Method for calculating a target curve of an injection actuator of a molding machine and / or for simulating the injection of molding material into a mold cavity

Abstract

The present invention relates to a computer-implemented method for calculating a target curve of motion for an injection actuator (8) for a molding machine (1), wherein: - a simulation region (13) is defined, wherein the simulation region (13) includes at least one cavity (3) of a mold (2) mounted on the molding machine (1); - at least one simulation (15) is performed within the simulation region (13), wherein, with at least one volume flow curve (19) of an entry surface (14) at the edge of the simulation region (13) and / or at least one pressure curve at the entry surface as boundary conditions, the injection of molding material (10) into the at least one cavity (3) of the molding mold (2) is simulated; - the volume flow curve and / or the at least one volume flow curve (19) calculated by means of the simulation (15) is converted into a target curve of motion for the injection actuator (8), in particular a plasticizing screw (9), wherein the compressibility of the molding material (10) is taken into account when performing the conversion (16).

Description

Technical Field

[0001] This invention relates to a computer-implemented method for calculating a target curve for an injection actuator of a molding machine, and a computer-implemented method for simulating the injection of molding material into a mold cavity. Furthermore, this invention relates to a method for operating a molding machine and a method for transmitting and adapting a target curve for the motion of the injection actuator. This invention also relates to a molding machine and a computer program product. Background Technology

[0002] The computer-implemented methods and methods for operating molding machines of this type are known from the prior art.

[0003] US 10,960,592 B2 discloses a method for operating an injection molding machine, wherein, in particular, a simulation region is defined, comprising the cavity of a mold, the cylinder of the injection molding machine, and the injection actuator of the injection molding machine. At least one simulation is performed on a defined grid within this simulation region. Boundary conditions in the cylinder are determined taking into account the movement of the injection actuator. Thus, the injection of molding material from the cylinder into the cavity of the mold is simulated using numerical methods. The setup parameters thus obtained can be easily transferred to the injection molding machine, and then the actual injection molding process can be implemented. This allows, for example, the filling characteristics of the cavity to be simulated.

[0004] The drawback of the existing technology is that, in order to perform the simulation correctly, the operator must have knowledge of machine-specific details, such as screw diameter and metering stroke, especially since the movement of the injection actuator must also be simulated. Furthermore, optimization is difficult in such complex simulations that cover the entire injection process. Summary of the Invention

[0005] The objective of this invention is to provide a computer-implemented method for calculating a target curve for an injection actuator of a molding machine and a computer-implemented method for simulating the injection of molding material into a cavity, wherein the methods can be easily implemented by an operator and / or without in-depth knowledge of the molding machine and are easily optimized.

[0006] In the case of the computer-implemented method according to the invention for calculating the target curve of the injection actuator for a molding machine, and in the case of the computer-implemented method according to the invention for simulating the injection of molding material into a cavity, a simulation region is defined, wherein the simulation region includes at least one cavity of a mold mounted on the molding machine. It is also specified that at least one simulation is performed within the simulation region, wherein the injection of molding material into the at least one cavity of the molding mold is simulated with at least one volumetric flow profile (Volumenstromprofil) at the entry surface at the edge of the simulation region and / or at least one pressure profile (Druckprofil) at the entry surface pre-defined as boundary conditions.

[0007] According to the present invention, only the at least one cavity of the molding die needs to be constructed in the simulation area, and for example, a plasticizing screw or an injection actuator generally used for injection can be omitted.

[0008] Therefore, it is not necessary to simultaneously simulate the motion of the injection actuator at a high cost. As a result, the simulation can be performed faster and with less memory usage, thus enabling more efficient optimization.

[0009] Furthermore, the boundary conditions (volume flow rate curves and / or pressure curves) do not need to be predefined in absolute values, but can be parameterized, for example, by the desired injection time. This makes the simulation advantageously machine-independent.

[0010] According to the present invention, the volumetric flow rate curve calculated by means of simulation and / or at least one of the volumetric flow rate curves is converted into a target curve for the motion of the injection actuator, especially the plasticizing screw.

[0011] Because the volumetric flow rate curve through the entry surface is converted into a target curve for the motion of the injection actuator, the target curve for the injection actuator can still be calculated even when using a simplified simulation in the simulation region without considering the molding material between the injection actuator and the entry surface. This target curve can then be used to run the molding machine and / or for other simulations. No in-depth machine-specific knowledge is required, and the target curve can still be transferred to the molding machine without problems; thus, this method can be applied significantly more efficiently than known methods.

[0012] In other words, the present invention is based on the understanding that, by means of machine-independent simulation and subsequent calculations taking into account the compressibility of the molding material, simulations can be performed with appropriate accuracy at a faster pace than those of the prior art.

[0013] In the case of the computer-implemented method according to the present invention, it is possible to specify that, during conversion, a mathematical model is used to calculate the mass of the molding material between the injection actuator and the entry surface, taking into account the compressibility of the molding material.

[0014] It can be specified that the compressibility of the molding material between the injection actuator and the entry surface should be taken into account when making conversions.

[0015] Similarly, it can be specified that the compressibility of the molding material is considered during the conversion, in such a way that the target curve and / or the target volumetric flow rate curve is scaled such that, relative to the time index and / or volumetric flow rate index, the volume entering the entry surface derived from the target curve corresponds to the volume of the molding material calculated in the simulation. Here, the target curve is preferably calculated without considering compressibility before the scaling.

