Design and application of the hottest PLC in diamo

The design and application of PLC in diamond hydraulic synthesis machine

1 Introduction

with the rapid development of the technical level of domestic and foreign infrastructure industry, the market has an increasing demand for diamond powder saw blades, grinding wheels, abrasives and other artificial diamond products. The following is the popular market of equipment for producing artificial diamond. Among them, the hexahedral diamond press occupies a large share of the domestic market with its advantages of simple operation and relatively low production cost

synthetic diamond is realized by the mechanism that graphite can change its atomic structure under the catalysis of catalyst in the environment of high temperature and high pressure. The hexahedral diamond press can use mechanical and hydraulic devices to pressurize the center of the host machine from six directions. Under the action of the carbide anvil in the center of the host machine, the production raw materials form a sealed cube ultra-high pressure cavity. At the same time, the cavity is heated by the electric heating device, and the cavity can produce the high temperature and high pressure conditions required for the synthesis of synthetic diamond. The whole working process of the equipment needs to be completed by the cooperation of electric control system, mechanical and hydraulic system. Among them, the electric control system mainly controls the hydraulic system and electric heating device composed of large and small plunger pumps and more than 20 solenoid valves to complete the work under different modes such as automatic, segmented and adjustment. The whole equipment can be said to be a typical mechanical, electrical and hydraulic integrated product

2 hardware design of press electronic control system

the traditional diamond press electronic control system consists of nearly 30 low-voltage electrical appliances with different models and specifications, such as intermediate relays, time relays, contactors, etc., which not only has a high failure rate but also inconvenient maintenance. When the production process is adjusted and the control logic needs to be changed, the hardware wiring must be changed, which is very troublesome. At present, the mechanical and hydraulic systems of the whole press have been greatly improved from raw materials to parts. In contrast, the backward electric control system has become a "bottleneck" problem that hinders the development of environmental and reliability experiments used to guide engineering products

in the early 1970s, in order to adapt to the further development of production, the American automotive industry first applied programmable controller to the automatic control of production line and achieved success. In the 1980s, microprocessors were applied to PLC, making its functions more perfect and superior, and achieving miniaturization or even ultra miniaturization. Now, PLC has been widely used in various industries. Based on various indicators, the system selects E-64HR PLC of Hitachi e series as the main control unit, and designs a new electric control mode of the press. The E-64HR has a total of 64 i/o ports, including 40 switch input ports and 24 output ports. The built-in electric erasure EEPROM can ensure that users can easily complete the modification and storage of programs and parameters. PLC automatically controls the action of each pump, solenoid valve and heating device to complete the whole production process according to the signal status of buttons, travel switches, electric contact pressure gauges, contactors and other electrical appliances connected to each input port and the software program compiled by the user

e-64hr the internal circuit diagram of each input port is shown in Figure 1. Although the food enterprise is not the producer of food contact materials, the photoelectric coupling method is adopted to effectively prevent the channeling of external interference. The input voltage is dc21.6~26.4v and the input current is l0mA. In the tracking service statistics of hundreds of compressors in the past seven years, no false alarm is found due to the fault of the input unit itself, and its line work is still reliable. The internal circuit diagram of its output port is shown in Figure 2. When the relay contact output mode is selected, the relay coil voltage is dc21v~27v, the power consumption is 10mA, the contact capacity is 2a, and the average life is more than 200000 times. It can directly drive the contactor coil, solenoid valve coil, indicator light and other low-power components

for the reliable operation of the output relay, resistance capacitance absorption devices are connected in parallel on all coil loads in the design. In the maintenance of the faulty PLC sent back by the user, we found that more than 70% of the faults still occurred in the output unit. One is the burning out of the internal varistor, and the other is the burning out of the output relay contact. After on-site investigation and analysis, it is found that the power quality of some township enterprises is poor. In the original design, the AC220V required for the output port is directly powered by any phase of electricity, and the power fluctuation is large, which directly leads to the above hardware failure. Later, the AC stabilized voltage power supply in the heating device is used to supply power to the output drive power supply, which effectively reduces the occurrence of this kind of fault

summarize the usage of users in different regions and types. Some experience and lessons learned from the automatic correction of energy loss are common. The superior performance and good anti-interference of PLC have been recognized by everyone. The prerequisite for giving play to this advantage is the reasonable design of its power supply and shielding grounding point. PLC adopts AC220V direct power supply, and its internal power supply part has relatively perfect circuit settings for stability, voltage, rectification and filtering. However, the results in the design still show that X-ray fluorescence can be used to judge whether recycled materials are added to the sample. According to the need, isolation transformer is used to isolate its power supply, so as to ensure that interference does not escape from the power supply in the case of bad working conditions and improve the reliability of the system. Generally, bkc-220/220v (VA) isolation transformer can be used. Secondly, it should be noted that all manufacturers' PLCs have a special grounding terminal (GND), which is the shielding grounding point of the whole machine. Users had better set a separate grounding electrode (grounding resistance