the external circulation means that the ball returns to the screw nut through the spiral groove or the cannula on the outer surface of the nut and re-enters the circulation.The return mode of the outer circular ball screw nut pair is mainly the end cover type, the intubation type and the spiral groove type.The commonly used outer loop end cover type;Intubation type;Spiral groove type.End cover type, a longitudinal hole is processed on the nut, which is used as the return journey channel of the ball. The cover plate at both ends of the nut is opened with the return journey port of the ball, so that the ball enters the return journey tube and forms a cycle.Intubation type, it USES the elbow as the return pipe, this kind of structure has good manufacturability, but because the pipe protrudes the outside of the nut, the radial dimension is larger.Spiral groove type, it is in the nut outside the circle of the milling out of the spiral groove, groove at both ends of the drill hole and thread raceway tangent to form a return channel, this structure than the tube type structure radial size is small, but more complex to manufacture.External circulation ball screw external circulation structure and manufacturing process is simple, widely used.The disadvantage is that the raceway joints are difficult to be smooth, which affects the stability of the ball raceway.

(2) internal circulation: ball circulation is realized by using inverters in internal circulation. There are two types of inverters.Cylindrical convex key reverser, its cylindrical part is embedded in the nut, the end has a reverse groove 2.The reverse groove is positioned against the cylindrical outer surface and the circular key 1 at its upper end to ensure that it is aligned to the direction of the thread raceway.Flat round insert block inverter, inverter for the general round head flat key insert block, insert block embedded in the cutting groove of the nut, its end has a reverse slot 3, with the outline of the insert block positioning.Compared with the two inverters, the size of the latter is smaller, which reduces the radial dimension of the nut and shortens the axial dimension.However, the outer profile of the inverter and the dimension accuracy of the grooves on the nuts are required to be higher.The picture shows the end - cover cycle for reference only.

Type selection

Ball screw nuts, according to the circulation of the steel ball can be divided into: bend type, circulator type, end cover type.The specialty of these three circulation methods.

Ball screw

3) features:

(1) small friction loss and high transmission efficiency

As there are many ball bearings rolling between the screw shaft and the screw nut of the ball screw pair, higher movement efficiency can be obtained.Compared with the previous sliding screw pair, the driving torque is less than 1/3, that is, the power required to achieve the same motion result is 1/3 of the power required to use the sliding screw pair.It's very helpful in saving electricity.

(2) high precision

Ball screw is generally produced with the highest level of mechanical equipment in the world, especially in the grinding, assembly, inspection of the factory environment in each process, the temperature, humidity has been strictly controlled, thanks to the perfect quality management system to ensure the accuracy can be fully guaranteed.

(3) possibility of high-speed and micro-feed

Ball screw pair is the use of ball movement, so the starting torque is very small, will not appear as sliding movement crawling phenomenon, can ensure the realization of accurate micro feed.

(4) high axial stiffness

Ball screw pair can be added and pre-pressure, due to the pre-pressure can make the axial clearance to a negative value, and then get a higher rigidity (ball screw by adding pressure to the ball, in the actual use of mechanical devices, due to the repulsion of the ball can make the rigid part of the thread).

(5) it cannot be self-locked and has the reversibility of transmission

4) protection:

Ball screw pair can be lubricated to improve wear resistance and transmission efficiency.Lubricants are divided into two categories: lubricating oil and grease.Lubricating oil, turbine oil no. 90 ~ 180 or spindle oil no. 140.Lithium - based grease may be used.The grease is added to the threaded raceway and the housing space in which the nut is mounted, and the lubricating oil is injected into the housing space through the oil hole in the housing.

Ball screw pairs and other transmission elements of rolling friction can be considered to work with little wear as long as abrasive particles and chemically active substances are avoided.However, if you fall into dirt on the raceway or use dirty lubricating oil, not only will hinder the normal operation of the ball, but also cause a sharp increase in wear and tear.

Usually use felt ring to seal the nut pair, felt ring thickness is 2 ~ 3 times of the pitch, and the inner hole made into the shape of thread, so that it tightly covers the lead screw, and into the nut or sleeve at both ends of the slot.Sealing ring in addition to the use of soft felt, but also can be used oil resistant rubber or nylon material.Because of the direct contact between the sealing ring and the screw, the dust proof effect is better, but it also increases the friction resistance moment of the ball screw nut pair.In order to avoid this frictional resistance moment, a non-contact labyrinth seal ring made of hard plastic can be used, with the inner hole made in the opposite shape to the thread raceway of the lead screw, and some clearance left.

For the exposed lead screw, spiral rigid belt, telescopic sleeve, tapered sleeve and protective cover in the form of folding plastic or artificial leather are generally used to prevent dust and abrasive particles from sticking to the surface of the lead screw.Except for the protective cover similar to the guide rail, one end of these protective covers is connected to the end face of the ball nut and the other end is fixed to the supporting seat of the ball screw.This will make it more solid.

Introduction and application of ball screw part.1

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