Injection molding machine back pressure calibration hydraulic circuit and calibration method thereof

Abstract

The application discloses a kind of injection molding machine back pressure calibration hydraulic oil way and its calibration method, oil way includes hydraulic cylinder, hydraulic motor, three-position four-way valve, two-position three-way valve, pressure gauge, numerical control back pressure valve, oil inlet and oil outlet, hydraulic cylinder piston rod is fixed with injection molding machine screw rod, the rotating shaft of hydraulic motor is fixed with the piston rod of hydraulic cylinder, three-position four-way valve interface is respectively connected with oil inlet, oil outlet, hydraulic cylinder has rod cavity, hydraulic motor oil inlet, two-position three-way valve interface is respectively connected with oil inlet, hydraulic cylinder without rod cavity, numerical control back pressure valve liquid inlet, numerical control back pressure valve liquid outlet is connected with oil outlet, pressure gauge is connected between two-position three-way valve and numerical control back pressure valve;Calibration method includes the following steps: one: the pressure value of numerical control back pressure valve is P0;Two: injection molding machine screw rod shoots back;Three: read pressure display number P;Four: adjust voltage / current value to |P-P0|≤ΔP;Five: set the voltage / current when finally |P-P0|≤ΔP as the input parameter corresponding to numerical control back pressure valve P0 pressure value.

Description

Technical Field

[0001] The present invention relates to a hydraulic oil circuit for calibrating the back pressure of an injection molding machine and a calibration method therefor. Background Art

[0002] Back pressure is one of the important parameters for controlling the quality of molten materials and products in the injection molding process. Appropriate back pressure plays an important role in improving product quality. Currently, the back pressure of an injection molding machine is generally generated by a numerical control back pressure valve. During the melting and plasticizing process of plastics, the molten materials continuously move towards the metering chamber at the front end of the barrel, and more and more, gradually forming a pressure that pushes the screw of the injection molding machine backward, thereby pushing the injection cylinder backward. The oil return pipeline of the cylinder returns to the fuel tank after passing through the numerical control back pressure valve. Since the pressure value of the numerical control back pressure valve is linearly proportional to the input voltage / current value, by adjusting the voltage / current input to the numerical control back pressure valve, the back pressure can be adjusted.

[0003] In the actual application process, in order to ensure the accuracy of the back pressure value, it is often necessary to finely adjust and calibrate the numerical control back pressure valve. However, generally, an injection molding machine can only read the back pressure data during the melting process. Therefore, when calibrating the numerical control back pressure valve, a melting operation needs to be performed. The calibration process is as follows: Add rubber materials to the barrel, heat to a certain temperature, set the pressure values of the numerical control back pressure valve to 25%, 50%, 75%, and 100% of the range respectively, set the maximum melting speed for the melting operation, read the actual pressure value P before the valve of the numerical control back pressure valve, and compare it with the set back pressure value P0. When |P - P0| is greater than the allowable error range and P > P0, appropriately reduce the output current / voltage value corresponding to the set back pressure value; when |P - P0| is greater than the allowable error range and P < P0, appropriately increase the output current / voltage value corresponding to the set back pressure value. Adjust in such a cycle until |P - P0| is less than or equal to the allowable error range, then the calibration of the back pressure value is completed.

[0004] This calibration process requires repeated melting operations, which takes a lot of time. At the same time, the melting process also consumes rubber materials, resulting in material waste.

[0005] Therefore, how to overcome the above-mentioned defects has become an important issue that needs to be urgently solved by those skilled in the art. Summary of the Invention

