滚珠丝杠由螺杆、螺母、滚珠和回珠器组成,主要功能是将旋转运动转换成直线运动。在精密设备尤其是数控设备上广泛使用,由控制系统发出的脉冲信号控制伺服电机的旋转,再由精密滚珠丝杠将伺服电机的旋转运动转换成工作台的直线运动,从而实现工件的加工轨迹控制。因此,装配工艺及精度检测都很严格,对装配工人的技术要求也较高。

　　A ball screw is composed of a screw, nut, ball, and ball return device, and its main function is to convert rotational motion into linear motion. Widely used in precision equipment, especially CNC equipment, the pulse signal emitted by the control system controls the rotation of the servo motor, and then the precision ball screw converts the rotational motion of the servo motor into linear motion of the worktable, thereby achieving the control of the machining trajectory of the workpiece. Therefore, the assembly process and precision testing are very strict, and the technical requirements for assembly workers are also high.

　　一、故障现象　　某数控设备有限公司在数控车床精密滚珠丝杠装配后进行静态精度检查时合格,但在试车后或使用一段时间后出现精密滚珠丝杠的轴向跳动严重超差,影响了机床的加工精度,设备返修率为43%,给企业带来巨大的经济损失和声誉损失。

　　1、 Fault phenomenon: A certain CNC equipment Co., Ltd. passed the static accuracy inspection after assembling the precision ball screw of the CNC lathe. However, after testing or using it for a period of time, the axial runout of the precision ball screw seriously exceeded the tolerance, affecting the machining accuracy of the machine tool. The equipment repair rate was 43%, causing huge economic and reputation losses to the enterprise.

　　二、故障原因分析

　　2、 Fault cause analysis

　　1.精密滚珠丝杠精度达不到要求　　滚珠丝杠在入库时已进行了精度检验,可排除本身的质量问题。但细长轴类零件(机床丝杆等)在保管时应该采用垂直放置,以免受重力变形影响精度。该滚珠丝杠采专用包装箱垂直放置,在装配后的静态检查合格,因此可以排除此项。

　　1. The precision of the precision ball screw does not meet the requirements. The ball screw has undergone precision inspection when it is stored, and its own quality problems can be ruled out. However, slender shaft components (such as machine tool screws) should be placed vertically during storage to avoid accuracy being affected by gravity deformation. The ball screw is placed vertically in a special packaging box and passed the static inspection after assembly, so this item can be excluded.

　　2.装配不当损坏了丝杠的精度　　通过了解,装配工人对精密滚珠丝杠组件熟悉的,装配时也是格外小心,完全按装配工艺进行的,因此也排除了这种可能。

　　2. Improper assembly damaged the accuracy of the screw. Through understanding, assembly workers are familiar with precision ball screw components and are particularly careful during assembly, completely following the assembly process. Therefore, this possibility has also been ruled out.

　　3.机床行程超程,工作台发生碰撞,导致精度损坏　　操作机床时发生超程,容易导致机床碰撞而引起的。但经了解机床的行程限位开关没有问题,用户也没有这方面的意见反馈。

　　3. Machine tool travel overtravel, worktable collision, resulting in accuracy damage. Overtravel during machine tool operation can easily lead to machine tool collision. But after investigation, it was found that there is no problem with the travel limit switch of the machine tool, and the user has not provided any feedback in this regard.

　　4.检测方法不正确,导致精度超差　　检验员采用千分表配合磁力表座,以工作台直线导轨滑座为检测基准进行检测,检测方法及检测基准也符合要求。　　5.装配工艺不正确,造成装配误差

　　4. The detection method was incorrect, resulting in the accuracy exceeding the tolerance. The inspector used a dial gauge in conjunction with a magnetic gauge holder to perform the detection based on the workbench linear guide slide seat. The detection method and benchmark also met the requirements. 5. Incorrect assembly process leading to assembly errors

　　原装配步骤是:先装好直线导轨,以直线导轨的滑座为基准校正丝杠,再以丝杠两端支承座安装孔配作固定螺纹孔。用螺钉固定丝杠后,用磁力表座将千分表固定在直线导轨滑座上,测量丝杠、侧母线和丝杠径向跳动量,保证丝杠的平行度及跳动量在要求范围内。

　　The original assembly steps are: first install the linear guide rail, calibrate the lead screw based on the sliding seat of the linear guide rail, and then match the mounting holes of the support seats at both ends of the lead screw as fixed threaded holes. After fixing the lead screw with screws, use a magnetic gauge holder to fix the dial gauge on the linear guide slide, measure the lead screw, side busbar, and radial runout of the lead screw, ensuring that the parallelism and runout of the lead screw are within the required range.