[0016] In short, that is, in this implementation, the compressibility of the molding material can be simply considered for the conversion, in such a way that the target curve and / or target volumetric flow rate curve is scaled such that the volume of the molding material arriving in the simulation area at a specific time (e.g., time index = predefined injection time) or at a specific volumetric flow rate (e.g., time index = predefined volumetric flow rate parameter) according to the target curve and / or target volumetric flow rate curve matches the volume calculated in the simulation within the simulation area.

[0017] As mentioned, according to the present invention, it is not necessary to simultaneously simulate the molding material between the injection actuator and the entry surface, and it is still possible to obtain an accurate target curve of the injection actuator while taking compressibility into account.

[0018] Furthermore, in the case of a computer-implemented method, it is specified that an overall simulation is performed, wherein the overall simulation simulates the injection of molding material into the cavity of the molding die while taking into account the movement of the injection actuator according to the target curve and simulates the molding material in the cylinder of the molding machine (machine-related simulation).

[0019] Therefore, simulations that can be easily and efficiently performed without considering the molding material between the injection actuator and the entry surface can provide or improve target curves suitable for overall simulations that also simulate the molding material between the injection actuator and the entry surface.

[0020] Thus, for example, the desired simulation results can be easily optimized using the initial simulation, and then the target curve of the injection actuator can be used for the overall simulation. Therefore, for example, further optimization can be performed at the level of the overall simulation, where the target curve from the initial simulation provides suitable initial values.

[0021] The volumetric flow rate curve calculated in the simulation is particularly suitable for use at the edges of the simulation area, especially at the entry surface. It should be noted that there is typically a difference between the volumetric flow rate curve predefined as boundary conditions and the volumetric flow rate curve calculated in the simulation that reflects the optimization performed in the simulation. This constitutes a feature of commercially available software for simulating molding processes, especially injection molding processes.

[0022] Molding machines can be understood as injection molding machines, die casting machines, presses, and similar equipment.

[0023] In one embodiment, the boundary conditions are optimized. Preferably, multiple simulations are performed iteratively with different boundary conditions. Particularly preferably, it is possible to specify that the boundary conditions are adjusted based on the simulation results of at least one previously performed simulation. This allows optimization towards a desired simulation outcome. For example, it is possible to expect the flow front velocity in the cavity to be as constant as possible.

[0024] In another embodiment, the simulation area includes at least one gate area. Therefore, the molding material within both the gate area and the cavity is simulated during the simulation.

[0025] Alternatively or as an addition, it can be specified that the simulation area includes at least one machine nozzle. In the case of simulation, the molding material in the gate area, within the machine nozzle, and in the cavity can be simulated together, for example.

[0026] Alternatively or as an addition, it can be specified that the simulation area includes at least one cylinder flange. In the case of simulation, the molding material in the gate area, machine nozzle, cylinder flange, and cavity is simulated together, for example.

[0027] In all the examples above for the simulation region, the motion of the injection actuator need not be considered. Therefore, simulation can be performed easily.

[0028] Similarly, hot channels can be simulated as an alternative or as an addition. If hot channels are not simulated together, approximate calculations about the hot channels can be used.

[0029] In one embodiment, the simulation and / or overall simulation is a CFD simulation. CFD here stands for "Computational Fluid Dynamics," i.e., numerical flow dynamics. For this purpose, a mesh is typically introduced into the simulation domain.

[0030] As a boundary condition, the volumetric flow rate curve of the ingress surface at the edge of the simulation region can be predefined.

[0031] Alternatively or as an addition, the at least one simulation can be performed with at least one pressure curve on the entry surface predefined as a boundary condition.

[0032] The pressure curve can be calculated from the volumetric flow rate curve, and the volumetric flow rate curve can be calculated from the pressure curve. Thus, at the inlet surface, for example, at least one volumetric flow rate curve or at least one pressure curve at a fixed time point has been predetermined as boundary conditions.

[0033] In principle, a hybrid form consisting of volumetric flow rate curves and pressure curves (at different time points) can also be envisioned as the boundary condition.

[0034] It is possible to specify that the density curve at the inlet surface can be calculated from the volumetric flow rate curve and / or pressure curve at the inlet surface. For this purpose, it is preferable to apply a physical model relating pressure, temperature, and density, particularly the Tait model, Renner model, and / or IKV model. Thus, the compressibility of the molding material at the inlet surface can be considered, regardless of whether compressibility in other regions is also taken into account. Therefore, the mass curve of the mass flowing through the inlet surface can be calculated together with the volumetric flow rate curve at the inlet surface. Of course, specific volume can also be used instead of density, as is commonly practiced.

[0035] It should be noted here that the mathematical model used in one step of this embodiment to calculate the mass of the molding material between the injection actuator and the entry surface includes a physical model relating to the relationship between pressure, temperature, and density. In other words, the compressibility of the molding material is taken into account, particularly with the aid of the physical model, when making conversions.

[0036] In principle, the different models mentioned (Tait, Renner, IKV) are well known to those skilled in the art. As an additional reference, please see the article "Schmelzekompression praxisnah berechnen" published in the journal Kunststoffe on June 9, 2020.

[0037] Regarding the IKV model, additionally see Hans-Jürgen Luger's master's thesis entitled "Reale und virtuelle Prozessoptimierungeiner Spiegelantriebskomponente" (August 2013), submitted to Montan Universität Leoben.

[0038] In another embodiment, it is possible to specify, when using at least one pressure profile on the entry surface, a molding material distribution cylinder pressure profile and / or a spatial pressure distribution profile between the injection actuator and the entry surface. This also obtains pressure values ​​outside the simulation area.

