Power consumption calculation device and method for use with an injection molding machine

Abstract

Power consumption calculation device used for an injection molding machine (1), wherein a cycle of an injection molding process of the injection molding machine (1) has a plurality of predetermined processes, and wherein the power consumption calculation device comprises the following: an input part that is capable of entering a form condition for one or more of the predetermined processes; a memory section (262) that is able to store for each of the predetermined processes an approximation expression suitable for calculating the power consumption for the predetermined process in question, when the injection molding machine (1) is operated under the molding condition for the relevant predetermined process, which was entered by the input part; a power consumption calculation part (261) that is capable of calculating the power consumption in one or more of the plurality of predetermined processes included in the cycle of an injection molding process of the injection molding machine (1) using the approximation expression stored in the memory part (262), based on the molding condition entered by the input part; and a calculation part for the optimal shape condition, which calculates a shape condition under which the power consumption assumes a predetermined value or a minimum value subject to a restriction that a shaped item fulfills a predetermined, corresponding item condition.

Description

TECHNICAL AREA

[0001] The present invention relates to a power consumption calculation device and a method for use in an injection molding machine. BACKGROUND OF THE TECHNOLOGY

[0002] Typically, an injection molding process includes a mold closing process to close the molds; a mold clamping process to clamp the molds together; and a nozzle assembly or...A nozzle contact process to position the nozzle on the sprue of the molds; an injection process to move the screw in a cylinder to inject the molten resin, stored in the front part of the screw, into a mold cavity; a holding process to maintain holding pressure subsequently for a period of time to prevent the formation of air bubbles and sink marks; a plasticizing / metering process and a cooling process to melt the resin and store the molten resin in the front part of the cylinder by rotating the screw to prepare for the subsequent cycle, utilizing the time it takes for the molten resin being filled into the cavity to cool and harden; a mold opening process to open the molds; and a mold ejection process to push out the molded part using the ejector pins provided in the mold.

[0003] The electrical power consumed in a motorized injection molding machine includes the power for a heating device surrounding a heating cylinder to melt resin, as well as the power consumption of various electric motors. These electric motors include, for example, an injection motor, a screw motor, a mold opening / closing motor, an ejector motor, and so on.

[0004] JP 2007-83432 A discloses a control device for an injection molding machine for detecting power consumption during operation and for displaying a power consumption indicator. The disclosed control device comprises a detection section for detecting power consumption during operation and an electrical energy calculation section that calculates the electrical energy during an arbitrarily specified detection period based on the detected power consumption. The disclosed control device determines predetermined conversion information, such as information on carbon dioxide emissions, electrical power rates, etc., based on the calculated electrical energy and then displays the conversion information along with the electrical energy.

[0005] However, the actual shape condition can change in many ways, and consequently, actually measuring electrical energy on a shape condition basis is not efficient, requiring a lot of effort in terms of both time and resources.

[0006] JUNGE, Mark: Simulation-based development and optimization of an energy-efficient production control system, Vol. 1, Production & Energy, Kassel; Kassel University Press, 2007, ISBN: 978-3-89958-301-9, pages 56-62, 74, 76 and 92-93 discloses some model approaches for the manufacturing process of plastic injection molding and served as the basis for the preamble of claims 1 and 4.

[0007] Furthermore, with regard to the state of the art, reference is made to AT 401 116 B, DE 102 47 565 A1, DE 30 43 369 A1 and DE 10 2006 031 268 A1. SUMMARY OF THE INVENTION

[0008] Therefore, an objective of the present invention is to provide a power consumption calculation device and method that can be used for an injection molding machine and that can predict the power consumption of the injection molding machine according to a molding condition.

[0009] To achieve the above-mentioned objective, a power consumption calculation device as defined in claim 1 is provided according to a first aspect of the present invention.

[0010] Furthermore, according to another aspect of the present invention, a power consumption calculation method for an injection molding machine is provided, as defined in claim 5.

[0011] According to the present invention, a power consumption calculation device and a method, which can be used for an injection molding machine and which can predict the power consumption of the injection molding machine according to a mold condition, can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a diagram illustrating an example of a main configuration of an injection molding machine 1 to which a power consumption calculation device according to an embodiment of the present invention is applied; Fig. 2 is a function diagram for representing a main functional part belonging to a power consumption calculation function of a control device 26; Fig. Figure 3 is a flowchart illustrating an example of a main process of a power consumption calculation method, which is executed by a control device 26; Fig.Figure 4 is a function diagram for representing a main functional part belonging to a form condition calculation function of the control device 26; and Fig. Figure 5 is a flowchart illustrating an example of a main process of a method for calculating the optimal shape condition by a control device 26.

