What Is a Heating System?

The heating system is very important in the process of manufacturing micro-structured polymer optical fibers (MPOF), and it directly affects the quality of the final drawing result. A partition heating system that separates the preheating zone from the high temperature zone and uses a partition to isolate it from the outside air can achieve a relatively ideal temperature curve and meet the needs of making MPOFs with different structures.

Wire drawing is to make microstructured polymers

Microstructured plastics

The extruder is an important component of the extruder. The design of the heating temperature control system of the extruder is the focus and difficulty of the automatic control of the extruder. The traditional heating control of the extruder has only constant temperature control, and the means of constant temperature control is backward, the accuracy is poor, and the heating process of the extruder is completely controlled by manual control. In order to obtain an ideal extrusion barrel heating process, it is necessary to adjust and control the temperature of the extrusion barrel and the rate of change of temperature over time. Therefore, it is required to perform program control on the temperature, so that the temperature strictly changes according to a given temperature control curve, so as to ensure the uniformity and accuracy of the temperature of the extrusion cylinder. Here, zone-type resistance heating is adopted. The heating of the extrusion cylinder is divided into three zones along the horizontal direction. The three zones are independently controlled. Each zone has a temperature display. It is required to perform temperature control according to a given temperature control curve. Insulation control, temperature control is closed-loop control. The heating power is 165kW, and the rated voltage of the power element is AC380V.

Software Design of District Heating System

The program design adopts a modular and functional structure, which consists of several major modules: system main program, temperature setting, temperature detection, closed-loop control, given curve correction and fault alarm. The program design fully took into account various interferences that may be encountered during system operation, and adopted digital filtering and field data protection technologies to ensure the reliability of the system. The functional modules are interconnected and relatively independent. The entire program is very readable and portable, and easy to maintain and expand.

Zoned heating system temperature closed-loop control

The PLC's closed-loop control of heating power is implemented using PLC output contacts. This control is actually an incremental control, that is, the PLC controller gives an increase in its deviation control value. The absolute value of the increase determines the pulse width. The pulse width is proportional to the heating time of the heating rod in a cycle Proportionally, thereby changing the heating power of the heating rod in a unit cycle. The specific control rules are as follows:

(1) When the absolute value of the temperature difference is greater than the set threshold, keep the output contacts closed to reduce the temperature difference as soon as possible.

(2) When the temperature difference is less than the set threshold, an improved PID control algorithm with functions such as variable speed integral, controlled variable differentiation and incomplete differentiation is used.

(3) When the temperature difference is less than the set dead zone, the control is stopped.

(4) Considering that the switching value cannot respond to the pulse output that is too narrow, set the minimum limit of the pulse width, and do not output when the pulse width is less than this value.

District heating system research results

Compared with the single-zone heating mode in the past, the heating temperature of the extrusion barrel is more uniform and meets the requirements of the extrusion process. The construction mode of connecting heating rods with a circular wire greatly reduces the heating elements. The occurrence of faults such as phase-to-phase short circuit and ground short circuit reduces the downtime of the fault and makes the replacement of the heating rod simple and fast. The PLC switching output is adopted, and the control performance is greatly improved through the pulse width closed-loop control mode . This control system has been applied in multiple extruder production lines. ^[3]