A high-speed machining center for mold processing, a common structural feature is the use of gantry-type frame structure, in order to enhance the rigidity of the machine, and easy to make full use of space in the processing area. The material of the machine tool bed is mostly made of polymer concrete. Because this material has better damping performance and lower thermal conductivity, it is beneficial to improve the processing accuracy of the mold. At present, according to the configuration of coordinate axes, five-axis machining centers can basically be divided into two types of structures. One is that the three linear axes (X/Y/Z) are used for the tool motion and the two additional rotary axes (A and C) are used for the structure type of rotation and oscillation of the workpiece. This type of high-speed machining center, such as the RXP500DS/RXP800DS from Räder, Germany, the GS1000/5-T from Alzmetall, Germany, the HSM400U/HSM600U from Mikro, Switzerland, and the XSM400U/XSM600U, called Ultra High Speed ​​Machining Center, and Germany Hermle's C30U/C40U/C50U and so on. The other is that one of the five coordinate axes (A) is arranged on the spindle head. The fork spindle head allows the spindle tool to oscillate, and the swing spindle head can also be clamped tightly to make it Position at any position within the swing angle range. This type of machine tools such as DMC75Vlinear/DMC105Vlinear from DMG, MHPRO HPM1850U from Germany and RolfWisser from Germany, GAMMA605/1200. There are individual machine tools that have oscillating and rotary axes on the spindle head, such as the G996V/BSH/5A high-speed milling center of the Parat company in Germany and the five- or six-axis gantry milling machine of the German Edel company. The five-axis high-speed machining center is much more expensive than the three-axis machining center. According to the price comparison between the five-axis machining center and the three-axis machining center of the DMG75 DMC75V series, the five-axis price is about 50% higher than the three-axis machining center. Although the high-speed five-axis machining center is expensive, this high-end machine tool is particularly suitable for machining complex-shaped molds. In the machining of deeper and steeper cavities, the five-axis machining center can create the optimum process conditions for the end mills through the additional rotation and swinging of the workpiece or the spindle head, and avoid the tool, the arbor and the cavity wall. Collisions occur, reducing the risk of chattering and tool breakage during tool processing, which helps improve the surface quality of the mold, machining efficiency, and tool durability. When a user purchases a machining center, whether to use a three-axis machining center or a five-axis machining center should be determined according to the complexity and accuracy of the mold cavity geometry. From the process of continuous innovation in high-speed machining centers, it can be seen that making full use of the latest achievements in today's technology fields, especially the latest achievements in driving and control technologies, is the key to continuously improving the high-speed performance, dynamic characteristics and machining accuracy of machining centers. . Conclusion In the past ten years, great progress has been made in the drive technology and control system, which has promoted continuous innovation in the structure of machining centers and continuous improvement in performance. The application of electric spindles, linear motors, torque motors and fast numerical control systems has played a decisive role in improving the high speed, high dynamics and high machining accuracy of machining centers. Torque motors play a particularly important role in the various structural innovations of mold processing machines. It is not only applied to the rotary and swing drive of a rotary table, but also applied to the swing of a fork-shaped spindle head or the swing and rotary drive of a spindle head, thereby constituting various types of five-axis machining centers. The application of rotary and swing spindle heads provides technical support for the development of 5-axis gantry type high-speed precision milling machines for processing large-size molds. In the future, further improvement of spindle speed, dynamic performance and stroke speed is still the focus of the development of high-speed machining centers. This will not only depend on the further development of drive technology and numerical control technology, but also depend on the development of machine tool components and the parallel machine tools. Development. It can be expected that in the next five years, the axis acceleration of a high-speed machining center or a high-speed milling machine is expected to reach 3 to 4 g, and the rapid stroke speed of a coordinate axis can reach 100 to 140 m/min. Cheap Kayak,Inflatable Canoe,Fishing Kayak With Pedals,Inflatable Fishing Kayak Ningbo Haishu Hongkang Outdoor Industry & Trade Co., Ltd , https://www.nbhk2012.com
Electric spindle
High-speed spindles are the core components of high-speed machining centers. In the processing of mold freeform surfaces and complex contours, end mills with smaller diameters of 2 to 12 mm are often used, and in the machining of electrodes for electric discharge machining of copper or graphite materials, high cutting speeds are required. Therefore, electricity is required. The spindle must have a very high speed. At present, the spindle speed of the machining center is mostly 18,000 to 42,000 r/min, and the spindle speed of the XSM400U/XSM600U of the Mikro high-speed machining center in Switzerland has reached 54,000 r/min. For the micro-milling of the die (usually 0.1 to 2 mm in diameter), higher speeds are required. Such as the German Kugler's five-axis high-precision milling machine, the maximum spindle speed of 160000r/min (using air bearings), such a high speed, when the use of 0.3mm diameter milling cutter steel mold, it can reach 150m/min Cutting speed. At present, the Fraunhofer Production Technology Research Institute in Germany is developing spindles with an air bearing support of 300000 r/min. In the processing of molds, high speeds are always used, and the heat generated by high speeds and the vibrations that may occur during cutting are important factors affecting the accuracy of mold processing. In order to ensure the stability of high-speed spindle operation, sensors for measuring temperature, displacement and vibration are mounted on the spindle to monitor the temperature rise, axial displacement and vibration of the motor, bearings and spindle. This provides correction data for the CNC system of the high-speed machining center to modify the spindle speed and feedrate, and optimize the machining parameters. When the spindle produces axial displacement, it can be compensated by zero correction or trajectory correction.
