TWI735327B - Control method of electric injection-molding machine - Google Patents

Abstract

A control method for an electric injection-molding machine is disclosed. The control method comprises steps of: (S1) sampling a driving current received by an injection motor to obtain a first current value; (S2) calculating an operating current value, wherein the operating current value at least includes the current required for injection motor performing the speed control; (S3) subtracting the first current value from the operating current value to obtain a second current value; (S4) converting the second current value into a thrust given from a plastic injection screw to a feed tube, and converting the thrust into an estimated value which reflects the pressure at a front end of an injection nozzle according to a cross-sectional area of the feed tube.

Description

Control method of all-electric plastic injection molding machine

This case belongs to the field of plastic injection molding machines, especially a control method for an all-electric plastic injection molding machine.

In recent years, as the awareness of environmental protection has gradually received attention, many industrial equipment have undergone great changes, and the evolution of process equipment in the injection molding industry has become an obvious example. The general hydraulic equipment in the past has been converted to a more environmentally friendly concept. Of all-electric equipment. As the name suggests, the power system of the all-electric plastic injection molding machine is driven by electric motors, which means that the original hydraulic or pneumatic cylinders are replaced by servo motors or induction motors. The all-electric plastic injection molding machine has the characteristics of fast, accurate, stable, quiet, power saving, and clean, which can be called a revolutionary milestone for the plastic injection molding machine. Therefore, the application market of all-electric plastic injection molding machines is quite extensive, from general industrial products (for example, silicone products, PET containers, auto parts, cosmetic containers, household containers, precision gears, etc.), Furthermore, with the advantages of fast, stable and quiet all-electric plastic injection molding machine, it is applied to the precision injection market (for example, semiconductor components, information computer products, optical lenses, liquid crystal light guide plates, IC cards, electronic material components... etc.) , Seems to be all-encompassing. At present, in the operation process of the all-electric plastic injection molding machine, the pressure-holding phase of the plastic injection and the material storage metering phase need to be applied to the load cell belonging to the pressure sensor, namely The all-electric plastic injection molding machine uses the load cell to sense the pressure when the plastic is pushed out by the barrel, and adjust the control strategy accordingly based on the pressure sensing value returned by the load cell.

However, since the all-electric plastic injection molding machine usually requires more than 4 high-wattage servo drives and servo motors, the cost pressure is very high, so reducing the cost is a very important part of the all-electric plastic injection molding machine. At present, some companies are considering removing the load cell to achieve cost savings. However, how to make the all-electric plastic injection molding machine without the load cell still have good pressure control to maintain the injection effect is the current research and development focus.

The purpose of this case is to provide a control method for an all-electric plastic injection molding machine, so that the all-electric plastic injection molding machine does not require a load element and saves production costs while maintaining a good injection effect.

In order to achieve the above purpose, one of the broader implementation aspects of this case is to provide a control method which is applied to an all-electric plastic injection molding machine. The all-electric plastic injection molding machine includes an injection motor, a reduction mechanism, an injection screw, and a barrel. And the nozzle, the reduction mechanism uses the reduction ratio to increase the torque of the injection motor. The injection screw is driven by the torque output from the injection motor through the reduction mechanism to rotate and move, thereby pushing the barrel to turn the plastic in the barrel into The glue is melted and ejected from the nozzle. The control method includes: S1 samples the drive current received by the plastic injection motor when the all-electric plastic injection molding machine is operating to obtain the first current value; S2 calculates the operating current value, where the operation The current value includes at least the current required for the speed control of the rubber injection motor; S3 subtracts the operating current value from the first current value to obtain the second current value; and S4 converts the second current value into the injection screw to feed the barrel According to the cross-sectional area of the material pipe, the thrust is converted into an estimated value of the pressure at the front end of the reverse mapping nozzle.

