Molten plastic heating and stirring system of injection molding machine

Abstract

The utility model discloses a molten plastic heating and stirring system of an injection molding machine, which is characterized by comprising a three-phase power supply; the three-phase power supply is connected with a circuit breaker QF; the circuit breaker QF is connected with a main circuit and a control circuit; wherein the main circuit comprises a three-phase asynchronous motor M, a heating resistor R, a first contactor KM1, a second contactor KM2, a third contactor KM3, a first thermal relay FR1 and a second thermal relay FR2; the control circuit comprises a starting control loop, a forward stirring control loop, a reverse stirring control loop and a heating control loop; the three-phase asynchronous motor M is used for stirring molten plastic in the injection molding machine; the first contactor KM1 is used for controlling forward stirring of the motor; the second contactor KM2 is used for controlling reverse stirring of the motor; and the third contactor KM3 is used for controlling the operation of the heating resistor R. The injection molding machine has the following beneficial effects that automatic heating and forward and reverse alternate stirring control of molten plastic in the injection molding machine are realized.

Description

Technical Field

[0001] This utility model relates to the field of injection molding machine control technology, and in particular to a heating and stirring system for molten plastic in an injection molding machine. Background Technology

[0002] Injection molding machines are key pieces of equipment in the plastics processing industry. Their working principle involves heating and melting plastic granules, then injecting the molten plastic into a mold through an injection system to form the final product. During this process, the quality of the melt directly affects the quality of the final product. Therefore, the heating and stirring processes are crucial for obtaining high-quality molten plastic.

[0003] Traditional injection molding machine molten plastic systems typically suffer from the following problems: First, the heating system lacks effective temperature control, which can easily lead to overheating and degradation of the plastic or insufficient melting due to insufficient temperature; second, the stirring system usually uses unidirectional stirring, which makes it difficult to achieve uniform mixing, resulting in the presence of incompletely melted particles or air bubbles in the molten plastic; third, there is a lack of coordinated control between the heating and stirring systems, making it impossible to automatically adjust the working state according to process requirements; fourth, there are insufficient safety protection measures, which can easily cause equipment damage or production accidents under equipment overload or abnormal conditions.

[0004] While some highly automated injection molding machine control systems exist on the market, most are expensive, complex in structure, and require high maintenance costs, making them unsuitable for small and medium-sized plastic processing enterprises. Furthermore, most of these systems employ unidirectional stirring, which fails to meet the stringent requirements for uniform mixing. In the processing of high-viscosity or specialty plastics, the uniformity of the molten plastic has a decisive impact on the performance of the final product, a requirement that unidirectional stirring often cannot satisfy.

[0005] Therefore, developing a control circuit that can achieve precise temperature control, alternating forward and reverse stirring, and coordinated heating and stirring is of significant practical value. Utility Model Content

[0006] The purpose of this invention is to provide a heating and stirring system for molten plastic in an injection molding machine. This control circuit enables automatic heating control and alternating forward and reverse stirring of the molten plastic, improving the uniformity and stability of the molten plastic and enhancing the quality of injection molded products.

[0007] The above-mentioned technical objective of this utility model is achieved through the following technical solution:

[0008] A heating and stirring system for molten plastic in an injection molding machine includes: a three-phase power supply comprising three-phase power lines L1, L2, L3 and a protective grounding wire PE; the three-phase power supply is connected to a circuit breaker QF; the circuit breaker QF is connected to a main circuit and a control circuit; wherein, the main circuit includes a three-phase asynchronous motor M, a heating resistor R, a first contactor KM1, a second contactor KM2, a third contactor KM3, a first thermal relay FR1 and a second thermal relay FR2; the control circuit includes a start control circuit, a forward stirring control circuit, a reverse stirring control circuit and a heating control circuit; the three-phase asynchronous motor M is used to stir the molten plastic in the injection molding machine; the first contactor KM1 is used to control the forward stirring of the motor; the second contactor KM2 is used to control the reverse stirring of the motor; and the third contactor KM3 is used to control the operation of the heating resistor R.

