Ball screw pair is the feed transmission chain of NC machine tool. Its assembly method and precision determine the positioning accuracy of NC machine tool, and also affect the stability of feed shaft interpolation operation.

一、滚珠丝杠副安装方法及受力

I. Installation Method and Force of Ball Screw Pair

控机床进给轴常见的丝杠支撑有如下几种方法：

There are several common methods of screw support for feed shaft of CNC machine tools:

1、一端固定一端自在

1. One end fixed and one end free

丝杠一端固定，另一端自在。固定端轴承一起接受轴向力和径向力，这种支承方法用于行程小的短丝杠或者用于全闭环的机床，由于这种结构的机械定位精度是较不可靠的，特别是关于长径比大的丝杠，热变性是很明显的，1.5m长的丝杠在冷、热的不同环境下变化0.05~0.10mm是很正常的。可是由于他的结构简单，安装调试便利，许多高精度机床依然选用这种结构，可是必须加装光栅，选用全闭环反应。

One end of the lead screw is fixed and the other end is free. Fixed end bearings accept both axial and radial forces. This support method is used for short lead screw with small stroke or machine tool with full closed loop. Because the mechanical positioning accuracy of this structure is the most unreliable, especially for the lead screw with large aspect ratio, the thermal variability is very obvious. It is normal that the lead screw with 1.5m length varies from 0.05 mm to 0.10mm in different cold and hot environments. However, because of its simple structure and convenient installation and debugging, many high-precision machine tools still choose this structure, but grating must be installed, and full-closed-loop response must be selected.

2、一端固定另一端支承

2. One end is fixed and the other end is supported.

丝杠一端固定，另一端支承。固定端一起接受轴向力和径向力；支承端只接受径向力，并且能作微量的轴向起浮，可以削减或防止因丝杠自重而出现的弯曲，一起丝杠热变形可以自在的向一端伸长。这种结构使用较广泛，目前国内中小型数控车床、立式加工中心等均选用这种结构。

One end of the lead screw is fixed and the other end is supported. The fixed end receives both the axial force and the radial force together; the supporting end receives only the radial force, and can make a small amount of axial buoyancy, which can reduce or prevent the bending caused by the self-weight of the lead screw, and the thermal deformation of the lead screw can extend freely to one end. This structure is the most widely used. At present, this structure is used in small and medium-sized CNC lathes and vertical machining centers in China.

3、两头固定

3. Fixation at both ends

丝杠两头均固定。固定端轴承都可以一起接受轴向力，这种支承方法，可以对丝杠施加适当的预紧力，提高丝杠支承刚度，可以部分补偿丝杠的热变形。

Both ends of the lead screw are fixed. Fixed end bearings can accept the axial force together. This support method can exert appropriate preload on the screw, improve the support stiffness of the screw, and partly compensate the thermal deformation of the screw.

关于大型机床、重型机床以及高精度镗铣床常选用此种计划。可是，这种丝杠的调整比较繁琐，假如两头的预紧力过大，将会导致丝杠终究的行程比规划行程要长，螺距也要比规划螺距大。

This plan is often used for large machine tools, heavy machine tools and high precision boring and milling machines. However, the adjustment of this kind of screw is rather tedious. If the pre-tightening force at both ends is too large, the final stroke of the screw will be longer than the planned one, and the pitch of the screw will be larger than that of the planned one.

假如两头锁母的预紧力不行，会导致相反的结果，并简单引起机床震动，精度降低。所以，这类丝杠在拆装时一定要按照原厂商说明书调整，或凭借仪器（双频激光测量仪）调整。

If the pre-tightening force of the lock mother at both ends is not good, it will lead to the opposite result, and simply cause the vibration of the machine tool, and reduce the accuracy. Therefore, this kind of screw must be adjusted according to the manufacturer's instructions or by means of instruments (dual-frequency laser measuring instrument).

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The above information is our guide screw finishing and publishing hope to help you all on our website is: http://tianboo.net!