The highly efficient machining of highly complex surfaces and multi-process workpieces is the main processing feature of a vertical machining center. With the continuous development of processing operations, some highly complex curved workpieces and multi-processed workpieces have become commonplace, and their fine processing requirements have also increased. The requirements for its final machining accuracy and surface quality are all at 0.01mm or even higher. It is very difficult to finish this kind of workpiece through traditional processing machine. Especially for complex surface workpieces, because the traditional processing equipment is controlled by hand, it is impossible to carry out high-precision curve taking and thus it cannot be processed. For the processing of multi-process workpieces, it can only be said that it is barely competent. However, the processing efficiency is very low.
We know that multi-process workpieces are traditionally processed on ordinary processing equipment and need to be flowed on several or even more than ten different processing machines. Many times of setup and waiting for machining will consume a lot of non-processing time, and thus the processing efficiency. It is difficult to improve. In order to break this processing limitation, it is not surprising that vertical machining centers have been used in batches. The reason is that this machine tool is not only controlled by a CNC system, but also equipped with a tool magazine and an automatic tool changer. Through the control of these advanced functional components, it is possible to realize a highly automated and compounded machining capability. Therefore, it is the main production equipment for high-precision and high-efficiency machining of highly complex workpieces and multi-processed workpieces. The author has many years of experience in first-line processing, briefly introducing several important aspects affecting high-speed machining of vertical machining centers, hoping to bring us some inspiration.
The highly efficient machining of highly complex surfaces and multi-process workpieces is the main processing feature of a vertical machining center. In addition to the configuration of a tool magazine and an automatic tool changer, the processing equipment enables the machine tool to perform automatic replacement of the machining tools of the workpiece, as well as high-speed machining characteristics. Its spindle speed is generally at 8000 rpm. Some models even reach tens of thousands of revolutions. The rapid movement speed of the feed system is more than 24 meters per minute. These excellent machine properties lay the foundation for high-speed cutting of workpieces. However, high-speed cutting is different from ordinary cutting, and there are many factors that affect the final machining accuracy and surface quality of the workpiece. To sum up, there are several important aspects such as machine tool factors, tool factors, process system factors, processing technology factors, and artifacts themselves. We will focus on a few typical factors.
First, the factors of the machine tool
The high-speed cutting of workpieces we refer to refers to high-efficiency machining performed under the premise of ensuring the accuracy of workpiece machining. Of course, high-speed cutting performance is a necessary condition for high-speed cutting of workpieces. As we said before, vertical machining centers have such high-speed machining characteristics.
In general, the following aspects are needed to implement this type of machine tool:
1、High speed spindle and feed system
The core components of the vertical machining center are the spindle and the feed system. The accuracy and rotation speed of the spindle system are the key to ensure high-speed cutting of the workpiece. This requires that the configured spindle system should be compact, lightweight, rigid and inertial. There are several key indicators such as minimum and corresponding characteristics.
In addition to the requirements of the spindle, the feed system also ensures that high-speed feeds, as well as the positioning accuracy and repeatability of the machine tool, must meet the parameters set by the machine tool.
2, more flexible lubrication and cooling
High-speed operation of the machine tool spindle will inevitably produce a lot of high temperature. In order to prevent the high temperature from deforming the spindle system, lubrication and cooling are very important. Generally, we use the vertical machining center spindle that is used in high-speed rotation for a long time. Install an oil cooler for cooling. Lubrication generally uses a closed oil-immersed type. By using these two methods, the accuracy of the machine tool spindle at high speed can be ensured.
Second, the tool aspects
The tool is a component that directly acts on the workpiece. Its advantages and disadvantages are directly related to whether the high-speed machining of the vertical machining center is normal or not. In addition to the rational choice of geometric parameters, the material of the tool is the key factor.
In general, the tool material suitable for high-speed cutting of workpieces should have the following points:
The first is that the used tools must have high wear resistance. Only in this way can they ensure that the cutting tools do not form intermittent chips with sawtooth shape and thickness variation during high-speed cutting, which effectively prevents the dynamic balance of the tool from being destroyed, which leads to tool acceleration. Wear.
The second is to have a higher hardness and toughness. At the same time to meet these two can withstand the impact and vibration generated by the high-speed rotation of the tool, no chipping and fracture phenomenon.
Third, the processing technology factors
We know that the vertical machining center completes its processing tasks by executing the workpiece machining program. The pros and cons of NC programming directly affect the final machining accuracy and machining efficiency of high-speed cutting. The key to processing programming is the choice of workpiece processing. The cutting process mainly includes the process route for the high-speed cutting, the cutting mode, the cutting path, the optimized high-speed machining parameters, and the way to fully cool and lubricate.
High-speed cutting tool trajectory in principle, the use of layered ring cutting process, the general use of slash trajectory approach, direct vertical downward feed easily chipping and other phenomena, it should not be used; slash path infeed milling method The force is gradually increased, so the impact on the spindle of the tool and the vertical machining center is smaller than that of the vertical cutting tool, which can significantly reduce the phenomenon of knife collapse.
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