[0009] The present invention is further configured such that: the start control circuit includes a start button SB1; after the start button SB1 is pressed, the control circuit is energized, triggering the subsequent system to work in a loop.

[0010] The present invention is further configured such that the forward stirring control circuit includes: a first time relay KT1; the first time relay KT1 has contacts 3-4 for interlocking with the second time relay KT2, and contacts 1-2 for controlling the first relay KM1 to make the motor run in the forward direction and to perform forward stirring on the molten plastic.

[0011] The present invention is further configured such that the reverse stirring control circuit includes: a second time relay KT2; the second time relay KT2 has contacts 7-8 for interlocking with the first time relay KT1, and contacts 5-6 for controlling the second relay KM2 to reverse the motor and stir the molten plastic in reverse.

[0012] The present invention is further configured such that the heating control circuit includes a third time relay KT3 and a fourth time relay KT4; the third time relay KT3 has contacts 11-12 for controlling the third time relay KT3 to start the heating system.

[0013] The present invention is further configured such that: the first thermal relay FR1 is installed in the common circuit of the first contactor KM1 and the second contactor KM2, and has contacts 7-8, for monitoring the motor load and cutting off the power supply to protect the motor when the motor is overloaded; the second thermal relay FR2 is installed in the circuit of the third contactor KM3, and has contacts 9-10, for monitoring the heating system load and cutting off the power supply when the heating system is overloaded.

[0014] The present invention is further configured such that: the contacts 3-4 of the first time relay KT1 and the contacts 7-8 of the second time relay KT2 are connected by interlocking contacts to form an alternating working mechanism, so that the motor will not receive forward and reverse operation commands at the same time.

[0015] The present invention is further configured such that the contacts 9-10 of the fourth time relay KT4 are provided with a cooling time, and the heating system is allowed to restart after a preset time after the heating system is turned off, so as to realize automatic cycle control of heating and cooling.

[0016] In summary, this utility model has the following beneficial effects:

[0017] 1. This utility model employs a first time relay KT1 and a second time relay KT2 to alternately control the forward and reverse operation of the motor, achieving bidirectional stirring of the molten plastic. Compared with traditional unidirectional stirring, bidirectional alternating stirring greatly improves the uniformity of the molten plastic, avoids dead zones and stratification phenomena that are easily formed by traditional unidirectional stirring, and improves the quality stability of the final product.

[0018] 2. Through the coordinated operation of contacts 11-12 of the third time relay KT3 and contacts 9-10 of the fourth time relay KT4, this system achieves precise time control of the heating system. The third time relay KT3 automatically cuts off the heating power after the preset heating time to prevent the plastic from degrading due to prolonged heating. Simultaneously, the fourth time relay KT4 sets a cooling time before resuming heating, forming a heating-cooling cycle that keeps the molten plastic within the optimal processing temperature range.

[0019] 3. The system monitors the load of the stirring motor and heating system in real time through contacts 7-8 of the first thermal relay FR1 and contacts 9-10 of the second thermal relay FR2. When the stirring motor is overloaded due to excessively high plastic viscosity or foreign matter intrusion, the first thermal relay FR1 will immediately cut off the motor power to prevent the motor from burning out. Similarly, when the heating system is overloaded due to aging or short circuit of the heating element, the second thermal relay FR2 will cut off the heating system power to avoid safety accidents, greatly improving the system's operational reliability and service life.

[0020] 4. The circuit design of this system ensures that the first contactor KM1 and the second contactor KM2 cannot be closed simultaneously. Through the interlocking design of contacts 3-4 of the first time relay KT1 and contacts 7-8 of the second time relay KT2, the possibility of the motor receiving forward and reverse operation commands at the same time is eliminated from the electrical control level. This avoids the risk of the motor burning out due to wiring errors or relay failures, and enhances the safety and reliability of the system.