[0012] A preferred embodiment of the present invention is described in detail below with reference to the accompanying drawings.

[0013] Fig. Figure 1 is a diagram illustrating an example of a main configuration of an injection molding machine 1 to which a power consumption calculation device according to an embodiment of the present invention is applied.

[0014] The injection molding machine 1, which in the illustrated example is a motor-driven injection molding machine, includes a servo motor for injection 11. The rotation of the servo motor for injection 11 is transmitted to a ball screw 12. A nut 13, which is moved forward and backward by the rotation of the ball screw 12, is attached to a pressure plate 14. The pressure plate 14 is configured to be movable along guide columns 15 and 16, which are attached to a base frame (not shown). The forward and backward movement of the pressure plate 14 is transmitted to a screw 20 via a bearing 17, a load cell 18, and an injection shaft 20. The screw 20 is mounted in a heating cylinder 21 in such a way that it can rotate and move axially within the heating cylinder 21.A feed device 22 for supplying a resin is provided in a rear part of the heating cylinder 21. The rotary motion of a servo motor for screw rotation 23 is transmitted to the injection shaft 19 via a coupling element 24, such as a belt, a pulley, etc. In other words, the screw 20 is rotated when the injection shaft 19 is driven to rotate the servo motor for screw rotation 24.

[0015] In a plasticizing / dosing process, the screw 20 is rotated and moved forward and backward in the heating cylinder 21, causing the molten resin to be stored in the front part of the screw 20, i.e., on one side of a nozzle 21-1 of the heating cylinder 21. In an injection process, molds (molded parts) are filled with the molten resin stored in the front part of the screw 20, and the molding is carried out by applying pressure. At this point, a force pressing the resin is detected by the force sensor 18 as a reaction force. In other words, the resin pressure in the front part of the screw 20 is detected. The signal representing the detected pressure is amplified by a force sensor amplifier 25 and fed into a control device 26, which acts as a control element.Furthermore, in a holding process, the pressure of the resin that is filled into the mold is maintained at a predetermined pressure.

[0016] A position detector 27 for detecting the amount of movement of the screw 20 is attached to the pressure plate 14. The detection signal of the position detector 27 is amplified by a force cell amplifier 28 and fed into the control device 26. This detection signal can be used to detect the speed of movement of the screw 20.

[0017] Servomotors 11 and 24 are equipped with encoders 31 and 32, respectively, for detecting the number of revolutions. The number of revolutions detected by encoders 31 and 32 is entered into the control device 26.

[0018] A servomotor 42 is provided to open and close the molds, and a servomotor 44 is provided to eject a molded part. The servomotor 42 drives a toggle lever or changeover switch (not shown), for example, to implement mold opening / closing. Furthermore, the servomotor 44 moves an ejector rod (not shown) via a ball screw mechanism, for example, to implement ejection of the molded part. The servomotors 42 and 44 are equipped with encoders 43 and 45, respectively, for detecting the number of revolutions. The number of revolutions detected by the encoders 43 and 45 is input into the control device 26.

[0019] The control device 26, for example, mainly comprises a CPU, a ROM in which the control programs are stored, a RAM in which the calculation results are stored, a timer, a counter, an input interface, an output interface, etc.

[0020] The control device 26 transmits the current (torque) instructions to the servo motors 11, 24, 42, and 44 according to the respective processes. For example, the control device 26 controls the number of revolutions of servo motor 24 to implement the plasticizing / dosing process. Furthermore, the control device 26 controls the number of revolutions of servo motor 11 to implement the injection and holding processes. The control device 26 also controls the number of revolutions of servo motor 42 to implement the mold opening and closing processes. Finally, the control device 26 controls the number of revolutions of servo motor 44 to implement the mold ejection process.

[0021] A user interface 35 comprises an input setting section with which the mold conditions for the corresponding processes, such as a mold opening / closing process, an injection process, etc., can be set. Furthermore, the user interface 35 comprises an input section with which the mold conditions required to calculate the power consumption, as described below, for the corresponding processes, such as a mold opening / closing process, an injection process, etc., can be entered. Finally, the user interface 35 comprises an input section with which a user enters the various instructions and an output section (for example, a display section) that is configured to output the various elements of the information.