[0006] The present invention overcomes the above-mentioned technical deficiencies and provides a hydraulic oil circuit for calibrating the back pressure of an injection molding machine and a calibration method therefor.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A hydraulic circuit for back pressure calibration of an injection molding machine includes a hydraulic cylinder 1, a hydraulic motor 2, a three-position four-way valve 3, a two-position three-way valve 4, a pressure gauge 5, a CNC back pressure valve 6, an oil inlet 7, and an oil outlet 8. The piston rod of the hydraulic cylinder 1 is fixedly connected to the injection molding machine screw 9 to drive the screw 9 to move back and forth. The rotating shaft of the hydraulic motor 2 is also fixedly connected to the piston rod of the hydraulic cylinder 1 to drive the screw 9 to rotate. The four ports of the three-position four-way valve 3 are respectively connected to the oil inlet 7, the oil outlet 8, the rod chamber of the hydraulic cylinder 1, and the oil inlet of the hydraulic motor 2. The three ports of the two-position three-way valve 4 are respectively connected to the oil inlet 7, the oil outlet 8, the rod chamber of the hydraulic cylinder 1, and the oil inlet of the hydraulic motor 2. The rodless chamber of cylinder 1 is connected to the inlet of the CNC back pressure valve 6. The outlet of the CNC back pressure valve 6 is connected to the outlet 8. The pressure gauge 5 is connected to the oil line between the two-position three-way valve 4 and the CNC back pressure valve 6 to detect the hydraulic pressure value before the valve of the CNC back pressure valve 6. The first position of the three-position four-way valve 3 is: the inlet 7 is connected to the rod chamber of hydraulic cylinder 1, and the inlet of hydraulic motor 2 is connected to the outlet 8. The second position is: the inlet 7 is connected to the inlet of hydraulic motor 2, and the rod chamber of hydraulic cylinder 1 is connected to the outlet 8. The first position of the two-position three-way valve 4 is: the rodless chamber of hydraulic cylinder 1 is connected to the inlet of the CNC back pressure valve 6, and the inlet 7 is blocked.

[0009] Preferably, the third position of the three-position four-way valve 3 is: the rod chamber of the hydraulic cylinder 1 is connected to the oil outlet 8, the oil inlet 7 is blocked, and the inlet of the hydraulic motor 2 is blocked; the second position of the two-position three-way valve 4 is: the oil inlet 7 is connected to the rodless chamber of the hydraulic cylinder 1, and the inlet of the CNC back pressure valve 6 is blocked.

[0010] Preferably, the three-position four-way valve 3 is provided with an injection coil 31 for switching the three-position four-way valve 3 to the first position and a melt coil 32 for switching the three-position four-way valve 3 to the second position; the two-position three-way valve 4 is provided with an injection coil 41 for switching the two-position three-way valve 4 to the second position.

[0011] Preferably, the third position of the three-position four-way valve 3 is the normal position; the first position of the two-position three-way valve 4 is the normal position.

[0012] A method for calibrating the back pressure of an injection molding machine, comprising the following steps using the aforementioned hydraulic circuit for calibrating the back pressure of the injection molding machine:

[0013] Step 1: Set the pressure value of the CNC back pressure valve 6 to P0;

[0014] Step 2: Control the screw 9 of the injection molding machine to perform the injection retraction action;

[0015] Step 3: Read the reading P of pressure gauge 5;

[0016] Step 4: If |P - P0| > ΔP and P > P0, then decrease the input voltage / current value of the numerical control back pressure valve (6) and jump back to Step 2; if |P - P0| > ΔP and P < P0, then increase the input voltage / current value of the numerical control back pressure valve (6) and jump back to Step 2; if |P - P0| ≤ ΔP, then do not adjust the input voltage / current value of the numerical control back pressure valve (6) and execute Step 5. Here, ΔP is the extreme value of the acceptable error of the injection back pressure.

[0017] Step 5: Set the input voltage / current when finally |P - P0| ≤ ΔP as the input parameter corresponding to the pressure value of P0 of the numerical control back pressure valve 6.

[0018] Preferably, during calibration, P0 is respectively set to 25%, 50%, 75%, and 100% of the total range of the numerical control back pressure valve 6, and Steps 1 to 5 are each executed once.

[0019] Preferably, ΔP = 1.6% * (P , max , min , min ,

[0022] ,

[0021] , ,

[0020] , - P min ), where P max is the upper limit value of the indication of the pressure gauge 5, and P min is the lower limit value of the indication of the pressure gauge 5.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. When the back pressure calibration hydraulic oil circuit in this case positions the three-position four-way valve at the first position and the two-position three-way valve at the first position, the oil inlet can be connected to the rod chamber of the hydraulic cylinder, and the non-rod chamber of the hydraulic cylinder can be connected to the liquid inlet of the numerical control back pressure valve. In this way, the hydraulic cylinder will drive the injection molding machine screw to retreat and perform the injection retreat action. At this time, the pressure in the non-rod chamber of the hydraulic cylinder is controlled by the numerical control back pressure valve and can be obtained in real time through the pressure gauge. Thus, the numerical control back pressure valve can be calibrated by performing the injection retreat action, rather than through the melting action, which greatly reduces the time required for the calibration process. At the same time, since the injection retreat operation does not require the participation of the rubber material, calibrating the numerical control back pressure valve through the injection retreat operation can also avoid wasting the rubber material. And only by positioning the three-position four-way valve at the second position and the two-position three-way valve at the first position, the oil inlet can be connected to the liquid inlet hole of the hydraulic motor, the rod chamber of the hydraulic cylinder can be connected to the oil outlet, and the non-rod chamber of the hydraulic cylinder can be connected to the liquid inlet of the numerical control back pressure valve, then the hydraulic motor can be made to work to drive the injection molding machine screw to rotate and melt the rubber. At the same time, when the rubber material accumulates in the barrel to form pressure and pushes the injection molding machine screw backward, the numerical control back pressure valve can provide an accurate back pressure for the injection molding machine screw. In this way, the back pressure calibration hydraulic oil circuit in this case can simultaneously realize the injection retreat and melting actions, and can quickly complete the calibration of the numerical control back pressure valve without consuming the rubber material through the injection retreat action, ensuring the accuracy of the back pressure during melting.

