CNC machine tools are commonly used in the production process, but the high cost of CNC machine tools often restricts the progress and development of production.In order to enrich the functions of existing CNC machine tools in China, this study explores the important technical problems of low-cost transformation of CNC machine tools by using open controller, taking the application of 802Dsl as the main line in the transformation of CNC machine tools under the requirement of low-cost control manufacturing enterprises.It provides some theoretical support and solutions for the low-cost transformation of CNC machine tools.CNC machine tool is an important force in the current production development process, and its own demand for high accuracy and quality greatly improves the overall efficiency of production.
However, the high rhythm of CNC machine tool updating speed and the relatively poor adaptability in some respects have increased the use cost and difficulty of CNC machine tool to a certain extent.Therefore, how to maximize the role of existing CNC machine tools in enterprises through system transformation under existing conditions is an important issue for enterprises and researchers.This paper will explore the application of open controller in the low-cost transformation of NC machine tools, in order to lay a theoretical foundation for the low-cost transformation of NC machine tools.Firstly, the characteristics of manufacturing industry and the application status of NC machine tools are described.Then, the main problems in the application of NC machine tools in industry and the market demand for the improvement are briefly analyzed.
At the same time, the feasibility and expected effect of the transformation are analyzed from the technical point of view.Then, a low-cost scheme of reforming NC machine tools with open controllers is given.Finally, the core technology is studied from two aspects of hardware design and software development in the process of transformation.It basically solves the core task of using open controller in the transformation of CNC machine tools in China under the low cost requirement.Costs are generally high.On the one hand, the cost of CNC machine tools refers to the purchase cost of CNC machine tools. The price of CNC machine tools is very high, and a production line is often tens of millions of dollars. There is a certain pressure on the general enterprises to re-invest. Especially in the current general depression of manufacturing industry in China, enterprises are not confident in the high-value investment of manufacturing equipment.On the other hand, it also refers to maintenance costs, high-end machine tools rely on manufacturers’maintenance and accessories. Once machine tools fail, manufacturers’ follow-up costs are a big expense. Serious problems will delay product delivery and affect the reputation of manufacturing enterprises.Renewal is difficult.It is difficult to operate in the process of equipment management, and different brand ages are not conducive to the Co-manufacture of a product.The most serious problem is that the updating and upgrading of CNC machine tool servo system is difficult and costly.Functional adaptability is poor.Enterprise products are generally relatively fixed, resulting in a waste of some machine tool functions, and enterprises can not delete or change these functions, seriously affecting the cost-performance ratio of machine tools.Especially for special or special machine tools, there are few special controllers, and it is difficult for enterprises to load the desired special functions in the existing general controllers.Many domestic manufacturing enterprises have introduced CNC equipment in the process of automation transformation. Now it seems that the equipment has become obsolete, but it can still be used after transformation. Therefore, the transformation of CNC machine tools is a very market work [2].
