Injection molding machine melt glue back pressure control system and melt glue back pressure calibration method

Abstract

The invention discloses a melt back pressure control system of an injection molding machine and a melt back pressure calibration method, and the melt back pressure control system is characterized by comprising an injection oil cylinder for driving a screw of the injection molding machine to move forward or backward, a loosening valve, an injection valve, a cartridge valve, a melt back pressure proportional valve, an oil tank and an oil pump. When the melt back pressure is calibrated, raw materials do not need to be added for melt glue, and the output voltage of the melt back pressure proportional valve corresponding to the corresponding melt back pressure can be calibrated.

Description

Technical Field

[0001] The invention relates to the technical field of injection molding machines, and in particular to a melt back pressure control system and a melt back pressure calibration method for an injection molding machine. Background Art

[0002] When the injection molding machine is melting the raw materials (i.e., melting the glue, the screw only rotates), the molten material is constantly pushed into the metering chamber at the front end of the barrel, and more and more, gradually forming a reverse pressure to push the screw backward. In order to prevent the screw from retreating too quickly and ensure that the molten material is evenly compacted, it is necessary to provide a reverse pressure to the screw. This reverse pressure that prevents the screw from retreating is called the melt back pressure. The role of the melt back pressure in injection molding is very important, and it directly affects the filling of the melt and the quality of the product.

[0003] The size of the melt back pressure is controlled by the melt back pressure proportional valve set in the melt back pressure system. The output voltage of the melt back pressure proportional valve determines the size of the melt back pressure. The output voltage value of a melt back pressure proportional valve corresponds to a melt back pressure value. Therefore, before formal production, it is necessary to know the output voltage value of the melt back pressure proportional valve corresponding to the corresponding melt back pressure value. For each different injection molding machine, in order to obtain an accurate melt back pressure value, the output voltage value of the corresponding melt back pressure proportional valve may be deviated, so it is necessary to calibrate before formal production. In the melt back pressure control system of a conventional injection molding machine, the return oil of the screw for loosening and retracting does not pass through the melt back pressure proportional valve, so it needs to be calibrated through a test sample (that is, the screw performs a melt action). A lot of raw materials will be consumed during the test process, and the raw materials of the test sample will remain in the screw and barrel of the machine, causing contamination of the screw and barrel, as well as consumption of raw materials. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide an injection molding machine melt back pressure control system and a melt back pressure calibration method, which can achieve calibration without the need for samples, thereby solving the problems in the prior art of raw material consumption caused by calibrating the melt back pressure and contamination of the screw and barrel by the samples.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: The plastic melt back pressure control system of the injection molding machine includes an injection cylinder, a release valve, an injection valve, a cartridge valve, a plastic melt back pressure proportional valve, an oil tank and an oil pump for driving the screw of the injection molding machine to move forward or backward; The first working oil port of the release valve is connected to the release oil port of the injection cylinder, the injection oil port of the injection cylinder is connected to the second working oil port of the injection valve, the oil inlet of the injection valve is connected to the oil inlet of the release valve to form a common oil circuit connected to the oil tank through the oil pump, the oil return port of the injection valve is connected to the oil inlet of the cartridge valve, the oil return port of the cartridge valve is connected to the oil tank, the control oil port of the cartridge valve is connected to the oil inlet of the melt back pressure proportional valve, and the oil return port of the melt back pressure proportional valve is connected to the oil tank; A pressure gauge is arranged on the oil circuit formed by connecting the oil return port of the injection valve with the oil inlet of the cartridge valve.

[0006] The release valve is a two-position four-way electromagnetic reversing valve.

[0007] The injection valve is a two-position four-way electromagnetic reversing valve.

[0008] The sol back pressure proportional valve is a proportional directional valve.