[0022] 2. When the three-position four-way valve is turned to the third position and the two-position three-way valve is turned to the second position, the rod chamber of the hydraulic cylinder is connected to the oil outlet and the oil inlet is connected to the rodless chamber of the hydraulic cylinder. This drives the screw of the plastic injection machine to extend and perform the injection action. This allows the back pressure calibration hydraulic circuit in this case to complete the melting, injection and ejection actions through only one oil circuit.

[0023] 3. The calibration method in this case can obtain the input voltage / current value that accurately corresponds to the pressure value of the CNC back pressure valve by using the injection retraction action of the injection molding machine. In this way, the time spent calibrating the CNC back pressure valve can be greatly reduced, without waiting for the melt and without wasting the rubber material. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the hydraulic circuit for back pressure calibration in this case.

[0025] Figure 2 This is a schematic diagram of the state of the hydraulic circuit during the back pressure calibration and ejection action in this case.

[0026] Figure 3 This is a schematic diagram of the state of the hydraulic circuit during the back pressure calibration process in this case.

[0027] Figure 4 This is a schematic diagram of the state of the hydraulic oil circuit during the injection action in this case, which is used for back pressure calibration. Detailed Implementation

[0028] The following examples further illustrate the features and other related characteristics of the present invention in detail, to facilitate understanding by those skilled in the art:

[0029] like Figures 1 to 3As shown, a hydraulic circuit for back pressure calibration of an injection molding machine includes a hydraulic cylinder 1, a hydraulic motor 2, a three-position four-way valve 3, a two-position three-way valve 4, a pressure gauge 5, a CNC back pressure valve 6, an oil inlet 7, and an oil outlet 8. The piston rod of the hydraulic cylinder 1 is fixedly connected to the injection molding machine screw 9 to drive the injection molding machine screw 9 to move back and forth. The rotating shaft of the hydraulic motor 2 is also fixedly connected to the piston rod of the hydraulic cylinder 1 to drive the injection molding machine screw 9 to rotate. The four ports of the three-position four-way valve 3 are respectively connected to the oil inlet 7, the oil outlet 8, the rod chamber of the hydraulic cylinder 1, and the oil inlet of the hydraulic motor 2. The three ports of the two-position three-way valve 4 are respectively connected to the oil inlet 7, the oil outlet 8, the rod chamber of the hydraulic cylinder 1, and the oil inlet of the hydraulic motor 2. The rodless chamber of the pressure cylinder 1 is connected to the inlet of the CNC back pressure valve 6. The outlet of the CNC back pressure valve 6 is connected to the outlet 8. The pressure gauge 5 is connected to the oil circuit between the two-position three-way valve 4 and the CNC back pressure valve 6 to detect the hydraulic pressure value before the valve of the CNC back pressure valve 6. The first position of the three-position four-way valve 3 is: the inlet 7 is connected to the rod chamber of the hydraulic cylinder 1, and the inlet of the hydraulic motor 2 is connected to the outlet 8. The second position is: the inlet 7 is connected to the inlet of the hydraulic motor 2, and the rod chamber of the hydraulic cylinder 1 is connected to the outlet 8. The first position of the two-position three-way valve 4 is: the rodless chamber of the hydraulic cylinder 1 is connected to the inlet of the CNC back pressure valve 6, and the inlet 7 is blocked.