[0039] Preferably, it is specified here that the cylinder pressure curve or pressure distribution curve of the molding material between the injection actuator and the entry surface is assumed to be spatially consistent and / or corresponds to the pressure curve at the entry surface. That is, the pressure is generally applied to areas outside the simulation region. It is also possible to specify that the pressure curve of the molding material between the injection actuator and the entry surface is assumed to have a gradient increase or decrease. Therefore, more realistic results may be achieved.

[0040] In another embodiment, the density curve and / or spatial density distribution curve of the molding material between the injection actuator and the entry surface are calculated from the cylinder pressure curve and / or spatial pressure distribution curve of the molding material between the injection actuator and the entry surface. Here, it is preferable to apply a physical model relating pressure, temperature, and density, particularly the Tait model, the Renner model, and / or the IKV model. This allows the compressibility of the molding material between the injection actuator and the entry surface to be considered. Consequently, the volume of the molding material between the injection actuator and the entry surface can also be calculated based on a known mass.

[0041] In another embodiment, the mass profile of the molding material between the injection actuator and the inlet surface is determined, in particular, iteratively via mass balancing. Preferably, the mass of the molding material flowing into the simulation region is calculated from the at least one volumetric flow rate curve through the inlet surface and the at least one cylinder pressure curve on the inlet surface, and particularly preferably iteratively subtracted from the mass in the cylinder. For this calculation, the aforementioned physical model relating pressure, temperature, and density is particularly preferably applied. The mass flowing into the simulation region can be calculated from the product of the volumetric flow rate on the inlet surface, the density on the inlet surface, and the time interval.

[0042] Furthermore, it can be specified that the quality of the molding material flowing out through the check valve of the injection actuator can be taken into account. This allows for a more accurate conversion.

[0043] In another embodiment, a target volumetric flow rate curve of the molding material between the injection actuator and the entry surface is calculated from the mass curve. The target volumetric flow rate curve describes the change in volume of the molding material at different time points. Preferably, the density curve and / or density distribution curve of the molding material between the injection actuator and the entry surface are used when performing the calculation.

[0044] From the target volumetric flow rate curve, a target curve for the motion of the injection actuator can be calculated. Particularly preferably, the geometry of the injection actuator and the cylinder can be taken into account here.

[0045] It is possible to specify that the number of points on the target curve for the motion of the injection actuator can be reduced to a level suitable for machine control of the molding machine using a reduction algorithm. This facilitates the transfer of the target curve for the motion of the injection actuator to the molding machine.

[0046] For example, the Ramer-Douglas-Peucker algorithm can be used as a reduction algorithm.

[0047] The method for operating the molding machine includes the following steps:

[0048] - According to the present invention, a target curve for the motion of the injection actuator used in a molding machine is calculated.

[0049] - The target curve for the motion of the injection actuator is transmitted to the molding machine.

[0050] - The molding process is carried out on the molding machine using the target curve of the motion for the injection actuator.

[0051] Therefore, the target curve with advantageous properties derived from simulation can be used in the actual molding process.

[0052] Alternatively, the target curve of the motion for the injection actuator can be transferred to software, such as a virtual molding machine (e.g., VirtMould).

[0053] In practice, there may be situations where it is necessary to transfer a mold mounted on another molding machine to the aforementioned molding machine; that is, to remove it from the other molding machine and install it on the aforementioned molding machine. In other words, there may be situations where it is necessary to transfer the molding process performed using a molding die from one molding machine to the aforementioned molding machine.

[0054] This leads to another aspect of the invention, namely, that the method according to the invention, including the conversion according to the invention, can also be used to calculate a target curve of motion for the injection actuator of the molding machine from a molding process already set up and running on another molding machine.

[0055] The corresponding method for transferring and adapting the target curve for the motion of the injection actuator from another molding machine to the at least one molding machine includes the following method steps:

[0056] In the first method step, at least one molding process is performed on at least one additional molding machine in accordance with a target curve of motion for the first injection actuator.

[0057] In the second method step, at least one additional overall simulation of the at least one molding process is performed on the additional molding machine. This allows the process variables of the simulation of the at least one molding process to be stored.

[0058] In the third method step, an additional simulation area is defined, wherein the additional simulation area includes the at least one cavity of the mold mounted on the additional molding machine.

[0059] In the fourth method step, the target curve of the motion of the additional injection actuator for the additional molding machine is converted into a volumetric flow rate curve through the entry surface and / or at least one pressure curve at the inlet region at the edge of the additional simulated region.

[0060] In the fifth method step, the computer-implemented method according to the invention is then executed according to the volumetric flow rate curve and / or pressure curve.

[0061] Therefore, that is, specifically calculating the target curve of the motion of the injection actuator used in the molding machine. Thus, the target curve has been transferred from the other molding machine to said molding machine and matched to it. This is especially useful if the same mold is used on both the other molding machine and the other molding machine.

[0062] If the simulation area only includes the mold, then the simulation area and the other simulation area are the same; otherwise, a corresponding other simulation area similar to the simulation area will be selected.

[0063] A molding machine is also specified, which is suitable for implementing the method for operating the molding machine and the method for transferring and adapting the target curve of motion for the injection actuator from another molding machine to the at least one molding machine.

[0064] A computer program product is also specified, comprising instructions for inducing a molding machine to perform the method for operating the molding machine and the method for transferring a target curve for motion of an injection actuator from one other molding machine to the at least one molding machine.

[0065] Finally, protection is also required for a computer program containing instructions that cause a computer implementing the method according to the invention to perform the method using a predefined simulation area.

