[Abstract] This article focuses on the application of two different models of Delta temperature controllers in plastic extruders. These two applications demonstrate that extruder temperature controllers now offer a completely new option, which will undoubtedly represent a new trend in extruder technology.
【Abstract】 This article introduces the application of two kinds of Delta temperature controller in the plastic extrusion machine. Through this case, we can see a new choice of the temperature controller of this filed. It also will be a new trend.
[ Keywords ] Cooling control, dual PID, human-machine interface
【 Keyword 】Cooling process control; dual PID control function; Human Machine Interface;
Introduction: Temperature control has always been a core component of screw extruders. During plastic extrusion, the friction between the screw and the plastic material generates significant heat, making temperature maintenance difficult. Balancing heat supply and timely dissipation has become a perennial challenge in screw extrusion. Currently, intelligent PID temperature controllers are the preferred choice due to their low cost and ease of use. However, with the widespread adoption of PLCs and HMIs in extruders, temperature modules and modular temperature control are beginning to challenge the dominance of traditional instruments. This article examines the application of Delta temperature control products in screw extruders to analyze application trends.
Keywords: cooling, dual PID, instrumentation, centralized control, human-machine interface
text:
With the increasing application of PLCs, HMIs, and other products in plastic extruders, the concepts of intelligent and centralized control have begun to be accepted by a wide range of customers. However, the parameter operation of instruments and the non-Chinese display of these parameters are becoming obstacles to this trend. Delta's modular DTC and DTE temperature controllers, as signature products, offer standard Modbus communication protocols, enabling excellent communication with various PLCs and HMIs, and are characterized by their compact size and modular design. As a multi-channel temperature control product, the DTE10T single unit provides 8 temperature control channels, perfectly meeting the needs of extruders requiring multiple temperature control channels, while its compact size saves installation space.
Many forward-thinking manufacturers have begun to use DTE to replace traditional instruments in order to improve their products. With the help of human-machine interface, the integration of control has been greatly improved, and the size of electrical control cabinets has also been greatly reduced, which has won unanimous praise from customers.
This article describes the screw extruder section of a film production line, where each unit controls the barrel temperature zone and die head, using a total of 16 units of the DTA4896R1 product. See Figure 1.
Figure 1. Screw extruder on a film production line
Due to the presence of a certain number of temperature controllers, a relatively large electrical control cabinet was used. This temperature control system employs an alarm-based activation method to start the cooling fans on the cylinder. The alarm method is characterized by fast activation and clear response. However, it also has the drawback of unstable temperature control. Because a fixed-point temperature start-up method is used, the thermal inertia of the temperature control system is completely ignored. When encountering materials with a high coefficient of friction, temperature overshoot may occur. The specific temperature control structure is shown in Figure 2.
Figure 2. Schematic diagram of temperature control structure
With the increasing application of PLCs, HMIs, and other products in plastic extruders, the concepts of intelligent and centralized control have begun to be accepted by a wide range of customers. However, the parameter operation of instruments and their non-Chinese display are becoming obstacles to this trend. As a signature product of Delta temperature controllers, the modular DTC and DTE series both provide standard Modbus communication protocols, enabling excellent communication with various PLCs and HMIs. They are also characterized by their compact size and modular design. As a multi-channel temperature control product, the DTE10T single unit can provide 8 temperature control channels, perfectly meeting the needs of extruders requiring multiple temperature control channels. Its compact body also saves installation space.
Many forward-thinking manufacturers have begun using DTE (Designed Electrical Equipment) to replace traditional instruments in order to improve their products. Combined with human-machine interface (HMI) technology, the integration of control has been greatly improved. The size of electrical control cabinets has also been significantly reduced, earning consistent praise from customers.
Figure 3 shows the dual PID control method provided by DTE.
Thanks to the adoption of DTE (Design for Equipment), the entire device can be reduced in size. The control panel only includes a human-machine interface, an emergency stop switch, and a working indicator. The simplified control panel and fully Chinese interface are more intuitive and easier to understand than the LED displays of traditional instruments. (See Figure 4.)
Figure 4. The compact DTE saves installation space and features a vibrant Chinese user interface (Delta DOP-B HMI).
DTE not only brings a revolution in the user interface, but its dual PID control (bidirectional control) further enhances the temperature control performance of extruders. Bidirectional control means the temperature controller provides two outputs: one for heating and the other for cooling. The alternating or simultaneous operation of these two outputs effectively stabilizes the temperature. This is particularly useful in situations involving self-heating. During material extrusion, the self-generated heat due to friction is significant. While a large amount of heat is initially supplied by the heater, as extrusion continues, the heat generated by friction becomes the primary cause of temperature overshoot.
After expanding the output module, the SUB1 output port of the DTE10T can be defined as a cooling output control port. Utilizing dual PID calculations, the temperature controller can start the cooling fan in advance before the temperature exceeds the set value, preventing the temperature from remaining high and maintaining temperature stability. I personally believe that alarm-driven cooling modes will eventually be phased out due to unstable temperature control. Dual PID control is undoubtedly the preferred method for achieving higher temperature control accuracy. (See Figure 5.)
Figure 5 shows the dual PID control method provided by DTE.
The DTE10T's dual PID control also incorporates the concept of a deadband. This refers to a specific temperature range where no heat is supplied or cooled; OUT1 and OUT2 have no output. Thermal balance is maintained entirely by the system's own heating, external heat dissipation, and heat loss from material flow. In specialized extruder applications, the deadband plays a crucial role in achieving effective temperature control. Furthermore, each DTE channel is isolated, and parameter settings do not affect each other. Each channel can have its own deadband and other parameters set independently, as shown in Figure 6.
Figure 6. Deadband in dual PID control of DTE10T
The parameters for DTE can be set entirely using DTE's dedicated PC software, with a user-friendly, all-Chinese interface. Parameters such as the stationary zone need to be analyzed and set based on the actual on-site operating conditions. For plastic extruders, settings can generally be between 0 and 2, while PID parameters can be automatically configured using AT (Automatic Test) software.
Figure 7. DTE settings screen in full Chinese.
Although the hardware architecture for cooling is the same as the alarm method, the output of the cooling fan is calculated by PID control. Compared with the two-digit alarm cooling method, this method can more accurately ensure the rationality of cooling output and effectively suppress temperature overshoot. It represents a significant step forward in temperature control.
Conclusion:
With its dual PID control, standard 485 communication, and compact installation size, the DTE is increasingly favored by users. Its structure caters to customers' needs for centralized control. Furthermore, the dual PID control method further enhances temperature control performance. As automated equipment becomes increasingly miniaturized and modular, the requirements for temperature control naturally lean towards agility, convenience, and modular integration. The DTE's design perfectly aligns with this trend.
About the author:
Zong Wei was born in June 1981. He graduated from the Department of Mechanical Engineering and Automation at Shanghai Dianji University. He currently works in the Instrument Product Development Department of Delta Electronics Co., Ltd., where he mainly focuses on technical support and market development for Delta instruments.
