Bearings are a key component of many mechanical structures. They can limit relative motion to the specific range of motion and can reduce friction between moving parts. The design of the spindle bearing can make the moving parts move linearly freely, or rotate freely around the fixed axis.
One of the main purposes of the spindle is to process work pieces as quickly and accurately as possible. Therefore, the bearings used for the spindle need to have a structure that can adapt to high-speed running, excellent accuracy and rigidity. The spindle bearings are mainly used to bear radial load and axial load.
The spindle as a key component of the machine tool, its performance will directly affect the parameters such as the rotation accuracy, speed, rigidity, temperature rise and noise of the machine tool, which will affect the processing quality of the work piece, such as the dimensional accuracy of the parts, surface roughness and other indicators. Therefore, in order to maintain excellent machining capabilities, high-performance bearings must be used.
P5 or P4 is the accuracy grade of ISO standards. The accuracy of the bearing used on the machine tool spindle should be ISO P5 or above, and for the spindle of high-speed, high-precision machine tools such as CNC machine tools and machining centers, the accuracy of ISO P4 or above should be selected; the spindle bearing includes angular contact balls Bearings, tapered roller bearings, and cylindrical roller bearings.
Angular contact ball bearing: Among the above bearings, angular contact ball bearings are the most widely used in machine tools. The rolling element of an angular contact ball bearing is a ball; compared to the linear contact of a roller bearing, it is a point contact, so it can provide higher speed, less heat generation, and higher rotation accuracy. They are especially suitable for ultra-high speed spindle applications.
Angular contact ball bearings have inner and outer ring raceways that move relative to each other in the direction of the bearing axis. This means that these bearings are designed to withstand combined loads, that is, radial and axial loads acting simultaneously.
Tapered roller bearings: In some heavy-duty machine tools with certain speed requirements, such as forgings, heavy-duty lathes and heavy-duty milling machines, tapered roller bearings are an ideal solution. Since the rollers of the tapered roller bearing are designed with linear contact, it can provide high rigidity and load to the spindle. In addition, the tapered roller bearing has a rolling bearing design, which can well reduce the running torque and heat of the bearing, So as to ensure the speed and accuracy of the spindle.
Among other types of bearings, cylindrical roller bearings will also be used in spindles. They are usually used in combination with angular contact ball bearings or thrust bearings. This type of bearing can withstand larger radial loads and allow higher speeds.
RPM (Revolutions per minute) is the calculation unit of spindle speed. Generally, high-speed spindles are strictly used in specialized metal processing machine tools, such as CNC milling machines. Different spindle speeds need to be matched with appropriate bearings, otherwise it may cause problems such as stall or overhearing.
In practical applications, some machine tools dedicated to mass production are equipped with a set of four, five or even six spindles. Such a machine tool is called a multi-spindle machine tool. For example, gang drills and many screw machines are multi-spindle machines that can process simultaneously. Although the bench lathe has several spindles, it does not belong to the category of multi-spindle machine tools due to its structure and application purpose.
In the field of machining centers, more and more machining centers are equipped with motorized spindles for high speed and multi-task machining. A spindle motor is equipped in spindle sleeve, so the multi-axis head can rotate more freely and work at a faster speed, which means that many curve machining and complex cutting can be realized.
Therefore, compared with other spindle types, vertical machining centers, horizontal machining centers, double-column machining centers, and moving-column machining centers install motorized spindles in order to achieve perfect production efficiency and quality.
All metal cutting tasks need to be performed through the spindle, so the spindle is regarded as the core of the machine tool, which controls the ultimate cutting speed, machining torque, and work productivity of the machine tool and even the entire production line. The research on the machining spindle is a lot and in-depth, which provides workers and engineers with more smart maintenance methods, which can more efficiently check and overcome the spindle problem.
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