[0021] 5. The entire system achieves fully automatic control of the heating and stirring process. Operators only need to press the start button SB1, and the system will automatically execute forward stirring, reverse stirring, and heating and cooling cycles according to the preset program without manual intervention, which greatly improves production efficiency and reduces the labor intensity of operators and the possibility of human error.

[0022] 6. This design adopts conventional relay control technology, eliminating the need for complex programmable controllers and frequency converters. It features a simple structure, low cost, and easy maintenance, making it particularly suitable for small and medium-sized plastic processing enterprises and highly practical.

[0023] 7. By adjusting the timing parameters of each time relay, the system can flexibly adapt to the processing requirements of different types of plastics. For high-viscosity plastics, the stirring time can be increased; for heat-sensitive plastics, the heating time can be shortened and the cooling interval increased. This parameter adjustment capability allows the system to adapt to the production requirements of various plastic products.

[0024] 8. Energy efficiency optimization: By automatically controlling the heating and cooling cycle, the energy waste caused by continuous heating, which is common in traditional systems, is avoided, thus optimizing energy utilization, conforming to the concept of energy conservation and emission reduction, and also reducing production costs. Attached Figure Description

[0025] Figure 1 This is a circuit diagram of the molten plastic heating and stirring system for an injection molding machine according to this utility model. Detailed Implementation

[0026] In the description of this utility model, it should be understood that the terms center, longitudinal, transverse, length, width, thickness, upper, lower, front, back, left, right, vertical, horizontal, top, bottom, inner, outer, clockwise, counterclockwise, etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0027] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0028] In the description of this utility model, "multiple" means two or more, unless otherwise explicitly specified. In this utility model, unless otherwise explicitly specified and limited, terms such as installation, connection, linking, and fixing should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0029] The present invention will be further described in detail below with reference to the accompanying drawings.

[0030] like Figure 1 As shown, this utility model provides a heating and stirring system for molten plastic in an injection molding machine. The control circuit mainly includes three parts: a power input section, a main circuit, and a control circuit.

[0031] The power input section includes three-phase power lines L1, L2, and L3 and a protective earth wire PE, which are connected to the system via circuit breaker QF to provide power support for the entire system. Circuit breaker QF acts as a main switch and provides short-circuit protection, ensuring the safety of the system's electrical supply.

[0032] The main circuit primarily includes a three-phase asynchronous motor M, a first contactor KM1, a second contactor KM2, a third contactor KM3, a first thermal relay FR1, a second thermal relay FR2, and a heating resistor R. The three-phase asynchronous motor M is controlled by either the first contactor KM1 or the second contactor KM2 to achieve forward or reverse rotation, respectively, for stirring and melting plastic. The heating resistor R is controlled by the third contactor KM3 to heat the plastic and melt it. The first thermal relay FR1 monitors the motor's load current to prevent motor overload; the second thermal relay FR2 monitors the heating system's load current to prevent heating system overload.

[0033] The control circuit is divided into four main functional loops: start-up control loop, forward stirring control loop, reverse stirring control loop, and heating control loop.

[0034] 1. Start-up control circuit: including start button SB1. After pressing start button SB1, the control circuit is powered on, starting the entire system's workflow.

[0035] 2. Forward stirring control circuit: This includes a first time relay KT1. The coil of the first time relay KT1 starts timing after the control circuit is energized. Its contacts 1-2 are closed, controlling the coil of the first contactor KM1 to energize, causing the three-phase asynchronous motor M to run forward, thus stirring the molten plastic. Contacts 3-4 of KT1 are interlocked with contacts 7-8 of KT2, preventing forward and reverse stirring from occurring simultaneously.

[0036] 3. Reverse stirring control circuit: including the second time relay KT2. The coil of the second time relay KT2 is energized after the timing of the first time relay KT1 ends through contact switching. Its contacts 5-6 close, controlling the coil of the second contactor KM2 to energize, causing the three-phase asynchronous motor M to run in reverse, thus reversing the molten plastic.