1: All-electric plastic injection molding machine

10: Motor driver

11: Injection motor

12: Deceleration mechanism

13: Injection screw

14: Material pipe

15: Shooting mouth

i: drive current

S1~S4: Steps of the control method

Figure 1 is a step flow diagram of the control method of the all-electric plastic injection molding machine according to the first preferred embodiment of the present invention; Figure 2 is the all-electric plastic injection molding machine used in the control method described in Figure 1 Schematic diagram of simple component structure; Figure 3 is the traditional all-electric plastic injection molding machine using the load cell to sense the tip pressure of the nozzle, and the all-electric plastic injection molding machine in this case uses the control method shown in Figure 1 A schematic diagram of the comparison between the estimated front end pressure of the nozzle; Figure 4 is a schematic diagram of the step flow diagram of the control method of the all-electric plastic injection molding machine according to the second preferred embodiment of this project; Figure 5 is This is the front end pressure of the nozzle sensed by the traditional all-electric plastic injection molding machine using the load cell, and the front end of the nozzle estimated by the all-electric plastic injection molding machine in this case using the control method shown in Figure 4 Comparison diagram between the two pressures; Figure 6 is a schematic diagram of the relationship between the damping force applied to the injection motor of the all-electric plastic injection molding machine in operation and the rotation speed of the injection motor; Figure 7 is the case Schematic diagram of the relationship between the dynamic friction applied by the injection motor of the all-electric plastic injection molding machine and the rotation speed of the injection motor; Figure 8 is a traditional all-electric plastic injection molding machine with a load cell for 200 molds Schematic diagram of the relationship between mold number and weight during the injection molding experiment; Figure 9 is a schematic diagram of the relationship between the number of molds and the weight of the all-electric plastic injection molding machine shown in Figure 2 when the control method shown in Figure 4 is used and the 200-mold injection molding experiment is performed.

Some typical embodiments embodying the features and advantages of this case will be described in detail in the following description. It should be understood that the case can have various changes in different aspects, which do not depart from the scope of the case, and the descriptions and diagrams therein are essentially for illustrative purposes, rather than being constructed to limit the case.

Please refer to Figure 1 and Figure 2. Figure 1 is a schematic diagram of the step flow diagram of the control method of the all-electric plastic injection molding machine according to the first preferred embodiment of the present invention. Figure 2 is the control method described in Figure 1 A schematic diagram of the simple component structure of the all-electric plastic injection molding machine used. As shown in Figures 1 and 2, the control method of this embodiment can be applied to the all-electric plastic injection molding machine 1, and can be operated in the all-electric plastic injection molding machine 1 during the injection stage and storage metering, respectively. The structure and operation of the all-electric plastic injection molding machine 1 are similar to those of the generally widely used all-electric plastic injection molding machine 1. The only difference is that the all-electric plastic injection molding machine uses the control method of this embodiment. The injection molding machine 1 does not need to have a load element. Therefore, in Figure 2, only some component structures of the all-electric plastic injection molding machine 1 that are related to the control method of this embodiment are marked, and the all-electric plastic is not marked. The detailed structure and overall operation of the injection molding machine 1 are described.

In this embodiment, the all-electric plastic injection molding machine 1 mainly includes a motor driver 10, an injection motor 11, a speed reduction mechanism 12, an injection screw 13, a barrel 14 and an injection nozzle 15. The motor driver 10 is used to provide a driving current i to drive the injection motor 11 to operate, and is based on the all-electric plastic injection molding machine 1’s internal detection elements (not shown) in a feedback manner regarding the all-electric plastic injection molding The operating parameters of the machine 1, such as the driving current i, etc., are adjusted accordingly. The deceleration mechanism 12 is connected to the glue injection motor 11 and has A reduction ratio. The reduction mechanism 12 can use the reduction ratio to reduce the speed of the rubber injection motor 11 but increase the torque. The material tube 14 is connected with the nozzle 15 and can be filled with plastic. The injection screw 13 is connected with the speed reduction mechanism 12 and the material pipe 14. The injection screw 13 can be driven by the torque output from the injection motor 11 through the reduction mechanism 12 to move back and forth, and then push the plastic in the material pipe 14 to be melted into melt. After the glue is glued, the molten glue is injected from the nozzle 15 connected to the barrel 14 to the mold (not shown) in a moving manner.

