With the rapid development of numerical control technology, "composite, high speed, intelligent, precise, environmental protection" has become the main trend of the development of today's machine tool industry technology. Among them, high-speed machining can effectively improve the machining efficiency of the machine tool and shorten the machining cycle of the workpiece. This requires the machine tool spindle and its related components to meet the requirements of high-speed machining. Similarly, the precision bearings assembled in the spindle and feed part of the high-precision CNC machining center must meet the requirements of high precision, high speed, low noise, no fault and high reliability of the machine. The assembly quality of precision bearings directly affects their working condition and service life. Many CNC machining center failures are caused by improper assembly of bearings, so the assembly technology of precision bearings should be given enough attention. The assembly points of high-speed precision bearings are briefly described below.
First, the removal and cleaning of precision bearings
1. Keep your hands clean and dry When the precision bearings are removed from the package, the operator's hands should be kept clean and dry, as the sweat on the hands can cause rust and gloves can be worn if necessary.
2. Ensure good lubrication effect. The precision bearing that is taken out should be immediately loaded with grease and oiled. After the greased precision bearing is taken out, it will be installed without pollution, and it will not be loaded with grease and oil. When filling the grease, the gap between the cage and the outer ring of the bearing must be greased. The precision bearing is greased to 30% of the cavity, and the high-speed precision bearing is greased to 20% of the cavity.
3. The package should be sealed and the precision bearing can only be taken out of the original packaging before assembly. After removing several of the multiple precision bearing packages sealed by the volatile corrosion inhibitor, the package should be sealed immediately, as the shielding gas of the VIC paper can only be retained in the sealed package.
4. Wash not the correct greasing bearings precision cleaning prior to assembly, without greasing precision bearings must be cleaned prior to assembly, should be immediately dried and mounted on anti-rust oil or grease, in order to avoid corrosion after washing. For the degreasing and cleaning of precision bearings, the following cleaning agents can be used: aqueous cleaning agent - neutral, acidic or alkaline cleaning agent, check the compatibility of alkaline cleaning agent with aluminum parts before cleaning; organic cleaning agent - acid and Anhydrous kerosene, light gasoline (non-vehicle gasoline), Freon 12 substitute or chlorine-containing hydrocarbon cleaning agent. Precautions must be taken when cleaning precision bearings: environmental protection, health and work safety; the cleaning agent must be operated in accordance with the product instructions to avoid danger.
Second, precision bearing installation and installation tools
Precision bearings for spindles and lead screws are used as the basic components of machine tools. Their performance directly affects the speed, rotation accuracy, rigidity, anti-shake vibration cutting performance, noise, temperature rise and thermal deformation of the machine tool, which affects the precision of the machined parts. , surface quality, etc.
1.Precision bearing installation precautions
The precision bearing assembly site should be kept as clean as possible; to avoid the contamination of precision bearings or the entry of foreign matter, the pollutants have a great adverse effect on the operation and service life of the bearing; check the geometric accuracy and dimensional accuracy of the bearing seat hole and the matching surface on the shaft and Cleanliness; when installing, apply a little oil or a little grease on the mating surface of the ferrule, the precision bearing is easier to install to the design part; when designing the bearing housing hole and the shaft, there should be a 100-150 installation guide chamfer; do not overcool Bearings, because condensation can cause the bearing and bearing mating surfaces to rust; bearing inner ring and spindle assembly need to adopt the directional assembly method or angle matching method, which is to artificially control the direction of the radial runout error of each assembly, so that the error mutual Offset rather than accumulate; the bearing should be rotated and flexed without resistance after the bearing is pressed into the bearing; after the installation is completed, check whether the precision bearing system is working properly.
2. Reasonable use of the installation tool
(1) When the interference is large, it can be installed by heating box, oil bath heating or inductor heating bearing. The heating temperature range is 80 °C ~ 100 °C, and the maximum can not exceed 120 °C. At the same time, the bearing is tightened by a nut or other suitable method to prevent the bearing from shrinking in the width direction after cooling and causing a gap between the ferrule and the shoulder. (2) When the bearing is installed, it is necessary to apply equal pressure on the circumference of the end face of the ferrule to press the ferrule into it. Do not directly hit the bearing end face with tools such as hoes to avoid damage. In the case of a small amount of interference, the end face of the bearing ring can be pressed with a sleeve at normal temperature, and the center of the assembly sleeve can be tapped with a hammer to press the ferrule evenly through the sleeve. The assembly force must never be transmitted through the rolling elements, avoiding direct hammering of the bearing rings. When pressing in, ensure that the end face of the outer ring and the shoulder end face of the outer casing, the end face of the inner ring and the end face of the shoulder of the shaft are pressed tightly, and no gap is allowed. (3) The mechanical press or hydraulic press must be press-fitted with the assembly sleeve and ensure that it is in a horizontal state. If it is tilted, the bearing channel will be damaged due to the force, and the bearing will produce abnormal noise. The assembly sleeve must be in full contact with the entire circumference of the end ferrule or outer end of the outer ring of the bearing.
Third, the removal of precision bearings
The designer should consider the disassembly problem in the precision bearing installation. The precision bearing is generally installed with interference fit. When designing, the groove on the shaft or the bearing housing hole should be provided for disassembly. If the removed precision bearing is to be reused, the disassembly process must be handled with care. When disassembling the precision bearing, pay attention to the following points: avoid direct impact on the bearing ring; the disassembly force should not be transmitted through the bearing rolling body. When the precision bearing is removed from the shaft, the disassembly force should be transmitted through the bearing inner ring, from the bearing housing hole. When disassembling the precision bearing, the disassembly force should be transmitted through the bearing shell; once the precision bearing is disassembled, it should be cleaned, dried and coated with anti-rust oil or greased to avoid the bearing being rusted.
In the assembly process of precision bearings, if you pay attention to the above points, it will have an ideal effect on the control of the spindle temperature rise, the spindle high-precision high-speed trouble-free operation, and the transmission accuracy control.
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