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High system reliability measures. The technology can be applied to refrigerators, pharmaceuticals and chemical industries.
Automatic Vacuum Plastic Forming Machine (abbreviation referred to as Blister Machine) is a large-scale equipment for thermoforming of molds for thin and soft non-metallic materials (mainly thermoplastic plastics). It is mainly used for the production of refrigerators and refrigerators for semiconductor refrigerators and refrigerators. lining. At present, in domestic refrigerator production lines, automatic vacuum plastic molding machines mainly rely on imports from countries and regions such as Europe, the United States, Japan and South Korea. After deeply understanding the thermoforming processing technology of thermoplastics and the main functions of the entire control system of imported equipment, the author developed the automatic three-station vacuum blister using the industrial computer as the core, in accordance with the specific requirements of Hebei Aokelai Electronic Refrigerator Co., Ltd. Forming machine, the system can achieve 208 pieces of far-infrared heating plate sucker is completed, when the material is in place, used to press the sheet into the drive chain flap cylinder action, after pressing the sheet material feeding motor starts, the sheet Send to heating station. In this station, the heating cylinder drives the upper and lower heating plates to advance and heat the sheet according to a preset time and power. After the heating is completed, the sheet is driven into the forming station by the chain.
Because the molding area of ​​the refrigerator liner is large and the molding depth is deep, the molding process is difficult to control, so the molding station is the key station for the most actions and the most complicated process of the vacuum molding machine. The molding process includes the upper mold press and the sheet material. Blowing, mould rising, vacuum forming, sheet cooling, mould stripping, etc. In this way, the blank of the refrigerator liner is obtained, and the refrigerator liner is formed after the trimming, punching, and other post-processing.
2 The hardware structure of the control system The main issues to be considered in the control system design are to reduce costs, improve reliability, and have a friendly and intuitive control interface. For this purpose, a control system with an industrial control computer as the core is adopted, and its hardware structure is as shown. The system takes the research company EVOC810 IPC as the core, adopts two data acquisition cards plus four terminal board optimal control schemes, and successfully solves 20 output signals, 22 input signals and 208 far-red heating controls and 22 The logical control of the road input signal and the 20-channel output signal has reached a relatively high level in terms of economy, reliability, convenience, practicality, and advancedness.
1 Typical Station The machine is mainly composed of 3 loading stations, heating stations and forming stations. The 3 stations are relatively independent and can perform their own actions at the same time. The sheet is transported by the toothed transmission chain. , as shown. The feeding of the machine is driven by the feeding cylinder to control the vacuum external heating plate. PCL812PG is a multifunctional data acquisition card developed by the company. It has 16 DI/DO channels, 8 differential mode AD inputs, and 1 12-bit DA output. The A628 is a digital-to-analog conversion card from ICP DAS and has 8 channels. The DA output and 16 DI/DO channels, the total number of digital input/output channels of both cards are 32 channels, which fully meets the design requirements, but the 208-channel analog control cannot be solved. To this end, the author carefully studied the thermoforming process and designed the LF398SH terminal board. The 208 heating plates are divided into upper and lower two layers, each with 104 blocks, composed of 8 rows and 13 columns of heating blocks. The outermost heating block is mainly used for isolation of temperature zones, that is, the heating temperature of the sheet is isolated from the ambient temperature, so the most A heating block in the outer layer can be regarded as a control point in the control. Since then, the upper and lower layers have been composed of 6 rows and 11 columns plus 1 control point, and each layer has 67 control points totaling 134 points. Even so, simply using 9 DA outputs on 2 cards will still not solve the 134 control points. Taking into account the characteristics of the 1F398 sample-and-hold device, 9-channel DA and 16-channel DI can be used to control the 145 heater chips in a cyclic scan output mode. The control principle is: the LF398's sample-and-hold characteristics are controlled by high and low levels, and high power. Flat sampling low-level hold, when the first 9-circuit DA output of industrial computer, using the first DO output on April 2005 China manufacturing information. 119 samples, hold, and then control the second 9 DA output, and then use the second DO output sample, hold, and so on until the 16 DA output of the 16th DO, constitute an output scan cycle, complete the 145 Block heater control. According to the characteristics of the LF398 and the size of the retention capacitor, the scan time can be determined.
3 software design of the control system The current popular development tools can almost complete the task of this topic, such as VB, Delphi, VC and configuration software, but due to problems of VB and Delphi in version compatibility, hardware accessibility, etc. And the cost of the configuration software, and ultimately chose Visual C + +6.0 as a development tool for the system, it has the characteristics of short code execution, fast execution, and can use MFC library with APP-Wizard, Classizard and AppStudio To greatly improve the development efficiency.
The software of this control system is a desktop-level application with a Windows-style friendly interface. The development process mainly involves switching and analog I/O operations, the design of multi-threaded programs, database access, and the use of timers. The space is no longer exemplified by the source code of the program. The system has the following features: With the Chinese interface, the window layout is consistent with the actual layout of the heating plate, and the operation and parameter modification are very convenient.
The system can accurately control the temperature of each heating plate on the heating plate, and automatically memorize its control parameters. It is not necessary to re-enter the temperature control parameters every time the product is changed. Simply input the corresponding mold (or sheet) Code can be, the interface is as shown.
Parameter modification interface. It is convenient for manual and automatic conversion. The manual mode is mainly to realize the manual single-step movement of various moving parts to facilitate the installation, debugging or some special needs of the equipment. The automatic mode means that the IPC automatically completes all the logic actions of the whole machine during normal work and produces a qualified The product's typical interface is shown.
The single-step action interface can realize the automatic monitoring of the working status of the whole machine. Problems (such as the empty of material, failure of a certain action, or the disconnection of a certain heating block, etc.) can be automatically shut down and alarmed.
Greatly reduce the operation buttons of the device, simplify the control circuit and reduce the failure rate.
With the exception of the power switch and emergency button, most operations can be done via the computer keyboard or by clicking on the on-screen menu with the mouse.
It can automatically record the output per class and daily output, and can print out the report.
4 Reliability Measures The system integrates data acquisition, control, display, printing, and management into one, with no intermediate links and communications equipment, and thus a high cost performance ratio. However, because the control and management are highly concentrated in IPCs, the system risks are more concentrated. To solve this problem, the following measures are taken.
In the field environment, electromagnetic interference and voltage fluctuations may cause the electronic components to deviate from the original working conditions, causing performance fluctuations, affecting system accuracy and product stability. Therefore, the installation and wiring of sensors and meters should try their best to avoid strong electromagnetic fields, and use high-precision power supply; IPC is powered by an isolated regulated power supply to avoid the interactive interference of the power supply; the input and output of the signal adopt optocoupler isolation device; Use a shielded cable to connect the shield to a little ground to avoid ground loop currents. These measures can effectively reduce electromagnetic interference in space and power.
Automatic, manual control of backup redundancy, each execution has a manual button, once the system failure due to virus attacks and other reasons, you can use the manual button to continue production. Each heater chip corresponds to an ammeter for monitoring the on-off and current magnitudes, so as to avoid a large amount of waste products due to continued production after the heater chip is blown.. In order to improve the reliability of data acquisition, multiple (up to 1000) samplings are used and Digital filter technology to eliminate errors caused by singular point data and random interference.
5 Concluding remarks This system has been put into operation for half a year. It has stable operation, high production efficiency, and good economic returns. It only saves electricity, which amounts to 180,000 yuan per year and is well received by users. The development model and frame structure of this system can also be promoted and applied in the fields of medicine and chemical industry.
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