Vibration reduction of linear rolling guide system

In recent years, with the development of numerical control machine tools and precision machining, the requirements for the guidance system of machine tools have become higher and higher. It is an important factor that determines the machining precision, work efficiency and service life of the machine tools. Many equipments use the machine tool functional parts, which are produced by domestic and foreign specialized craft equipment factories, as linear guide rails. Since the linear rolling guide uses hardened guide rails and pre-tightened (without clearance) balls or roller sliders as contact pairs, it has the characteristics of small friction coefficient, large bearing capacity, good rigidity, and long service life, and can reach high values. The feed rate and positioning accuracy. However, compared with the traditional plane sliding guides, the rolling guides have relatively poor vibration damping performance because their rolling contact surfaces are points or lines. Some rail manufacturers have used the method of adding preload to the rolling guide system to improve the damping performance. However, actual tests show that this method is not effective. Increasing the preload just changes the resonant frequency, and there is not much improvement in damping. On the contrary, due to the increase of the preload of the rolling guide system, the deformation of the rolling elements is increased, the displacement resistance of the guide mechanism is increased, and the wear of the contact surface is accelerated, which will inevitably affect the working life of the guide elements. An effective vibration reduction method can be achieved by adding a vibration-reducing element. In the development process of “SHZ1044 Twin-spindle Vertical Turning Center”, a cooperation project of production, education and research, we adopted two types of rolling guide vibration reduction measures to achieve good results. 1 Linear rolling guide equipped with a damper carriage One of the front ends of the "SHZ1044 Twin Spindle Vertical Turning Center" uses a built-in spindle motor and is inverted. When working upside down, the front spindle rotates at a high speed and moves in the horizontal (X) and vertical (Z) directions, which is prone to vibration. For this purpose, we chose the roller guide mechanism (Fig. 1) with a damper carriage as the X-way guide.

(a) Roller Guide with Damper Slide
(b) Damper slider profile Figure 1 The roller guide mechanism damper carriage with vibration reduction function consists of a steel structure body. Its inner surface is sprayed with a sliding bearing material by a special spraying process. During manufacture, the matched guide rail is equipped with a grinding process to make this layer. The sliding bearing material forms a 0.03 mm gap with the corresponding rail surface, see Figure 1b. The damping slide is not in direct contact with the surface of the guide rail, leaving a certain gap in the middle. The clearance is filled with lubricating oil. This layer of oil film can act as a squeeze oil film shock absorber, which can achieve good damping effect. Since this layer of 0.03mm oil film is very thin, it can produce capillary action, so it consumes little oil. When it is working, it only needs to drop the lubricant oil into the oil hole of the slide at the same time as the rolling slider. This vibration-reducing type rolling guide system not only maintains the characteristics of the original linear rolling guide running light and fast, but also has the advantage of good damping performance of the sliding guide rail.

Figure 2 squeeze film damping diaphragm vibration damping principle shown in Figure 2, the damping factor d is d = h b2 l h2 Where: h - oil viscosity b - squeeze film width h - Squeeze film height l - damping element length is very obvious width b is the main factor in vibration reduction, this factor must be taken into account in the design; in addition to increase the length l theoretically can also get a good damping effect, and then in fact with An increase in length will encounter a "saturation point" for vibration reduction. Above this point, the damping performance will no longer increase. The damper carriage can be customized with the corresponding rolling slider, and the installation is also very convenient. When installing, adjust the slide to the same clearance on both sides, and then tighten the bolt. At present, this type of damper carriage is only suitable for the linear roller guide system, but no application is found on the guide system of the ball slide. The reason is that the guide surface of the ball contact is a curved surface, corresponding to this layer of the slide coupler element 0.03 The gap of mm is difficult to process and the squeeze film is easily lost.

(a) Rolling guides with damping shoes

(b) Self-made damping blocks Figure 3 Rolling guide mechanism with vibration reduction capability 2 Rolling shoe additional damping block For the linear rolling guide pair consisting of a rectangular steel rail and a roller rolling shoe, a damping block can be attached to its work plane. This kind of damping block is also called damping shoe or damping shoe. It is produced by specialized bearing factories or machine tool functional parts factories. It is used on some imported machine tools, and it achieves good damping performance after installation. See Figure 3 for an example of its application. The damping block is disposed in the guide mechanism and covers the largest possible area. The gap between the surface and the steel guide is also left to form a squeeze film. This damping block is actually a plane sliding guide that does not directly contact and can be designed and manufactured on its own. We designed this damping block on the inverted front longitudinal rail (Z) of the “SHZ1044 Twin Spindle Vertical Turning Center”. The damping block can be made of steel or cast iron as the base body. After processing, the guide rail is attached to the mating surface (we use TURCITE soft band material), and then it is matched with the corresponding guide rail (grinding or scraping) to make the two surfaces. Between the formation of 0.03mm gap, and drilled oil hole, and finally installed between the two roller sliding shoes, which constitute a rolling guide with vibration damping mechanism, as shown in Figure 3. Another effect of using a damping slide or a damping shoe is to improve the impact safety performance, suppress the plastic deformation caused by the impact, and reduce the damage of the mechanism. 3 Application of vibration-reducing guide mechanism The above-mentioned two kinds of rail vibration-reducing methods are applied on the "SHZ1044 twin-spindle vertical turning center", which proves that the effect is good. The horizontal direction (X) guide rails are equipped with RUDS damping slides produced by Germany INA Bearing Co., Ltd.; the inverted head vertical (Z) guide rails are made of self-designed and manufactured plastic damping slide shoes. The cost of the self-made damping shoe is lower than that of the imported damping shoe, and the length of the damping shoe can be arbitrarily set according to the size of the guide mechanism, which is economically feasible. The damping rolling guide system with damper slide or damper shoe is rarely used in China's machine tools. An important reason is that there is no professional factory in China to support it. We hope that through the introduction of this article, we can produce and manufacture such rolling vibration-damping components domestically, and promote the use of domestically-produced equipment, which will contribute to the advancement of China's machine tool manufacturing industry in the world.

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