An all-electric injection molding machine barrel pressure control method

Abstract

The application discloses a kind of full electric injection molding machine cylinder pressure control method, with PI control parameter acquisition stage, single P control stage and PI control stage, in PI control parameter acquisition stage, the actual pressure of cylinder is periodically obtained, the pressure variation of cylinder is obtained, the proportional term K p And integral term T i Two PI control parameters, in single P control stage, the proportional term of PI control parameter acquisition stage is used to control the deceleration process of injection, in PI pressure control stage, the integral term of PI control parameter acquisition stage is introduced to eliminate static deviation, so that the injection pressure is stable to set pressure, PI control parameter self-learning is replaced by manual to adjust cylinder pressure, and automatic PI control parameter setting control is realized;The advantage is not only time-saving and labor-saving, but also will not affect the normal use of full electric injection molding machine, and the working efficiency of full electric injection molding machine can be guaranteed.

Description

Technical Field

[0001] This invention relates to a barrel pressure control method, and more particularly to a barrel pressure control method for an all-electric injection molding machine. Background Technology

[0002] Currently, all-electric injection molding machines play an irreplaceable role in the industrial sector, and pressure control within these machines is a crucial issue. Pressure control in all-electric injection molding machines primarily involves controlling the barrel pressure. The accuracy of the barrel pressure significantly impacts the quality of the produced products. Insufficient barrel pressure fails to meet production requirements, while excessive pressure easily leads to flash (burrs) in the finished products. Furthermore, it requires greater energy consumption for the screw to drive the molten material during injection, and may even damage the screw or the injection port of the all-electric injection molding machine. Therefore, how to achieve precise control of the barrel pressure in all-electric injection molding machines has attracted considerable attention and widespread research from researchers both domestically and internationally.

[0003] Currently, the main control method for barrel pressure in all-electric injection molding machines is proportional-integral (PI) control. PI control is a model-free control method; different all-electric injection molding machines use different PI control parameters, and even the same all-electric injection molding machine requires different PI control parameters under different operating conditions. Adjusting these PI control parameters relies heavily on the industry experience of the commissioning personnel. They repeatedly adjust the PI control parameters based on the actual performance of the barrel pressure to achieve minimal barrel pressure overshoot. Furthermore, during the commissioning process, the all-electric injection molding machine cannot be used normally and must wait until commissioning is complete before it can be used normally. Therefore, the existing method of manually adjusting PI control parameters to control the barrel pressure of all-electric injection molding machines is not only time-consuming and labor-intensive but also affects the normal operation of the all-electric injection molding machine, thus impacting its working efficiency. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a barrel pressure control method for a fully electric injection molding machine that uses PI control parameter self-learning to replace manual adjustment of the barrel pressure, thereby achieving the goal of minimizing barrel pressure overshoot. This method not only saves time and effort but also does not affect the normal operation of the fully electric injection molding machine, ensuring the working efficiency of the fully electric injection molding machine.

[0005] The technical solution adopted by this invention to solve the above-mentioned technical problems is: a method for controlling barrel pressure in an all-electric injection molding machine, comprising the following steps:

[0006] Step 1: Install a pressure sensor at the end of the barrel of the all-electric injection molding machine to collect barrel pressure. The pressure sensor is connected to the controller of the all-electric injection molding machine. When the all-electric injection molding machine is performing injection, the controller sends a speed command to its motor driver. The motor driver controls the motor to rotate according to the speed command. The ball screw is rigidly connected to the motor, converting the rotational motion of the motor into linear motion, pushing the molten material in the barrel into the mold, forming barrel pressure. Set the deceleration time parameter in the controller of the all-electric injection molding machine. The deceleration time parameter represents the time required for the motor driver to control the motor to decelerate from the maximum speed to 0, denoted as T. d Set the pressure control cycle to T c T c The value ranges from 0.5 to 2.0 ms, and the maximum speed of the motor is denoted as n. max Let the set speed of the melt injection be n. s The set pressure for melt injection is p s n s and p s Based on the actual production process;

