Linear Module Overview: Long linear guides are now widely used in various automated machine tool production lines and some non-standard equipment. Generally, due to the constraints of the machined surface as the installation reference and the length of use, debugging and measurement are relatively simple. However, for ultra-long guides (greater than 8 meters), debugging and measurement become a challenge. Further Knowledge: Several points should be noted when using linear guides on machine tools. To meet the high demands of industrialization on the machine tool industry, the machine tool equipment industry is increasingly adopting linear guides and other rolling element guidance systems. Servo electric cylinders have accelerated the traditional rapid forward and backward speed of a few meters per minute to tens of meters per minute.
The use of linear rolling guides significantly improves machine tool productivity, reducing the number of repairs throughout its useful life and enabling continuous operation. However, the following issues need to be considered during machine tool design and manufacturing: Machine tools require high vibration resistance; those using linear rolling guides are prone to vibration. The high-speed forward and backward movement of moving parts causes significant impacts on the machine bed. Linear module linear rolling guide pairs have low damping, and linear motors have relatively poor vibration resistance. This can easily lead to vibrations in the machine tool due to periodic impacts, resulting in shape errors and ripples on the machined surface. This is especially pronounced in grinding machines, which may be affected by high-precision machine tools. Furthermore, it can cause instability in closed-loop servo control systems. The machine tool oscillation model using linear guides is similar to undamped forced oscillation. This model can be approximated using the principles of momentum and energy conservation: Where: m—mass of the moving parts; M—mass of the machine tool body; k—static stiffness of the machine tool; v—rapid forward and backward speed of the moving parts; Amax—maximum amplitude of the machine tool. From the above formula, we can see the conclusion. Decreasing m, increasing M, and adding k will all decrease the maximum amplitude Amax of the machine tool. However, increasing the mass of the machine tool body is less commonly used because increasing the machine tool body M will lower the machine tool's natural frequency, leading to a lower resonant frequency, which is detrimental to eliminating resonance. Therefore, simply increasing the wall thickness to improve the machine tool's stiffness, especially with a single-axis arm, does not help improve the machine tool's vibration resistance. In design, we should pay attention to improving the static stiffness per unit mass. For example, we can add appropriate reinforcing ribs, arrange reasonable cross-sectional shapes and dimensions, minimize the opening area on the bed surface, and improve the rigidity of the connection between the machine tool and the foundation. Some linear rolling guide manufacturers believe that applying a large preload to linear rolling guides can effectively eliminate vibration. However, practice has shown that increasing the preload can only change the resonant frequency and has little effect on vibration reduction. Excessive preload will only easily lead to deformation of the rolling elements, which in turn increases the resistance to displacement of the guide system. This causes the service life of the guide elements to be drastically reduced, to one-thirtieth of their normal lifespan. Therefore, the method of excessively increasing the preload is not allowed.
Machine tools should pay attention to adding damping reasonably to improve dynamic stiffness. There are many ways to increase the damping of machine tools, such as adding a layer of high internal resistance viscoelastic material such as asphalt-based polymers and paint soaps to the outer wall of the machine tool; embedding viscoelastic damping materials in the structure; retaining molding sand in the casting or sealing special fine iron shot in the casting.
