Injection molding process using a plasticizing unit with an ultrasonic unit

Abstract

The invention relates to an injection molding process using a plasticizing unit (1) which is fluidically connected to a molding tool (3) via a melt channel (2), wherein an ultrasonic unit (4) is provided which is designed and configured to deliver ultrasonic energy to a plastic melt (5), wherein the injection molding process comprises the following steps: A) in a learning phase: A.1) Carrying out at least one learning injection moulding cycle, with the application of ultrasonic energy A.2) Determining at least one representation parameter (RP), A.3) Recording of the at least one learning injection molding cycle, wherein at least one representation parameter (RP) is used as a reference representation parameter (RP ref ) is recorded and B) in a production phase: B.1) Carrying out at least one production injection molding cycle, wherein ultrasonic energy is applied at least temporarily to the plastic melt (5); B.2) where a current value for the representation parameter (RP act ) is determined; B.3) Comparison of the value of the reference representation parameter (RP ref ) with the current value for the representation parameter (RP act ); B.4) Adaptation of a current ultrasound energy.

Description

[0001] The invention relates to an injection molding process using a plasticizing unit which is fluidly connected to a molding tool via a melt channel, wherein an ultrasonic unit is provided which is designed and configured to deliver ultrasonic energy to a plastic melt.

[0002] WO 2021 / 245 185 A1 discloses a control method for controlling ultrasonic transmitters within an injection molding machine. This document also discloses methods that enable viscosity measurement, particularly represented by a viscosity index of the melt flow. The instantaneous power consumption of a sonotrode is used as a starting point.

[0003] Furthermore, it is known from the prior art that, for example, due to changing environmental conditions (e.g. temperature, humidity, melt composition), the viscosity of the plastic melt can fluctuate, which can lead to defective parts or rejects.

[0004] To prevent such effects of viscosity fluctuations, it is also known to influence downstream process parameters in the same injection molding cycle based on process parameters detected during an injection molding cycle in such a way that different melt viscosities can be compensated for and thus rejects / defective parts can be avoided. Downstream process parameters include, for example, a holding pressure switchover point or a holding pressure of the injection molding process. Such a basic approach is disclosed, for example, in DE 10 2018 126 313 A1.

[0005] Further methods for dealing with viscosity aspects in a plastic melt are known from the patent documents WO2016149550A1 and CN118769493A as well as from the scientific publications "BI, Mingcheng, et al. Simultaneously enhancing the flow properties and mechanical strength of polyphenylene sulfide via in-mold ultrasonic-assisted injection molding. Journal of Applied Polymer Science, 2024, 141st vol., no. 36, p. e55927" and "GAO, Shan, et al. Flow properties of polymer melt in longitudinal ultrasonic-assisted microinjection molding. Polymer Engineering & Science, 2017, 57th vol., no. 8, pp. 797-805".

[0006] In light of this prior art, it is therefore an object of the invention to provide an injection molding process which does not rely on the control of the effects of viscosity fluctuations and in particular enables the viscosity of the plastic melt to be kept constant or at least within a narrow tolerance window despite variable ambient conditions and / or active or passive process changes, e.g. temperatures.

[0007] A further object of the invention is to ideally make an adjustment of downstream process parameters unnecessary.

[0008] These objects are achieved by an injection molding process having the features of claim 1. Advantageous embodiments are specified in the dependent claims.