[0066] The computer-implemented method can be implemented on the computing unit of the molding machine. However, the computer-implemented method is preferably implemented on an external computer (e.g., connected to the molding machine via a data remote transmission connection) and / or the cloud (e.g., implemented as a client of the molding machine manufacturer). It can be in a data connection with the molding machine.

[0067] In this application, the term "profil" refers to the change of a process variable at a specific point in time over time. It can also refer to the change of a process variable in relation to other continuous process variables. A volumetric flow rate profile can be, for example, a volume change over time or a volume change with the filling degree of the cavity. Preferably, this refers to the change within a portion of a single cycle of the molding process.

[0068] The at least one volumetric flow rate curve and / or the at least one pressure curve are sometimes simply referred to as volumetric flow rate curve and / or pressure curve in this application because, in most cases, a single volumetric flow rate curve and / or pressure curve is used. However, it will be apparent to those skilled in the art that multiple volumetric flow rate curves and / or pressure curves can also be used. Attached Figure Description

[0069] Further embodiments and details can be found in the accompanying drawings. The drawings are as follows:

[0070] Figure 1 A schematic diagram of the injection unit and mold of the molding machine is shown.

[0071] Figure 2 The cavity, gate area, machine nozzle, and cylinder flange are shown.

[0072] Figure 3a This shows the flow front in the mold cavity before optimization.

[0073] Figure 3b This shows the optimized flow front in the cavity.

[0074] Figure 4a The volumetric flow rate curve at the inlet surface, which is a function of the mold cavity filling degree, is shown as the boundary condition for the simulation.

[0075] Figure 4b The volumetric flow rate curves calculated in the simulation as a function of time are shown.

[0076] Figure 4c The pressure curve as a function of time, calculated in the simulation, is shown.

[0077] Figure 4d The target volumetric flow rate curve of the molding material between the injection actuator and the inlet surface is shown as a function of time.

[0078] Figure 5 The target volumetric flow rate curve of the molding material as a function of time is shown between the injection actuator and the entry surface, with a decreasing number of points.

[0079] Figure 6 This illustrates the flow front in the cavity when using a target curve for the motion of the injection actuator.

[0080] Figure 7a This shows the volumetric flow rate associated with the filling volume.

[0081] Figure 7b The volumetric flow rate is shown in relation to time.

[0082] Figure 8 Shown for illustration Figure 7a and 7b A simplified diagram for conversion between them.

[0083] Figure 9 The volumetric flow rate curves, calculated in the simulation and expressed in relative units, are shown.

[0084] Figure 10 An excerpt showing examples of simulation results,

[0085] Figure 11 Show Figure 9 The volumetric flow rate curve in the figure has a clear interpolation point.

[0086] Figure 12 A simplified diagram illustrating an embodiment of the conversion according to the present invention is shown. Detailed Implementation

[0087] Figure 1 A schematic diagram of the injection unit 18 of the molding machine 1, on which the mold 2 is mounted, is shown. The molding machine includes an injection actuator 8 in the form of a plasticizing screw 9. Particle-like thermoplastic material is fed into the cylinder 7 via a feeding funnel 11, and the thermoplastic material is plasticized by the plasticizing screw 9. The resulting molding material is metered in front of the plasticizing screw 9.

[0088] During the injection process, the molding material is injected through the machine nozzle 5 and through the gate area 4 and cavity 3 of the mold 2.

[0089] Figure 2 Detailed views of the gate area 4, machine nozzle 5, and cylinder flange 6 with inlet face 14 are shown. Volumetric flow rate. At time t i By entering surface 14, where pressure p exists. i .

[0090] This invention relates to the simulation of the injection process. Thus, for example, it is possible to predict the filling characteristics of the cavity 3 of the mold 2. Optimization can also be performed relatively easily, wherein at least one specific process variable that cannot be obtained experimentally can be optimized. For example, optimization can be performed towards a constant flow front velocity.

[0091] In the case of the computer-implemented method according to the invention for calculating the target curve of the motion of the injection actuator 8 for the molding machine 1, and in the case of the computer-implemented method for simulating the injection of molding material 10 into the cavity 3, a simulation region 13 is defined, wherein the simulation region 13 includes at least one cavity 3 of the mold 2 mounted on the molding machine 1. Figure 1 In the embodiments described, the simulated area 13 also includes the gate area 4, the machine nozzle 5, and the cylinder flange 6.

[0092] In this embodiment, the boundary of the simulation region 13, visualized as a vertical dashed line, is located on the right side of the figure. This makes it theoretically feasible for the plasticizing screw 9 to enter the simulation region 13, but this is generally not the case. The injection actuator 8 is not considered in simulation 15. It cannot be assumed that this will result in a decrease in accuracy according to the method of the present invention.

[0093] Furthermore, according to the present invention, the edge of the simulation area 13 may be further to the left, such that it includes only the cavity 3 or includes the cavity 3 together with the gate area 4 and / or the machine nozzle 5.

[0094] In this embodiment, at least one simulation 15 is performed on the simulation region 13, wherein the injection of molding material 10 into at least one cavity 3 of the molding die 2 is simulated with at least one volumetric flow rate curve 19 passing through the entry surface 14 at the edge of the simulation region 13 predefined as boundary conditions. The simulation 15 can be performed, for example, as a CFD simulation. Compression of the molding material 10 within the simulation region 13 is also taken into consideration.

[0095] By means of simulation 15 within a limited simulation region 13, it is relatively easy to optimize the boundary conditions, wherein it is preferred to perform multiple simulations 15 iteratively with different boundary conditions and particularly preferably, the boundary conditions are adjusted based on the simulation results of at least one previously performed simulation 15.