[0007] Step 2: Denote the proportional term of the PI control parameter as K. p , for K p Perform initialization, let K p =(K p ) max , where (K p ) max The upper limit of the proportional term, (K) p ) max The value is 5-10; the maximum change in barrel pressure of the all-electric injection molding machine is denoted as Δp. max For Δp max Perform initialization, let Δp max =0; Set parameters to obtain the pressure control cycle variable, denote it as t, initialize t by setting t=0; Start the all-electric injection molding machine to perform injection;

[0008] Step 3: Simultaneously enter the barrel pressure control stage of the all-electric injection molding machine, specifically as follows:

[0009] Step 3-1: Update the value of t by adding 1 to the current value of t, and enter the t-th pressure control cycle. The specific control process is as follows:

[0010] Step 3-1-1: Collect the actual pressure of the barrel during the current pressure control cycle using a pressure sensor, and record it as p. t ;

[0011] Step 3-1-2: Calculate the pressure change Δp during the current pressure control cycle using equation (1). t :

[0012] Δp t =p t -p t-1 (1)

[0013] Where, p t-1 This represents the actual pressure of the barrel during the (t-1)th pressure control cycle. When t = 1, Δp t =0;

[0014] Step 3-1-3, Determine Δp t Is it greater than Δp? max The current value, if Δp t Less than or equal to Δp max If the current value is Δp, then... max If Δp remains unchanged, its current value remains unchanged. t Greater than Δp max If the current value is Δp, then first set Δp max The value is updated to Δp t Then Δp max Substituting the current value into equation (2) for the proportional term K p Update the value:

[0015]

[0016] Step 3-1-4: Determine the proportional term K p Is the current value greater than (K)? p ) max If the proportional term K p The current value is greater than or equal to (K) p ) max Then update it to (K) p ) max If the proportional term K p The current value is less than (K) p ) min Then update it to (K) p ) min , (K p ) min For the proportional term K p The lower limit value, (K) p ) min The value ranges from 0.5 to 1.0;

[0017] Step 3-1-5: Calculate the pressure error value e for the current pressure control cycle using equation (3). t :

[0018] e t =p s -p t (3)

[0019] Step 3-1-6: Calculate the speed command n for the current pressure control cycle using equation (4). t :

[0020] n t =K p ·e t (4)

[0021] Step 3-1-7, Determine n t Is it greater than or equal to n? s If n t Greater than or equal to n s Then, at this time, the speed command sent by the controller of the all-electric injection molding machine to the motor driver is n. s The current motor driver follows the speed command n s Control the motor to rotate and return to step 3-1-1; if n t Less than n s Then, at this time, the speed command sent by the controller of the all-electric injection molding machine to the motor driver is n. t The current motor driver follows the speed command n t Control the motor to rotate, proceed to step 3-2, and calculate the integral term T using equation (5). i Value:

[0022] T i =K p / 20 (5)

[0023] Step 3-2: Update the value of t by adding 1 to the current value of t, and enter the t-th pressure control cycle;

[0024] Step 3-2-1: Collect the actual pressure of the barrel in the current pressure control cycle using a pressure sensor, and record it as p. t ;

[0025] Step 3-2-2: Calculate the speed command n for the current pressure control cycle using equations (3) and (4). t Determine n t Is it greater than or equal to n? s If n t Greater than or equal to n s Then the speed command sent by the controller of the all-electric injection molding machine to the motor driver is n. s The current motor driver follows the speed command n s Control the motor to rotate; if n t Less than n s Then the speed command sent by the controller of the all-electric injection molding machine to the motor driver is n. t The current motor driver follows the speed command n t Control the motor rotation;

[0026] Step 3-2-3: Determine whether the speed command sent by the controller of the current all-electric injection molding machine to the motor driver is less than n. trans , where n trans The switching speed for transitioning from single-P control to PI control is 50-200 RPM. This is based on the condition that the current controller of the all-electric injection molding machine sends a speed command to the motor driver that is greater than or equal to n. trans If the speed command sent by the controller of the current all-electric injection molding machine to the motor driver is less than n, then return directly to step 3-2; trans Then, the PI-controlled integral accumulator is denoted as I, I is initialized by setting I = 0, and then proceeds to step 3-3;

[0027] Step 3-3: Update the value of t by adding 1 to the current value of t, and enter the t-th pressure control cycle;

[0028] Step 3-3-1: Collect the actual pressure of the barrel during the current pressure control cycle using a pressure sensor, and record it as p. t ;

[0029] Step 3-3-2: Calculate the pressure error value e for the current pressure control cycle using equation (3). t ;

[0030] Step 3-3-3: Add e to the current value of the integrator accumulator I. t The value of the updated integral accumulator I is then updated.