[0009] A method for calibrating the back pressure of a molten plastic injection molding machine, having the above-mentioned molten plastic injection molding machine back pressure control system, comprises the following steps: (1) Control the injection valve and the melt back pressure proportional valve to cut off the power and the release valve to get power; (2) Start the oil pump, so that the hydraulic oil in the oil tank enters the release chamber connected to the release port of the injection cylinder through the release valve. Driven by the hydraulic oil, the injection cylinder moves backward with the screw connected to it. At this time, observe the pressure value displayed on the pressure gauge, which should be 0; (2) Set the target melt back pressure value P0; (3) Adjust the output voltage of the melt back pressure proportional valve, power it on, and observe the pressure value P on the pressure gauge: If the pressure value P is equal to the preset value P0, it indicates that the current output voltage correctly corresponds to the set target melt back pressure value, the calibration process is completed, and the output voltage value is recorded; If the pressure value P does not match P0, it is necessary to continue adjusting the output voltage of the melt back pressure proportional valve until the pressure value P reaches the preset P0.

[0010] Take multiple different target melt back pressure values ​​P0 and repeat the above steps (2) to (3) to establish the relationship between the melt back pressure and the output voltage, form multiple sets of data, and finally plot these data points into a graph to form a linear relationship graph between the melt back pressure and the output voltage.

[0011] Compared with the prior art, the advantages of the present invention are: simple structure, convenient operation, no need to add raw materials to make melt when calibrating the melt back pressure, only need to control the screw to loosen and retract, and at the same time allow the melt back pressure proportional valve to be energized and assign a corresponding output voltage value to establish the back pressure. When the pressure value displayed on the pressure gauge is equal to the predetermined melt back pressure value, the calibration is completed. At this time, the output voltage value of the corresponding melt proportional valve corresponds to the required melt back pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is the hydraulic principle diagram of the present invention.

[0013] Figure 2 Graph showing the linear relationship between the melt back pressure and the output voltage obtained in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0014] The present invention is further described in detail below with reference to the accompanying drawings.

[0015] As shown in the figure, the melt back pressure control system of the injection molding machine includes an injection cylinder 1 for driving the screw of the injection molding machine to move forward or backward, a release valve 2, an injection valve 3, a cartridge valve 4, a melt back pressure proportional valve 5, an oil tank 6 and an oil pump 7; The first working oil port A of the release valve 2 is connected to the release oil port of the injection cylinder 1, the injection oil port of the injection cylinder 1 is connected to the second working oil port B of the injection valve 3, the oil inlet of the injection valve 3 is connected to the oil inlet P of the release valve 2 to form a common oil circuit connected to the oil tank 6 through the oil pump 7, the oil return port T of the injection valve 3 is connected to the oil inlet of the cartridge valve 4, the oil return port of the cartridge valve 4 is connected to the oil tank 6, the control oil port of the cartridge valve 4 is connected to the oil inlet of the melt back pressure proportional valve 5, and the oil return port of the melt back pressure proportional valve 5 is connected to the oil tank 6; A pressure gauge 8 is provided on the oil circuit formed by connecting the oil return port T of the injection valve 3 and the oil inlet of the cartridge valve 4 .

[0016] In this specific embodiment, the release valve 2 is a two-position four-way electromagnetic reversing valve.

[0017] In this specific embodiment, the injection valve 3 is a two-position four-way electromagnetic reversing valve.

[0018] In this specific embodiment, the sol back pressure proportional valve is a proportional directional valve.

[0019] When the injection molding machine is performing normal injection action, the injection valve 3 is energized, and the release valve 2 is not energized (the return oil port T of the release valve 2 is connected to the first working oil port A). Through the cooperation of the oil tank 6, the oil pump 7 and the injection valve 3, the hydraulic oil in the oil tank 6 enters the injection chamber connected to the injection oil port of the injection cylinder 1. Driven by the hydraulic oil, the injection cylinder 1 moves forward with the screw connected to it to complete the injection.

[0020] When the injection molding machine is performing normal injection and release actions, the melt back pressure proportional valve 5 is in a non-energized state. Only when performing the melt action, the melt back pressure proportional valve 5 is controlled to be energized, and the corresponding output voltage value is assigned to the melt back pressure proportional valve 5 according to the corresponding required melt back pressure value.