[0096] For example, the optimization of the flow front velocity can be defined as the optimization objective. Figure 3aThe diagram illustrates flow fronts 17 entering simulation region 13 at fixed time intervals under constant volumetric flow rate conditions. If the flow fronts 17 are close together, the flow velocity is low. If the flow fronts 17 are far apart, the flow velocity is high. Excessively high or low flow front velocities can, in particular, lead to surface defects on the component. Therefore, the goal is to maintain the most constant flow front velocity possible. That is, the flow fronts 17 should have the most constant spacing possible between them.

[0097] This is relatively easy to achieve by means of the simulation 15 within a limited simulation region 13, by changing the boundary conditions. Figure 3b The results of the optimization are shown: the flow fronts 17 have a relatively constant spacing between each other.

[0098] The optimized simulation area 13 includes the cavity 3, the gate area 4, the machine nozzle 5, and the cylinder flange 6. The compression of the molding material 10 is also taken into account in this simulation area 13.

[0099] The volumetric flow rate curve 19 that caused the above optimization results is in Figure 4a As shown in the figure. The volumetric flow rate curve 19 is expressed in relative units, i.e., the filling degree of cavity 3 in percentage.

[0100] The volumetric flow rate curves calculated in Simulation 15 and similarly (via the inlet surface or at the inlet surface) pressure curves are obtained respectively. Figure 4b or Figure 4c As shown, these variables are described with respect to time (absolute volumetric flow rate and absolute pressure).

[0101] It should be noted that the volumetric flow rate curve 19, which serves as a boundary condition, can also be easily converted into an absolute value, for example, by pre-defining the injection time to be achieved.

[0102] It is equally feasible to convert volumetric flow rate curve 19 into a time-varying volumetric flow rate curve via absolute volume conversion; see [reference needed]. Figure 7a , Figure 7b , Figure 8 And the following related implementation plan.

[0103] Furthermore, it should be noted that the volumetric flow rate curve 19, which serves as a boundary condition and has been converted to absolute values, is readily comparable to the volumetric flow rate calculated in the simulation. Figure 4b This can be distinguished from other methods. The reason for this might lie in the conversion itself, for example, because the predetermined injection time was not accurately achieved in the simulation, or it might be due to the numerical nature of the simulation. For the conversions described later, not only can the simulation results ( Figure 4b The volumetric flow rate curve in the image), and it is also possible to use optimized boundary conditions ( Figure 4a(The volumetric flow rate curve). This also applies to the pressure at the inlet surface.

[0104] Therefore, the at least one volumetric flow rate curve (the volumetric flow rate curve calculated in the simulation in this embodiment) should be converted into a target curve for the motion of the injection actuator 8 (see [reference]). Figure 1 (Conversion 16 in the text). Then, the molding machine 1 can be parameterized or further simulations can be performed over a larger area using this target curve. For example, the results can be forwarded to the drive unit 12 of the injection actuator 8, as in... Figure 1 As shown in the diagram.

[0105] The simulation over a larger area is referred to in this application as the overall simulation 20, wherein the overall simulation 20 simulates the injection of molding material 10 into the cavity 3 of the molding die 2 and the molding material 10 in the cylinder 7 of the molding machine 1, taking into account the target curve motion of the injection actuator 8 according to the conversion 16.

[0106] The conversion 16 is achieved by means of a mathematical model for calculating the mass of the molding material 10 located between the injection actuator 8 and the entry surface 14, wherein the compressibility of the molding material 10 is taken into account when the conversion 16 is performed.

[0107] From simulation 15, at least one volumetric flow rate curve 19 and at least one pressure curve are known at the entry surface 14 at the edge of simulation region 13 (either as the volumetric flow rate curve calculated in the calculation or as the boundary condition of the simulation). In other words, at a specific time point t... i The pressure p entering surface 14 i and volumetric flow rate It is known.

[0108] As the first step in conversion 16, a physical model relating pressure, temperature, and density is used. Thus, the density curve at the point of entry into surface 14 can be calculated from the pressure curve at surface 14.

[0109] For example, the Tait model can be used as a physical model of the relationship between pressure, temperature, and density. If density is expressed in terms of specific volume...

[0110]

[0111] The Tait model can then be mathematically represented as follows:

[0112]

[0113] Where T is absolute temperature, p is pressure, and C is a constant. Coefficients b1m to b4m and b5 are model parameters suitable for the measured data.

[0114] Of course, any other physical relationship between pressure, temperature, and density can also be used, such as the Renner model and / or the IKV model.

[0115] Compressibility is considered using a physical model of the relationship between pressure, temperature, and density.

[0116] In a separate step, a mathematical model is used to calculate the mass of the molding material 10 located between the injection actuator 8 and the entry surface 14. Specifically, the mass profile of the molding material 10 between the injection actuator 8 and the entry surface 14 is determined iteratively via mass balancing. Therefore, at time point t... i The mass of the molding material 10 located between the injection actuator 8 and the entry surface 14 can be calculated using the following formula:

[0117]

[0118] Here, m i Indicates the quality of iterative computation. ρ represents volumetric flow rate. i Let represent density, and Δt represent the time step indicated by the exponent i.

[0119] In other words, the mass of the molding material 10 flowing into the simulation region 13 is calculated from and iteratively subtracted from the at least one volumetric flow rate curve 19 passing through the entry surface 14 and the at least one density curve at the entry surface 14. The density curve can be calculated from the pressure curve using a physical model of the relationship between pressure, temperature, and density, as described above, and the pressure curve is known from the boundary conditions of the simulation 15. Here, Δt is the step size between two time steps.