[0037] 4. Heating Control Circuit: This includes a third time relay KT3 and a fourth time relay KT4. The coil of the third time relay KT3 is energized when the control circuit is powered, and its contacts 11-12 close, controlling the coil of the third contactor KM3 to energize the heating resistor R, thus initiating the heating of the plastic. When the timer on the third time relay KT3 ends, relay KM3 is de-energized, and heating ceases. Contacts 9-10 of the fourth time relay KT4 open after the set time, restarting the heating system.

[0038] Working principle:

[0039] 1. System Start-up: Connect the three-phase power supply, close the circuit breaker QF, and prepare to start the injection molding machine's molten plastic heating and stirring system.

[0040] 2. Press the start button SB1: The control circuit is energized, and the system enters automatic control mode. At this time, the first time relay KT1 and the third time relay KT3 start timing simultaneously, with KT1 controlling the forward stirring and KT3 controlling the heating system. Simultaneously, the fourth time relay KT4 also starts timing.

[0041] 3. Forward stirring stage: The coil of the first time relay KT1 is energized, and its contacts 1-2 are closed, energizing the coil of the first contactor KM1. This controls the three-phase asynchronous motor M to run forward, stirring the molten plastic. Due to the interlocking of contacts 3-4 and 5-6 of KT1, the contacts of KT2 remain open, preventing the motor from receiving reverse rotation commands.

[0042] 4. Reverse Stirring Stage: When the first time relay KT1 finishes timing, its contact 3-4 opens, disconnecting the control circuit of the first contactor KM1 and triggering the second time relay KT2 to start timing. Contact 5-6 of KT2 closes, energizing the coil of the second contactor KM2, controlling the three-phase asynchronous motor M to run in reverse, thus stirring the molten plastic. Due to the interlocking design between contacts 3-4 and 5-6 of KT1, the contacts of KT1 remain open at this time, preventing the motor from receiving forward operation commands.

[0043] 5. Heating stage: During the forward and reverse stirring process, the coil of the third time relay KT3 remains energized, and contacts 11-12 are in the closed state, which energizes the coil of the third contactor KM3, controls the heating resistor R to work, and continuously heats the plastic. When the KT3 timer ends, the relay KM3 is de-energized and the heating stops.

[0044] 6. Overheating and Cooling Cycle: From the end of the third time relay KT3 to the time when the fourth time relay KT4 reaches the set value, there is a cooling time to prevent overheating. When the fourth time relay KT4 ends, its contacts 9-10 open. After a cooling period, the KT4 contacts return to their original position, allowing the heating system to work again, forming a heating-cooling cycle, so that the plastic is always kept within the optimal processing temperature range.

[0045] 7. Cyclic Operation: During the operation of the entire system, the forward stirring control loop and the reverse stirring control loop work alternately to achieve bidirectional stirring of the molten plastic; at the same time, the heating control loop executes the heating-cooling cycle according to the control of the fourth time relay KT4. The entire system forms an automated closed-loop control system that can work continuously and stably without manual intervention.

[0046] 8. Safety Protection: Throughout the entire operation, contacts 7-8 of the first thermal relay FR1 monitor the load current of the stirring motor in real time. When the motor is overloaded due to excessively high plastic viscosity or foreign matter entering, FR1 will automatically disconnect, cutting off the power supply to the motor and protecting it from damage. Contacts 9-10 of the second thermal relay FR2 monitor the load current of the heating system in real time. When the heating system is overloaded due to aging of the heating element or short circuit, FR2 will automatically disconnect, cutting off the power supply to the heating system and preventing fires and other safety accidents.

[0047] The molten plastic heating and stirring system of this injection molding machine achieves automatic heating control and alternating forward and reverse stirring of molten plastic through the precise coordination of time relays and contactors. This greatly improves the uniformity and stability of molten plastic, effectively solves the problems of uneven plastic melting, unmelted particles or bubbles in traditional injection molding machines, and improves the quality of injection molded products.