[0009] An injection molding process according to the invention uses a plasticizing unit which is fluidically connected to a mold via a melt channel, wherein an ultrasonic unit is provided which is designed and configured to deliver ultrasonic energy to a plastic melt, wherein the injection molding process comprises the following steps: A) in a learning phase: A.1) Carrying out at least one learning injection moulding cycle, for example a learning injection moulding cycle to obtain a good part; A.2) Determining at least one value of a representation parameter RP at least at one point in time or during a period of time of the molding process; A.3) Recording of at least one learning injection molding cycle to obtain the good part as a reference cycle, wherein for this purpose at least one representation parameter RP is used as a reference representation parameter RP refor at least one course of the representation parameter RP as a reference representation parameter course RP ref (t) is recorded at least during the period of the molding process, in particular during the injection phase, and B) in a production phase: B.1) Carrying out at least one production injection molding cycle, wherein ultrasonic energy is delivered to the plastic melt at least temporarily during a molding process of the production injection molding cycle; B.2) wherein at least during the molding process of the production injection molding cycle, continuously or at least at one or more process points, a current value for the representation parameter RP act at least the ongoing molding process is determined; B.3) Comparison of the value of the reference representation parameter RP refwith the current value for the representation parameter RP act of corresponding process points of the learning injection molding cycle and the production injection molding cycle; B.4) Introduction and / or adaptation of a current ultrasonic energy of the current production injection molding cycle at a level of a value for the current ultrasonic power P us_act during the current production injection molding cycle, if the current value for the representation parameter RP act from the corresponding value for the reference representation parameter RP ref deviates by more than a maximum deviation.

[0010] The method according to the invention makes it possible to influence the main cause of rejects or defective parts, namely the fluctuating viscosity of the plastic melt due to ambient conditions, so that the melt viscosity can be kept constant or at least within a narrow tolerance window despite changing ambient conditions or changing melt composition, for example due to varying recycled material content.

[0011] Furthermore, the goal is achieved to at least minimize, and ideally even avoid, the consequences of viscosity fluctuations by influencing downstream process parameters.

[0012] With the injection molding process according to the invention, viscosity fluctuations of the melt as a cause of rejects, for example due to varying mold fillings, are eliminated within one and the same injection molding cycle using ultrasonic energy.

[0013] In an advantageous embodiment, during the molding process of the learning injection molding cycle of a plastic melt, ultrasonic energy is applied at least temporarily at a level of a starting value for an ultrasonic power P us_start is supplied

[0014] This is useful in order to provide a good starting point for the production process for a current ultrasonic power P us_act from which an adaptation of the ultrasonic power P us_act towards achieving the best possible approximation of the current representation parameter RP act to the reference representation parameter RP ref can be done quickly and with as few adaptation steps as possible.

[0015] The supply of ultrasonic energy can advantageously take place both in the learning phase and in the production phase during an injection phase and / or during a holding pressure phase.

[0016] In principle, both the injection phase and the holding pressure phase are suitable for effectively influencing the viscosity of the plastic melt by applying ultrasonic energy. However, this preferably occurs during the injection phase, as this allows for a residual period of time between the injection phase and the entire holding pressure phase to influence the current injection molding cycle and its process parameters.

[0017] Advantageously, the emission of ultrasonic energy at the beginning of step B.1) occurs at the level of the starting value for the ultrasonic power P us_start the learning injection molding cycle.

[0018] With a starting value for the ultrasonic power, which is initially determined from empirical values ​​in the learning injection molding cycle, a starting point is created from which a sufficient injection molding process, ideally a good part injection molding process, can be achieved as quickly and effectively as possible for determining the values ​​of the reference parameters RP. It should be expressly emphasized that it is not absolutely necessary to achieve a good part injection molding cycle in the learning phase A). Rather, an injection molding cycle that, while not yet producing a good part, represents a useful part formation process for determining the values ​​of the desired reference parameters is sufficient.

[0019] It is also advantageous that, for example, if there is a sufficiently high control reserve of the ultrasonic unit, a reduction in the heating energy of a cylinder heater of the plasticizing unit, a reduction in the hot runner temperature, a reduction in the mold temperature and / or a reduction in the cycle time or an increase in the injection speed takes place.

[0020] These measures enable significant energy savings to be achieved, resulting in a significant improvement in process efficiency.

