In the early 1980s, NSK developed and sold the LY series of precision linear guides for machine tools, a new series of machine guides developed on the basis of the LA series. In order to meet the needs of machine tools, such as higher speed and higher precision of the machining center, the LA series includes those features inherent in the LY series, and by displaying the number of raceways for the rolling elements, it shows more advanced performance, such as symmetrical. Load capacity, rigidity and friction.
Recently, the need for higher rigidity and greater load capacity of linear guides for machine feed mechanisms has steadily increased. Correspondingly, the application of roller linear guides using rollers as rolling elements has been increasing, such as lathes, which have been considered in terms of system stiffness in the past. Slide rails have always been used, and for machine tools equipped with linear motion motors, the main disadvantage is the gravitational force formed by strong magnetism. Moreover, the use of roller guides for the machine tool – a more luxurious appearance concept – has also contributed to the increasing use of roller guides on machine tools.
The functional requirements of the machine guide rails, such as large capacity and high rigidity, are undoubtedly important. In addition to the greater pollution resistance under severe operating conditions, the importance of higher motion accuracy and running performance cannot be ignored. To this end, NSK has successfully developed and marketed RA series roller guides: a new type of linear guide for machine tools with greater load capacity and higher rigidity than other roller guides found on the market.
1 Features
The RA series (Fig. 1) has the same mounting dimensions as the other roller guides of the LA series and is completely interchangeable. Below, the other main features of the RA series are described in more detail.
1.1 large capacity
The load capacity of the RA series is superior to the load capacity of the LA series and other existing roller guides. This is done by increasing the roller diameter and roller length to a maximum. The chamfer on the end of the roller is minimized.
1.2 High rigidity
Through the optimal configuration of the circulation hole on the roller slider, the roller is arranged in the form of DB, and the hundred is not the DF structure (Fig. 2).
And quantitatively consider the opening deformation of the roller slider to design the internal detailed dimensions and other measures to obtain an optimized cross section. The end result is a more rigid roller guide with equal or better than the LA series or its existing roller guide. In the development stage, in order to determine the degree of deformation of the roller slider caused by the load, the FEM analysis of the RA series roller guide was carried out. The results of the analysis (Fig. 3) are invaluable and noteworthy in the design of the optimum cross section of the roller slider, in addition to the requirements for the raceway.
The rigidity of the NSK RA35 roller guide was measured and compared to the rigidity of a commercially available roller guide (Fig. 4). The design of the RA35 roller guide was as expected.
In the direction of compression (the roller slider is advancing towards the track) and in the direction of stretching (the roller slider is pulled away from the track) it is more rigid than similar products.
1.3 High motion accuracy
By designing the optimum crown on both ends of the rolling surface of the roller slider, it is possible to suppress the vibration caused by the passage of the roller (the roller passes the vibration) and achieve high motion accuracy. The roller slip of the RA35 roller guide and the motion accuracy of the competitively produced universal roller guide were measured (Fig. 5).
The results show that the roller is vibrated (converted into displacement) by a roller that vibrates on 100 mm, and the NSK roller guide roller is significantly reduced by half compared with the vibration of the same product.
1.4 High running performance
The high deflection performance is achieved by the retaining block embedded between the rollers, which limits the deflection movement unique to the rollers. Moreover, the guide rail with the retaining block has a significant improvement in roller retention compared to existing roller guides. In fact, there is no need to make large bevels at the ends of the rollers, which is an advantage for load capacity, rigidity and cost.
1.5 High dust resistance
In the case of contamination, excellent dust resistance is achieved by installing a dust seal around the rolling surface of the roller slider. The cover on the upper track surface provides additional protection for demanding work environments.
2 Product Specifications
The current RA series are available in RA35, RA45 and RA55 (small to large cross-section sizes) and are available in high capacity (standard length roller sliders) and ultra high capacity (long roller sliders). Can be equipped with a square roller slider or a flanged roller slider. LA35, LA45 of the LA series. The LA55's form factor and mounting dimensions are interchangeable with other roller guides on the market. In addition, the accuracy of the RA series is the same as that of the LA series. Since the rigidity of the RA roller guide is inherently very high, the difference in preload has little effect on the rigidity of the entire guide rail. Therefore, the roller slider for the RA毓 can be assembled with only one preload level to ensure sufficient rigidity.
3 Summary
NSK has successfully developed and sold RA series roller guides to meet the need for greater capacity and rigidity of machine guides. The next goal is to produce RA25, RA30 and RA65 on an expanded production line and improve its functionality to meet or exceed customer expectations.
Suzhou FUJI Precision Elevator Co.,Ltd , https://www.profuji.com