1. Introduction In recent years, with the rapid development and application of rapid prototyping (RP&M) technology, rapid prototyping (RT) has also emerged and developed rapidly, becoming a research frontier of RP&M technology. Direct and rapid manufacturing of metal parts and molds is a research frontier of rapid prototyping and manufacturing (RP&M) technology. The goal of this technology is to apply RP&M technology to the manufacturing process of metal parts and molds, which can greatly reduce manufacturing cycles and costs. Plasma deposition rapid prototyping technology is a new type of RT technology, which is actually a composite technology of multi-layer plasma welding and surface finishing. The plasma deposition process is complex, with strict requirements on the sequence and timing of actions such as gas supply, powder supply, arc initiation, movement start, arc decay, movement stop, powder stop, and gas stop. Therefore, multi-layer plasma deposition manufacturing is more complex than plasma welding, mainly due to: the need for multiple arc initiations in the middle of a layer; the need for automatic control of surface finishing between layers to avoid manual intervention; and the need for intelligent control and feedback of complex process parameters. The automatic control system for plasma deposition forming is one of the key technologies in direct rapid manufacturing of plasma deposition. The development of this system makes direct and rapid manufacturing of metal molds possible, and is a prerequisite for the practical application of rapid mold-making technology. This paper introduces the research and implementation of the automatic control system software for the plasma deposition process based on configuration software. Some key technologies involved in the control also have positive implications for other industrial manufacturing methods. 2. Overall Structure of the Plasma Deposition Rapid Mold-Making Control System Analyzing the plasma deposition process, from gas supply to product forming, each process action must be connected in a certain sequence and time interval. The rationality of the selected process action sequence has a significant impact on the stability of the process and the quality of the weld layer. A typical plasma deposition process can be divided into three stages: arc initiation, deposition, and arc extinguishing. According to the process requirements, the connection between each process action sometimes requires a delay, and sometimes they need to be simultaneous or simultaneously stopped. The generally selected process action sequence is shown in Figure 1. As can be seen from the figure, the process control of the control system is relatively complex, especially the initiation of powder feeding, non-arc and arc switching, as well as the control of attenuation, which have the greatest impact on the product forming result and are difficult to control. The essence of rapid plasma deposition manufacturing is multi-layer deposition forming. In addition to considering delay and motion coordination, it is also necessary to consider multiple arc initiation in one layer and finishing processing after one or more layers are formed. In order to simplify the hardware structure of the control system and improve its visualization, an industrial computer + board form is adopted. In order to realize the reading and control of I/O quantities and the acquisition and control of analog quantities, the VIDA I/O board P32C32, the VIDA analog quantity control board A626, and the Advantech data acquisition board PCL-818L are used. The industrial computer mainly manages the plasma deposition process (such as gas supply, water supply, arc initiation, etc.), while the CNC machine tool mainly manages the deposition motion process (thereby forming parts of a certain shape). The signals that need to be acquired are (1) digital quantities: water supply, gas supply, high frequency status, and motion control status of CNC machine tool. (2) analog quantities: powder supply, current and voltage during plasma deposition, temperature, etc. (3) video signals: surface shape of the molten pool during deposition. The signals that need to be controlled include (1) digital quantities: water supply, air supply, high-frequency switching, and sending control signals to CNC machine tools. (2) analog quantities: powder supply (i.e., motor speed), current during plasma deposition, etc. The overall structure of the plasma deposition control system is shown in Figure 2. 3 Control methods based on configuration software In the development of domestic industrial control projects, there are two main ways to implement the host computer control system: one is to use visual high-level languages ​​such as VB and VC++ for low-level development, which can realize the technical requirements of the control system. The biggest drawback of this development method is that the development cycle is long and maintenance is inconvenient. The other is to use industrial control configuration software for secondary development. In industrial control software, configuration software can make full use of the graphical editing function of Windows to easily form a monitoring screen, display the status of the control equipment in an animated manner, have alarm windows, real-time trend curves, and can use the rich software resources of PC for secondary development, conveniently generate various reports, and provide a very convenient software platform for application development. This method has been widely used in the field of industrial control due to its advantages of being simple to learn, having a short development cycle, and being easy to maintain. Furthermore, there are many industrial control configuration software options available both domestically and internationally. These include products like the FIX series and INTOUCH from