[0021] For example, if it becomes apparent during a prolonged production phase that the maximum available ultrasonic power is not being reached, or not even close to being reached, it may be advisable to slightly reduce the electrical energy used, for example, for heating the plasticizing unit or other measures mentioned above, and to achieve any resulting increased degree of necessary viscosity reduction through increased ultrasonic input. This measure can be more energy-efficient overall.

[0022] A further advantageous embodiment of the method according to the invention is characterized in that the maximum deviation is less than or equal to 10% of the value of the corresponding reference representation parameter (RPref), in particular less than or equal to 5% of the value of the corresponding reference representation parameter (RPref), particularly preferably less than or equal to 2.5% of the value of the corresponding reference representation parameter (RPref), ideally 0% of the value of the corresponding reference representation parameter (RPref).

[0023] As a result, the control sensitivity and thus the accuracy of the process control relative to the reference process is increasingly improved.

[0024] Particularly suitable parameters for the representation parameter RP are parameters that represent a melt characteristic, in particular a viscosity of the melt or an injection work, or are formed from a melt viscosity and a cavity pressure.

[0025] Examples of suitable representation parameters RP are given in the following paragraph, which gives examples of the reference representation parameter RP refThese examples are also suitable for the representation parameter RP. It is essential that a representation parameter RP is selected that allows the most direct statements about the melt viscosity, either instantaneously or over time. In particular, parameters should be selected that, with regard to a change in melt viscosity, also change significantly with the change in viscosity in order to obtain the most accurate statement possible about the viscosity behavior of the melt.

[0026] It is useful that the reference representation parameter RP ref which is determined at least once during a molding process and / or during a time period of the molding process, at least one parameter or a combination of parameters from the following group or a derivation from these reference representation parameters RP ref is: - a reference viscosity index VI ref the plastic melt of the reference cycle; - a reference pressure p ref an injection pressure or a holding pressure of the reference cycle; - a reference screw position s ref a plasticizing screw of the plasticizing unit of the reference cycle; - a reference time t ref the reference cycle; - a reference mold wall temperature (T wand_ref ); - a reference measurement value from an ultrasonic sensor arranged in the tool; - a reference injection work (W inj_ref ); - a reference cavity pressure p WID_ref is.

[0027] With these reference representation parameters RP refThe current viscosity of a plastic melt or its temporal progression during a certain period of time as well as any changes in it can be determined in a suitable manner with sufficiently good accuracy.

[0028] It is also useful that the current representation parameter RP act, which is determined at least once during a molding process and / or during a time period of the molding process, at least one parameter or a combination of parameters from the following group or a derivation from these reference representation parameters RP act is: - a current viscosity index VI act the plastic melt of the current production cycle; - a current print p act an injection pressure or a holding pressure of the current production cycle; - a current screw position s act a plasticizing screw of the plasticizing unit of the current production cycle; - a current time t act the current production cycle; - a current cavity pressure p WID_act - a current mold wall temperature (T wand_act ) - a current measured value of an ultrasonic sensor located in the tool; a current injection work (W inj_act ) is.

[0029] With these current representation parameters RP act can be analogous to the above-mentioned reference representation parameters RP ref The current viscosity of a plastic melt or its temporal progression during a specific period of time as well as any changes therein can be determined with sufficient accuracy in a suitable manner.

[0030] In particular, if it is possible to adjust the viscosity of the plastic melt in a suitable manner by using ultrasonic energy, the injection molding process, in particular the current molding process, is particularly simplified if no adjustment of a switchover point and / or no adjustment of a holding pressure or the holding pressure curve takes place during the current production cycle.

[0031] It is particularly advantageous that during the molding process of the production cycle, the viscosity and / or one or more representation parameters RP ref the plastic melt.

[0032] This is particularly advantageous because after adjusting the viscosity by introducing ultrasonic energy, there is still enough time within the current molding process to be able to carry out further adjustments of process parameters, if necessary, in particular with regard to the switchover point or during the holding pressure phase.