[0120] The initial mass m0 can be obtained by using the required molding material's metrological volume V0 and density ρ0 under material temperature and ambient pressure in Simulation 15. To calculate. For example, if the thermal aisles are not modeled together, a different initial volume V0 may need to be selected.

[0121] In a further step of the conversion 16, a pressure curve and / or spatial pressure distribution curve are assigned to the molding material 10 between the injection actuator 8 and the entry surface 14, using the at least one pressure curve on the entry surface 14. That is, pressure outside the simulation region 13 is assumed.

[0122] The density curve and / or spatial density distribution curve of the molding material 10 between the injection actuator 8 and the entry surface 14 can be calculated from the pressure curve and / or spatial pressure distribution curve of the molding material 10 between the injection actuator 8 and the entry surface 14. Preferably, a physical model relating to the relationship between pressure, temperature and density is applied, particularly preferably the Tait model, the Renner model and / or the IKV model.

[0123] In this illustrated embodiment, it is assumed that the pressure profile of the molding material 10 between the injection actuator 8 and the entry surface 14, and therefore its density profile, is spatially consistent and / or corresponds to the pressure profile on the entry surface 14. A constant temperature is also assumed.

[0124] Alternatively, pressure and / or temperature gradients can be assumed, which may lead to density distribution.

[0125] Using the distributed density, the calculated mass m can be obtained. i The volume of the molding material between the injection actuator 8 and the entry surface 14 is calculated. In this embodiment, this corresponds to the molding material in cylinder 7.

[0126] Therefore, it is also possible to calculate the volume change of the molding material 10 located between the injection actuator 8 and the entry surface 14, specifically in the cylinder 7, within the time step Δt. The volume change curve can be understood as the target volume flow rate curve 21.

[0127] Figure 4d The target volumetric flow rate curve 21, which is a function of time, is shown in cylinder 7.

[0128] Then, the target curve for the motion of the injection actuator 8 can be calculated from the target volumetric flow rate curve 21 calculated in this way. For this, only geometric data, such as the cylinder diameter, needs to be known. This calculation can also be performed automatically on the molding machine 1. Therefore, the target volumetric flow rate curve 21 can also be directly input on the molding machine 1.

[0129] Before being transferred to the molding machine 1, the number of points of the target curve for the motion of the injection actuator 8 can be reduced to a level suitable for machine control of the molding machine 1 by means of a reduction algorithm.

[0130] Correspondingly, Figure 5 The target volumetric flow rate curve 21 of the molding material 10 between the injection actuator 8 and the entry surface 14 is shown as a function of time. The number of points is reduced, and the target volumetric flow rate curve can be converted on the molding machine 1 into a target curve with a reduced number of points for the movement of the injection actuator 8.

[0131] Furthermore, additional optimization can be performed before or after reducing the number of points on the target curve by reusing the calculated target volumetric flow rate curve 21 as the boundary condition for simulation 15, thereby creating a feedback loop. This is in Figure 1 The arrow pointing from Conversion 16 to Analog 15 is used to represent this.

[0132] Subsequently, an overall simulation 20 can be performed, wherein the overall simulation 20 simulates the injection of molding material 10 into the cavity 3 of molding die 2 and the molding material 10 in the cylinder 7 of molding machine 1, taking into account the motion of injection actuator 8 according to the target curve from conversion 16.

[0133] exist Figure 6 As shown in the figure Figure 3a and Figure 3b The filling image, created using the overall simulation 20 and the target curve for the motion of the injection actuator 8 obtained from the conversion 16, shows that the flow fronts remain constantly spaced apart from each other. Figure 3b Only minor differences exist. That is to say, the easily implemented optimizations already performed on simulation region 13 for simulation 15 can always be seen in the results of the overall simulation 20.

[0134] Further optimization is possible at the overall simulation level 20. The calculated target curve for the motion of the injection actuator 8 provides suitable initial values ​​for this purpose.

[0135] exist Figure 7a The diagram shows an additional (predefined or calculated) volumetric flow rate curve 19, which is plotted against the absolute filling volume. This volumetric flow rate curve can be converted into a time-varying volumetric flow rate curve 19, which is... Figure 7b As shown in the image.

[0136] To illustrate how this conversion can be performed, for example, in Figure 8 The diagram shows a simplified representation where the volumetric flow rate varies with the absolute filling volume and is shown as a range of values ​​(small triangles), within which the following observations can be made.

[0137] In principle, within this region, volumetric flow rate and volume are linearly related, making Where k is a pre-defined proportionality constant. Therefore:

[0138]

[0139]

[0140] We obtain it by integration.

[0141]

[0142] For the i-th time interval, we derive (a representation related to the degree of filling rather than the absolute volume, known as the Delta-t equation)

[0143]

[0144] Among them, %V i The fill percentage is used to indicate the degree of filling, while "volume to be filled" refers to the total volume of simulated region 13. Alternatively, "volume to be filled" could be the initially unfilled volume (e.g., cavity 3 along with gate 4). In the first step, for volumetric flow rate... Assuming that the relative representation is a unit volumetric flow rate, i.e.

[0145] The inaccuracies introduced in this way are corrected by scaling, which will be described later.

[0146] These observations reveal another possibility: taking into account the compressibility of the molding material 10 when performing the aforementioned conversion 16.

[0147] The starting point is, on the one hand, the calculated or pre-defined volumetric flow rate curve 19. According to the present invention, taking into account the compressibility of the molding material 10, this volumetric flow rate curve 19 should be converted, for example, in... Figure 9 The target curve is shown in the figure.