The control method of this embodiment can be executed by the motor driver 10. The principle of the control method is mainly because the feedback value of the driving current i received by the glue injection motor 11 contains a lot of information, one of which is the injection The pressure at the front end of the nozzle 15 is traditionally detected by the load cell. In order to save the cost of the all-electric plastic injection molding machine 1 by removing the load cell, the control method of this embodiment is based on The driving current i received by the injection motor 11 separates the front end pressure of the injection nozzle 15 so that the operation of the all-electric plastic injection molding machine 1 can be adjusted correspondingly according to the front end pressure of the separated injection nozzle 15.

Therefore, in the control method of this embodiment, step S1 is implemented first. When the all-electric plastic injection molding machine 1 is operating, the driving current i received by the injection motor 11 is sampled by feedback to obtain the first current value.

Then, step S2 is executed to calculate and obtain an operating current value, where the operating current value at least includes the current required for controlling the rotational speed of the glue injection motor 11. In the driving current i received by the injection motor 11, the current component that accounts for the largest proportion is the current required for the injection motor 11 to accelerate or decelerate. In order to accurately estimate the pressure at the front end of the injection nozzle 15, it is necessary The current required to accelerate or decelerate the glue injection motor 11 is preferentially excluded from the driving current i. Therefore, in step S2, the rotation speed, such as acceleration, of the glue injection motor 11 is used to calculate the acceleration or deceleration of the glue injection motor 11 Or the electricity needed to decelerate Flow where. The unit of the rotation speed of the glue injection motor 11 is rad/sec. Next, step S3 is executed to subtract the operating current value from the first current value to obtain the second current value.

It can be seen from the above that the component of the second current value actually excludes the current required by the glue injection motor 11 to accelerate or decelerate, so the second current value can more accurately reflect the pressure at the front end of the nozzle 15. However, in this embodiment The subsequent step of the control method of step S3 is how to estimate the pressure at the front end of the nozzle 15 from the second current value. Therefore, after step S3 is executed, step S4 is executed, and the second current value is converted into a thrust given by the injection screw 13 to the barrel 14, and the thrust is converted into the anti-mapping nozzle 15 according to the cross-sectional area of the barrel 14. Estimated front-end pressure. Since the material tube 14 is connected to the injection nozzle 15, the plastic injection screw 13 can push the plastic in the material tube 14 to be melted into melt and then be injected from the injection nozzle 15 to the mold. Therefore, in step S4, according to the injection screw 13 Given the thrust of the material tube 14 and the cross-sectional area of the material tube 14, the estimated value of the pressure at the front end of the nozzle 15 can be obtained.

In the above embodiment, in step S2, the position of the glue injection motor 11 can be sampled by an encoder (not shown), etc., and the acceleration and deceleration α of the glue injection motor 11 can be calculated according to the position. In addition, multiplying the acceleration and deceleration α of the injection motor 11 by the overall inertia J of the injection screw 13 driven by the injection motor 11 can obtain the torque T _acc required for the acceleration and deceleration of the injection motor 11, as shown in the following equation (1) : T _acc =J* α ...(1).

再結合方程式(1)及(2)，可得方程式(3)如下，即藉由方程式(3)將加速度換算成射膠馬達11進行加減速時所需要的電流：

其中針對前述之扭力常數Kt，其數值可由射膠馬達11對應的規格書得知，且其數值接近常數而可直接視為常數。而針對射膠馬達11帶動射膠螺桿13的整體慣量J，由於全電式塑膠射出成型機1運轉前，都會進行慣量估測的動作，包含射膠馬達11的部分，而慣量估測的法則寫在伺服驅動器裡，其中慣量估測是透過已知的射膠馬達11的轉動慣量(可由射膠馬達11的規格書得知，數值為常數)，針對射膠馬達11帶動的整個機構去估測射膠馬達11與帶載端的慣量比，包含減速機構12的轉動慣量及射膠螺桿13的轉動慣量，所以慣量估測可測出射膠馬達11的慣量，進而可以求出射膠馬達11帶動射膠螺桿13的整體慣量J，因此射膠馬達11帶動射膠螺桿13的整體慣量J的求得方法已常見於業界，於此不再贅述。 The torque T _acc required for the acceleration and deceleration of the rubber injection motor 11 mentioned in equation (1) _{can be used to calculate the current I acc} required by the injection motor 11 for acceleration and deceleration through the torque constant Kt of the rubber injection motor 11 , As shown in the following equation (2):