[0022] Typically, a cycle of the injection molding process in the injection molding machine 1 comprises a mold closing process to close the molds; a mold clamping process to clamp the molds together; a nozzle contact process to bring a nozzle (not shown) onto a sprue (not shown) of the molds; an injection process to move the screw 20 in the heating cylinder 21 to inject the molten resin, which is stored in the front part of the screw, into a mold cavity (not shown); and a holding process to maintain a holding pressure subsequently for a period of time to prevent the formation of air bubbles and sink marks.a plasticizing / dosing process and a cooling process for melting the resin and storing the molten resin in the front part of the heating cylinder 21 by rotating the screw 20 to prepare the next cycle, utilizing the time until the molten resin filled into the mold cavity has cooled to harden; a mold opening process for opening the molds; and a mold ejection process for pushing out the molded part with the ejector pins (not shown) provided in the mold.

[0023] In the exemplary embodiment, the control device 26 includes a power consumption calculation function that calculates the power consumption due to the operation of the injection molding machine 1 in a predictive manner.

[0024] Fig.Figure 2 is a function diagram illustrating a main functional part belonging to the power consumption calculation function of the control device 26.

[0025] The control device 26 comprises a power consumption calculation part 261 and an approximation expression memory part 262. The power consumption calculation part 261 is implemented by a CPU of the control device 26, which calculates the approximation expression stored in the approximation expression memory part 262, using the input form conditions as input parameters. The approximation expression memory part 262 can be implemented by a ROM memory of the control device 26.

[0026] The power consumption calculation part 261 calculates in a predictive manner the power consumption due to the operation of the injection molding machine 1 by calculating the approximation expression stored in the approximation expression memory part 262 and using the mold conditions as input parameters entered via the user interface 35.

[0027] Here, an example of the approximation expression, which is stored in the approximation expression memory part 262, is described.

[0028] Initially, parameters of the form condition (e.g., input parameters) are given, for example, as follows. T cycle time T M-OC Mold opening / closing time T ME Dosage time T CA Form clamping time F CA Form clamping force S M-OC Mold opening / closing stroke V M-OC Mold opening / closing speed S S Fill quantity V S Injection speed V ME Screw speed 20 in the dosing process P HP Holding pressure T HP Holding time

[0029] The power consumption W M-OC The following approximation expression is used to calculate the result in the mold opening / closing process. WM−OC=a1⋅SM−OC+a2⋅VM−OC+a0 a1, a2, and a0 are predetermined coefficients and can be adjusted by multiple regression analysis. Consequently, the motor power consumption W1 of the servomotor 42 in one cycle of the mold opening / closing process is calculated as follows: W1=WM−OC×TM−OC / T

[0030] The power consumption W S The following approximation expression is used to calculate the opening / closing of the mold. WS=b1⋅SS+b2⋅VS+b0 b1, b2, and b0 are predetermined coefficients and can be fitted by multiple regression analysis. Consequently, the motor power consumption W2 of servomotor 11 in one cycle of the injection process can be calculated as follows: W2=WS×(SS / VS) / T

[0031] The engine power consumption W ME The dosing process is calculated using the following approximation expression. WME=c1⋅VME+c2 c1 and c2 are predetermined coefficients and can be adjusted using the least squares method. Consequently, the motor power consumption W3 of servomotor 24 in one cycle of the dosing process can be calculated as follows: W3=WME×TME / T

[0032] The power consumption W CA The following approximation expression is used to calculate the result in the form clamping process. WCA=d1⋅FCA+d2⋅TCA+d3 d1, d2, and d3 are predetermined coefficients and can be fitted by multiple regression analysis. Consequently, the motor power consumption W4 in one cycle of the clamping process can be calculated as follows: W4=WCA×TCA / T

[0033] The power consumption W H The holding process is calculated using the following approximation expression. WHP=e1⋅PHP+e2⋅THP+e3 e1, e2, and e3 are predetermined coefficients and can be fitted by multiple regression analysis. Consequently, the motor power consumption W5 of servomotor 11 in one cycle of the holding process can be calculated as follows: W5=WHP×THP / T