[0033] In order to obtain the effect of the desired viscosity change, it is advisable that in case the current value for the representation parameter RP act a lower value for the current melt characteristic, e.g. the current viscosity of the melt, than the value of the reference representation parameter RP ref has the current ultrasonic power P us_act is reduced.

[0034] In order to obtain the effect of the desired viscosity change, it is advisable that in case the current value for the representation parameter RPact a larger value for the current melt characteristic, e.g. the current viscosity of the melt, than the value of the reference representation parameter RP ref is the current ultrasonic power P us_act is increased.

[0035] It is advantageous that the starting value for the ultrasonic power P us_start a value is selected which is below the corresponding maximum value of the ultrasound unit used, so that a control reserve is provided.

[0036] Maintaining a control reserve is advisable because, depending on the long-term drift of the melt viscosity, the ultrasonic unit used has sufficient power reserves to be able to provide even unexpectedly high values ​​of the required ultrasonic power.

[0037] In addition to the above-mentioned determination of the representation parameter RP and the reference representation parameter RPref It may also be advantageous if during the learning phase A) a variation of the ultrasonic power P us during a molding process of a learning injection molding cycle, whereby the resulting fluctuations of the reference representation parameter RP ref an influence characteristic of the ultrasonic power P us on the viscosity of the plastic melt.

[0038] Knowledge of the influence characteristics of the ultrasonic power P US facilitates the subsequent design of the molding process during the production phase, since the reaction of the melt viscosity to different values ​​of the ultrasonic power P US are known.

[0039] In order to obtain meaningful reference representation parameters, it is advisable to determine the reference representation parameter RP refduring the molding process, at least n values ​​of the reference representation parameter RP ref recorded, whereby the number n is preferably determined process-specifically.

[0040] A suitable number n of defined part formation sub-phases results essentially from the intended accuracy of the reference representation parameters RP to be fulfilled in the production cycle ref With increasing numbers, greater accuracy can be expected, as smoothing errors are minimized. Conversely, it makes sense to choose the number n only large enough to minimize unnecessary computational effort and thus potentially occurring delays.

[0041] In order to reduce the computational effort and thus also to reduce possible time delays, it may be expedient, particularly in the case of short injection molding processes, for example for smaller parts, to determine average reference values ​​for the at least one reference representation parameter RP for at least one, preferably several, molding part formation phases of the molding process of at least one reference cycle ref be calculated.

[0042] To simplify the adaptation effort from the findings of the learning phase to the production phase, it may be expedient that during the learning phase A) for setting up the at least one learning injection molding cycle to obtain a good part (reference cycle), the ultrasonic energy introduced into the plastic melt during the molding process, in particular the ultrasonic power P introduced into the plastic melt usand / or the ultrasonic amplitude A introduced into the plastic melt us is kept constant.

[0043] In particular, for the effective regulation of long-term trends in the change of melt viscosity, it is advisable to use as the starting value of the ultrasonic power P us at the beginning of a subsequent production cycle a final value of the ultrasonic power P us of the previous production cycle or an average value of the ultrasonic power (P us ) from one or more of the previous production cycles

[0044] This ensures that only small changes in the ultrasonic power or ultrasonic amplitude are necessary from production cycle to production cycle, since the starting value of the production cycle changes with any long-term trend in the viscosity change of the plastic melt.

[0045] Method according to one of the preceding claims, characterized in that in the event of reaching or imminently reaching the maximum ultrasonic energy that can be emitted by the ultrasonic unit, additional process parameters which influence one or more representation parameters RP of the plastic melt are adjusted in such a way that the ultrasonic unit has a sufficiently high control reserve.

[0046] By maintaining the control reserve of the ultrasonic unit or by restoring it when the maximum ultrasonic power that can be delivered is about to be reached, it can be ensured that sufficient ultrasonic power is always available at short notice in the event of an abrupt drop in the melt viscosity.

