Selection and configuration of CNC system for the

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Selection and configuration of CNC system of MC340 machining center

at present, the domestic economy has not developed rapidly, and the automation degree of the mechanical industry needs to be improved urgently. The vast majority of enterprises in China have outdated equipment, backward technology, poor efficiency and lack of funds, so equipment transformation has become the first link of economic construction. How to choose and configure the numerical control system is the primary problem in the transformation of numerical control equipment. How to reduce the transformation cost and optimize the comprehensive indicators of the transformation project is the most concerned and worried problem. This paper will introduce the selection and configuration of CNC system in the reconstruction of MC340 machining center, the general situation of actual configuration and economic benefits, hoping to be helpful to the equipment reconstruction

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1 the choice of CNC system

1) the significance of transforming MC340 machining center

after the CNC system of MC340 machining center of a factory was accidentally injured, it cannot be repaired, but there are some problems in the original design. In order to repair the machine tool and overcome the shortcomings of the original design, the transformation is proposed

the so-called transformation is to add new functions, or improve performance, or improve technical indicators on the basis of maintaining the original functions and performance, so as to achieve the purpose of improving productivity and increasing economic benefits

the primary problem in the transformation of CNC machine tools is how to choose CNC system. The performance of a numerical control equipment mainly depends on the performance of the numerical control system. The performance of the equipment after transformation is better than that before transformation, which is the purpose of its transformation. To achieve this goal, the performance and configuration of the selected CNC system should be improved

the first step of the transformation work is to comprehensively analyze and understand the performance, function and various technical indicators of the transformed equipment, master the electrical working principle, preliminarily determine the goal of the transformation work, formulate the transformation plan according to the market research situation, propose comprehensive indicators, and then demonstrate and review the transformation plan according to the comprehensive indicators in combination with the market situation, so as to achieve the best comprehensive indicators of the transformation project

2) introduction to the original configuration of MC340 machining center

mc340 machining center is a CNC machine tool with high precision, high efficiency and high reliability. It is the latest achievement developed by German STAMA company in 1994. The machine tool has 8 axes in total and 4 axes are linearly interpolated. When working, it requires Z, x, y and a four axis linkage. The CNC system adopts the 32bit-fs15m CNC system, AC 200V drive system and S series servo system of Japanese FANUC company, Through the interface and other components developed by STAMA company, the AC 165V analog drive and servo system of Siemens in Germany is integrated. CNC controls one spindle and four feed axes. PMC controls the tool magazine, the linear motion of the manipulator and three analog axes of the tilting table through the interface. Before 1995, such a configuration could be described as leading the new trend of the world. Fanuc-15 system has fast calculation speed and large program storage capacity. However, it controls one main shaft and four feed shafts, resulting in five NC shafts and three PLC shafts for one equipment. A set of control system is composed of three companies' products, which makes the structure decentralized, the electrical working principle and logical relationship complex, the control is not strict enough, the failure rate is high, and it is not convenient for maintenance

3) particularity of MC340 machining center tool magazine

mc340 machining center tool magazine servo uses Siemens 4.5nm, the output shaft diameter is small 19mn: servo motor, the transmission part adopts gear cross chain, and the driving gear tooth root edge is 30. The minimum shaft diameter of FANUC servo motor output end is 31, and the shaft diameter of products of other companies is large. If you use products of other companies, the mechanical structure of the tool magazine will be greatly changed, which requires a lot of manpower and material resources, which directly affects the transformation cycle. The linear motion of the manipulator and the tilting table will also be greatly changed accordingly. Because of this particularity, Siemens Servo motors are used for these three axes

4) basic configuration of Siemens CNC system

siemens-805 system can control 1 spindle, 4 feed shafts, 611A analog drive and 3 linear interpolation shafts. Siemens-810 system can control 2 spindles, 5 feed shafts, 611A analog drive and 3 linear interpolation shafts. Siemens-840d/ncu572 and 573 can control 5 spindles, 8 feed shafts, 611D full digital drive and 8 linear interpolation shafts. Siemens-840c can control 15 analog axes, 15 digital axes, 6 spindles and 5 linear interpolation axes

5) determination of transformation scheme

according to the above situation, two transformation schemes can be proposed. The first scheme uses fanuc-18 numerical control system, all digital drive system and a servo motor. NC controls 5 axes and develops the interface. PLC controls the drive of 3 axes through the interface. These three PLC axes use Siemens 611A drive system and AC 380V analog servo motor. The second scheme uses Siemens 840d/ncu572 full digital numerical control system, 611D full digital drive, 1FT6 servo motor and 1ph7 spindle motor, and NC directly controls 8 axes

through market research, the first scheme, fanuc-18 numerical control system, 5-axis full digital drive and a servo motor cost 450000 yuan, other accessories 120000 yuan, and Siemens' 3 analog drive and servo systems 96000 yuan. The material cost for developing the interface is 50000, and the total external expenditure is 716000. After analysis, the working cycle of developing the interface takes one year, and the possibility of success is small. In the second scheme, Siemens CNC system includes all accessories, with a total cost of 430000. According to the comparison of the two schemes, the first scheme has long transformation cycle, great difficulties, many defects, great technical difficulties and low success rate. The second scheme has short transformation cycle, tight structure, centralized control, simple electrical working principle, high performance and technical indicators, and high success rate. Moreover, the second plan costs 286000 yuan less than the first plan. Due to the short transformation work cycle, a lot of human and material resources can be saved. According to the current development trend of CNC system, it is predicted that the siemfns-840d CNC system will not fall behind within five years. After repeated demonstration, the second plan was finally determined