[0034] The heating device power consumption W H-ME The dosing process is calculated using the following approximation expression. WH−ME=f1⋅VME2+f2⋅VME+f3 f1, f2, and f3 are predetermined coefficients and can be adjusted using the least squares method. Consequently, the heating device power consumption W6 in one cycle of the dosing process is calculated as follows: W6=WH−ME×TME / T

[0035] The power consumption calculation part 261 calculates the total power consumption W Totalby substituting the parameters of the shape condition into the corresponding approximation expressions as follows: WTotal=W1+W2+W3+W4+W5+W6+W7+W8

[0036] Here, W7 represents the standby power consumption of the motors in one cycle and can be derived through measurements. W8 represents the standby power consumption of the heating device in one cycle of the dosing process and can be determined by W8 = W H ×T ME / T using standby power consumption W H (Measurement) of the heating device will be calculated.

[0037] Fig. Figure 3 is a flowchart illustrating an example of the main process of a power consumption calculation method by the control device 26.

[0038] In step 300, the parameters of the mold conditions, which the user enters via user interface 3, such as a cycle time, a mold opening / closing time, a dosing time, etc., are entered.

[0039] In step 302, the approximation expressions stored in the approximation expression memory part 262 are read out.

[0040] In step 304, the power consumption calculation part 261 calculates the power consumption W1, W2, W3, W4, W5, etc. of the corresponding processes in a predictive manner in order to determine the total power consumption W Total to calculate by calculating the approximation expressions read out in step 302, using the form constraints entered as input parameters in step 300.

[0041] In step 306, the power consumption calculation result, calculated in step 304, is output via the user interface 35. The control device 26 can then display the power consumption calculation result W1, W2, W3, W4, W5, etc., of the corresponding processes individually, as well as the calculation result of the total power consumption W. Total This arrangement allows the user to see the power consumption when performing injection molding under the entered mold conditions. Consequently, the user can re-enter the mold conditions after verifying the calculation result, for example, to recheck the mold conditions. In this case, the user can see how the power consumption changes under the new mold conditions. This way, the user can adjust the mold conditions in advance while taking power consumption into account.

[0042] In the exemplary embodiment, the control device 26 can further include a calculation function for the optimal forming condition, which calculates the optimal forming conditions reflected by the power consumption.

[0043] Fig. Figure 4 is a function diagram to represent a main function part relating to the calculation function of the optimal shape condition of the control device 26.

[0044] The control device 26 comprises a computation part 263 for optimal shape conditions and an approximation expression memory part 262. The computation part 263 for optimal shape conditions is implemented by a CPU of the control device 26, which determines the optimal shape conditions under a constraint in such a way that the power consumption calculated with the approximation expressions stored in the approximation expression memory part 262 meets a predetermined requirement. The approximation expression memory part 262 can be implemented by a ROM memory of the control device 26.

[0045] Fig. Figure 5 is a flowchart illustrating an example of a main process of a calculation method for the optimal shape condition, which is implemented by the control device 26.

[0046] In step 500, the parameters of the constraints are entered, which the user specifies via user interface 35. The constraints can be within a variable range (an upper limit and / or a lower limit) for the mold condition parameters, such as cycle time, mold opening / closing time, dosing time, etc. For example, the constraints can be within a permissible range for the mold condition, such as a range T1-T2 for the cycle time, a range T3-T4 for the mold opening / closing time, etc. The variable range can correspond to a condition appropriate to the item. In other words, the variable range for the mold condition can be set in such a way as to achieve the appropriate condition for the item.Furthermore, the restrictions may include a target for power consumption in the relevant process or a target for total power consumption.

[0047] In step 502, the approximation expressions stored in the approximation expression memory part 262 are read out.

[0048] In step 504, the calculation part 263 of the optimal shape condition searches for the optimal shape conditions under the constraints entered in step 500, in such a way as to minimize the power consumption calculated using the approximation expressions read out in step 502. It should be noted that if the constraints entered in step 500 include the power consumption target, the calculation part 263 for the optimal shape condition searches for the optimal shape conditions under the constraints entered in step 500, in such a way that the power consumption calculated using the approximation expressions read out in step 502 is lower than the target. In this case, the ranges of optimal shape conditions can be searched.