[0047] Finally, it is possible that the adaptation or variation of the ultrasound power (P us) by influencing an ultrasound amplitude (A us ) and / or by influencing an ultrasonic frequency (f us ) takes place.

[0048] A suitable selection, whether by means of the ultrasound amplitude (A us ) or by means of the ultrasonic frequency (f us ) the adjustment of the ultrasonic power (P us ) depends essentially on the setting options of the ultrasound unit.

[0049] The invention is explained in more detail below using the drawings as examples. They show: Fig. 1: highly schematic longitudinal section through a plasticizing unit with an ultrasonic unit and a molding tool, wherein the ultrasonic unit is arranged in the region of a melt channel; Fig. 2: a flow chart showing method steps of the method according to the invention during the learning phase A) for the purpose of determining the reference representation parameters; Fig. 3: an example of a representation of possible molding process sub-phases using the example of an injection phase, ie before the switching point of a reference cycle in the learning phase A) with temporally constant ultrasonic power P us ; Fig. 4: an example of a flow diagram of the viscosity adjustment / viscosity control according to the invention during a molding process in the production phase B) of the method according to the invention; Fig. 5: an example of a representation of an adapted ultrasonic power curve during a production process to approximate the curve of a current representation parameter RP act to a course of a reference representation parameter RP ref during an injection phase; Fig. 6: an example of a further adapted ultrasonic power curve during a production process to approximate the curve of a current representation parameter RP act to a course of a reference representation parameter RP ref , which extends into a post-pressure phase;

[0050] Fig. Figure 1 schematically shows the apparatus structure with which the method according to the invention can be carried out. The injection molding method according to the invention uses a plasticizing unit 1, which is fluidically connected to a mold 3 via a melt channel 2, wherein an ultrasonic unit 4 is provided, by means of which ultrasonic energy can be delivered to a plastic melt 5. The ultrasonic unit 4 has a sonotrode 6, which in the example shown is arranged according to Fig. 1 is embodied, for example, as a rod sonotrode. Preferably, the sonotrode 6 emits ultrasonic energy directly to the plastic melt 5, i.e., an ultrasound-emitting region of the sonotrode 6 is in direct contact with the plastic melt 5, for example, is immersed in it. Definitions: a) Ultrasonic energy, as defined by the invention, is understood to mean mechanical vibration energy in a frequency range above 16 kHz. Such ultrasonic energy can be a mechanical vibration of ambient air (airborne sound) or structure-borne sound transmitted by the sonotrode 6 to the plastic melt 5. b) Under ultrasonic power P us In the sense of the invention, this is to be understood as meaning which ultrasonic energy content is introduced into the plastic melt 5 per unit of time.

[0051] In principle, an ultrasonic power P usan ultrasonic unit, for example the sonotrode 6, can be influenced by an amplitude of the mechanical vibration and / or by a frequency of the mechanical vibration. In practice, it is often easier to adjust the ultrasonic power P delivered to the plastic melt 5. us about the ultrasound amplitude A us to influence. Influencing the ultrasonic frequency f us However, it is equally possible. Therefore, if the melt viscosity of the plastic melt 5 is adjusted either by introducing, adjusting, adapting or varying the ultrasonic power P us In general terms, this means that this can be done either by adjusting the ultrasound amplitude A us or by adjusting the ultrasonic frequency f us A realistic power range for an ultrasonic power P us, which is introduced into the plastic melt 5, lies in a range between several hundred watts up to several kilowatts, which depends in particular on the amount of melt whose viscosity is to be influenced. Ultimately, the ultrasonic power P to be used is us depends on the size of the part to be produced.

