As a key transmission component, the appropriate selection of linear guides directly affects the service life and performance of the guides. Faced with the dazzling variety, models, and specifications of linear guides on the market, how can we make wise choices and find the one that truly suits us?
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Determine the type of KGT linear guide rail
KGT linear guides can be classified into different types based on their functions and characteristics. When making a selection, it should be based on actual needs:
(1) Roller linear guide: This type of guide has excellent rigidity and load-bearing capacity, especially suitable for situations that require heavy loads.
(2) Four column ball linear guide: This type of guide can adapt to various types of sliders and has the characteristics of high speed and low resistance.
(3) Six column ball linear guide: Compared with four column ball, its radial rigidity and load-bearing capacity have been further improved, while significantly reducing the vibration between the ball and the channel.
(4) Static pressure guide rail: The bearing oil chamber of its slider is filled with hydraulic oil, so that there is only pure liquid friction between the slider and the guide rail. This design not only provides excellent lubrication, but also effectively absorbs vibrations. In terms of rigidity and load-bearing capacity, static pressure guide rails are comparable to roller linear guides.
(5) Micro rails: Generally, rails with a width of less than 15mm are classified as micro rails. This type of guide rail is known for its compact size, high-speed performance, and excellent corrosion resistance, making it very suitable for use in fields such as microelectronics, optical instruments, and precision measuring equipment.
Micro rails are not only compact and have excellent performance, but can also be flexibly matched with sliders of different sizes, further expanding their application range. For example, elongated sliders can effectively enhance load-bearing capacity and meet heavier load requirements; The flange type slider is a standard configuration, and its bolt design can be connected to the lock on the workbench to achieve a stable fixing effect. These flexible and diverse combinations enable micro rails to play a greater role in fields such as microelectronics, optical instruments, and precision measurement equipment.
(6) The square slider is more compact compared to the flange type, and its narrow size is particularly suitable for work environments with limited width. However, it should be noted that the square slider can only be connected to the lock on the workbench through a threaded blind hole. -
Determine the configuration of the guide rail and slider
The number and spacing of guide rails and sliders have a direct impact on the load borne by each slider. Therefore, in the preliminary design stage, it is necessary to make preliminary selections based on space constraints and actual experience, and to supplement them with detailed calculations for verification. Common configuration schemes include:
(1) Single rail with single slider
(2) Single rail with multiple sliders
(3) Double rail with single slider
(4) Double rail with double slider
(5) Multiple guide rails with multiple sliders
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Draw a motion state diagram
In each complete stroke of the slider, it will go through three stages: acceleration, uniform speed, and deceleration. Especially during the acceleration and deceleration stages, the slider is not only affected by the machining load, the weight of the worktable, and the weight of the machine head, but also needs to consider the effect of inertial forces. For more accurate analysis and calculation, we can use motion state diagrams, such as velocity time diagrams, to depict in detail the states of the slider at each stage and further calculate the actual load at each state. -
Calculate the load of the slider
KGT linear guides can withstand radial and lateral loads. In the calculation process, we first apply the principles of force balance and moment balance to obtain the specific values of the radial force Fz and lateral force Fy borne by each slider. Next, we will calculate the combined load of the slider based on these values. The calculation formula for combined load is:
When considering the load calculation of KGT linear guide, we need to pay attention to a phenomenon: when using a single axis, due to the existence of overturning moment, the rolling body will experience uneven force. Therefore, in order to more accurately reflect this situation, we need to further convert the overturning moment into the corresponding load force. The calculation formula is as follows:
In the load calculation of KGT linear guide, we introduce two important concepts: dynamic combined load Fcomb and static combined load Focomb. These two are respectively used to calculate the lifespan and static load coefficient of the guide rail, in order to more comprehensively reflect the stress situation of the guide rail in actual use. -
Calculate lifespan
The calculated lifespan L10 of a linear guide rail refers to the 90% probability that under the same conditions, the same group of guide rail systems can achieve the same lifespan, that is, without fatigue damage. This lifespan can be expressed in units of length or time. This concept is particularly important when using ball guides.
In the case of using roller guides,We also need to consider its computational lifespan. The calculated lifespan of roller guide rail is also the period during which the guide rail system can maintain a 90% probability of reaching the same service life under specific conditions, that is, the period without fatigue damage. This indicator is crucial for ensuring the stability and durability of roller guides. -
Calculate static load factor
When considering the calculated lifespan of roller guides, we need to further investigate the static load factor. This coefficient reflects the ability of the guide rail to withstand static loads and is an important indicator for evaluating its performance stability and safety. By calculating the static load coefficient, we can gain a more comprehensive understanding of the load-bearing capacity of roller guides in practical applications.
The static load factor, also known as the safety factor, is an indicator for evaluating the safety performance of roller guides under static loads. The larger the value, the higher the safety of the guide rail. In general, the static load factor should follow the following principles:
after completing the preliminary selection of linear guides, we also need to further determine some key parameters, such as preload level, accuracy level, and select appropriate accessories, such as seals, special function sliders, and special coatings. These choices will directly affect the performance and service life of the guide railApplication SO There are unknown loads in dangerous working conditions such as high altitude or hanging upside down, and less than 4 sliding blocks can bear the load 12~20 Extremely high rigidity requirements
High dynamic load (vibration)
Severe pollution
The installation surface accuracy cannot meet the standard requirements8~12 The actual load can be basically determined or estimated based on data 5~8 The load is relatively light and has been determined <5