[0049] In step 506, the calculation result of the optimal molding conditions, calculated in step 504, is output via the user interface 35. The control device 26 can then display the calculated power consumption results W1, W2, W3, W4, W5, etc., of the corresponding processes under the optimal molding conditions individually, as well as the calculated total power consumption W. Total . This arrangement allows the user to identify the optimal molding conditions, as well as the power consumption when performing injection molding under the optimal molding conditions.

[0050] The present invention is disclosed with reference to preferred embodiments. However, it should be recognized that the present invention is not limited to the embodiments described above and that variations and modifications can be made without departing from the scope of the present invention.

[0051] For example, in the embodiments described above, the power consumption calculation function, the optimal mold condition calculation function, and the calculation result output function are implemented by the control device 26 of the injection molding machine 1; the power consumption calculation function and / or the optimal mold condition calculation function and / or the calculation result output function can be implemented by an external computer, such as a PC (PC = Personal Computer). In this case, the external computer can include the power consumption calculation function and / or the optimal mold condition calculation function adapted to different types of injection molding machines.

[0052] Furthermore, in the embodiments described above, it is possible to take into account the power consumption of other processes by calculating them with a similar approximation expression. For example, it is possible to take into account the power consumption of the servo motor 44 in the mold ejection process by calculating it with a similar approximation expression.

[0053] Furthermore, in the embodiments described above, the power consumption is calculated on a process basis; however, the power consumption can also be calculated on a motor basis (e.g., as servomotors 11, 24, 42, 44, etc.) or on a heating device basis using appropriate approximation expressions. Additionally, in the embodiments described above, the total power consumption in a cycle is predicted by calculating the power consumption on a process basis; however, it is possible to predict the power consumption or the total power consumption for a specific process or a specific combination of processes. Similarly, it is possible to predict the power consumption or the total power consumption for a specific motor or a specific combination of motors.Similarly, it is possible to predict the power consumption or total power consumption for a specific heating device or a specific combination of heating devices.

[0054] Furthermore, if the form condition for the unit whose power consumption is highest within the power consumptions calculated on a unit basis (on a process basis, a motor basis or a heating device basis) is changed (within a corresponding article range), it is possible to efficiently reduce the power consumption.

Claims

[1] Power consumption calculation device used for an injection molding machine (1), wherein a cycle of an injection molding process of the injection molding machine (1) has a plurality of predetermined processes, and wherein the power consumption calculation device comprises: an input part that is capable of entering a form condition for one or more of the predetermined processes; a memory section (262) that is able to store for each of the predetermined processes an approximation expression suitable for calculating the power consumption for the predetermined process in question, when the injection molding machine (1) is operated under the molding condition for the relevant predetermined process, which was entered by the input part; a power consumption calculation part (261) that is capable of calculating the power consumption in one or more of the plurality of predetermined processes included in the cycle of an injection molding process of the injection molding machine (1) using the approximation expression stored in the memory part (262), based on the molding condition entered by the input part; and a calculation part for the optimal shape condition, which calculates a shape condition under which the power consumption assumes a predetermined value or a minimum value subject to a restriction that a shaped item fulfills a predetermined, corresponding item condition. [2] Power consumption calculation device according to claim 1, which further comprises an output part that outputs the power consumption calculated by the power consumption calculation part (261). [3] Power consumption calculation device according to claim 1, wherein the power consumption calculation device is integrated in the injection molding machine (1) or is integrated in an external computer that is independent of the injection molding machine (1). [4] Power consumption calculation device according to claim 1, wherein the power consumption calculation part (261) is able to calculate the power consumption in each of the plurality of predetermined processes included in the cycle of the injection molding process of the injection molding machine (1) and to calculate a total power consumption per cycle based on the calculated power consumption of each of the predetermined processes. [5] Power consumption calculation method for an injection molding machine (1), wherein a cycle of an injection molding process of the injection molding machine (1) has a plurality of predetermined processes, wherein the method comprises the following: Entering a form condition for one or more of the predefined processes (S300); Reading an approximation expression for one or more of the predetermined processes from a memory portion, wherein the approximation expression can be used to calculate the power consumption for the predetermined process in question when the injection molding machine (1) is operated under the input molding condition for the predetermined process in question (S302); Calculating the power consumption of the injection molding machine (1) in each of the predetermined processes using the read-out approximation expression, based on the mold condition input (S304); and Calculating an optimal shape condition under which the power consumption assumes a predetermined value or a minimum value subject to a constraint that a shaped object fulfills a predetermined, corresponding object condition.

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