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Plastic extruder is an important equipment in the wire and cable processing industry. In the production and use, the extruder temperature control system is the part with frequent failures. In this paper, the common problems of the extruder temperature control system are summarized, hoping to help the friends in need.
The heating device of extruder generally adopts heating pipe, heating ring and heating pad. The contactor or solid-state relay is controlled by temperature controller for heating control. The cooling fan is installed on the body part to control the temperature of the body.
The principle of the temperature control system is not complex, and the problems that often occur are summarized in four categories
1. The heating device does not heat and has no current. The reasons for this problem are as follows:
① Power failure or open circuit of each part of the connecting wire and whether the high temperature plug is in good contact.
② Its damage can be judged by measuring the resistance.
③ Contactor or solid state relay open circuit.
④ The temperature controller is damaged and there is no corresponding signal output.
⑤ Thermocouple or thermoelectric blocking line, temperature controller can not detect the signal does not work.
⑥ If the fault occurs in the head part, whether the heating plug and thermocouple are mixed should also be considered.
⑦ For the system with ammeter connected in series in the line, the open circuit of ammeter is considered.
2. The actual temperature exceeds the set temperature and is not controlled. The reasons for this problem are as follows:
① Contactor adhesion or solid state relay breakdown.
② The temperature controller is damaged and the control signal cannot be turned off.
③ The thermocouple or the thermal resistance falls off, or the short circuit occurs before the measured position, and the low temperature of the position is always measured.
④ If the problem occurs in the head position, the plug and thermocouple should also be considered.
⑤ For the single-phase heating device which controls the zero line on-off, the grounding of the heating device should be considered.
⑥ The heat generated by mechanical friction cannot be solved by electrical means.
3. The difference between the measured temperature and the actual temperature is too large. The reasons for this problem are as follows:
① Temperature controller error setting is not correct, change the temperature controller parameters.
② The selection of thermocouple or thermal resistance does not match the temperature controller. For example, if K-type thermocouple is selected for E-type temperature controller, the error is very large.
③ Thermocouple or thermal resistance is not inserted or virtual connection.
④ The temperature controller is damaged.
4. Although heated, it can not reach the set temperature. The reasons for this problem are as follows:
① The heating device is not installed tightly and cannot be close to the heating surface.
② The heating device was partially damaged and the power was reduced.
③ The cooling fan runs prematurely or is in forced air cooling state.
This is my usual work summed up in some aspects, I hope to give friends some help, these are suitable for most of the use of electric heating system. There are limitations in ability and incompleteness in consideration. I hope my friends can add and correct them.
