The Critical Speed parameter should be paid a high degree of attention when designing ball screw driven systems.  The Critical Speed can be obtained by calculating, or from "Allowable Speeds" nomogram provided in our catalog.  It can be observed from the nomogram that smaller the diameter and longer it is, the shaft will become critical at lower speeds (Critical Speed is low).   In addition, any imbalances in other rotating elements within the system will contribute in abnormal vibrations.  Careful design considerations ensuringto eliminate any axial concentricity errors in the support bearings, and to avoid any bending forces on the screw shaft.当设计滚珠丝杠的驱动系统的时候，应该对临界速度予以高度的重视。临界速度可以通过计算获得，或者通过样本中的允许速度获得。通过表格数据可以看出,直径越小,长度越大,临界速度越小.此外,在整个系统中,其他任何部件的不平衡都会导致不正常的振动。设计是应考虑到支撑的同轴度，不要让丝杠受到弯曲力。

Since the nuts travel in ball screws acting as moving supports, and the operation of ball screws involve reversing at their stroke ends, it is generally understood that the oscillation amplitudes of ball screws are smaller than that of common drive shafts.因为螺母在丝杠上的运动相当于一个移动的支撑。这样，丝杠比一般的轴类驱动的振摆幅度要小一些。

When designing with ball screws, evaluation of "DmN value" is also required in addition to the Critical Speeds.当设计滚珠丝杠的时候，“DmN”值也相当重要。

If ball screws are operated beyond their critical speeds, the accuracy of the machinery systems may be degraded due to the vibrations generated by the screw shaft.  It is recommended that all ball screws to be operated at 80% or below of their Critical Speeds.  Furthermore, the Critical Speeds may be improved by evaluating the shaft mounting methods (Fixed – Supported, etc.).  Selections in shaft-end bearings may also help to extend the high-speed capabilities.如果丝杠在超过其临界速度的范围内工作时，整个机器的精度会因为剧烈的振动而下降。所以，建议所有的丝杠都在其临界速度的80%或者更低的情况下工作。此外，临界速度可以通过调整支撑方式（固定-支撑等）得到提高。支撑轴承的选择也有益于临界速度的提高。

As a general rule of thumb, please contact Kuroda Technical Support for consultations if the ball screws are to be operated at speeds higher than 2,000 rpm.非常值得注意得是，当丝杠的速度超过2000rpm时候，请咨询黑田精工的技术服务部门以获得必要的帮助。