At present, high-speed turning and milling technology has entered a relatively mature application stage in some industrial developed countries, such as West Germany, the United States, France, and Japan. Among the 11 important mechanical manufacturing research centers in Germany, there are two research centers for turning and milling, high-speed cutting, engaged in various theoretical and applied research, leading in the world, and there are many factories producing various types of special milling. The center; the United States is more emphasis on practical applications, high-speed turning and milling technology has been widely used in the automotive, defense, aircraft manufacturing and other industries. However, the research application in this field in China is not ideal. Only a small number of enterprises and universities have engaged in research in this field. Luoyang, Wuxi and other places introduced German electric spindle grinding head production technology during the Eighth Five-Year Plan period and have been mass-produced.
At present, large-scale rotary parts in China's military products still use turning, with low processing precision and low efficiency, and the processing of complex structural parts is more difficult to achieve. To solve these problems, the turning and milling technology should be adopted as soon as possible.
1Proposal of the problem The turning and milling center with the turning and milling motion as the main form is an integrated turning center with turning, milling, boring, drilling, broaching and even grinding functions, which can realize complex turning in one loading. Processing of most or all of the body parts. Take the CX600 CNC machine tool as an example, the CNC turning and milling machining center for processing the full arc type jujube nuclear bomb and the heavy anti-tank missile bin. As shown in the figure, the processing of jujube nuclear bombs in the military field. In the traditional process, the projectile and the directional rudder blade can only be processed separately, and then welded into one body by welding technology. However, with the use of turning and milling, the combination of the main shaft, the X-axis and the Z-axis can integrally process the projectile and the directional rudder, improving flight reliability and flight accuracy.
When machining the jujube nuclear bomb with turning technology, the spindle, X-axis and Z-axis are interpolated at the same time, and the workpiece rotation speed is required to be 0. 2 r/min, while the spindle rotation speed is 1600 r/min during simple turning. That is to say, the same CNC The spindle speed range of the machine tool is from 0.2 to 1600 r/min, that is, the gear ratio is 1:8000. Such a large gear ratio cannot be achieved by the conventional shifting method. Even if it is realized, the structure of the machine tool will be very large. Make people unacceptable. It is impossible to achieve it by mechanical means.
In order to achieve the requirements of low speed and high power, some foreign machine tool manufacturers have also tried the machine tool with a sample size of 200 mm. In order to achieve low speed and high power and meet the requirements of cutting torque, a 63 kW spindle motor is used. A veritable big horse-drawn car can't be accepted by people.
2NU M system main motor characteristic curve In order to realize this requirement of turning and milling technology, CX600 type turning and milling machining center adopts NU M1060 CNC numerical control system. After ingenious function conversion, using CN C system and Cs axis function, it realizes High torque and low speed during turning and milling, special requirements for high power and high speed during turning. The characteristic curve of the main motor is shown.
It can be seen from the characteristic curve that the NUM system realizes the full torque of the main motor at low speed 0~50 r/min (C-axis state), which satisfies the special requirements for spindle rotation during turning and milling.
Control of the 2Cs axis There are two options for controlling the Cs axis. The first is mechanical. There are two sets of transmission systems on the main shaft, which are respectively driven by the spindle motor and the C-axis servo motor. The spindle movement or servo motion is required to determine the machining program command to handle the gearing or disengagement of the gear to form the transmission. chain. The second is to directly perform C-axis control on the spindle motor through the CNC system with Cs axis function, and select the spindle state or C-axis state of the motor by command.
The NUM CNC system uses the Cs axis function to directly control the spindle motor for C-axis. The advantages are that the mechanical structure is simplified, the cost is low, the precision is high, and the reliability is good. The disadvantage is that the price of the motor and the servo system is high and the control is complicated. The servo controller of this system is different from the ordinary servo controller. The meaning of the interface board "ma" with the CNC system is as follows: Drive Ok: the servo controller is ready; the internal relay contact; Servo Enable: the CNC system sends out Servo enable control; Stop Relay: servo inhibit control issued by the CNC system, the input is zero when the servo system is working; Reference: terminals 10 and 11 are the first input of the control signal, here is the C axis; Switch Reference : Terminals 30 and 31 are the second input of the control signal, here is the spindle; External Protect: external protection input, 24V when no external protection is taken; Input C Axis Switch: when 24V is connected, the second input is valid; At 0V, the first input is valid.
3 function switching NUM CNC system is a multi-tasking multi-processor CNC device, with a modular structure, each microprocessor is responsible for their respective tasks, forming a specific functional module. Compared with the single-processor CNC device, the calculation speed is greatly improved, and it is suitable for multi-axis control, high feed rate, high precision, high efficiency numerical control requirements.
NUM CNC is equipped with a built-in PLC module, which can complete the input and output management of the machine's switch quantity, and complete the communication between PLC and CNC. The NU M system offers two spindle control methods: CNC system control and PLC control. Since there is a problem of switching between the C-axis state and the spindle state, PLC control is employed.
Set M 200 as the C axis function code, which belongs to the front and modal functions; M 100 is the C axis stop code, which belongs to the post and non-modal functions; %M 5. 0 is the C axis mark. Initialization time %M 5. 0= 0. Only when M05= 1, M 200 = 1, %M 5. 0= 1, output %Q605. 0= 0, make interface board “maâ€
The input voltage of terminal 24 is 0 V, and the C axis is valid. When M 100 = 1, %M 5. 0 = 0, output %Q 605. 0 = 0, so that the input voltage of the interface board "ma" terminal 24 is 24 V, the spindle is valid. This way, although the M code is more, the ladder diagram is more complicated, but the user will be very convenient. The ladder diagram is as shown.
4 Conclusion This paper takes the CX600 type milling and milling machining center as an example to discuss how to use the C-axis function of the main motor to realize the special requirements of low-speed and high-torque during turning and milling, high-speed and high-power during turning, and develop high-grade CNC system for us. The research and milling machining center provides experience and basis.
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