Through the transformation of the control system, that is, using the structural characteristics of the open controller, matching the realization of the relevant functions, finally achieving a variety of needs of manufacturing enterprises at a lower development cost.The use of enterprise’s original resources and equipment to make up for the waste and incompleteness of the performance of existing CNC machine tools, and ultimately meet the high-quality manufacturing needs.Cost reduction as far as possible: In the process of transformation, we should make full use of the original equipment of the manufacturing enterprise, determine the scope of transformation relying on the actual situation of the enterprise, and do not do too much magic to meet the needs of the enterprise, so as not to cause secondary waste of function.Improve the efficiency of man-machine: In view of the above problems, we need to reform the purpose is not to create difficulties in use and maintenance, pay attention to the unification of the user experience interface, reform the standards that are conducive to the operation of workers to allocate the image of hardware, so that not only the cost can be controlled, but also later failure enterprises can solve themselves.At the same time, modular structure is adopted, which can further enhance the reliability of the machine, and is also convenient for later maintenance.Further improvement of flexibility: From a simple mobile phone, it can be seen that the requirements of market consumers for products are individualized, so the manufacturing process will also face the same problem. In fact, the emergence of CNC machine tools itself is a further exploration of human flexibility in manufacturing, so the transformation needs to further realize multi-variety and small batch manufacturing environment. 。Especially, we should try our best to meet the control requirements of special equipment in enterprises.Open controllers can be said that the choice of controllers or control systems is the key to the transformation, because they have to meet the performance of the transformation purpose.Now the more advanced control in the market, such as Delta Taut, Galil’s Galil series motion controller, Austrian PCC and German Siemens controller, etc. [3].These controllers generally have the characteristics of open interface function, strong functionality, compatibility of various software and wide application.In this paper, we choose 802Dsl controller, which is the controller module of SIMMERIK 802Dsl control system. The manufacturer is Siemens.It has programmable logic controller, loaded with ISO language editing, with the characteristics of easy to become, diverse cycle.He broke the transmission barrier of RS232 port and paid more attention to efficiency in production.The most surprising thing is that the operation interface is simple, through the simple “Ctrl c” and “Ctrl v” can achieve the selection and editing of the program, easy to change in the future.The whole system can connect six axes, one of which is the PLC axle.The schematic diagram of the open control system is shown in Figure 1.The transformation process of NC machine tools is mainly the transformation of control platform and supporting hardware. The general process is shown in Figure 2.Work (Revamp) Task: Work task is to use the reset of 802Dsl controller and programming to make the NC machine meet the new work requirements.The determination of main technical indicators.Here is the performance indicators after the subsequent transformation, that is, to achieve the goal of parameterization, so different tasks of his indicators are not the same, which is also the standard and basis for the transformation.Generally speaking, the main types are: the performance of the NC machine tools to be improved, including the scope of the process, the material, quantity, quality and shape parameters of the workpiece.To improve the production efficiency and flexibility of CNC machine tools.That is to say, he can process that kind of workpiece, how many can be processed at a time, the number of knives added, batch production and environmental requirements, and so on.Performance parameters of products, such as CNC machine tools, often need to consider its accuracy, strength, stiffness, reliability, thermal deformation, noise, magnetic induction and other indicators.The NC system and driving mode of the transformation process [4].Cycle and cost, our transformation to facilitate enterprise application, while taking into account the transformation cycle and cost, the previous emphasis on low-cost transformation, the same index is very important.The formulation, evaluation and optimization of the overall transformation plan.It should be said that this step is the core work, and the quality of this work is directly related to the specific implementation and results.At the same time, it is a process with strong technology content. The overall plan is designed according to the actual production needs and manufacturing requirements of enterprises.For some variable projects, such as CNC system, it is often possible to choose the economic type of two-axis linkage, control mode has a variety of vector mode, servo motor selection and so on.The most important thing is the control mode, control principle, control system diagram design and so on.The basic scheme also needs to be evaluated simply, that is, considering the comprehensive factors such as cost, cycle and so on, and putting forward optimizing suggestions.The final plan is determined.Implementation of specific transformation.It is the process in which the designer, the producer and the construction engineer communicate and cooperate more with each other without discounting, so as to ensure the time limit and quality of the project.Evaluation after transformation.According to the above requirements, the CNC machine tool after reconstruction is evaluated, such as mechanical performance and electrical stability, and even the cutting of test workpiece can be observed.According to the parameter table of this retrofitted NC machine tool, we can know that this machine tool is different from the AC servo motor of the general mainstream equipment, but DC motor. After testing, it is found that the basic performance of the DC motor is better, and there is no change, etc. But there are some controllable defects in the V5 DC speed regulating system. When the motor is reformed, it does not change the nature of the motor, but it needs to remove the DC control device and load 590 DC governor at the same time.
Finally, the spindle becomes the driving method of DC servo motor and forms a semi-closed loop. Its principle is shown in Fig.
2.The DC speed regulating device (Continental 590) is used in the corresponding transformation process. This driver is a three-phase four-limit. Other parameters are: I input max = 110A, three-phase AC voltage U ~= 380V, auxiliary AC control voltage U ~= 220V.The peak speed of the motor, the torque during acceleration and deceleration, the continuous load cycle, load torque and other reasons will have an impact on the performance of the motor.The smaller the motor is, the better its dynamic performance will be. At the same time, the energy consumption of the motor will be enhanced.The effect of balancing acceleration torque can be achieved by controlling it at (x < 2.5, Z < 3).The speed and position feedback of the DC servo motor can be converted by a resolver via the selected ACC8Dopt7 12 bit RDC to form a digital feedback of 4096 pulses per revolution.Stepper motor driver can obtain pulse instructions directly from 802 Dsl.From this example, it can be seen that the opening characteristics of 802Dsl controller can be used for several modifications of the original CNC machine tools, so that the existing equipment of the enterprise can be fully excavated and used [5].Common jobs such as: a.
Replacement of CNC systems.B. Replacement of CNC systems and all servo systems.C. Replace the CNC system and servo driver, and retain the servo motor.D. Replacement of CNC system and spindle driver [6].Programmable Logic Controller S7-200 series can meet the requirements of series control, and it is used frequently in small-scale modifications.At the same time, it should be pointed out that it has a variety of CPU types and voltage levels, which makes it have a strong adaptability to the automation process.Generally speaking, S7-200 PLC has the following characteristics: a. It can regulate the power-down protection area; B. It can write and read I/O; C.
It can work out the output value when stopping state; D. It can simulate potentiometer; E. high-speed I/0.Its working process is: the first is sampling stage, the second is execution stage, and the third is refresh stage.Correspondingly, it is divided into three parts: power-on processing, scanning processing and error processing.We have adopted 820Dsl NC system, which is embedded PLC. That is to say, the NCU of this embedded PLC integrates CPU and NC. When controlling various executing equipment of NC machine tools, only the input signal of stroke switch and the output signal of solenoid valve and contactor can be connected with the input and output module, which greatly upgrades the system. The integration and stability of the system can ultimately realize the transformation of CNC.At the same time, the external interface of embedded PLC has two interfaces: drive and feedback, which can avoid the barriers in the process of information transmission, and make the controllability of the system strengthened [8].Figure 3 shows the system of PLC for NC lathe.The 802Dsl CNC system we choose carries a PLC subroutine library to our customers. In the program given in this bitterness, we can realize the function of general control. The method is the copy and paste proposed above.But the different workpieces machined by machine and the characteristics of equipment make it necessary to develop the program again, but the development here is based on the basic program library, that is to say, rewrite the PLC program according to the type of machine tools in the enterprise, which greatly improves the efficiency.The design of the main program of PLC includes many aspects, which should be treated according to the realization of functions, such as machine tool overload, workpiece falling off, fixture alignment and other emergency procedures, as well as the process control of tool holder change and manual operation control.Special emphasis should be placed on assistant function pressure detection, travel control, alarm lamp control, etc. [9].This research process combines the library with the specific situation of the NC lathe after modification, and compiles the PLC program. The process of the main program is shown in Figure 4.When compiling, it is required to be carried out under the auxiliary main frame.
After the CNC machine tool is powered on, thermostatic element the main program starts to run, resets before the system is initialized, and then monitors the system. In the middle, the signal is recognized and judged. The control signal MCP works according to the received signal, and if there is automatic operation, it is converted to the system operation program. If it receives the manual program, it will be operated manually, and then it will be able to control the steps, open the refrigerant, and carry out (automatic/manual) processing.If there is a state of emergency, it must enter the corresponding emergency stop processing program.Firstly, this paper explains the significance and Prospect of open controller in the process of low-cost transformation of NC machine tools, and then makes a simple analysis of the market demand and feasibility, and then gives suggestions for the transformation, builds and designs the framework of hardware design and software development, and provides a reference for the specific transformation work.As mentioned above, based on the backward status of CNC machine tools in many manufacturing enterprises in China, the lifetime and function continuity of CNC machine tools through the transformation of controller will reduce the production cost of enterprises.Technically speaking, the open architecture CNC system will build a customer-oriented and widely compatible controller according to the production needs of customers, to meet the customer’s substitution for CNC machine tools of different countries, types and ages, and to improve equipment performance.