Combining equations (1) and (2), equation (3) can be obtained as follows, that is, through equation (3), the acceleration is converted into the current required for the acceleration and deceleration of the rubber injection motor 11:

For the aforementioned torque constant Kt, its value can be known from the specifications corresponding to the glue injection motor 11, and its value is close to a constant and can be directly regarded as a constant. As for the overall inertia J of the injection screw 13 driven by the injection motor 11, since the all-electric plastic injection molding machine 1 will perform the inertia estimation action before the operation, including the injection motor 11, the law of inertia estimation It is written in the servo drive, where the inertia estimation is based on the known moment of inertia of the glue injection motor 11 (it can be known from the specification of the glue injection motor 11, the value is a constant), and it is estimated for the entire mechanism driven by the glue injection motor 11. The ratio of inertia between the injection motor 11 and the loaded end includes the moment of inertia of the speed reduction mechanism 12 and the rotational inertia of the injection screw 13, so the inertia estimation can measure the inertia of the injection motor 11, and then the injection motor 11 can be obtained. Drives the overall inertia J of the rubber injection screw 13, so the method for obtaining the overall inertia J of the rubber injection screw 13 driven by the injection motor 11 is common in the industry, and will not be repeated here.

In addition, in step S4, equation (1) and the following equations (4)-(6) are used to derive equation (7), so as to use equation (7) to convert the second current value, I _f , to The injection screw 13 gives the thrust of the barrel 14, where the equations (4)-(7) are as follows: I _f = I _m - I _acc ... (4)

F = α ₁ × I _f × Kt ... (5)

其中I _m 為為射膠馬達11運作時的電流，可由伺服驅動器內之電流感測器(未圖示)求得，I _acc 為射膠馬達11進行加減速所需要的電流，F為射膠螺桿13給予料管14的推力，單位為Kg，α ₁為將射膠馬達11施加在射膠螺桿13的扭矩轉換為推力的既有方程式，e為射膠螺桿13將扭力轉換成推力的轉換效率，R為減速機構12之減速比，P為射膠螺桿13的導程，單位為mm。其中射膠螺桿13的導程、減 速機構12之減速比及導螺桿效率皆可從全電式塑膠射出成型機1的規格書及射膠馬達11規格書預先得知。

Where I _m is the current when the glue injection motor 11 is operating, which can be obtained from the current sensor (not shown) in the servo driver, I _acc is the current required for the glue injection motor 11 to accelerate and decelerate, and F is the glue injection motor 11 The thrust given by the screw 13 to the barrel 14 is in Kg, α ₁ is the existing equation that converts the torque applied by the injection motor 11 to the injection screw 13 into thrust, and e is the conversion of the injection screw 13 from torque into thrust. Efficiency, R is the reduction ratio of the speed reduction mechanism 12, P is the lead of the injection screw 13 in mm. The lead of the injection screw 13, the reduction ratio of the reduction mechanism 12 and the efficiency of the lead screw can all be known in advance from the specifications of the all-electric plastic injection molding machine 1 and the injection motor 11.

其中P0為射嘴15前端壓力之推估值，r為料管14截面積的半徑。 In step S4, the following equation (8) is used to convert the thrust F into an estimated value of the pressure at the front end of the reverse mapping nozzle 15:

Where P0 is the estimated pressure of the front end of the nozzle 15 and r is the radius of the cross-sectional area of the material tube 14.

In addition, in some embodiments, in step S4, after converting the thrust F into an estimated value of the pressure at the front end of the anti-mapping nozzle 15, low-pass filtering may be performed, wherein the cut-off frequency of the low-pass filtering is set to 5~ 20hz, and the main purpose of low-pass filtering is to simulate the delay time from the output of the glue injection motor 11 to the front end pressure of the injection nozzle 15.