[0052] Fig. 2 shows a flow chart illustrating process steps of the injection molding process according to the invention during the learning phase A) for the purpose of determining the reference representation parameter RPref or a temporal progression of the reference representation parameter RP ref (t). To determine the reference representation parameter RP ref more suitable representation parameters RP are used. These are, for example, reference pressures p ref , such as a reference pressure p refan injection pressure or a holding pressure of the reference injection molding cycle or a reference cavity pressure p WID_ref , a melt viscosity VI of the plastic melt, which can be used as a reference viscosity index VI ref Furthermore, suitable representation parameters RP are a screw position s and its reference screw position s ref , a time t, or its reference time t ref of the reference cycle. A mold wall temperature T wand or a reference mold wall temperature T wand_ref , a reference measurement value of an ultrasonic sensor, which is arranged in the tool or an injection work W inj or a reference injection work W inj_ref is also suitable.

[0053] In a step L100, for example, a learning injection molding cycle with an integrated active ultrasonic unit 4 is first set up. This is done, for example, for a specific component to be manufactured based on the experience of an experienced operator. To set up the learning injection molding cycle, the ultrasonic unit 4 is set up in a step L101 so that it starts with a fixed starting value for the ultrasonic power P us_start which is kept constant throughout the learning injection molding cycle. Alternatively, the ultrasonic unit 4 can also be set up in this step L101 so that it operates with a fixed starting value for the ultrasonic amplitude A us_start or a fixed starting value for the ultrasonic frequency f uswhich is kept constant throughout the learning injection molding cycle. These starting values ​​are advantageously chosen so that they are below the maximum ultrasonic power P us_max of the ultrasonic unit 4, for example, at 80% of the stated maximum values. With these settings, for example, a control reserve remains up to the maximum ultrasonic power P US_Max of 20%. In the illustration according to Fig. 2 finds the referencing, i.e. the search for a suitable reference representation parameter RP ref during the injection phase of the learning injection molding cycle. However, referencing is also possible in a later stage of a molding process, for example, during a holding pressure phase.

[0054] In the simplest possible embodiment, it is also possible not to apply any ultrasonic energy to the melt during the learning injection molding cycle. The reference representation parameters RP ref can also be determined in a learning injection molding cycle without any ultrasonic energy supply.

[0055] The representation according to Fig. 2, according to which referencing takes place during the injection phase, is to be seen merely as an example. In principle, the entire method according to the invention can also be carried out throughout the entire molding process, i.e., for example, both during the injection phase and in the holding pressure phase. However, the injection phase of a molding process is preferred over the holding pressure phase of the molding process because the injection phase precedes the holding pressure phase and thus allows more time in one and the same injection molding cycle to incorporate findings from the injection phase into the further molding process, for example, by changing the ultrasonic power Pus.

[0056] In a step L102, the learning injection molding process is preferably but not necessarily set up in such a way that a stable good part production takes place during associated learning injection molding cycles, wherein the ultrasonic unit 4 is operated with the above-determined starting value of the ultrasonic power P us_start , which is kept constant, in particular, during the respective learning injection molding cycles.

[0057] In a subsequent step L103, at least one reference learning injection molding cycle is selected and / or recorded from the learning injection molding cycles during the learning phase A). In the embodiment according to Fig. 2, at least one suitable representation parameter RP for at least one injection phase or at least one molding process phase can be calculated and / or determined from the recorded reference learning injection molding cycle. The representation parameter RP represents or maps a melt viscosity. For example, a reference viscosity index VI ref which is determined according to a method as disclosed in DE 10 2013 111 257 B3. Additional or alternative representation parameters RP can be, for example, the screw position s and, if applicable, associated pressures p (see also the list above).

[0058] Representation parameters RP determined during the reference learning injection molding cycle are then used as reference representation parameters RP ref designated and reused.

[0059] In a subsequent step L104, average reference values ​​of the reference representation parameters RP ref be calculated.

