1, bearing error
The bearing error mainly refers to the roundness error and waviness of the main journal and the inner bore of the bearing.
First, a detailed analysis is carried out by taking a spindle driven by a single oil wedge dynamic pressure sliding bearing as an example. When using a lathe to turn the outer circle, the spindle of the lathe drives the workpiece to rotate at a high speed, and the turning tool moves linearly along the guide rail. At this time, the cutting force acting on the workpiece maintains a relatively stable direction, and the cutting force is fixed in this direction. The main shaft should be in contact with a fixed part of the inner diameter of the sliding bearing at different positions. If the main journal is elliptical, the main shaft rotation axis will generate two radial runouts every one rotation of the main shaft; if there is a waviness on the main journal surface, the main shaft rotation axis will generate high frequency radial runout. Therefore, the roundness error and waviness of the main journal are the main influencing factors, and the roundness error of the inner diameter of the sliding bearing is a secondary factor.
2, bearing clearance
In the case where the bearing clearance is too large, if the load or the rotational speed is changed, the error will inevitably increase rapidly. The bearing clearance not only causes a certain static displacement of the main shaft, but also makes the axis of the main shaft perform a very complicated periodic motion.
Countermeasures: The proper preload of the rolling bearing can eliminate the gap well. Because the inner and outer rings of the bearing and the elastic deformation of the rolling elements are mutually influential, this not only increases the bearing stiffness, but also equalizes the error, thereby improving the accuracy.
3, matching parts
If the inner and outer rings or the bearing bush are deformed, the roundness error of the journal and the box support hole will occur; if the end faces of the spindle shoulder, bearing end cover, washer, etc. are not perpendicular to the axis of rotation of the main shaft, the bearing will be stressed due to assembly. Unevenness causes the raceway to tilt, which in turn produces radial and axial errors.
4, spindle speed
Due to the imbalance of the spindle component itself and the random vibration of the machine tool, the displacement of the spindle rotation axis increases rapidly when the spindle speed increases, so the spindle speed is preferably within the optimal speed range, and the machine tool should be avoided as much as possible. Resonance zone to improve machining accuracy.
Drilling machines are versatile machine tools for a wide range of applications, such as drilling, reaming, reaming, boring and tapping. When the drilling machine is equipped with process equipment, it can also be used for drilling, and the universal table can also be used for drilling, reaming and reaming.
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