The hottest precision and high quality milling die

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The CNC control system for precision and high-quality milling dies can accelerate production, which is beneficial for tool and die manufacturing, which has not acquired the remaining 75.01% of the company's shares at present. Due to the fierce competition from countries with low labor costs, mold manufacturers need to greatly improve their production efficiency. In order to achieve this goal, tool and mold manufacturers can further automate their production, and the cutting process can be accelerated through the CNC control system. Therefore, the industrial automation and drive technology department of Siemens developed new processing cycles and new functions for mold manufacturing, and integrated them into the CNC control system of SINUMERIK 840D. These new machining cycles and new functions are high speed setting cycle (HSC) 832 and pre position control (APC). In particular, cycle 832 is used to assist in machining free-form surfaces in the field of three-axis and five axis high-speed machining. This cycle combines important program instructions and machine data required to implement high-speed machining, as well as assisting in the generation of simple and structured programs

at present, there is no new function added to the cycle, and it is more the best to integrate some control functions. These functions, through the actual CNC control system, reduce the work of machine tool operators and cad/cam manufacturers

in the range of high-speed machining, when executing the cam program of a very short program segment, the control system must reach a higher feed speed of more than 10m/min. In addition, users also expect better surface quality and higher accuracy in the micron range. Given the various processing strategies, cycle 832 can accurately adjust the necessary procedures

the characteristic of this cycle is that it can realize different strategies of rough machining process and finish machining process. For the rough machining process, the continuous path machining method of circulating through the contour focuses on improving the machining speed; In finish machining, on the contrary, focus on the machining accuracy and surface quality. In both cases, the machining profile is maintained through tolerance data in order to obtain the required machining quality. Cycle 832 supports machine tools with up to three linear axes and two rotary axes to process workpieces at the same time

cycle 832 includes four processing methods: finish machining, semi finish machining, rough machining and cancellation (here the original text is abwahl, which means "Cancel", which is regarded as a processing type, because the changed machine tool data and set values can be returned to the values preset by the machine tool manufacturer for processing by calling "abwahl cancel" - translation note). In the cam program, these four processing cycles, It is directly related to the machining accuracy of the contour and the machining speed that can be achieved

in mold manufacturing, in addition to some geometric functions such as splines (free curves), the point cloud that can generate workpiece contour must be controlled first. In order to generate these point clouds, the cam system uses tolerance values that may produce deviations in the X, y, and Z directions. Within this tolerance range, the final determined points are calculated and stored in the new NC program. At this time, with the help of the control system, the high-speed setting cycle can execute different tolerance values and adjust them with its emphasis on one of the four machining methods. The machine operator can store the tolerance from the cam system in the high-speed setting cycle of SINUMERIK

Figure 1 milling free-form surface: the special high-speed setting cycle "cycle 832" is used to support the machining of free-form surface contour in the field of three-axis and five axis high-speed machining

higher machine rigidity improves the machined surface quality of the workpiece

on the one hand, the SINUMERIK compressor uses this tolerance as the tolerance zone for calculating the spline. On the other hand, in the trajectory control operation, this tolerance is used as deceleration control. In this way, the contour straight line segment specified by the G1 program segment in the tolerance zone can be integrated into the spline whether the power plug in the control system is inserted, This spline makes the CNC control system directly used for trajectory control

in a certain processing, the steel tool function and the performance of the machine tool can never be used for the cleaning screw people want to call. Each machine tool manufacturer can determine its own machine tool and the products to be processed. In the future, users only need to have knowledge of its NC program and its machining type

for rough machining, the user only programs the tolerance value, and then obtains the workpiece geometric data as G1 program segment. In NC programming, adhering to these rich functions can significantly improve production efficiency

now we should pay attention to two challenges:

◆ first, improve the processing speed, and do not damage the processing surface quality due to vibration

◆ secondly, the natural frequency of the machine tool cannot limit the maximum speed of the machine tool shaft

the new function of a newly developed SINUMERIK CNC system has withstood the test of the above two requirements. This new function significantly improves the gain coefficient of the machine tool without changing the transmission mechanism of the machine tool. The gain coefficient (known by every machine tool manufacturer) describes the "hard" characteristics of the machine tool. This gain coefficient specifies how many meters per minute a shaft can move until the position lag distance of one millimeter. (lag distance s refers to the deviation between the given position and the actual position. The lag position error depends on the gain coefficient kV and the travel speed V of the machine tool axis, that is, the travel speed of the axis divided by the gain coefficient, s=v/kv - translation note)

figure 2 surface quality: using the CNC function APC (pre position control), the gain coefficient (kv_faktor) can be significantly improved, as shown by production practice, Under the same surface quality, higher processing speed can be adopted to shorten the processing time

Figure 3 improves production efficiency: when processing workpieces, now the new control cycle can improve production efficiency. This can increase the efficiency by 25% when executing the finishing procedure and improve the surface quality of the milled die

sinumerik CNC system's new function pre position control (APC) can have a very good impact on this. The actual production has shown that people have successfully verified the effective vibration suppression of APC on many machine tools

the result is that in most cases, the gain coefficient kV is doubled, and some even tripled. This can significantly improve the so-called acceleration on the machine tool. Express the acceleration of the distance to the third power of time to limit the maximum acceleration (the unit of acceleration is m/s3). In other words, a higher acceleration speed is conducive to improving the acceleration, which can lead to a very short processing time. Undoubtedly, an effective prevention of machine tool shaft vibration is conducive to obtaining a high-quality workpiece surface

Figure 4 SINUMERIK 840D: as shown in the figure, the system variant SINUMERIK 840D solution line and sinumics drive standard parts, as well as high-performance servo motor 1ft7

Figure 5 modern machining cycle: when machining molds, this modern machining cycle helps to best combine the three main requirements of surface quality, accuracy and speed

vibration suppression can be achieved technically by feedback and access to the appropriate signal of the direct measurement system of the shaft (working at a given speed value)

the application of APC must meet the following conditions:

◆ there must be two measurement systems, one is the motor measurement system, and the other is the direct measurement system on the same (coordinate) axis

◆ APC can only operate in combination with Siemens' efficient general components and high-level general components

◆ the driving device to be suppressed must be suitable. Because many tests show that APC cannot meet all machine tools

however, APC function is the most suitable for high-speed milling. The application of this function can significantly improve the production efficiency, because it can increase the running speed of the finishing program by 25% and improve the surface quality of machining. Through APC, the gain coefficient can be adjusted up to 60%, and the natural frequency of the machine tool can be reduced accordingly

these new cycles and functions developed by Siemens for its NC control system have significantly improved the performance of the machine tool. It provides users in the mold and tool manufacturing industry with more possibilities than companies such as Shimadzu in Japan and landmark in Beijing, and helps users complete their production tasks at a faster speed and at a lower cost. (end)

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