[0031] Step 3-3-4: Calculate the speed command n for the current pressure control cycle using equation (6). t :

[0032] n t =K p ·e t +T i ·I (6)

[0033] Step 3-3-5, Determine n t Is it greater than or equal to n? s If n t Greater than or equal to n s Then, at this time, the speed command sent by the controller of the all-electric injection molding machine to the motor driver is n. s The current motor driver follows the speed command n s Control the motor to rotate; if n t Less than n s Then, at this time, the speed command sent by the controller of the all-electric injection molding machine to the motor driver is n. t The current motor driver follows the speed command n tControl the motor to rotate and return to step 3-3 to enter the next pressure control cycle, repeating this cycle until the injection work of the all-electric injection molding machine is completed.

[0034] Compared with the prior art, the advantage of this invention is that during the operation of the all-electric injection molding machine, the barrel pressure control stage is divided into a PI control parameter acquisition stage, a single-P control stage, and a PI control stage. In the PI control parameter acquisition stage, the actual pressure of the barrel is periodically acquired to obtain the pressure change of the barrel and determine the proportional term K. p and integral term T i These two PI control parameters, in the single-P control stage, use the proportional term from the PI control parameter acquisition stage to control the deceleration process of injection. In the PI pressure control stage, the integral term from the PI control parameter acquisition stage is introduced to eliminate static deviation, so that the injection pressure is stabilized to the set pressure. The method of this invention replaces manual adjustment of the barrel pressure by self-learning the PI control parameters, realizing automated PI control parameter setting and control. It does not rely on the industry experience of engineers or technicians. The control process is simple and fast, and it can automatically adjust the PI parameters. Moreover, normal pressure control can be performed immediately after the PI parameter value is set, without affecting the normal use of the barrel of the all-electric injection molding machine. Therefore, this invention not only saves time and effort, but also does not affect the normal use of the all-electric injection molding machine, and can ensure the working efficiency of the all-electric injection molding machine. Attached Figure Description

[0035] Figure 1 This is a comparison diagram showing the barrel pressure control method of the all-electric injection molding machine before and after the application of the method of the present invention. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0037] Example: A method for controlling barrel pressure in an all-electric injection molding machine, comprising the following steps:

[0038] Step 1: Install a pressure sensor at the end of the barrel of the all-electric injection molding machine to collect barrel pressure. The pressure sensor is connected to the controller of the all-electric injection molding machine. When the all-electric injection molding machine is performing injection, the controller sends a speed command to its motor driver. The motor driver controls the motor to rotate according to the speed command. The ball screw is rigidly connected to the motor, converting the motor's rotational motion into linear motion, pushing the molten material in the barrel into the mold, forming barrel pressure. Set the deceleration time parameter in the controller of the all-electric injection molding machine. The deceleration time parameter represents the time required for the motor driver to control the motor to decelerate from the maximum speed to 0, denoted as T. d Set the pressure control cycle to T c T c The value ranges from 0.5 to 2.0 ms, and the maximum speed of the motor is denoted as n.max Let the set speed of the melt injection be n. s The set pressure for melt injection is p s n s and p s Based on the actual production process;

[0039] Step 2: Denote the proportional term of the PI control parameter as K. p , for K p Perform initialization, let K p =(K p ) max , where (K p ) max The upper limit of the proportional term, (K) p ) max The value is 5-10; the maximum change in barrel pressure of the all-electric injection molding machine is denoted as Δp. max For Δp max Perform initialization, let Δp max =0; Set parameters to obtain the pressure control cycle variable, denote it as t, initialize t by setting t=0; Start the all-electric injection molding machine to perform injection;

[0040] Step 3: Simultaneously enter the barrel pressure control stage of the all-electric injection molding machine, specifically as follows:

[0041] Step 3-1: Update the value of t by adding 1 to the current value of t, and enter the t-th pressure control cycle. The specific control process is as follows:

[0042] Step 3-1-1: Collect the actual pressure of the barrel during the current pressure control cycle using a pressure sensor, and record it as p. t ;

[0043] Step 3-1-2: Calculate the pressure change Δp during the current pressure control cycle using equation (1). t :

[0044] Δp t =p t -p t-1 (1)

[0045] Where, p t-1 This represents the actual pressure of the barrel during the (t-1)th pressure control cycle. When t = 1, Δp t =0;

[0046] Step 3-1-3, Determine Δp t Is it greater than Δp? max The current value, if Δp t Less than or equal to Δp max If the current value is Δp, then... maxIf Δp remains unchanged, its current value remains unchanged. t Greater than Δp max If the current value is Δp, then first set Δp max The value is updated to Δp t Then Δp max Substituting the current value into equation (2) for the proportional term K p Update the value:

[0047]

[0048] Step 3-1-4: Determine the proportional term K p Is the current value greater than (K)? p ) max If the proportional term K p The current value is greater than or equal to (K) p ) max Then update it to (K) p ) max If the proportional term K p The current value is less than (K) p ) min Then update it to (K) p ) min , (K p ) min For the proportional term K p The lower limit value, (K) p ) min The value ranges from 0.5 to 1.0;

[0049] Step 3-1-5: Calculate the pressure error value e for the current pressure control cycle using equation (3). t :

[0050] e t =p s -p t (3)

[0051] Step 3-1-6: Calculate the speed command n for the current pressure control cycle using equation (4). t :

[0052] n t =K p ·e t (4)

[0053] Step 3-1-7, Determine n t Is it greater than or equal to n? s If n t Greater than or equal to n s Then, at this time, the speed command sent by the controller of the all-electric injection molding machine to the motor driver is n. s The current motor driver follows the speed command ns Control the motor to rotate and return to step 3-1-1; if n t Less than n s Then, at this time, the speed command sent by the controller of the all-electric injection molding machine to the motor driver is n. t The current motor driver follows the speed command n t Control the motor to rotate, proceed to step 3-2, and calculate the integral term T using equation (5). i Value:

[0054] T i =K p / 20 (5)

[0055] Step 3-2: Update the value of t by adding 1 to the current value of t, and enter the t-th pressure control cycle;

[0056] Step 3-2-1: Collect the actual pressure of the barrel in the current pressure control cycle using a pressure sensor, and record it as p. t ;

[0057] Step 3-2-2: Calculate the speed command n for the current pressure control cycle using equations (3) and (4). t Determine n t Is it greater than or equal to n? s If n t Greater than or equal to n s Then the speed command sent by the controller of the all-electric injection molding machine to the motor driver is n. s The current motor driver follows the speed command n s Control the motor to rotate; if n t Less than n s Then the speed command sent by the controller of the all-electric injection molding machine to the motor driver is n. t The current motor driver follows the speed command n t Control the motor rotation;

[0058] Step 3-2-3: Determine whether the speed command sent by the controller of the current all-electric injection molding machine to the motor driver is less than n. trans , where n trans The switching speed for transitioning from single-P control to PI control is 50-200 RPM. This is based on the condition that the current controller of the all-electric injection molding machine sends a speed command to the motor driver that is greater than or equal to n. trans If the speed command sent by the controller of the current all-electric injection molding machine to the motor driver is less than n, then return directly to step 3-2; trans Then, the PI-controlled integral accumulator is denoted as I, I is initialized by setting I = 0, and then proceeds to step 3-3;

[0059] Step 3-3: Update the value of t by adding 1 to the current value of t, and enter the t-th pressure control cycle;

[0060] Step 3-3-1: Collect the actual pressure of the barrel during the current pressure control cycle using a pressure sensor, and record it as p. t ;

[0061] Step 3-3-2: Calculate the pressure error value e for the current pressure control cycle using equation (3). t ;

[0062] Step 3-3-3: Add e to the current value of the integrator accumulator I. t The value of the updated integral accumulator I is then updated.

