I ball screw installation process is very rigorous, because if it is not installed in place, it will cause great trouble to its efficiency, so every step needs to be careful.

滾珠絲杠副作為數(shù)控機床的進給傳動鏈，其裝配形式和精度決定了數(shù)控機床的定位精度，也影響著進給軸插補運行的平穩(wěn)性。

As the feed transmission chain of CNC machine tool, the assembly form and precision of ball screw pair determine the positioning accuracy of CNC machine tool, and also affect the stability of feed shaft interpolation operation.

一、tbi滾珠絲杠副安裝形式及受力

1、 Installation form and force of TBI ball screw

控機床進給軸常見的絲杠支撐有如下幾種形式：

The common screw supports for the feed shaft of control machine tools are as follows:

1、一端固定——一端自由

1. One end fixed - one end free

絲杠一端固定，另一端自由。固定端軸承同時承受軸向力和徑向力，這種支承方式用于行程小的短絲杠或者用于全閉環(huán)的機床，因為這種結(jié)構(gòu)的機械定位精度是更不可靠的，特別是對于長徑比大的絲杠（滾珠絲杠相對細長），熱變性是很明顯的，1.5m長的絲杠在冷、熱的不同環(huán)境下變化0.05~0.10mm是很正常的。但是由于他的結(jié)構(gòu)簡單，安裝調(diào)試方便，許多高精度機床仍然采用這種結(jié)構(gòu)，但是必須加裝光柵，采用全閉環(huán)反饋。

One end of the screw is fixed and the other is free. The fixed end bearing bears both axial force and radial force. This support method is used for short lead screw with small stroke or full closed-loop machine tool, because the mechanical positioning accuracy of this structure is the most unreliable, especially for the lead screw with large length diameter ratio (ball screw is relatively slender), the thermal denaturation is obvious. The 1.5m long lead screw changes by 0.05 ~ 0.10mm under different cold and hot conditions It's normal. However, because of its simple structure and convenient installation and debugging, many high-precision machine tools still use this structure, but it must be equipped with grating and adopt full closed-loop feedback.

2、一端固定——另一端支承

2. Fixed at one end - supported at the other end

絲杠一端固定，另一端支承。固定端同時承受軸向力和徑向力；支承端只承受徑向力，而且能作微量的軸向浮動，可以減少或避免因絲杠自重而出現(xiàn)的彎曲，同時絲杠熱變形可以自由的向一端伸長。這種結(jié)構(gòu)使用更廣泛，目前國內(nèi)中小型數(shù)控車床、立式加工等均采用這種結(jié)構(gòu)。

One end of the screw is fixed and the other end is supported. The fixed end can bear both axial force and radial force; the supporting end only bears radial force and can make a small amount of axial floating, which can reduce or avoid the bending due to the self weight of the lead screw. At the same time, the thermal deformation of the screw can freely extend to one end. This structure is the most widely used structure, which is widely used in domestic small and medium-sized CNC lathes and vertical machining centers.

3、兩端固定

3. Fixed at both ends

絲桿兩端均固定。固定端軸承都可以同時承受軸向力，這種支承方式，可以對絲杠施加適當?shù)念A緊力，提高絲杠支承剛度，可以部分補償絲杠的熱變形。

Both ends of the screw rod are fixed. The fixed end bearing can bear the axial force at the same time. This kind of bearing can exert appropriate pre tightening force on the lead screw, improve the supporting stiffness of the screw, and partially compensate the thermal deformation of the screw.