[0030] As described above, when the three-position four-way valve 3 is turned to the first position and the two-position three-way valve 4 is turned to the first position, the oil inlet 7 can be connected to the rod chamber of the hydraulic cylinder 1, and the rodless chamber of the hydraulic cylinder 1 can be connected to the inlet of the CNC back pressure valve 6. In this way, the hydraulic cylinder 1 will drive the injection molding machine screw 9 to retract and perform the injection retraction action. At this time, the pressure of the rodless chamber of the hydraulic cylinder 1 is controlled by the CNC back pressure valve 6 and can be obtained in real time through the pressure gauge 5. Thus, the CNC back pressure valve 6 can be calibrated by performing the injection retraction action instead of calibrating through the melting action, thereby greatly reducing the time required for the calibration process. At the same time, since the injection retraction operation does not require the participation of the rubber material, calibrating the CNC back pressure valve 6 through the injection retraction operation can also avoid wasting the rubber material. By simply switching the three-position four-way valve 3 to the second position and the two-position three-way valve 4 to the first position, the oil inlet 7 can be connected to the hydraulic motor 2's inlet port, the rod chamber of the hydraulic cylinder 1 to the oil outlet 8, and the rodless chamber of the hydraulic cylinder 1 to the inlet of the CNC back pressure valve 6. This allows the hydraulic motor 2 to drive the injection molding machine screw 9 to rotate and melt the adhesive. Simultaneously, when the adhesive accumulates in the barrel and creates pressure that pushes the injection molding machine screw 9 backward, the CNC back pressure valve 6 can provide an accurate back pressure to the injection molding machine screw 9. In this way, the back pressure calibration hydraulic circuit of this invention can simultaneously achieve injection retraction and discharging actions. Furthermore, the calibration of the CNC back pressure valve 6 can be quickly completed through the injection retraction action without consuming adhesive, ensuring accurate back pressure during discharging.

[0031] like Figure 1 , Figure 4As shown, preferably, the third position of the three-position four-way valve 3 is that the rod chamber of the hydraulic cylinder 1 is connected to the oil outlet 8, the oil inlet 7 is throttled, and the liquid inlet hole of the hydraulic motor 2 is blocked; the second position of the two-position three-way valve 4 is that the oil inlet 7 is connected to the rodless chamber of the hydraulic cylinder 1, and the liquid inlet of the numerical control backpressure valve 6 is blocked. Thus, when the three-position four-way valve 3 is switched to the third position and the two-position three-way valve 4 is switched to the second position, the rod chamber of the hydraulic cylinder 1 is connected to the oil outlet 8, and the oil inlet 7 is connected to the rodless chamber of the hydraulic cylinder 1. In this way, the plastic injection machine screw 9 can be driven to extend for the injection action, enabling the backpressure calibration hydraulic oil circuit in this case to complete the plasticizing, injection, and injection withdrawal actions respectively through only one oil circuit.

[0032] As Figures 1 to 4 shown, preferably, the three-position four-way valve 3 is provided with a retraction coil 31 for switching the three-position four-way valve 3 to the first position and a plasticizing coil 32 for switching the three-position four-way valve 3 to the second position; the two-position three-way valve 4 is provided with an injection coil 41 for switching the two-position three-way valve 4 to the second position. Thus, by controlling the retraction coil 31 to be powered on and the other coils to be powered off, the oil circuit for the retraction action can be switched; by controlling the plasticizing coil 32 to be powered on and the other coils to be powered off, the oil circuit for the plasticizing action can be switched; by controlling the injection coil 41 to be powered on and the other coils to be powered off, the oil circuit for the injection action can be switched, thereby realizing the fast switching function.

[0033] As Figure 1 shown, preferably, the third position of the three-position four-way valve 3 is the normal position; the first position of the two-position three-way valve 4 is the normal position. Thus, in the standby state, the oil inlet 7 is intercepted in all flow directions, ensuring that both the hydraulic cylinder 1 and the hydraulic motor 2 do not work.

[0034] An injection molding machine backpressure calibration method uses the above injection molding machine backpressure calibration hydraulic oil circuit to perform the following steps:

[0035] Step 1: Set the pressure value of the numerical control backpressure valve 6 to P0;

[0036] Step 2: Control the injection molding machine screw 9 to perform the retraction action;

[0037] Step 3: Read the indication P of the pressure gauge 5; <​​​​Step 5: Set the input voltage / current to the input parameters corresponding to the pressure value of the CNC back pressure valve 6P0 when |P-P0|≤ΔP.

[0040] As described above, the calibration method in this case can obtain the input voltage / current value that accurately corresponds to the pressure value of the CNC back pressure valve 6 by using the injection retraction action of the injection molding machine. In this way, the time spent calibrating the CNC back pressure valve 6 can be greatly reduced, without waiting for the melt and without wasting the rubber material.

[0041] Preferably, during calibration, P0 is set to 25%, 50%, 75%, and 100% of the total range of the CNC back pressure valve 6, and steps one to five are performed once each.

