Application trend of temperature controller in scr

2022-08-06
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Discussion on the application trend of temperature controller in screw extruder Abstract: This paper focuses on the application of two different models of delta temperature controller in plastic extruder. Through the above two applications, it can be seen that the temperature controller of the extruder has a new choice. This will be the new trend of extruder

introduction: temperature control has always been the core part of screw extruder products; In the process of extruding plastic, the friction between screw and plastic material will produce large amount of heat, which makes it difficult to keep the temperature constant. How to balance the heat supply and timely heat dissipation has become the eternal theme of screw extrusion. At present, intelligent PID temperature control instrument has become the primary choice because of its low cost and ease of use. However, after PLC and man-machine appeared in a large number of extruders, temperature module and modular temperature control began to challenge the status of traditional instruments. In this paper, the application of delta temperature control products in screw extruders is investigated to analyze the application trend

key words: cooling, double PID, instrument, centralized control, man-machine

text:

with the continuous application of PLC, man-machine and other products to plastic extruders, the concept of intelligent control and centralized control has begun to be accepted by customers. The parameter operation of instrument operation and the non Chinese display of its parameters began to become an obstacle to this trend. As a characteristic product of delta thermostat, modular DTC and DTE provide standard Modbus communication protocol, which can communicate well with all kinds of PLC and man-machine, and are small and modular. As a multi-channel temperature control product, dte10t single machine can provide 8-channel temperature control channels, which can well meet the characteristics that the extruder needs multi-channel temperature control channels. The compact body can save installation space

many forward-looking manufacturers began to use DTE to replace traditional instruments to improve their products. With the help of man-machine, the integration of control has been greatly improved, and the volume of electric control cabinet has also been greatly reduced, which has won unanimous praise from customers

for the screw extruder part of the film production line introduced in this paper, its single machine is used to control the temperature area of the barrel and the die head. A total of 16 sets of TAD therefore ta4896r1 products are used. As shown in Figure 1

Fig. 1 screw extruder on film production line

due to a certain number of temperature control, a large electric control cabinet is used; The temperature control system uses the alarm mode to start the cooling fan on the cylinder. The alarm mode has the characteristics of fast driving and obvious response. But it also has the disadvantage of unstable temperature control. Due to the fixed-point temperature startup, the thermal inertia in the temperature control system is completely ignored. Some materials with high friction coefficient also have temperature overshoot. See Figure 2 for temperature control structure

Figure 2. Schematic diagram of temperature control structure

with the continuous application of PLC, man-machine and other products to plastic extruders, the concept of intelligent control and centralized control has begun to be accepted by customers. The parameter operation of instrument operation and the non Chinese display of its parameters began to become an obstacle to this trend. As a characteristic product of delta thermostat, modular DTC and DTE provide standard Modbus communication. There is an undeniable gap protocol between Chinese instruments and meters and foreign products, which can communicate well with all kinds of PLC and man-machine. And they are small and modular. As a multi-channel temperature control product, dte10t single machine can provide 8-channel temperature control channels. It can meet the need of multi-channel temperature control channel of extruder. The compact body can save installation space

many forward-looking manufacturers began to use DTE to replace traditional instruments to improve their products. Cooperate with man-machine. The integration of control is greatly improved. The volume of the electric control cabinet has also been greatly reduced, and the average plastic consumption of the car will reach 500kg/vehicle, which has been highly praised by customers

as shown in Figure 3, the dual PID control mode provided by DTE

due to the use of DTE, the whole equipment body can be reduced, and only one man-machine, one emergency stop switch, and one work indication are installed on the control panel. The simple control panel and the all Chinese operation interface are more intuitive and easy to understand than the LED display parameters of traditional instruments. As shown in Figure 4

Figure 4. Compact DTE saves installation space

dte not only brings about changes in the operation interface, but also provides a dual PID control mode (bidirectional control) that can improve the temperature control effect of the extruder. The so-called two-way control means that the thermostat provides two sets of outputs, one for heating and the other for cooling. It can control the temperature stably under the condition that two groups of outputs operate alternately or jointly. It can be well applied in some cases with self heating. The spontaneous heat of extruder can not be underestimated due to friction. Although a large amount of heat supply from the electric heater is required at the beginning of extrusion, with the continuous extrusion. The heat generated by friction will be the main cause of temperature overshoot

dte10t after expanding the output module, the sub1 output port can be defined as cooling output control. Using double PID calculation, when the temperature does not exceed the set value, the temperature controller can start the cooling fan in advance, avoiding the situation that the temperature is too high and maintaining the temperature stability. Personally, I think the alarm driven cooling mode will always be eliminated due to unstable temperature control and other reasons. Dual PID control mode must be the first choice to pursue higher temperature control accuracy. As shown in Figure 5

Figure 5. The dual PID control mode provided by DTE

dte10t also adds the concept of dead band. That is, within a specific temperature range. There is neither heat supplement nor cooling action, and out1 and out2 have no output. The heat balance is completely maintained by the self heating of the system and the heat loss of external heat dissipation and material flow. In the special application of extruder, the non action zone plays a special role for good temperature control effect. Moreover, every time DTE presses the "input 1/5" key, the channels are isolated from each other, and the parameter settings do not affect each other. Each channel can set parameters such as immovable zone separately. As shown in Figure 6

Fig. 6, in the dead band of dual PID control in dte10t,

dte can completely use the special PC software for DTE to set parameters, and the DTE setting screen in Chinese is simple and clear. The parameters such as immovable area shall be analyzed and set in combination with the actual working conditions on site. Generally, the plastic extruder can be set at: 0~ 2, and PID parameters can be automatically completed with the help of at

Figure 7. DTE setting screen in Chinese

although the cooling hardware architecture is the same as the alarm mode, the output of the cooling fan is calculated by PID. Compared with the two digit alarm cooling mode, it can more accurately ensure the rationality of the cooling output and effectively suppress the temperature overshoot. The way of temperature control has reached a new level

conclusion:

DTE with dual PID control, standard 485 communication, small installation volume and other characteristics is more and more popular with users. In structure, it meets the needs of centralized control of customers. In the temperature control mode, the dual PID mode improves the temperature control effect. With the trend of miniaturization and modularization of automation equipment, the requirements for temperature control naturally tend to be smart, convenient and modular integration. The original intention of DTE design meets this trend very well. (end)

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