[0060] Optional additional procedural steps during learning phase A) can be, for example, the following procedural steps: a) a step L105 can, for example, perform an automatic fine-tuning of the reference ultrasonic power P us_ref depending on material fluctuations with the aim of achieving the highest possible value for the reference ultrasonic power P us_ref while ensuring sufficient control reserve. This optional step is conveniently performed at approximately the same time as process step L101. b) A further optional method step L106 takes place at approximately the time of step L104 and can involve a variation of the ultrasonic power P us which, deviating from the respective starting value, can be used to determine the strength of the influence of an ultrasound input from the ultrasonic unit 4 on the melt viscosity. This step serves to parameterize the power control or the amplitude control of the ultrasonic energy.

[0061] At the end of the referencing according to Fig. 2 there are one or more individual values ​​of the reference representation parameters RP ref or temporal courses of the reference representation parameters RP ref (t) as shown below using the example of Fig. 3 are described.

[0062] In Fig. In Figure 3, all curves shown are plotted against time t on the x-axis. The reference value of the ultrasonic power P us_refis constant over time and is shown as a thick black continuous line. In this case, the time axis reflects Fig. 3 represents an injection phase of the reference injection molding cycle and is subdivided into a number n of injection phases. Below the time axis, examples of the corresponding reference representation parameters RP are shown for each injection phase. ref These reference representation parameters RP ref For example, this could be a pressure p1 at the end of the first injection phase, a screw position s1 at the end of the first injection phase, a time t1, or a viscosity index VI1 at the end of the first injection phase. The reference values ​​for subsequent injection phases are specified in the same way. A screw position curve s ref (t) during the reference cycle is shown as a dashed, downward-sloping line. A reference injection pressure curve p ref(t) is plotted over time t as a thin continuous line.

[0063] The reference representation parameters RP determined here ref are now used as target values ​​for a production injection molding cycle of production phase B).

[0064] A process sequence during the production phase B) is shown as an example using the Fig. 4 shown.

[0065] First, in a step P100, the viscosity control, i.e. the control of the ultrasonic unit 4, is activated.

[0066] Then, in a step P101, a new production injection molding cycle is started during production phase B).

[0067] After this step P101, a continuous measurement of one or more of the current representation parameters RP is carried out in a step P102 actduring at least one of the n molding process sub-phases, for example injection sub-phases, where these current representation parameters RP act in turn are parameters that depict or represent the current melt viscosity in the current production injection molding cycle.

[0068] As a starting value for the ultrasonic power P us_act or the ultrasound amplitude A us_act of the current production injection molding cycle, the corresponding reference value from the learning phase A) is used, i.e. the reference ultrasonic power P us_ref or the reference ultrasound amplitude A US_ref .

[0069] This is followed by a comparison of the reference values ​​and the current values ​​for the melt viscosity of the plastic melt until the end of the nth injection phase or the nth molding process phase.

[0070] In a decision step P104, the current melt viscosity is compared with the reference melt viscosity of the respective nth injection sub-phase or the respective nth molding process sub-phase.

[0071] If the current melt viscosity is greater than the reference melt viscosity, the value for the current ultrasonic power P US_act for the subsequent n+1-th injection part phase or for the subsequent n+1-th molding process subphase within the same production injection molding cycle in order to reduce the current viscosity of the plastic melt.

[0072] Conversely, if it is determined in decision step P104 that the current melt viscosity is smaller than the reference melt viscosity, the value for the current ultrasonic power P US_actfor the subsequent n+1-th injection part phase or the subsequent n+1-th molding process subphase within the same production injection molding cycle in order to increase the current viscosity of the plastic melt.

[0073] After performing step P105 or step P106, a further decision step P107 follows, in which it is queried whether the current injection subphase or the current molding process subphase is already the maximum possible injection subphase or the maximum possible molding process subphase. If this is the case, the production injection molding cycle is ended in step P108. If this is not the case, the value n for the injection subphase and / or the molding process subphase is increased by 1 in step P109. Subsequently, the previously described method is carried out again from step P103 for the injection subphase or the molding process subphase then increased by 1.

