With the increase of labor gap year by year, the skilled operators of some technical experience are less and less. In domestic machinery manufacturing enterprises, some machine tools have been unused because of the lack of skilled operators. The traditional mode that relies on the uninterrupted manipulating machine tools to complete the work of the workpiece has no longer adapted to the development of the society. In addition, the processing difficulty and the processing precision are also higher and higher. The form of workpiece processing through several or even more than a dozen machine tools has been phased out. In this context, the shift from labor intensive production to technology intensive processing has been the trend of the times.
Based on CNC CNC machining equipment, the automatic processing production line has become the first choice of the manufacturing enterprises of all sizes. Especially for vertical machining centers, we know that this kind of processing equipment is equipped with tool magazine and automatic tool changer, which can realize compound and centralized processing of all kinds of workpieces including complex curved surfaces. The precision and efficiency of milling, drilling, boring, hinges and attack can be completed in a single processing equipment at a time.
More importantly, workpiece processing in vertical machining center, including the replacement of machining tools, there is no need for front-line processors to do it themselves, and it is completely completed by machine tools. Basically, unattended processing can be realized. Of course, any processing equipment, no matter how excellent processing capacity and processing efficiency, the most important thing is to ensure the final machining accuracy of the workpiece. The author has been engaged in the experience of the first line processing for many years, and briefly introduces the main factors that affect the accuracy of the vertical machining center.
We know that the final machining accuracy of the vertical machining center can reach 0. 01mm is even higher. As a part of machine tool directly acting with the workpiece, the effect of the spindle on the machining of the workpiece and the retention of the precision of the machine tool is very important. In the actual processing, there are various error factors in the spindle assembly to affect the machining accuracy. The concrete manifestation is: when the axial error and angle error at the same time, it appeared to the spindle end face runout; when the radial error and angle error at the same time, there will be a spindle radial runout. The effect of the two errors on the final machining accuracy of the workpiece is very large. The reasons for these two errors are mainly caused by the influence of the bearing errors, the influence caused by the parts errors that are matched with the bearings, and the influence of spindle speed.
First, the influence factors of the spindle speed
We know that the spindle speed vertical machining center are generally higher, but with increasing the rotational speed of the main shaft, especially to the rapid, random vibration and the rotating axis of the instability is also increasing, when the fatigue strength exceeds the spindle spindle error leads to produce cocoa inverse increases, affecting the machining accuracy the final machine.
Two, the influence factors of the bearing error adopted
When the machine is used for a long time, the bearing will appear in the gap due to natural wear. When the bearing clearance is too large, the gap will be thicker oil films, when the vertical machining center, cutting force and speed will change, but the carrying capacity of the oil film thickness, oil wedge changes greatly, the result is the axis drift increases, thereby undermining the machining accuracy of machine tool retention reduce.
Three. Influence factors of part error with bearing
When the vertical machining center is used for a long time, there will be an increase in the bearing gap mentioned above. At the same time, the shaft diameter of the bearing, the supporting hole of the box, the shaft shoulder, the end cover of the bearing, the nut and so on, will also produce some deformation due to the force of the machine tool. Finally, it leads to the radial and axial drift of the spindle axis, which affects the rotation precision of the spindle and reduces the machining accuracy of the machine tool.