　　重新配作支承座定位锥销,装好锥销后再复检一次。装配各步骤采用的处理方法基本正确,检测基准与工艺基准也相符,检测量具精度也能满足要求,被测要素也正确。整个装配过程没有问题,但通过在现场观察,发现装配工艺中仍存在以下问题:

　　Reconfigure the supporting seat positioning cone pin, install the cone pin and recheck again. The processing methods used in each step of assembly are basically correct, the detection standards are consistent with the process standards, the accuracy of the detection measuring tools can also meet the requirements, and the measured elements are also correct. The entire assembly process was fine, but through on-site observation, it was found that there are still the following issues in the assembly process:

　　(1)使用手电钻铰孔时,由于铰削余量较大,振动较厉害,双手控制不稳,铰刀摆动过大,造成锥孔铰削后上大下小,锥度不是要求的1∶50。用涂色法进行检查,发现锥销与锥孔的接触部位不正确,位置靠近小头一端,不能保证良好的接触精度,受到交变应力与振动时容易松动,从而导致定位精度下降。

　　(1) When using a handheld drill for reaming, due to the large reaming allowance and severe vibration, the control with both hands is unstable, and the reamer swings too much, resulting in a tapered hole that is not the required 1:50 after reaming. Using the coloring method for inspection, it was found that the contact area between the taper pin and the taper hole is incorrect, located near the small end, which cannot guarantee good contact accuracy. When subjected to alternating stress and vibration, it is easy to loosen, resulting in a decrease in positioning accuracy.

　　(2)机铰后没有留精铰余量,也没有进行手工精铰。圆锥销的配合都是依靠配合面的过盈产生摩擦力来定位的。由于机铰后表面粗糙使实际过盈量减少,造成摩擦力不够,自锁性能下降,当受到交变应力与振动时容易松脱,从而导致定位精度下降。

　　(2) There is no margin left for precision hinges after machine hinges, nor is manual precision hinges performed. The fit of conical pins relies on the friction generated by the interference fit of the mating surface to locate them. Due to the rough surface of the machine hinge, the actual interference fit is reduced, resulting in insufficient friction and decreased self-locking performance. When subjected to alternating stress and vibration, it is easy to loosen, leading to a decrease in positioning accuracy.

　　(3)铰孔时孔径控制不严,铰削过程中没用锥销试配,装配时用铜棒轻轻敲入即可。由于不能保证足够的过盈量,装配后的摩擦力过小;受负荷及振动时易造成锥销松动,失去定位作用,导致工作台运动精度差。

　　(3) The aperture control during reaming is not strict, and no cone pin is used for trial fitting during the reaming process. During assembly, a copper rod can be gently tapped in. Due to the inability to ensure sufficient interference fit, the friction force after assembly is too low; When subjected to load and vibration, it is easy to cause the taper pin to loosen, lose its positioning function, and result in poor precision of the worktable movement.

　　(4)在钻孔铰孔等过程中,没有进行防尘处理。虽然丝杠副带有防尘圈,但铸铁粉尘非常细小,且极易粘附在丝杠表面。如有少量进入丝杠副传动面,粉尘的研磨作用会加剧丝杠副的磨损,导致丝杠精度下降,降低使用寿命。

　　(4) During the drilling and reaming process, no dust prevention treatment was carried out. Although the screw pair is equipped with a dust ring, the cast iron dust is very fine and easily adheres to the surface of the screw. If a small amount enters the transmission surface of the screw pair, the grinding effect of dust will intensify the wear of the screw pair, resulting in a decrease in the accuracy of the screw and a reduction in its service life.

　　三、故障处理办法

　　3、 Troubleshooting methods

　　1.使用机铰粗铰后必须留出精铰余量,再手工精铰　　这个方法可以纠正机铰后的锥度误差,降低孔壁的表面粗糙度值,提高配合面的接触精度,保证足够的摩擦力矩。

　　1. After using the machine hinge rough hinge, a margin for precision hinge must be left, and manual precision hinge can correct the taper error after machine hinge, reduce the surface roughness value of the hole wall, improve the contact accuracy of the mating surface, and ensure sufficient friction torque.

　　2.在铰孔时应及时用锥销试配　　目的是方便控制铰孔孔径。当锥销能用手插入销长的80%～85%左右时孔径才为合格;清理铁屑后,应在锥销上涂机油后再用铜棒打入与工件表面平齐,以保证足够的摩擦力矩,防止在使用中受载荷而松动。

　　2. When reaming, a cone pin should be used in a timely manner for the purpose of easy control of the reaming hole diameter. When the taper pin can be manually inserted into about 80% to 85% of the pin length, the aperture is considered qualified; After cleaning the iron filings, oil should be applied to the taper pin and then driven with a copper rod until it is flush with the surface of the workpiece to ensure sufficient friction torque and prevent loosening under load during use.

　　3.做好丝杠表面的防尘处理　　在钻孔、铰孔及攻螺纹过程中,应作好丝杠表面的防尘处理。用清洁的布包裹住丝杠的外露部分,防止粉尘进入丝杠副传动面,以延长精密元件的使用寿命,提高装配精度。

　　3. Proper dust prevention treatment should be carried out on the surface of the screw during drilling, reaming, and threading processes. Wrap the exposed part of the screw with a clean cloth to prevent dust from entering the transmission surface of the screw pair, in order to extend the service life of precision components and improve assembly accuracy.

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