久久青青草原av免费观看,国产极品久久久久久久久,亚洲午夜私人影院在线观看,亚洲午夜精品a片一区二区小蝌蚪,亚洲午夜精品a片一区二区小蝌蚪

What is Critical Speed?什么是臨界速度?

An elongated cylindrical object such as a ball screw shaft will always have a certain amount of sag at the middle due to its own mass (weight).  If such cylindrical object (a screw shaft) is held by rotary bearings at its ends and rotated, the sag would increase as the rotational speed is increased and may eventually reach a speed point that is destructive to the shaft.  This potentially destructive rotational speed is called the "Critical Speed".  It is also referred to as "Whirling Speed" or "Whipping Speed".

長軸形物體，比如絲杠，會因為重力的原因在中部形成下垂。這樣的長軸兩端軸承支撐并旋轉(zhuǎn)的時候，拱形會增大。當旋轉(zhuǎn)速度增大時，拱形會增大并最終導致絲杠遭到破壞。這個潛在的可以讓絲杠破壞的速度叫做“臨界速度”。
 

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.當設計滾珠絲杠的驅(qū)動系統(tǒng)的時候，應該對臨界速度予以高度的重視。臨界速度可以通過計算獲得，或者通過樣本中的允許速度獲得。通過表格數(shù)據(jù)可以看出,直徑越小,長度越大,臨界速度越小.此外,在整個系統(tǒng)中,其他任何部件的不平衡都會導致不正常的振動。設計是應考慮到支撐的同軸度，不要讓絲杠受到彎曲力。

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.因為螺母在絲杠上的運動相當于一個移動的支撐。這樣，絲杠比一般的軸類驅(qū)動的振擺幅度要小一些。

When designing with ball screws, evaluation of "DmN value" is also required in addition to the Critical Speeds.當設計滾珠絲杠的時候，“DmN”值也相當重要。


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.如果絲杠在超過其臨界速度的范圍內(nèi)工作時，整個機器的精度會因為劇烈的振動而下降。所以，建議所有的絲杠都在其臨界速度的80%或者更低的情況下工作。此外，臨界速度可以通過調(diào)整支撐方式（固定-支撐等）得到提高。支撐軸承的選擇也有益于臨界速度的提高。

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，當絲杠的速度超過2000rpm時候，請咨詢黑田精工的技術(shù)服務部門以獲得必要的幫助。


TAG: