Electric Modular Design Method of MJ Series CNC Lathes

There are 12 models and 23 specifications of MJ series CNC lathes, covering the scope of Ø200~1000mm rotation diameter. The mechanical structure of the MJ series CNC lathe follows the design philosophy of serialization and modularization since the design. Due to the fact that the former MJ series CNC lathes have a small variety of specifications, the stand-alone design mode has been adopted, that is, different designers make electrical designs for different types of machine tools. With the continuous increase in the variety of machine tools, the disadvantages of this design approach are: electrical ladder diagrams (PLC programs), electrical schematics, machine operator panels, inconsistencies in the content and format of alarm texts, and flexibility and extensibility of machine functions. Poor. Through the analysis of the PLC program, alarm text, electrical schematics, electrical wiring diagram, the relationship between the operating panel can be seen, PLC program and electrical schematic diagram is the root cause of the difference between the electrical design of various machine tools, and PLC program input The distribution of output addresses, the basic functions of the machine tool, the selection of functions, and the control of extended functions, etc., have a great influence on the design philosophy of electrical schematics. Therefore, the core of the electrical modular design of MJ series CNC lathes is to modularize and serialize the PLC program and electrical schematics, and the modular design of the PLC program is the focus of the two. 1 The modularization of the PLC program is divided into modules. The characteristics of the MJ series CNC lathes can be divided into 8 modules, namely the common signal module, the basic control module, the tool holder module, the spindle module, the chuck and the tail. Block module, selection function module, alarm module and extension function module. The common signal module mainly deals with the interface signals between PLC and NC. The basic control module is mainly used to deal with emergency stop, hydraulic pressure, lubrication, cooling, mode selection, manual feed, speed adjustment, program start and stop signals. The tool holder module is used to logically control the selection and positioning of the turret tool holder. There are four types of tool holders for MJ series CNC lathes, namely coded electric tool holders, coded hydraulic knife holders, counting electric knife holders and counting hydraulic knife holders. According to the similarities and differences of logic control, the tool carrier module can be divided into two types: coded tool holder module and counting type tool holder module. Each module also includes two control logics of electric tool holder and hydraulic tool holder. In the specific application, one of the coded or counted tool rest modules is selected according to the actual configuration of the machine tool, and then the control logic of the electric tool rest or hydraulic tool rest is selected by setting the PLC parameters. The spindle module controls the forward and reverse rotation of the spindle, spindle orientation, and spindle speed change. The module includes servo spindle and frequency conversion spindle control logic, which can be switched by modifying PLC parameters. The chuck tailstock module controls the functions of the chuck, tailstock body, and tailstock sleeve of the machine tool. The selection function module controls the selection of the functional components of the MJ series CNC lathes. This includes the control logic for components such as hydraulic center frames, tool setting tools, pneumatic gates, chip conveyors, workpiece counters, and tri-color light indicators. Each type of control logic has one or more PLC parameters, which can be defined whether the control logic is activated, the initial state of the control logic, or the like. The alarm module monitors the status of machine faults, misoperations, etc. and triggers corresponding alarm text messages. At the same time, it generates various safety interlock signals to prevent damage to the machine tool or the human body. The extended function module is mainly designed to meet the needs of special users and facilitate the expansion of the machine tool functions. For this purpose, input, output addresses and memory space are reserved for the module in the PLC program. When the user proposes special function requirements other than the standard function and the selected function (such as remote control, loading and unloading robot, bar conveying device, etc.), the module can be conveniently used to compile the required control logic. Module Structure Each module is divided into an input section, a main body logic section, and an output section. The input part converts the physical address of the input signal into the intermediate logical address of the PLC to maintain the independence of the main logic part from the input address. The main part of the logic is the main part of the module, completes the logic and arithmetic operations of the control process, and temporarily stores the result of the operation at the intermediate logical address. The output part has two functions: one is to transfer the operation result of the main logic part to the physical address of the output signal, to realize the action of each functional part of the machine tool, and to maintain the independence of the main logic part relative to the output address: the other is to other modules Interface signals are provided for various sequences or interlocking control functions. PLC internal resources allocation PLC internal resources include timers, counters, intermediate points (R byte address, R bit address, D byte address, D bit address), etc., must be reasonable according to the division of the module and the needs of each module Allocation, so that the resources allocated to each module can meet the current needs, while maintaining a modest margin, in order to facilitate the revision and upgrade of the module. The following table shows the distribution of internal resources of the PLC in the MJ series CNC lathes. Among them, 80 "D-bit addresses" are used as PLC control parameters, which can be set and modified through the man-machine interface to realize the combination of the modules and the selection of logic functions. PLC Internal Resource Allocation Table Sequencing Module Timer Counter R Byte R Bit Address D Byte D Bit Address 1 Common Signal T1~T2 C1~C4 B0~B1 20*8bit DB0 10*8bit 2 Basic Control T3~T4 B2~B6 20×8bit DB1 3 Tool Holder Control T5～T12 B7～B15 20×8bit DB2～DB3 4 Spindle Control T13～T15 B16～B20 10×8bit DB4～DB7 5 Chuck and Tailstock T16～T19 B21～B30 10×8bit DB8 to DB9 6 Selection function T20 to T22 B31 to B35 20×8bit DB10 to DB11 7 Alarm control T23 to T27 B36 to B40 20×8bit DB12 to DB13 8 Extended functions T28 to T30 B41 to B49 30×8bit DB14 to DB19 2 Electrical The modular design of the schematic diagram For the same type of numerical control system, when the input/output address of the PLC program and the division of the module are determined, the interface lines related to the PLC in the electrical schematic diagram can be basically determined. In order to achieve the purpose of modular design, there are still several issues that need to be addressed in the design process of electrical schematics. Connection with CNC system. According to the type of CNC system used in the machine tool, the entire series of machine tools must be designed for electrical schematics. The MJ series CNC lathes have a total of three sets of electrical schematics, corresponding to the FANUC 0TC CNC system, the SIEMENS 810D CNC system and the MITSUBISHI 50L CNC system. Depending on the direction in which the machine tool is sold (either domestic or export), the difference in power supply needs to be considered. The electrical schematic diagrams of the MJ series CNC lathes include two input voltage types, 3Ø380V and 3Ø220V, which can meet the needs of domestic sales and exports to Europe and the United States. According to the different models and specifications of the machine tool, differences in the types and specifications of electrical components must be considered. Under the premise of neither reducing the quality of the machine tool nor substantially increasing the cost, the electrical components can be classified and selected according to the principle of “minimum species”. For example, the MJ260, MJ360, and MJ460 CNC lathes require 18 kVA, 22 kVA, and 26 kVA for the main transformer capacity. In order to reduce the number of transformers, the 26 kVA main transformer can be used uniformly. If the machine tools of different models and specifications use different types and specifications of electrical components, the correct description and description shall be made in the electrical schematic diagram and the list of purchased parts. According to the configuration of the machine's standard functions, selection functions and extended functions, corresponding design and description should be made in the electrical schematic diagram. The lines related to the selection function are generally defined by a dashed box: only the corresponding interface is left for the extension function, and no specific design is made. 3 Conclusion MJ series CNC lathe uses a modular design of the PLC program, electrical schematics and machine tool operation panel, to the procurement of components, production organization and management, electrical assembly and other work has brought convenience, so that debugging and maintenance The work is more standardized and convenient. At the same time, production costs are reduced, product manufacturing cycles are shortened, and product reliability is improved. The idea of ​​electrical modular design can also be further applied to CNC boring and milling machines, machining centers and other CNC machine tools, resulting in greater economic and social benefits.

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