[0063] Step 3-3-4: Calculate the speed command n for the current pressure control cycle using equation (6). t :

[0064] n t =K p ·e t +T i ·I (6)

[0065] Step 3-3-5, Determine n t Is it greater than or equal to n? s If n t Greater than or equal to n s Then, at this time, the speed command sent by the controller of the all-electric injection molding machine to the motor driver is n. s The current motor driver follows the speed command n s Control the motor to rotate; if n t Less than n s Then, at this time, the speed command sent by the controller of the all-electric injection molding machine to the motor driver is n. t The current motor driver follows the speed command n t Control the motor to rotate and return to step 3-3 to enter the next pressure control cycle, repeating this cycle until the injection work of the all-electric injection molding machine is completed.

[0066] In this embodiment, the barrel pressure control method for an all-electric injection molding machine first puts the machine into operation. During operation, the barrel pressure control phase is divided into a PI control parameter acquisition phase, a single-P control phase, and a PI control phase. In the PI control parameter acquisition phase, the actual barrel pressure is periodically acquired to obtain the pressure change and determine the proportional term K. p and integral term T iThese two PI control parameters, in the single-P control stage, use the proportional term from the PI control parameter acquisition stage to control the deceleration process of the injection. Finally, in the PI pressure control stage, the integral term T from the PI control parameter acquisition stage is introduced. i To eliminate static deviations, the injection pressure of the all-electric injection molding machine is stabilized to the set pressure, thereby realizing the automatic setting and regulation of PI control parameters during the operation of the all-electric injection molding machine.

[0067] To verify the effectiveness of the present invention, the barrel pressure of the all-electric injection molding machine was compared between the method used without the present invention (i.e., after setting the default parameters in step 1, no subsequent steps were performed) and the method used with the present invention. The comparison is shown in the figure below. Figure 1 As shown. Analysis Figure 1 It can be seen that: after adopting the barrel pressure control method of the all-electric injection molding machine of the present invention, within the range of set speed 50-350mm / s and set pressure 50-180Mpa, the barrel pressure overshoot of the all-electric injection molding machine is reduced by an average of about 84%, and by a maximum of about 97%.

