In the machining of mechanical parts, the proportion of hole machining is quite large. High-speed, high-precision drilling processing similar to high-speed milling has been put on the agenda. High-efficiency hole processing is indispensable for promoting the rationalization of parts production. crafting process. In recent years, most parts and components have been produced in the form of CNC machine tools. When machining holes, most of them use advanced equipment such as machining centers and CNC electric machines. Regardless of the hole processing in any field, achieving high precision and high speed is an important competitive means to obtain user orders. Next page
1 Conditions for machining center (MC) used for high speed hole machining
A prerequisite for the high-speed machining of the hole is that a high-speed machining center must be used, and the speed of the machine must meet the following conditions.
1.1 The high-speed rotary spindle drill has the same center tooth as the end mill. Since there is a peripheral speed near the center tooth, the spindle speed must be increased when the cutting speed is increased. In particular, when a small-diameter drill is used, the speed of the spindle is indispensable. In the future, with the progress of high-speed hole processing, the demand for spindles with a rotational speed of 30,000 to 100,000 r/min is expected to increase. At the same time, since the time required to reach the specified high-speed rotation is short and the length of the spindle extending in the Z-direction (bit cutting direction) is required to be controlled to a minimum, the configuration of the high-speed spindle is indispensable for achieving high-speed and high-precision hole machining. condition.
1.2 The movable part has agile function spindles and movable parts such as worktables should be as light as possible to achieve quick action, which is also a necessary condition for high-speed hole machining. The processing time of one hole only takes a few seconds. Therefore, it is necessary to shorten the tool movement time between the hole and the hole, which is a key problem for achieving high-efficiency cutting. The solution to this problem is firstly that the movement of the movable part must be flexible. Fast. For example, even if high-precision positioning accuracy is achieved, if the movement of the movable part of the machine tool is not sensitive enough, it is impossible to meet the requirements of the current user for high-speed hole machining. Usually, the acceleration characteristic (G value) is used to judge the quick performance of the movable part of the machine. When G=0.8~1.5, the machine tool can be judged to be a machining center with high speed performance.
1.3 The ratio of the work area to the overall area of ​​the machine tool should be small as the user of the machining center. They hope that the space outside the workbench and the workbench should be as small as possible. In particular, in the field of processing where the processing cost is high and the added value is low, it is preferable to use a compact machining center. For example, the high-speed CNC milling machine prototyped by the Japan Institute of Physical and Chemical Research has a processing range of 300mm2, and the machine body occupies an area of ​​950mm2. The machine tool occupies about three times the largest workpiece size, and the whole structure is quite compact. The milling machine has a spindle speed of 45000r/min for high-speed cutting. The spindle is a moving structure in the XY direction (the table is only moved by the Z axis), and its acceleration characteristic value is G=1.5, indicating that the machine has a quick action function.
1.4 The main shaft can directly supply the coolant. During the drilling process, the hole with the L/D (the ratio of the drill diameter to the hole depth) of 5 or more must pay special attention to the chip removal problem. It is best to use the drill bit with the oil supply hole for the purpose of Stable processing. It is more convenient to replace the locking bolts of the fixture by adopting the method of supplying the coolant from the center of the spindle.
1.5 CNC tool interpolation function for hole machining CNC cutting is characterized by reasonable machining of the tool path. In the CNC machining of the hole, it can be used for helical cutting, contour cutting, and cutting. CNC control systems with these functions can be used in hole machining.
2 into the high-speed drilling in New <br> <br> long been processed using a drill through holes and the bolt holes precision holes, threaded holes, etc., and recently, this process has been the rapid development of high-speed cutting direction .