Intellution (USA), Citect from CIT (Australia), and WINZCON from PPCSOFT. While these foreign configuration products generally offer powerful and mature features, their higher prices make them less accessible to ordinary domestic users. Beijing Yacon's KingSCADA software incorporates many excellent features from foreign configuration software and utilizes advanced software design technologies. In many aspects, it rivals foreign configuration software, but at a relatively lower price, saving development costs. KingSCADA supports hardware devices including PLCs, intelligent modules, boards, intelligent instruments, frequency converters, and more. Engineers treat each lower-level machine as a device, without needing to worry about specific communication protocols. They simply select the device type from KingSCADA's device library and follow the wizard prompts to complete the installation. It supports most popular industrial A/D, D/A, and I/O boards, making them readily usable, and board definition is very simple. 4. Plasma Deposition Forming Control System 4.1 System Composition and Functions The hardware of the plasma deposition control system based on configuration software consists of a P32C32 I/O card from VEDA for process control of water and gas supply; an A626 D/A card from VEDA for control of powder feeding and current and voltage during deposition; an Advantech PCL-818L A/D card for acquisition of important on-site data; and an image processing card and camera from ADLINK for real-time tracking of the molten pool morphology. A graphical interface, such as a control system overview diagram, current and voltage waveform display diagrams, parameter setting diagrams, alarm diagrams, and reports, is developed on the on-site industrial control computer using KingSCADA software to monitor the deposition control system (see Figure 3). The main function of the system is to detect and control the movement, powder feeding, and current during the plasma deposition process to produce satisfactory products according to specified requirements. 4.2 KingSCADA Real-Time Database Design The real-time database is the core component of the KingSCADA software. During KingSCADA (TouchView) operation, the production status of the industrial site needs to be reflected on the screen in the form of animation. Simultaneously, instructions issued by process engineers in front of the computer must be quickly delivered to the production site. All of this is mediated by the real-time database, with the data dictionary serving as the bridge between the host computer and the slave computer. The KingSCADA system supports various variable types, which can be divided into two main categories: memory variables and I/O variables. The former mainly refers to intermediate variables, while the latter corresponds to the mapping of I/O cards, analog control cards, and data acquisition cards in KingSCADA. Note that since KingSCADA prices are calculated based on the number of points (variables), it is advisable to save resources when setting variables. For I/O quantities, it is best to read and write in words (int). For example, the P32C32 I/O card has 64 points (32 inputs, 32 outputs). If point-to-point reading and writing is used, KingSCADA's "point" resources will be quickly exhausted. If defined in words (int), only 4 "points" are needed. The specific I/O definitions are as follows: (1) Define the board. Double-click the board in the tool manager to add a new board. Just select the correct board manufacturer, model and board address. It is also very simple to determine whether the board can work properly after definition. Just perform the board test in KingSCADA. (2) Define the port. Define a variable such as “Input Con1” in the KingSCADA data dictionary. The variable type is “I/O Integer”. The connected device is the board just defined. The register is “DI1” and the data type is “int”. Then you can read all the input ports of the P32C3’s Con1 port. Similarly, you can define “Input Con2”, “Output Con1” and “Output Con2”. 4.3 Software process This part of the work involves the plasma deposition process. The deposition process generally includes three parts: arc initiation, welding and arc extinguishing. The timing is shown in Figure 1. First, the CNC machine tool and the deposition equipment need to be in a ready state, that is, they can complete independent functions respectively (the CNC machine tool completes the welding motion process and the deposition equipment completes the deposition process). First, the CNC machine tool issues a "ready to start arc ignition" command. Upon receiving the ignition signal, the welding equipment sequentially delivers air (opens the working air valve), feeds powder, initiates the non-arc phase, initiates the high-frequency phase, and initiates the rotating arc phase. This completes the arc ignition stage. The welding equipment then sends a "start movement" command to the CNC machine tool, finally entering the welding stage. Due to the characteristics of rapid prototyping path planning, multiple arc ignitions may be required during a single layer of welding, meaning the path may be discontinuous. Therefore, it's necessary to extinguish the rotating arc during a single layer of welding. For convenient and rapid arc ignition, we can consider retaining the non-arc phase. Thus, during the welding process, it's necessary to determine whether to extinguish the rotating arc and retain the non-arc phase, or extinguish both. To ensure welding quality, consider milling once after welding one or several layers. When milling is required, both the non-arc and rotating arc phases must be extinguished. When arc extinguishing is required, the CNC machine tool sends a start arc extinguishing command to the melting equipment according to G-code instructions. After receiving the command, the industrial control