Please refer to Figure 3, which is the traditional all-electric plastic injection molding machine using the load cell to sense the tip pressure of the nozzle, and the all-electric plastic injection molding machine in this case uses the control method shown in Figure 1. A schematic diagram of the comparison between the estimated tip pressure of the nozzle. As shown in the figure, the line with a relatively dark color represents the front end pressure of the nozzle sensed by the traditional all-electric plastic injection molding machine using a load cell, which is marked as a in the figure, and the line with a relatively light color represents the whole of the case. The estimated value of the tip pressure of the nozzle 15 estimated by the electric plastic injection molding machine using the control method shown in Figure 1, that is, the estimated value of the tip pressure of the nozzle obtained in step S4, is shown in the figure The middle mark is b, and the dashed box I indicates that the all-electric plastic injection molding machine is operating in the injection and pressure holding stage, and the dashed box II indicates that the all-electric plastic injection molding machine is operating in the material storage and measurement stage. It can be seen from Figure 3 that because the waveform of line b in virtual frame I and virtual frame II is actually close to the waveform of line a, it represents the nozzle estimated by the control method of the first preferred embodiment of this case The estimated value of the front-end pressure of 15 can indeed reflect the front-end pressure of the nozzle sensed by the traditional all-electric plastic injection molding machine using the load cell. Therefore, the all-electric plastic of the control method of the first preferred embodiment of this case is used. Injection molding machine 1 Therefore, the cost can be saved without using the load element, and at the same time, the estimated pressure of the front end of the nozzle 15 can be used to perform corresponding control to maintain a good injection effect.

However, because there is still a large offset between the line a and the line b in the virtual box II in Figure 3, in order to more accurately estimate the tip pressure of the nozzle 15, the first part of this case is The control method of the second preferred embodiment will further eliminate the influence of the damping force and dynamic friction force applied when the glue injection motor 11 is running from the driving current i (in order to simplify the calculation formula of the control method of the second embodiment, the second embodiment of this case The control method of the embodiment ignores the static friction force, regards the dynamic friction force as a fixed force, and regards the damping force as a linear force related to the rotational speed of the glue injection motor 11), which will be described below.

Please refer to Figures 4 and 5. Figure 4 is a schematic diagram of the step flow diagram of the control method of the all-electric plastic injection molding machine according to the second preferred embodiment of the present invention. Figure 5 is the traditional all-electric plastic injection Comparison between the nozzle tip pressure sensed by the molding machine using the load cell and the nozzle tip pressure estimated by the all-electric plastic injection molding machine in this case using the control method shown in Figure 4 Schematic. As shown in the figure, the control method of this embodiment is similar to the control method shown in Figure 1. However, in the control method of this embodiment, in step S2, the operating current value except for the injection motor 11 is required for speed control. In addition to the current, it also includes the current corresponding to the damping force applied when the glue injection motor 11 is running, and the current corresponding to the dynamic friction force applied when the motor 10 is running. Therefore, when step S3 is performed to subtract the operating current value from the first current value to obtain the second current value, the second current value has excluded the current required for the acceleration or deceleration of the glue injection motor 11, and when the glue injection motor 11 is running The current corresponding to the applied damping force and the current corresponding to the dynamic friction force applied when the motor 10 is running.

Please refer to Figure 5 again, where the relatively darker line represents the pressure at the front end of the nozzle sensed by the traditional all-electric plastic injection molding machine using the load cell, which is marked as a in the figure, and the relatively lighter line represents The all-electric plastic injection molding machine in this case uses the control method shown in Figure 4 to estimate the tip pressure of the nozzle 15, that is, the estimated value of the tip pressure of the nozzle 15 obtained in step S4. The middle mark is b, and the dashed frame I means that the all-electric plastic injection molding machine is operating in the injection and pressure holding stage, and the dashed frame II It means that the all-electric plastic injection molding machine is operating at the stage of material storage and measurement. It can be seen from Figure 5 that whether it is in virtual box I or virtual box II, the wave type of line b is actually close to the wave type of line a, and the offset value (offset) between line a and line b has been It is very small, so it represents that the estimated value of the tip pressure of the nozzle 15 estimated by the control method of the second preferred embodiment of this case can more accurately reflect the traditional all-electricity control method compared with the control method of the first preferred embodiment The type plastic injection molding machine uses the load cell to sense the front end pressure of the nozzle.