Linear Motor
At present, most of the high-speed machining centers or milling machines used for mold processing use servo motors and ball screws to drive the linear axes, but some machining centers have adopted linear motors, such as Röders' RXP500DS/RXP800DS high-speed milling machines and Dage. The company's DMC75Vlinear high-speed machining center (with an axis acceleration of 2g and a fast stroke speed of 90m/min). Since this linear drive eliminates the need for a transmission element that converts the rotary motion into a linear motion, the dynamic performance, moving speed, and machining accuracy of the shaft can be significantly improved. Machines driven by linear motors can significantly increase productivity. For example, when machining electrodes for EDM, the machining time is reduced by 50% compared to the use of a conventional high-speed milling machine. Linear motors can significantly increase the dynamic performance of high-speed machine tools. Since the mold is mostly a 3D surface, the tool axis is constantly braked and accelerated while the tool is machining the surface. It is only possible to ensure that a given profile is tracked with a constant feed per tooth on a shorter path of the track at very high path speeds with a higher axis acceleration. If the curvature radius of the surface profile is smaller, the higher the feed rate, the higher the required shaft acceleration. Therefore, the axis acceleration of the machine tool greatly influences the precision of the mold and the durability of the tool.
Torque motor
In the high-speed machining center, the swing of the rotary table and the swing and rotation of the fork-shaped spindle head have been widely used in the torque motor. A torque motor is a synchronous motor whose rotor is directly fixed to the part to be driven, so there is no mechanical transmission element and it is a direct drive like a linear motor. The angular acceleration that the torque motor can reach is 6 times higher than that of the traditional worm gear and the acceleration can reach 3g when swinging the fork spindle head. Because the torque motor can achieve extremely high static and dynamic load rigidity, the positioning accuracy and repeatability of the rotary axis and the swing axis are improved. At present, some manufacturers of high-speed machining centers have used linear motors and torque motors to drive linear axes (X/Y/Z) and swing axes (C and A), respectively. Such as Ræžer's RXP500DS/RXP800DS, DMC75Vlinear and Edel's CyPort five-axis portal milling machines from DMG. It should be mentioned that the combination of a direct-drive linear axis and a directly-driven rotary axis gives all the machine axes of the machine high dynamic performance and adjustment characteristics, which allows freedom of tooling for high speed, high precision and high surface quality. Surfaces provide the best conditions.
Control System
The CNC control system is an important part of the high-speed machining center. It largely determines the machining speed, accuracy and surface quality of the machine tool. Therefore, for high-speed machine tools that process freeform surfaces of the mold, the performance of the CNC system has special significance. When processing high-precision free-form surfaces, the tool path formed by micro-sections of straight lines and arcs creates a huge part program. These data streams need to be stored and processed by the machine tool control system. Therefore, the length of the block processing time determines the CNC control system. An important indicator of work efficiency. At present, the block processing time of high-end CNC control system can reach 0.5ms (such as the HEIDENHAIN iTNC530 CNC system), and the block processing time of individual CNC systems has been shortened to 0.2-0.4ms. Modern CNC systems used for high-speed machining of molds, in addition to the short program processing time required to ensure high-speed feed rates, should also have Nurbs and spline interpolation functions, and be able to work with nanometer resolution. In order to obtain high machining accuracy and surface quality in the case of high-speed machining. At present, high-end CNC systems can also be connected with CAD/CAM systems from different manufacturers. Data is transferred from CAD/CAM systems via Ethernet to the control system at a very high speed. The integration of CAD/CAM into the control system can, to a large extent, enable the machining of the complex contours of the mould to obtain good results and make a very important contribution to shortening the adjustment time and programming time. In the above-mentioned five-axis high-speed machine tool, except for Ræžer, which uses a numerical control system developed by itself, the others mainly use Siemens 840D and Heidenhain's iTNC530 numerical control system.