computer sequentially feeds powder to attenuate—arc attenuation—non-arc attenuation—and stops gas supply, then enters a waiting state, waiting for the next melting start command. The melting start and end procedures are as follows: 5 Software Implementation 5.1 Implementation of Control Timing KingSCADA provides users with a command language similar to C language, which engineers can use to enhance the flexibility of application engineering. The command language includes application command language, hotkey command language, event command language, variable change command language, user-defined function command language, animation connection command language, and screen attribute command language. The lexical syntax of the command language is very similar to that of C language, and is a subset of C. It has complete lexical syntax error checking functions and rich operators, mathematical functions, string functions, control functions, report functions, SQL functions, and system functions. Various command languages ​​are edited and input through the "Command Language" dialog box and compiled and executed in the "KingSCADA" runtime system. The timing control can be implemented with just a few simple lines of commands, and it also allows users to complete simple algorithms. The following is a list of some command statements for the timing control of this control system for reference only. When the deposition process is triggered: IO output Con2 = IO output Con2 | 256; // Gas supply indicator = 1; IO output Con2 = IO output Con2 | 512; // Powder supply indicator = 1; When the deposition process starts (set to scan once every 400ms): Start delay = Start delay + 1; if (start delay == 4) { IO output Con2 = IO output Con2 | 1024; // Non-arc/non-arc indicator = 1; } if (start delay == 10) { IO output Con2 = IO output Con2 | 4096; // High frequency started indicator = 1; } if (start delay == 14) { IO output Con2 = IO output Con2 & 61439; // High frequency stopped indicator = 0; IO output Con2 = IO output Con2 | 2048; // Arc transfer indicator = 1; } if (start delay == 16) { IO output Con2 = IO output Con2 | 1; // Send the start signal to the CNC machine tool: Workbench motion indicator light = 1; } 5.2 Implementation of Dynamic Screens KingSCADA excels at simulating the work environment and creating animated interfaces. In KingSCADA's development system, each element on the interface is considered an object that can be manipulated by the user. Through animation connections, users can connect an object to a variable to achieve actions such as blinking, moving, and rotating. KingSCADA provides 21 animation connection methods, allowing multiple connections to be defined for a single object, creating complex effects to meet the needs of any animation display in practice. Defining and modifying animations is very simple, and users can master it completely within one to two days. 5.3 Connecting KingSCADA to External Databases KingSCADA is a relatively open software that supports standard Windows functions such as DDE and SQL, enabling programs developed based on KingSCADA to exchange dynamic data with programs developed using visual high-level languages ​​such as VC and VB. It can also exchange data with Access, Excel, and other databases. The following example, using real-time current and voltage reports in a plasma deposition control system, illustrates the connection between KingSCADA and an external database. For in-depth analysis of the current and voltage in the deposition control system, real-time signals acquired on-site are crucial and must be saved promptly and at high speed. While KingSCADA allows data acquisition frequencies down to the millisecond level, its fastest data saving frequency is only 1 data entry per second, which is insufficient. By using KingSCADA's SQL function to promptly send data to an external database for saving, this problem is easily solved. KingSCADA's SQL Access Manager is used to establish the relationship between database columns and KingSCADA variables. It includes two parts: table templates and record bodies. Table templates create tables in the database; record bodies establish the relationship between database table columns and KingSCADA, allowing KingSCADA to directly manipulate data in the database through the record bodies. Both table templates and record bodies are created in the Project Browser. After creating the table templates and record bodies, we can create a new MS Access database in the Windows ODBC Data Source Administrator. The next step is to connect to the database. The command language is as follows: `SQLConnect(DeviceID,"dsn=mine;uid=;pwd=")`. This command establishes a connection with the database whose data source name (dsn) is `mine`. `uid` represents the user ID for logging into the database, and `pwd` is the login password. No user ID or password is set here. Each execution of the `SQLConnect()` function returns a `DeviceID` value, which is used in operations on the connected database. 6. Conclusion This research on the automatic control system based on the plasma deposition process aims to develop high-quality automatic control equipment at low cost and in a short time while meeting relevant technical requirements. This paper introduces the status of the plasma deposition system, fully analyzes the characteristics of multi-layer plasma deposition forming, and proposes an implementation method based on configuration software. In practical applications, the initial control tasks of the plasma deposition control system were completed in a short time and with high quality. The software and hardware development of the plasma deposition control equipment makes it possible to directly and quickly manufacture metal parts and molds, laying the foundation for the practical application of this technology. 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