[0042] Preferably, the ΔP = 1.6% * (P) max -P min ), the P max The upper limit of the pressure gauge reading is P. min This is the lower limit of the reading on pressure gauge 5.

[0043] As stated above, this case protects a hydraulic circuit for back pressure calibration of an injection molding machine and its calibration method. All technical solutions that are the same as or similar to this case should be considered to fall within the scope of protection of this case.

Claims

1. A hydraulic circuit for back pressure calibration of an injection molding machine, characterized in that... The system includes a hydraulic cylinder (1), a hydraulic motor (2), a three-position four-way valve (3), a two-position three-way valve (4), a pressure gauge (5), a CNC back pressure valve (6), an oil inlet (7), and an oil outlet (8). The piston rod of the hydraulic cylinder (1) is fixedly connected to the injection molding machine screw (9) to drive the injection molding machine screw (9) to move back and forth. The rotating shaft of the hydraulic motor (2) is also fixedly connected to the piston rod of the hydraulic cylinder (1) to drive the injection molding machine screw (9) to rotate. The three-position four-way valve (3) has four ports. The three ports of the two-position three-way valve (4) are respectively connected to the oil inlet (7), the oil outlet (8), the rod chamber of the hydraulic cylinder (1), and the oil inlet of the hydraulic motor (2). The three ports of the two-position three-way valve (4) are respectively connected to the oil inlet (7), the rodless chamber of the hydraulic cylinder (1), and the liquid inlet of the CNC back pressure valve (6). The liquid outlet of the CNC back pressure valve (6) is connected to the oil outlet (8). The pressure gauge (5) is connected to the oil line between the two-position three-way valve (4) and the CNC back pressure valve (6) to detect the hydraulic pressure value before the valve of the CNC back pressure valve (6). The first position of the three-position four-way valve (3) is: the oil inlet (7) is connected to the rod chamber of the hydraulic cylinder (1), and the liquid inlet of the hydraulic motor (2) is connected to the oil outlet (8). The second position is: the oil inlet (7) is connected to the liquid inlet of the hydraulic motor (2), and the rod chamber of the hydraulic cylinder (1) is connected to the oil outlet (8). The first position of the two-position three-way valve (4) is: the rodless chamber of the hydraulic cylinder (1) is connected to the inlet of the CNC back pressure valve (6), and the oil inlet (7) is blocked.

2. The hydraulic circuit for back pressure calibration of an injection molding machine according to claim 1, characterized in that... The third position of the three-position four-way valve (3) is: the rod chamber of the hydraulic cylinder (1) is connected to the oil outlet (8), the oil inlet (7) is blocked, and the inlet of the hydraulic motor (2) is blocked; The second position of the two-position three-way valve (4) is: the oil inlet (7) is connected to the rodless chamber of the hydraulic cylinder (1), and the inlet of the CNC back pressure valve (6) is blocked.

3. The hydraulic circuit for back pressure calibration of an injection molding machine according to claim 2, characterized in that... The three-position four-way valve (3) is provided with a ejector coil (31) for switching the three-position four-way valve (3) to the first position and a melt coil (32) for switching the three-position four-way valve (3) to the second position. The two-position three-way valve (4) is equipped with a glue injection coil (41) for switching the two-position three-way valve (4) to the second position.

4. The hydraulic circuit for back pressure calibration of an injection molding machine according to claim 2, characterized in that... The third position of the three-position four-way valve (3) is the normal position; The first position of the two-position three-way valve (4) is the normal position.

5. A method for calibrating back pressure in an injection molding machine, characterized in that... Perform the following steps using the hydraulic circuit for back pressure calibration of an injection molding machine as described in any one of claims 1 to 4: Step 1: Set the pressure value of the CNC back pressure valve (6) to... ; Step 2: Control the injection molding machine screw (9) to perform the injection retraction action; Step 3: Read the reading P of pressure gauge (5); Step 4: If and Then reduce the input voltage / current value of the CNC back pressure valve (6) and jump back to step two. and Then increase the input voltage / current value of the CNC back pressure valve (6) and jump back to step two. Then, without adjusting the input voltage / current value of the CNC back pressure valve (6), proceed to step five. The The upper limit of the pressure gauge (5) reading, the This is the lower limit of the pressure gauge (5) reading; Step 5: Set the final setting The input voltage / current at that time is the numerical control back pressure valve (6). The input parameters corresponding to the pressure value.

6. The injection molding machine back pressure calibration method according to claim 5, characterized in that... During calibration Steps one through five are executed once each at 25%, 50%, 75%, and 100% of the total range of the CNC back pressure valve (6).

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