I _k =I ₁-μ _d*V₁...(10)；I _d =μ _d*V...(11)；其中μ _d 為阻尼系數(即單位速度下時，所需要的電流)，V ₂為射膠馬達11運行的第一種轉速，V ₁為射膠馬達11運行的第二種轉速，I ₂為射膠馬達11運行在第一種轉速所需電流，I ₁為射膠馬達11運行在第二種轉速所需電流，I _k 為射膠馬達11克服 動摩擦力所需電流，V為射膠馬達11運行的轉速，I _d 為射膠馬達11在轉速V時克服阻尼力所需電流。請參閱第8圖及第9圖及下述表一及表二，其中第8圖為具荷重元之傳統全電式塑膠射出成型機進行200模的射出成型實驗時，模次與重量的關係示意圖，第9圖為第2圖所示之全電式塑膠射出成型機在使用第4圖所示之控制方法下，且進行200模的射出成型實驗時，模次與重量的關係示意圖，表一為對應第8圖之實驗數據表，表二為對應第9圖之實驗數據表。由第8圖、第9圖、表一及表二所示可知，當具荷重元之傳統全電式塑膠射出成型機進行200模的射出成型運作時，在各模次階段，CV值(變異係數值)約千分之九左右，而使用第4圖所示之控制方法之全電式塑膠射出成型機在進行200模的射出成型運作時，在各模次階端下，CV值(變異係數值)同樣皆約千分之九左右，與具荷重元之傳統全電式塑膠射出成型機並無太大差異，於此可證明本案第二較佳實施例之控制方法確實可準確地反映傳統全電式塑膠射出成型機利用荷重元感測到之射嘴的前端壓力。 Please refer to Figures 6 and 7. Figure 6 is a schematic diagram of the relationship between the damping force applied to the injection motor of the all-electric plastic injection molding machine in operation and the rotation speed of the injection motor. Figure 7 This is a schematic diagram of the relationship between the dynamic friction force applied to the injection motor of the all-electric plastic injection molding machine in operation and the rotation speed of the injection motor. As shown in the figure, in step S2 of the control method of the second embodiment, since the damping force applied when the glue injection motor 11 is running is actually proportional to the rotation speed of the glue injection motor 11, when the encoder is used After sampling the rotation speed of the glue injection motor 11, the damping force applied when the glue injection motor 11 is running can be deduced, and then the corresponding current value can be converted according to the damping force. Similarly, the dynamic friction force applied when the glue injection motor 11 is running is actually related to the rotation speed of the glue injection motor 11. Therefore, the rotation speed of the glue injection motor 11 can be deduced by sampling the rotation speed of the glue injection motor 11 by an encoder. The dynamic friction force applied by the glue injection motor 11 during operation can be converted into the corresponding current value according to the dynamic friction force. To further explain, in order to convert the corresponding current value according to the damping force and convert the corresponding current value according to the dynamic friction force, the injection motor 11 can be operated at two different speeds without any plastic in the barrel 14. To obtain the current required by the rubber injection motor 11 to overcome the damping force and dynamic friction force, and to obtain the current required to overcome the damping force and dynamic friction force, the following equations (9)-(11) can be used:

I _k = I ₁ - μ _d *V ₁ ...(10); I _d = μ _d *V...(11); where μ _d is the damping coefficient (that is, the current required at unit speed) , V ₂ is the first rotation speed of the rubber injection motor 11, V ₁ is the second rotation speed of the rubber injection motor 11, I ₂ is the current required for the rubber injection motor 11 to run at the first rotation speed, and I ₁ is the injection motor 11 The current required for the glue motor 11 to run at the second rotation speed, I _k is the current required for the glue injection motor 11 to overcome the dynamic friction, V is the rotation speed of the glue injection motor 11, and I _d is the glue injection motor 11 to overcome the damping at the rotation speed V Current required for force. Please refer to Figures 8 and 9 and Tables 1 and 2 below. Figure 8 shows the relationship between the number of molds and the weight of a conventional all-electric plastic injection molding machine with a load cell for a 200-mold injection molding experiment. Schematic diagram, Figure 9 is a schematic diagram of the relationship between the number of molds and the weight when the all-electric plastic injection molding machine shown in Figure 2 uses the control method shown in Figure 4 and performs an injection molding experiment of 200 molds. One is the experimental data table corresponding to Figure 8, and Table two is the experimental data table corresponding to Figure 9. As shown in Fig. 8, Fig. 9, Table 1 and Table 2, when a traditional all-electric plastic injection molding machine with a load element performs injection molding operations of 200 molds, the CV value (variation Coefficient value) is about 9/1000, and the all-electric plastic injection molding machine using the control method shown in Figure 4 is in the injection molding operation of 200 molds, at the end of each mold order, the CV value (variation The coefficient value) is also about 9/1000, which is not much different from the traditional all-electric plastic injection molding machine with load element. It can be proved that the control method of the second preferred embodiment of this case can indeed accurately reflect The traditional all-electric plastic injection molding machine uses the front end pressure of the nozzle sensed by the load cell.

In summary, this case provides a control method for an all-electric plastic injection molding machine, which can use the existing operating parameters of the all-electric plastic injection molding machine to accurately estimate the pressure at the front end of the nozzle, so that the control method can be used The all-electric plastic injection molding machine not only saves costs without having to install load cells, but also maintains a good injection effect.

S1~S4: Steps of the control method

Claims (6)

A control method for estimating the pressure at the front end of a nozzle is applied to an all-electric plastic injection molding machine. The all-electric plastic injection molding machine includes an injection motor, a reduction mechanism, an injection screw, and a barrel And the nozzle, the reduction mechanism is used to increase the torque of the injection motor, and the injection screw is driven by the torque output by the injection motor through the reduction mechanism to move, thereby pushing the barrel in the barrel The plastic is turned into melted glue and ejected from the nozzle. The control method includes: S1 when the all-electric plastic injection molding machine is operating, sampling a drive current received by the plastic injection motor to obtain a first current value S2 calculates and obtains an operating current value, where the operating current value includes at least the current required for the speed control of the rubber injection motor; S3 subtracts the operating current value from the first current value to obtain a second current Value; and S4 converts the second current value into a thrust given by the injection screw to the barrel, and converts the thrust into an estimated value reflecting the pressure at the front end of the nozzle according to a cross-sectional area of the barrel . The control method according to claim 1, wherein in step S2, a position of the glue injection motor is sampled, and an acceleration and deceleration of the glue injection motor is calculated according to the position, and then equations (1), ( 2), (3) Convert the acceleration and deceleration into the current required for the speed control of the rubber injection motor, where the equations (1), (2), (3) are as follows: T _acc =J* α ...( 1);

Where T _acc is the torque required for acceleration and deceleration of the injection motor, J is the overall inertia of the injection motor driving the injection screw, α is the acceleration and deceleration of _{the injection motor, and I acc is} the acceleration and deceleration of the injection motor. The required current, Kt, is the torque constant of the rubber injection motor. The control method according to claim 1, wherein in step S4, after converting the thrust into the estimated value reflecting the pressure at the front end of the nozzle, low-pass filtering is performed on the estimated value. The control method according to claim 3, wherein the cut-off frequency of the low-pass filter is set to 5-20hz. The control method according to claim 1, wherein in the step S2, the operating current value further includes the current corresponding to a damping force applied to the glue injection motor during operation, and the current corresponding to the damping force applied during the operation of the glue injection motor. Apply a current corresponding to a dynamic friction force. The control method according to claim 1, wherein the control method is respectively executed when the all-electric plastic injection molding machine is operated in an injection pressure holding stage and a material storage metering stage.

Images