Cutting by the hottest machine tool

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Cutting by machine tool

when you see the parallel mechanism for the first time, you will almost certainly have the problems raised above. Those who are interested must also want to know whether such a thin linear structure is really strong enough in actual production? First of all, we should explain what kind of parallel mechanism is. The moving parts (such as the spindle) on the parallel kinematic machine tool are connected with the frame by a certain number of support rods and universal hinges. A typical six legged machine tool has six support rods in the form of lifting cylinders, and its length is variable. When a suitable type of universal hinge is selected, and the hinge on the frame is connected with the hinge on the part to be moved by using the support rod, the six degrees of freedom of the moving part can be manipulated with the help of the change of the length of the support rod. The length of any supporting rod can be operated independently without jamming

for machine tools with five support rods, such as the parallel kinematic machine tool developed by metro company based in Chemnitz, five degrees of freedom can be manipulated. When the universal hinge is properly configured, the degree of freedom that is no longer manipulated overlaps the degree of freedom of rotation around the spindle axis. In this case, it means reducing to five support rods, but it does not limit the degree of freedom necessary to achieve five axis motion. However, using five support rods can achieve greater swing motion than the conventional six leg parallel machine tool. The deflection angle can be greater than 90 degrees. If the workpiece is fixed on the rotary workbench, the workpiece can be processed on five sides under one clamping

although the machine tool adopts five support rods and is connected by appropriate hinges, all accelerations of the spindle mass can only generate axial force on the support rods. For Metro's parallel kinematic machine tool, the supporting rod as a ball screw has high axial rigidity

machining steel parts with a large amount of material removal

chemnitz machine tool experts used a 63mm diameter ball screw transmission device on the P1000 machine tool. The configuration of the support rod is the best, so that the connection between the spindle and the frame has high rigidity in a large working range, whether in the vertical position or in the horizontal position. Metro designs the rack according to the same principle. The supporting rod of the rack mainly bears tensile load and pressure load. Thus, important conditions are met, for example, so that a higher acceleration limit value (500m/s3) can be adjusted. The rotary direct drive device can make the acceleration greater than 10m/s2 through higher adjustment and amplification. Due to the light weight of the mobile, the energy consumption and output power are very low

in addition, the spindle of this machine tool can have 88nm and 130nm (s1/s6) torque (S1 represents the load of the motorized spindle at 100% operation time, S6 represents the load at 40% operation time. S6>s1, this is due to the short on time, so the motorized spindle is allowed to overload for a short time) and 27kw power. The performance of the machine tool is not limited to these limit values. Therefore, using P1000 parallel kinematic machine tool can process steel parts and other hard materials with a large amount of material removal. At the same time, the so-called Canadian Japanese nonferrous metals giant Mitsubishi materials bowed in response to the fraud, apologized for the speed and acceleration, and adjusted the amplification, allowing the realization of high dynamic five axis linkage trajectory movement. Therefore, the same machine tool can also be used to efficiently process workpieces of light materials

how rigid is the parallel mechanism

the parallel motion mechanism of Metro Company in Chemnitz has been used for many years to directly mill the casting mold formed by molding sand sticking to the new production capacity in the current industry, which is difficult to cause a huge impact on the product price. This not only eliminates white pollution, but also allows higher cutting speed when processing materials, so the parallel mechanism is suitable for this kind of processing

based on years of use, what are the views on wear? During sand milling, particles with sharp edges are thrown into the whole processing area at a high speed. The application results show that even if the sand particles fly, the equipment has not been damaged, Metro believes so. Because at any position of the spindle, the direction of sand flow is perpendicular to the axis of the spindle. The supporting rod itself can use corrugated sleeve to protect sand particles in a simple way. For parallel kinematic machine tools, there is no guide rail that needs to be protected. Both ends of the ball screw drive are supported by universal hinges. In this way, for reasons of structural principle, there will be no bending load that causes serious wear of the ball screw drive in the transverse direction

collision prevention

to prevent collision, the spindle is not allowed to enter some positions in the working area. This kind of collision may occur because the folding angle of the universal hinge is too large, and the spindle collides with the frame components, or the support rods collide with each other. In this case, Metro adopts the control system to deal with it. Through the control system, any collision risk can be identified in time. However, the control system cannot prevent the collision between the spindle and the workpiece. Even if the parts are damaged, the superiority of this machine tool structure can still be shown here. Because of the modular machine structure, the repair cost is relatively reduced. And after the damaged parts are replaced and corrected again, the accuracy will not be affected, even if the whole frame is deformed due to collision

is the processed workpiece larger than the machine tool

the mechanical structure of Metro's parallel kinematic machine tool is composed of five support rods including universal hinges, a spindle component and a rigid frame. The frame can be manufactured with a large tolerance without affecting the accuracy of the machine tool

after installing the support rod into the frame that can be easily calibrated, start the calibration procedure. Through this program, the motion parameters are determined and input into the NC control system. Using these information, the control system converts each preset spindle position in the ordinary coordinate system into the position of all feed drive devices. Through this machine tool structure mode, it opens up a new way for supplementary processing of large workpieces. One popular idea is a movable modular milling center. For such machine tools, the workpiece is not transmitted. Simply build a frame within the range of the workpiece to be processed, and hang the support rod together with the universal hinge on the frame. To a large extent, processing can be started after the completion of the automatic calibration procedure. After that, the machine parts can be easily removed and can be reused in the future. This kind of machine tool is conducive to processing large parts effectively and with the help of magnetic field to help product molding at a low cost

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