[0148] On the other hand, information about the changes in the filling degree of simulation region 13 is usually available from simulation 15. For example, in Figure 10 The screenshot shown below displays a table that includes a time index and a fill percentage (see overlay box).

[0149] In the embodiment shown here, the objective is to first calculate the original target volumetric flow rate curve 22 (see also...). Figure 12 (wherein, the compressibility of the molding material 10 is not considered. In principle, as with the prior art, this can be accomplished simply based on considerations of volume in the material cylinder.)

[0150] Then, in the next step, the original target volumetric flow rate curve 22 is scaled so that the degree of filling at different times during the process corresponds to Figure 10The degree of filling is shown in the figure. Thus, the compressibility of the molding material 10 is at least approximately considered in a clever manner, since this compressibility is taken into account in simulation 15 within simulation region 13. Therefore, the compressibility of the molding material can be considered in a calculation without relying on a model in the region between the injection actuator 8 and the entry surface 14.

[0151] For the actual implementation of this embodiment, it can be specified that the volumetric flow rate curve 19 to be converted is sampled, that is, multiple numerical pairs are created on the graph of the volumetric flow rate curve 19 to be converted. This is in Figure 11 As shown in the image.

[0152] Alternatively, one or more scaling factors can be calculated. For example, results from Simulation 15 (see...) Figure 10 Substitute these values ​​into the Delta-t equation and sum over the corresponding time intervals.

[0153] When the desired injection time is predetermined (referred to as "nominal injection time"), it is used for Figure 12 The scale factor of the time axis in the calculation can be calculated as follows:

[0154]

[0155] Other possibilities for calculating the scaling factor include, for example, pre-defining the desired volumetric flow rate (referred to as "nominal flow rate") and the following equation:

[0156]

[0157] As mentioned above, the "volume to be filled" parameter can be the volume of simulated region 13.

[0158] For the sake of completeness, the following relationship should be noted:

[0159]

[0160] Therefore, for each of the points, the actual volumetric flow rate is obtained as a scaled-down version of the volumetric flow rate assumed when the first approximation was taken above:

[0161]

[0162] exist Figure 12 The original target volume flow rate curve 22 can be seen in the time scaling.

[0163] Figure 12 Time scaling in the process involves allocating scaled volumetric flow rates to the data in the time scaled process. Figure 10 The time is shown in relation to the corresponding fill level.

[0164] This means that, via Figure 10 The table in the table can assign the fill degree from these numerical pairs—if necessary, through interpolation—to absolute time, and thus the volumetric flow rate as the target volumetric flow rate curve 21 changes over time, thereby obtaining Figure 12 The scaled target volume flow rate curve in Figure 21.

[0165] The longer filling time is due to the compressibility of the molding material 10, which is taken into account by the aforementioned scaling.

[0166] It should be noted that numerical pairs can be reduced after scaling, for example, when using the Ramer-Douglas-Peucker algorithm.

[0167] As described, the target curve for the motion of the injection actuator 8 can be determined from the target volumetric flow rate curve 21 calculated in this way. It should be noted that the scaling can, in principle, be performed on the target curve instead of on the target volumetric flow rate curve 21.

[0168] The applicant's research has shown that the target curve for the injection actuator 8 can be calculated using the conversion according to this embodiment, resulting in extremely good consistency between the actual process and the simulation 15.

[0169] List of reference numerals

[0170] 1 Molding machine

[0171] 2. Mold

[0172] Type 3 cavity

[0173] 4. Gating area

[0174] 5. Machine nozzles

[0175] 6-cylinder flange

[0176] 7 cylinders

[0177] 8. Injection actuator

[0178] 9 Plasticizing Screw

[0179] 10 Molding Materials

[0180] 11. Charging funnel

[0181] 12 Drive unit

[0182] 13 Simulation Area

[0183] 14 Enter the face

[0184] 15 Simulation

[0185] 16 Conversion

[0186] 17. Flow Frontier

[0187] 18 injection units

[0188] 19. Volumetric Flow Rate Curve

[0189] 20 Overall Simulation

[0190] 21 Target volumetric flow rate curve

[0191] 22 Original target flow curve

Claims

1. A method implemented by a computer for calculating a target curve of motion of the injection actuator (8) of a molding machine (1), wherein - defining an analog region (13) in which, The simulated area (13) includes at least one cavity (3) of a mold (2) mounted on a molding machine (1). - At least one simulation (15) is performed within the simulation area (13), wherein, with at least one volume flow rate curve (19) at the entry surface (14) at the edge of the simulation area (13) as a boundary condition and / or with at least one pressure curve at the entry surface as a boundary condition, the simulation simulates the injection of molding material (10) into at least one cavity (3) of the molding die (2), and the injection actuator (8) is not considered in the simulation (15). - The volumetric flow rate curve calculated using the simulation (15) and / or the at least one volumetric flow rate curve (19) are converted into a target curve for the motion of the injection actuator (8). The feature is that the compressibility of the molding material (10) is taken into account when performing the conversion (16).

2. The method of claim 1, wherein, The injection actuator (8) is a plasticizing screw (9).

3. The method according to claim 1, wherein, Then, an overall simulation (20) is performed, wherein the overall simulation (20) simulates the process of injecting molding material (10) into the cavity (3) of molding die (2) while taking into account the movement of the injection actuator (8) according to the target curve from the conversion (16) and simulates the state of molding material (10) in cylinder (7) of molding machine (1).