對于大型機床、重型機床以及高精度鏜銑床常采用此種方案。但是，這種絲杠的調(diào)整比較繁瑣，如果兩端的預緊力過大，將會導致絲杠更終的行程比設(shè)計行程要長，螺距也要比設(shè)計螺距大。如果兩端鎖母的預緊力不夠，會導致相反的結(jié)果，并容易引起機床震動，精度降低。所以，這類絲杠在拆裝時一定要按照原廠商說明書調(diào)整，或借助儀器（雙頻激光測量儀）調(diào)整。

For large machine tools, heavy machine tools and high-precision boring and milling machines, this scheme is often used. However, the adjustment of this kind of screw is complicated. If the preload at both ends is too large, the final stroke of the lead screw will be longer than the designed stroke, and the pitch will be larger than the designed pitch. If the pre tightening force of the lock nut at both ends is not enough, it will lead to the opposite result, and it is easy to cause vibration of the machine tool and reduce the accuracy. Therefore, this kind of screw must be adjusted according to the original manufacturer's instructions or with the help of the instrument (dual frequency laser measuring instrument).

二、滾珠絲杠軸承的排列與命名

2、 Arrangement and nomenclature of ball screw bearings

我們了解典型的進給軸傳動鏈，更終支撐滾珠絲杠的是近端支承軸承和遠端支承軸承，這兩組軸承通過相互的作用，將軸向力頂住，也就是絲杠軸成巧妙地運用了“角接觸軸承”即可以承受徑向力，又可以承受軸向力的雙向受力特點。

First of all, we understand the typical feed shaft drive chain. The final support of the ball screw is the near end support bearing and the far end support bearing. These two groups of bearings can resist the axial force through the interaction, that is, the screw shaft skillfully uses the "angular contact bearing" which can bear both radial force and axial force.

當軸承內(nèi)擋圈和外擋圈受到一組相反方向的作用力時，軸承鋼珠承受著一對互為相反的作用力，從靜力學的角度上看，當物體靜止時，這一對作用力大小相等，方向相反。

When the inner and outer rings of the bearing are subjected to a group of forces in the opposite direction, the bearing steel balls bear a pair of opposite forces. From the static point of view, when the object is stationary, the force is equal and the direction is opposite.

作為機床絲杠傳動，來自工作臺的軸向力是作用在軸承的內(nèi)圈上，如果我們約束絲杠不竄動，只要在軸承外圈上作用一個方向相反、大小相等的力即可，這樣軸向受力是平衡的。又由于內(nèi)、外圈之間是滾動摩擦，因而保證了絲杠靈活的轉(zhuǎn)動。

As a machine tool lead screw drive, the axial force from the working table acts on the inner ring of the bearing. If we restrict the lead screw from moving, we only need to apply a force of opposite direction and equal size on the outer ring of the bearing, so that the axial force is balanced. Because of the rolling friction between the inner and outer rings, the flexible rotation of the lead screw is ensured.

對于數(shù)控機床絲杠傳動，需要根據(jù)不同的情況控制軸承的游隙（鋼珠與內(nèi)外環(huán)之間的間隙），對于低速大轉(zhuǎn)矩的傳動，需要這一游隙是過盈的，即要使鋼珠在滾到內(nèi)受擠壓變形，從配合角度講，間隙是負值。而對于高速小一點的負載，則需要游隙大一點，預留出高速運行后鋼珠和內(nèi)圈的熱膨脹系數(shù)。

For the screw drive of CNC machine tools, it is necessary to control the clearance of the bearing (the clearance between the ball and the inner and outer ring) according to different conditions. For the transmission with low speed and high torque, this clearance is required to be interference, that is, to make the steel ball be extruded and deformed from the rolling to the inside. From the perspective of matching, the clearance is negative. For the load with small speed, the clearance should be larger, and the coefficient of thermal expansion of steel ball and inner ring should be reserved after high speed operation.

絲杠的約束是通過近端軸承及遠端軸承的軸向和徑向約束來完成，不同安裝形式下的絲杠受力情況以及滾珠絲杠軸承安裝形式，對于今后日常維護，特別是傳動鏈的精度調(diào)整有所幫助。

The constraint of the lead screw is accomplished by the axial and radial constraints of the near end bearing and the far end bearing. The force condition of the lead screw under different installation forms and the installation form of the ball screw bearing are helpful for the daily maintenance in the future, especially for the accuracy adjustment of the transmission chain.