2 configuration of CNC system

· the spindle motor of the original machine tool is pe=18kw, n=1500 ~ 6000r/min. Use Siemens 1PH, pe=20kw, n=2000 ~ 8000r/min spindle motor

· X and Y axis servo, the original machine tool uses md=22nm, n=3000r/min servo motor. Use Siemens 1ft6086, md=30nm, n=3000r/min (without brake) servo motor

· z-axis servo, the original machine tool uses md=30nm, n=3000r/min servo motor. Considering that the z-axis is started under heavy load, which directly affects the tool change time, only servo motors with MD equal to or greater than 30nm and brakes can be selected, so Siemens 1ft6105, md=50nm, n=3000r/mic and servo motors with brakes are selected

· the dividing head servo motor originally used analog servo with md=12nm and n=3000r/min. The maximum load torque of the mechanical parameters of the dividing head is less than 450nm, and its mechanical transmission ratio is 180:1. If the transmission efficiency is calculated at 90%, the maximum driving torque should be

md=450 × 1/180 ÷ 90/100=2.8nm

so Siemens 1 ft6044 is selected, n 1D = 4 5nm, n=3000r/min servo motor

· the tool magazine, manipulator and tilting table were originally equipped with Siemens 1ft5064, md=4.5nm, n=2000r/min, and the servo motor with 1ft6044, md=4.5nm, n=3000r/min was used

analyze the wear state by analyzing and measuring the changes of surface morphology before and after wear. The configuration of power module: because the machine tool requires the spindle, z-axis, x-axis, Y-axis and a-axis to act at the same time, the other two axes do not operate synchronously with the spindle. Therefore, the power module

p= (ps+pz+px+pp+pa) ÷ 92%= (20+13+7+7+1.3) ÷ 92%=52.5kw

so Siemens 6snkw power module with AC 380V incoming line is selected

· cancel the original 8okw isolation transformer and add Siemens 6snl 155kw reactor to block the invasion of non sinusoidal waves

· the drive system uses 611D full digital AC drive system, and 60 is used to add its strength and wear resistance through appropriate heat treatment process (quenching and tempering, carburizing and quenching, etc.) Sometimes, special steel is inlaid at the jaw, or steel sand is sprayed on the jaw surface 0V DC bus and bus connection

· Siemens 840d-ncu572 is selected as the system

· cancel the operation panel of the original machine tool, and use the operation panel of Siemens mmc100.2 machine, but the growth rate slows down, simplifying the electrical control circuit

· use the 840D power display to replace the original spindle torque display, so that the display is concentrated in the display screen

· cancel the precision potentiometer and use the high-precision incremental encoder to realize coarse and fine positioning

3 results of system configuration

1) 840d-ncu572 performance characteristics

· 8 measuring circuits

· 8 feed shafts, 5 controllable spindles and 8 linear interpolation shafts

· 384 maximum i/o points of PLC

· zero program storage (expansion) 256Kb

· the minimum sampling time of the position controller is 1/0.5ms

· the minimum sampling time of interpolator is 4/2ms

· block cycle time 10/5ms

· maximum feed rate 999

· have Chinese environment, and input and execute the program at the same time

· with graphic simulation and polar coordinates

2) advantages

· the NC system of the original machine tool is decentralized assembly, takes up a large space, and has many and complex lines. 840D CNC system is all modular, with flexible configuration, convenient assembly, tight structure and few installation connecting lines

· the original NCU controls 5 axes, and PLC controls 3 axes through STAMA interface board. 840d-ncu572 CNC system directly controls 8 axes to realize 8-axis full digital processing, with fast operation speed and powerful function

· the original operation control uses ordinary buttons, with complex lines and high failure rate. The control panel of Siemens mm100.2 machine tool is highly integrated and compact, without connecting the control line

· it retains all the functions of the original system, adds blueprint programming, graphic simulation and background operation functions, and 840D has forward-looking function, friendly man-machine interface, and excellent dynamic characteristics of 611D all digital drive, which can improve processing accuracy, surface quality and processing efficiency

4 conclusion

in the equipment transformation work, the determination of the transformation scheme, the selection of the numerical control system, and the configuration of the system are very important, which are related to the success of the transformation project. Each link of the technical indicators, implementation methods, transformation work plan, economic benefits, and the prediction of future technological development should be carefully considered, demonstrated, and repeatedly compared to strive for high quality, high performance, high reliability Maintainability, short working cycle and high economic benefit make the performance and technical indicators of the transformed equipment exceed the original design. Make the comprehensive indicators of the transformation project reach the best, so as to improve the product quality of the enterprise, reduce production costs, improve production efficiency and economic benefits, and enhance the ability of the enterprise to participate in market competition. (end)

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