Claims

1. A method for controlling barrel pressure in an all-electric injection molding machine, characterized in that... Includes the following steps: Step 1: Install a pressure sensor at the end of the barrel of the all-electric injection molding machine to collect barrel pressure. The pressure sensor is connected to the controller of the all-electric injection molding machine. When the all-electric injection molding machine is performing injection, the controller sends a speed command to its motor driver. The motor driver controls the motor to rotate according to the speed command. The ball screw is rigidly connected to the motor, converting the rotational motion of the motor into linear motion, pushing the molten material in the barrel into the mold, forming barrel pressure. Set the deceleration time parameter in the controller of the all-electric injection molding machine. The deceleration time parameter represents the time required for the motor driver to control the motor to decelerate from the maximum speed to 0, denoted as T. d Set the pressure control cycle to T c T c The value ranges from 0.5 to 2.0 ms, and the maximum speed of the motor is denoted as n. max Let the set speed of the melt injection be n. s The set pressure for melt injection is p s n s and p s Based on the actual production process; Step 2: Denote the proportional term of the PI control parameter as K. p , for K p Perform initialization, let K p =(K p ) max , where (K p ) max The upper limit of the proportional term, (K) p ) max The value is 5-10; the maximum change in barrel pressure of the all-electric injection molding machine is denoted as Δp. max For Δp max Perform initialization, let Δp max =0; Set parameters to obtain the pressure control cycle variable, denote it as t, initialize t by setting t=0; Start the all-electric injection molding machine to perform injection; Step 3: Simultaneously enter the barrel pressure control stage of the all-electric injection molding machine, specifically as follows: Step 3-1: Update the value of t by adding 1 to the current value of t, and enter the t-th pressure control cycle. The specific control process is as follows: Step 3-1-1: Collect the actual pressure of the barrel during the current pressure control cycle using a pressure sensor, and record it as p. t ; Step 3-1-2: Calculate the pressure change Δp during the current pressure control cycle using equation (1). t : Δp t =p t -p t-1 (1) Where, p t-1 This represents the actual pressure of the barrel during the (t-1)th pressure control cycle. When t = 1, Δp t =0; Step 3-1-3, Determine Δp t Is it greater than Δp? max The current value, if Δp t Less than or equal to Δp max If the current value is Δp, then... max If Δp remains unchanged, its current value remains unchanged. t Greater than Δp max If the current value is Δp, then first set Δp max The value is updated to Δp t Then Δp max Substituting the current value into equation (2) for the proportional term K p Update the value: Step 3-1-4: Determine the proportional term K p Is the current value greater than (K)? p ) max If the proportional term K p The current value is greater than or equal to (K) p ) max Then update it to (K) p ) max If the proportional term K p The current value is less than (K) p ) min Then update it to (K) p ) min , (K p ) min For the proportional term K p The lower limit value, (K) p ) min The value ranges from 0.5 to 1.0; Step 3-1-5: Calculate the pressure error value e for the current pressure control cycle using equation (3). t : e t =p s -p t (3) Step 3-1-6: Calculate the speed command n for the current pressure control cycle using equation (4). t : n t =K p ·e t (4) Step 3-1-7, Determine n t Is it greater than or equal to n? s If n t Greater than or equal to n s Then, at this time, the speed command sent by the controller of the all-electric injection molding machine to the motor driver is n. s The current motor driver follows the speed command n s Control the motor to rotate and return to step 3-1-1; if n t Less than n s Then, at this time, the speed command sent by the controller of the all-electric injection molding machine to the motor driver is n. t The current motor driver follows the speed command n t Control the motor to rotate, proceed to step 3-2, and calculate the integral term T using equation (5). i Value: T i =K p / 20 (5) Step 3-2: Update the value of t by adding 1 to the current value of t, and enter the t-th pressure control cycle; Step 3-2-1: Collect the actual pressure of the barrel in the current pressure control cycle using a pressure sensor, and record it as p. t ; Step 3-2-2: Calculate the speed command n for the current pressure control cycle using equations (3) and (4). t Determine n t Is it greater than or equal to n? s If n t Greater than or equal to n s Then the speed command sent by the controller of the all-electric injection molding machine to the motor driver is n. s The current motor driver follows the speed command n s Control the motor to rotate; if n t Less than n s Then the speed command sent by the controller of the all-electric injection molding machine to the motor driver is n. t The current motor driver follows the speed command n t Control the motor rotation; Step 3-2-3: Determine whether the speed command sent by the controller of the current all-electric injection molding machine to the motor driver is less than n. trans , where n trans The switching speed for transitioning from single-P control to PI control is 50-200 RPM. This is based on the condition that the current controller of the all-electric injection molding machine sends a speed command to the motor driver that is greater than or equal to n. trans If the speed command sent by the controller of the current all-electric injection molding machine to the motor driver is less than n, then return directly to step 3-2; trans Then, the PI-controlled integral accumulator is denoted as I, I is initialized by setting I = 0, and then proceeds to step 3-3; Step 3-3: Update the value of t by adding 1 to the current value of t, and enter the t-th pressure control cycle; Step 3-3-1: Collect the actual pressure of the barrel during the current pressure control cycle using a pressure sensor, and record it as p. t ; Step 3-3-2: Calculate the pressure error value e for the current pressure control cycle using equation (3). t ; Step 3-3-3: Add e to the current value of the integrator accumulator I. t The value of the updated integral accumulator I is then updated. Step 3-3-4: Calculate the speed command n for the current pressure control cycle using equation (6). t : n t =K p ·e t +T i ·I (6) Step 3-3-5, Determine n t Is it greater than or equal to n? s If n t Greater than or equal to n s Then, at this time, the speed command sent by the controller of the all-electric injection molding machine to the motor driver is n. s The current motor driver follows the speed command n s Control the motor to rotate; if n t Less than n s Then, at this time, the speed command sent by the controller of the all-electric injection molding machine to the motor driver is n. t The current motor driver follows the speed command n t Control the motor to rotate and return to step 3-3 to enter the next pressure control cycle, repeating this cycle until the injection work of the all-electric injection molding machine is completed.

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