[0021] A method for calibrating the back pressure of a molten plastic injection molding machine, having the above-mentioned molten plastic injection molding machine back pressure control system, comprises the following steps: (1) Control the injection valve 3 and the melt back pressure proportional valve 5 to cut off the power and energize the release valve 2 (the oil inlet P of the release valve 2 is connected to the first working oil port A); (2) Start the oil pump 7, so that the hydraulic oil in the oil tank 6 enters the release chamber connected to the release port of the injection cylinder 1 through the release valve 2. Driven by the hydraulic oil, the injection cylinder 1 moves backward with the screw connected to it. At this time, observe the pressure value displayed on the pressure gauge 8, which should be 0; (2) Set the target melt back pressure value P0; (3) Adjust the output voltage of the melt back pressure proportional valve 5, and energize it, and observe the pressure value P on the pressure gauge 8: If the pressure value P is equal to the preset value P0, it indicates that the current output voltage correctly corresponds to the set target melt back pressure value, the calibration process is completed, and the output voltage value is recorded; If the pressure value P does not match P0, it is necessary to continue adjusting the output voltage of the melt back pressure proportional valve 5 until the pressure value P reaches the preset P0.

[0022] Take multiple different target melt back pressure values ​​P0 (5 bar, 10 bar, 15 bar, 20 bar, 25 bar, 30 bar, 35 bar, 40 bar), and repeat the above steps (2) to (3). This is used to establish the relationship between the melt back pressure and the output voltage, forming multiple sets of data (as shown in the table below). Finally, these data points are plotted into a graph to form a linear relationship graph between the melt back pressure and the output voltage (as shown in the table below). Figure 2 as shown).

[0023] <![CDATA[Target melt back pressure value P0 (bar)]]> Output voltage value of melt proportional valve (V) The corresponding pressure value P (bar) read by the pressure gauge 0 0 0 5 0.6 5 10 1.4 10 15 2.1 15 20 3.3 20 25 4.2 25 30 5.3 30 35 6.4 35 40 7.3 40

Claims

1. The plastic melt back pressure control system of the injection molding machine includes an injection cylinder, a release valve, an injection valve, a cartridge valve, a plastic melt back pressure proportional valve, an oil tank and an oil pump for driving the screw of the injection molding machine to move forward or backward; The first working oil port of the release valve is connected to the release oil port of the injection cylinder, the injection oil port of the injection cylinder is connected to the second working oil port of the injection valve, the oil inlet of the injection valve is connected to the oil inlet of the release valve to form a common oil circuit connected to the oil tank through the oil pump, the oil return port of the injection valve is connected to the oil inlet of the cartridge valve, the oil return port of the cartridge valve is connected to the oil tank, the control oil port of the cartridge valve is connected to the oil inlet of the melt back pressure proportional valve, and the oil return port of the melt back pressure proportional valve is connected to the oil tank; A pressure gauge is arranged on the oil circuit formed by connecting the oil return port of the injection valve with the oil inlet of the cartridge valve.

2. The injection molding machine melt back pressure control system according to claim 1, characterized in that The release valve is a two-position four-way electromagnetic reversing valve.

3. The injection molding machine melt back pressure control system according to claim 1, characterized in that The injection valve is a two-position four-way electromagnetic reversing valve.

4. The injection molding machine melt back pressure control system according to claim 1, characterized in that The sol back pressure proportional valve is a proportional directional valve.

5. A method for calibrating the back pressure of a plastic injection molding machine, comprising the plastic injection molding machine back pressure control system as claimed in claim 1, characterized in that The steps include: (1) Control the injection valve and the melt back pressure proportional valve to cut off the power and the release valve to get power; (2) Start the oil pump, so that the hydraulic oil in the oil tank enters the release chamber connected to the release port of the injection cylinder through the release valve. Driven by the hydraulic oil, the injection cylinder moves backward with the screw connected to it. At this time, observe the pressure value displayed on the pressure gauge, which should be 0; (2) Set the target melt back pressure value P0; (3) Adjust the output voltage of the melt back pressure proportional valve, power it on, and observe the pressure value P on the pressure gauge: If the pressure value P is equal to the preset value P0, it indicates that the current output voltage correctly corresponds to the set target melt back pressure value, the calibration process is completed, and the output voltage value is recorded; If the pressure value P does not match P0, it is necessary to continue adjusting the output voltage of the melt back pressure proportional valve until the pressure value P reaches the preset P0.

6. A method for calibrating the melt back pressure of an injection molding machine as claimed in claim 5, characterized in that Take multiple different target melt back pressure values ​​P0 and repeat the above steps (2) to (3).

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