4. The method of any one of claims 1 to 3, wherein, When performing the conversion (16), the compressibility of the molding material (10) located between the injection actuator (8) and the entry surface (14) is taken into consideration.

5. The method according to any one of claims 1 to 3, wherein, When performing the conversion (16), the compressibility of the molding material (10) is considered in such a way that the target curve is scaled such that the volume of the material entering the entry surface (14) at each time step obtained from the target curve corresponds to the volume of the molding material (10) in the simulation region (13) and / or in the cavity (3) calculated in the simulation (15) at the corresponding time step.

6. The method according to claim 5, wherein, The target curve is calculated without considering compressibility before scaling.

7. The method according to any one of claims 1 to 3, wherein, The boundary conditions are then optimized.

8. The method according to claim 7, wherein, Iteratively perform multiple simulations with different boundary conditions (15).

9. The method according to claim 8, wherein, The boundary conditions are adjusted based on the simulation results of at least one previous simulation (15).

10. The method according to any one of claims 1 to 3, wherein, The simulation region (13) includes - At least one gate area (4), and / or - At least one thermal aisle system, and / or - At least one machine nozzle (5), and / or - At least one cylinder flange (6).

11. The method according to claim 3, wherein, The simulation (15) and / or the overall simulation (20) are CFD simulations.

12. The method according to claim 11, wherein, The density curve at the inlet surface (14) is calculated from the volumetric flow rate curve and / or pressure curve at the inlet surface (14).

13. The method according to claim 12, wherein, A physical model is applied to the relationship between pressure, temperature, and density.

14. The method according to claim 13, wherein, The physical model is the Tait model, the Renner model, and / or the IKV model.

15. The method according to claim 12, wherein, In the case of using at least one pressure curve at the entry surface (14), the cylinder pressure curve and / or space pressure distribution curve are distributed to the molding material (10) between the injection actuator (8) and the entry surface (14).

16. The method according to claim 15, wherein, The cylinder pressure curve or the pressure distribution curve of the molding material (10) located between the injection actuator (8) and the entry surface (14). - Assumed to be spatially consistent and / or corresponding to the pressure curve at the entry surface (14), and / or - It is assumed that it rises or falls in a gradient.

17. The method according to claim 15, wherein, The density curve and / or spatial density distribution curve of the molding material (10) between the injection actuator (8) and the entry surface (14) are calculated from the cylinder pressure curve and / or the spatial pressure distribution curve of the molding material (10) between the injection actuator (8) and the entry surface (14).

18. The method according to claim 17, wherein, A physical model is applied to the relationship between pressure, temperature, and density.

19. The method according to claim 18, wherein, The physical model is the Tait model, the Renner model, and / or the IKV model.

20. The method according to any one of claims 1 to 3, wherein, The mass profile of the molding material (10) located between the injection actuator (8) and the entry surface (14) is determined by mass balance.

21. The method according to claim 15, wherein, The mass curve of the molding material (10) located between the injection actuator (8) and the entry surface (14) is determined iteratively via mass balance.

22. The method according to claim 21, wherein, - The mass of the molding material (10) flowing into the simulation region (13) is calculated by the at least one volumetric flow rate curve (19) through the entry surface (14) and the cylinder pressure curve at the entry surface (14) and is iteratively subtracted, and / or - The quality of the molding material (10) flowing out through the backflow valve of the injection actuator (8) is taken into consideration.

23. The method of claim 20, wherein, The target volume flow rate curve (21) of the molding material (10) between the injection actuator (8) and the entry surface (14) is calculated from the mass curve.

24. The method of claim 20, wherein, The target volume flow rate curve (21) of the molding material (10) between the injection actuator (8) and the entry surface (14) is calculated from the mass curve, using the density curve and / or density distribution curve of the molding material (10) between the injection actuator (8) and the entry surface (14), and the target curve for the motion of the injection actuator (8) is calculated from the target volume flow rate curve (21).

25. The method according to any one of claims 1 to 3, wherein, The number of points on the target volume flow curve for the motion of the injection actuator (8) is reduced to a level suitable for machine control of the molding machine (1) by means of a reduction algorithm.

26. A method for operating a molding machine (1), wherein, - Calculate the target curve of the motion of the injection actuator (8) for the molding machine (1) using the method according to any one of claims 1 to 25. - The target curve for the motion of the injection actuator (8) is transmitted to the molding machine (1). - The molding process is carried out on the molding machine (1) using the target curve of the motion for the injection actuator (8).

27. A method for transmitting and adapting the target curve of motion of another injection actuator of another molding machine to at least one molding machine (1), wherein, - At least one molding process is performed on at least one additional molding machine using a target curve of motion for another injection actuator. - Perform at least one additional overall simulation (20) of the at least one molding process on the additional molding machine. - Define an additional simulation area, wherein the additional simulation area (13) includes at least one cavity (3) of a mold (2) mounted on the additional molding machine. - The target curve of motion for the additional injection actuator of the additional molding machine is converted into a volumetric flow rate curve through the entry surface at the edge of the additional simulation area and / or at least one pressure curve at the entry surface, and - The method according to any one of claims 1 to 25 is performed using the volumetric flow rate curve (19) and / or the pressure curve.

28. A molding machine (1), said molding machine being constructed for carrying out the method according to claim 26 or claim 27.

29. A computer program product comprising instructions that, when executed by a computer, cause the computer to perform the method according to claim 26 or claim 27.

30. A computer program product comprising instructions that, when executed by a computer, cause the computer to perform the method according to any one of claims 1 to 25 using a predefined simulation area.

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