[0048] This system provides a comprehensive overload protection mechanism through thermal relays, effectively preventing damage to the motor and heating system due to overload; through the control of the fourth time relay KT4, a heating-cooling cycle is realized, effectively preventing the plastic from degrading and deteriorating due to prolonged continuous heating; through the interlock control of forward and reverse stirring, the possibility of the motor receiving forward and reverse operation commands at the same time is avoided, improving the safety and reliability of the system.

[0049] This system features a simple structure, low cost, and ease of implementation and maintenance, making it particularly suitable for small and medium-sized plastic processing enterprises. By adjusting the parameters of each time relay, it can flexibly adapt to the processing needs of different types of plastics, exhibiting good process adaptability.

[0050] The above time settings should be adjusted according to different plastic materials and corresponding working conditions.

[0051] This specific embodiment is merely an explanation of the present utility model and is not intended to limit the present utility model. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of the claims of the present utility model, they are protected by patent law.

Claims

1. A heating and stirring system for molten plastic in an injection molding machine, characterized in that, include: The three-phase power supply includes three-phase power lines L1, L2, L3 and a protective grounding wire PE; the three-phase power supply is connected to a circuit breaker QF; the circuit breaker QF is connected to a main circuit and a control circuit; wherein, the main circuit includes a three-phase asynchronous motor M, a heating resistor R, a first contactor KM1, a second contactor KM2, a third contactor KM3, a first thermal relay FR1 and a second thermal relay FR2; the control circuit includes a start control circuit, a forward stirring control circuit, a reverse stirring control circuit and a heating control circuit; the three-phase asynchronous motor M is used to stir the molten plastic in the injection molding machine; the first contactor KM1 is used to control the forward stirring of the motor; the second contactor KM2 is used to control the reverse stirring of the motor; The third contactor KM3 is used to control the operation of the heating resistor R.

2. The molten plastic heating and stirring system for injection molding machines according to claim 1, characterized in that: The start control circuit includes a start button SB1; when the start button SB1 is pressed, the control circuit is energized.

3. The molten plastic heating and stirring system for injection molding machines according to claim 1, characterized in that: The forward stirring control circuit includes: a first time relay KT1; the first time relay KT1 controls the first relay KM1 to make the motor run in the forward direction and to stir the molten plastic in the forward direction.

4. The molten plastic heating and stirring system for injection molding machines according to claim 1, characterized in that: The reverse stirring control circuit includes: a second time relay KT2; the second time relay KT2 controls the second relay KM2 to make the motor run in reverse and stir the molten plastic in reverse.

5. The molten plastic heating and stirring system for injection molding machines according to claim 1, characterized in that: The heating control circuit includes a third time relay KT3 and a fourth time relay KT4; the third time relay KT3 controls the third relay KM3 to start the heating system.

6. The molten plastic heating and stirring system for injection molding machines according to claim 1, characterized in that: The first thermal relay FR1 is installed in the common circuit of the first contactor KM1 and the second contactor KM2 to monitor the motor load and cut off the power supply to protect the motor when the motor is overloaded; the second thermal relay FR2 is installed in the circuit of the third contactor KM3 to monitor the heating system load and cut off the power supply when the heating system is overloaded.

7. The molten plastic heating and stirring system for injection molding machines according to claim 3, characterized in that: The first time relay KT1 and the second time relay KT2 are connected by interlocking contacts to form an alternating working mechanism, so that the motor will not receive forward and reverse operation commands at the same time.

8. The molten plastic heating and stirring system for injection molding machines according to claim 5, characterized in that: The fourth time relay KT4 is equipped with a cooling time. After the heating system is turned off, the heating system is allowed to restart after a preset time, so as to realize automatic cycle control of heating and cooling.

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