Performance characteristics of rolling linear guide pair
1. High positioning accuracy
The motion of rolling linear guide is realized by the rolling of steel ball. The friction resistance of guide pair is small, the difference between static and static friction resistance is small, and it is not easy to creep at low speed.High precision of repeated positioning, suitable for frequent starting or reversing of the moving parts.The positioning accuracy of the machine can be set to ultra micro meter level.At the same time, according to the needs, the pre-load is appropriately increased to ensure that the ball does not slip, so as to realize the smooth movement and reduce the impact and vibration of the movement.
2. Wear small
For the fluid lubrication of sliding guide surface, the motion accuracy error is unavoidable due to the floating of oil film.In most cases, fluid lubrication is confined to the boundary area, and direct friction caused by metal contact is unavoidable. In such friction, a large amount of energy is wasted by friction loss.On the contrary, the rolling contact reduces the friction loss of the rolling surface due to the low friction energy consumption, so the rolling linear guide system can be in a high-precision state for a long time.At the same time, the use of lubricating oil is also very small, which makes the lubrication system design and maintenance of machine tools become very easy.
3. Adapt to high-speed movement and greatly reduce driving power
The rolling linear guide machine tool due to small friction resistance, can make the required power source and power transmission mechanism miniaturization, so that the driving torque is greatly reduced, so that the machine needed to reduce 80% of the power, energy-saving effect is obvious.It can realize the high speed movement of the machine tool and improve the working efficiency of the machine tool by 20~30%.
4. Strong carrying capacity
The rolling linear guide pair has good bearing capacity and can withstand different directions of force and torque load, such as up, down, left and right direction forces, as well as the jolt moment, shaking moment and swinging moment.Therefore, it has good load adaptability.The damping can be increased and the vibration resistance can be improved by adding proper preload in the design and manufacture.However, the lateral load of sliding guide in the direction of parallel contact surface is small and easy to cause poor operation accuracy of machine tool.
5. Easy to assemble and interchangeable
The traditional sliding guide must be scraped on the guide surface, which is time-consuming and time-consuming, and once the accuracy of the machine tool is poor, it must be scraped again.The rolling guide has interchangeability, and the machine can regain high precision simply by replacing the slider or the guide or the whole rolling guide pair.
As mentioned earlier, friction loss can be reduced because the relative motion of the ball between the guide rail and the slider is rolling.Generally, the rolling friction coefficient is about 2% of the sliding friction coefficient, so the transmission mechanism using rolling guide is far superior to the traditional sliding guide.
Selection method of rolling linear guide pair
The rolling linear guide pair has the characteristics of large bearing capacity, high contact rigidity and high reliability. It is mainly used on the bed of the machine tool, the table guide and the upper and lower lifting guide of the column.We can choose according to the size of the load, the direction of the load, impact and vibration size.
1. Stress direction
As the slider of rolling linear guide pair and guide usually have four rows of arc raceway, it can withstand four direction load and rolling moment.The bearing capacity of guide rail increases with the increase of raceway center distance.
2. Load size
Different specifications of rolling linear guide have different carrying capacity, can be selected according to the size of the load.In order to make each set of rolling linear guide rail have an ideal service life, the rated life and rated hourly life can be calculated according to the approximate formula provided by the selected manufacturer, so as to set a reasonable maintenance and replacement cycle.Moreover, the influence of rolling resistance of each slider under load should be considered to calculate the rolling resistance so as to determine the reasonable driving force.
3. Selection of preloading
According to the impact, vibration and precision requirements of the design structure, select the appropriate preloading value.
Status of rolling linear guide pair
At present, foreign manufacturers of rolling linear guide pair are mainly concentrated in the United States, Britain, Germany and Japan.Domestic rolling linear guide pair manufacturing is still in the initial stage, compared with foreign countries, there is still a gap, the main performance is: less varieties, small output, low service life, noise, processing technology is not as advanced as foreign.The domestic enterprises represented by Nanjing Craft equipment Factory and Guangdong Kitt Precision Machinery Co., LTD are making great efforts to narrow this gap. Some of their products have reached the international advanced level.
Development trend of linear rolling guide pair
New types and functions of rolling linear guide pair are emerging constantly, and are developing towards combination, integration, high speed, low noise and intelligence.
1. Rolling linear guide pair held by ball
THK adopts the ball cage and ball to keep the ball moving smoothly and eliminate the friction between the balls. It has developed an ultra-high speed linear motion SSR guide set with low noise, no maintenance, long life and a speed up to 300m/min, which has been popularized.The noise of the guide pair is less than 50dB at 100m/min motion speed, and the friction fluctuation range is reduced to 1/5 of the previous products.In addition, the test of adding grease 2cm3 and running 2800km was passed.In the future, linear motion guide with ball cage will gradually become the mainstream of high-grade CNC machine tool selection.
2. Use linear motor and linear guide
The sliding table system using integrated linear motor has the characteristics of compact structure and large power in operation.At the same time, the positioning accuracy of the sliding platform system is also improved.SKF linear Systems Co., LTD. Cooperates with Pratec linear motor manufacturer and has started to promote integrated linear motor slide system products since 1996.
3.THK intelligent driving system
Japan's THK Intelligent Actutator USES DC servo motor as the power. It USES precision ball screw pair and new rolling linear guide pair to realize linear motion. It is a combination component with very compact structure.
4. Mixing table
Japan developed a new type of rolling linear guide pair table, which has a set of sliding electromagnetic block device, which can be attracted to the guide during positioning and processing to increase friction, thus improving the vibration resistance performance of the system. Therefore, it is also called hybrid Table System.
5. Rolling linear guide pair made of new materials
Due to the diversity of users' requirements and the different use environment, the rolling linear guide pair made of new materials appeared.For example, the products made of stainless steel, its guide shaft, slider, steel ball, sealing end and retainer are made of stainless steel materials, and the reverse device USES synthetic resin, so the corrosion resistance is improved.For high-temperature and vacuum applications, the inverters may be of stainless steel.In addition, rolling linear guides made of ceramic materials will be developed and applied.
6. Rolling linear guide pair with magnetic gate measuring system
Schneeber AG of Switzerland, in collaboration with Heidenhain GM.BH, has developed a rolling linear guide pair called Monorail, which combines the guiding function of linear motion with the magnetic grain-digital displacement detection function.The magnetized steel strip is attached to the side of the guide, and the head picking up the signal is fixed with the slider of the guide pair and moves synchronously with it.
7. Linear transmission combination unit
Germany's worst (NEFF) company, in the mid - 80 - s introduced WIESEL linear drive combination unit "and" allowed German patent, it is install the ball screw pair made of aluminum alloy rectangular in the inner chamber, in the aluminum alloy frame top inlay rolling guide, guide rail sliding block with fixed nut, ball screw pair with skateboard for reciprocating linear motion.The linear transmission device composed of rolling elements has the characteristics of high efficiency and high speed, which is the ideal actuator of industrial robot, automatic three-dimensional warehouse and factory automation (FAC).
At present, there are some limitations in the use of linear guide rail in harsh environments, such as high dust concentration, strong acid, strong alkali and high corrosion.But with the increasing perfection of linear guide technology, as well as linear guide with high-speed and control of many outstanding advantages, as well as rich types and functions, it can be expected that the mechanism as a functional component will be more and more used in CNC machine tools and other mechanical equipment.