[0074] After the end of the cycle (step P108), before starting a new, subsequent production injection molding cycle in production phase B), the current ultrasonic power P US_act of the completed production injection molding cycle can be used as starting values ​​for these variables for the subsequent production injection molding cycle. This can be done based on the melt viscosity of the previous cycle and / or based on information about the volume of the hot runner 2 and the decay behavior of the viscosity change of the plastic melt caused by the ultrasonic unit 4.

[0075] Using the following Fig. 5 shows the adjustment of a course of a current representation parameter RP act (t) to a desired course of the reference representation parameter RP ref (t) using the example of a suitable pressure curve (pact (t) / p ref (t)), for example, an injection pressure curve, a cavity pressure curve, or other suitable pressure curves. Instead of the explicit pressure curves shown, other representation parameters RP mentioned above, which depict or represent the melt viscosity, can also be selected.

[0076] The graphs in the representation according to Fig. 5 are also plotted against time t as the x-axis. The reference pressure curve p ref (t)is shown as a solid black thin line, taken from the Fig. 3, shown. The unaffected current pressure curve p act '(t) in the example shown is consistently above the reference pressure curve p ref (t) and is shown in a combined thin solid and dashed line. Such an unaffected current pressure curve p act'(t) would occur if no viscosity correction by ultrasonic energy input, as provided for in the invention, would take place.

[0077] At the end of the first injection phase (n=1) it is already evident that the current injection pressure p1 is increasing towards higher values ​​compared to the reference pressure p ref migrates, so that in this production cycle a higher melt viscosity VI act which leads to higher injection pressures p act Thus, at the end of the first injection phase (n=1) or at the end of the first molding process phase, the ultrasonic power P US_act increased (step P105), which leads to a reduction in the melt viscosity VI act As a result, during the second injection phase (n = 2) the current injection pressure curve p act (t) is flatter compared to the unaffected current injection pressure and approaches the reference pressure curve p refinitially and even falls below this value towards the end of the second injection phase. The corrected current injection pressure curve p act (t) is shown in the representation according to Fig. 5 is shown as a continuous grey line with occasional dots on this line.

[0078] At the end of the second injection phase (n=2) or at the end of the second molding process phase, there is a slightly lower current pressure p act before the reference pressure p ref at this time, so that the ultrasonic power P us_act is reduced according to step P106, which results in an increase in the viscosity of the plastic melt.

[0079] Already at the end of the third injection phase (n = 3) the current pressure p act due to the viscosity adjustment defined according to the invention using ultrasonic energy, almost identical to the reference pressure p refwhich should be achieved.

[0080] At the end of the illustrated injection phase (ie, at n = n Max ) the inventive objective is achieved, whereby the current representation parameter RP act (here the current injection pressure p act ) corresponds to the corresponding reference representation parameter RP ref (here the reference injection pressure p ref ) and at least partially coincides with it. In subsequent process phases, which follow the n max -th sub-phase, no further process interventions are necessary. For example, a switching point or a holding pressure curve can remain unchanged compared to the reference cycle determined in learning phase A). A key objective of the invention is thus achieved.

[0081] Using the following Fig. 6 shows the adjustment of a course of a current representation parameter RP to be achieved according to the invention act (t) to a desired course of the reference representation parameter RP ref (t), where the adjustment extends, for example, from the injection phase through a switching point UP into a holding pressure phase. A suitable representation parameter is a cavity pressure p WID In terms of equipment, when adjusting the viscosity after the switchover point, the sonotrode 6 is expediently arranged so that it can deliver ultrasonic energy to the melt that is still flowing in the mold. This ensures that the melt, whose viscosity has been influenced, still reaches a molded part cavity. The cavity pressure curve (p WID_act (t) / p WID_ref(t)). A switching point UP is located in the example shown between n=1 and n=2. The step P105 described above is therefore still in the injection phase. The step P106 is already in the pressure-controlled holding pressure phase. Unlike in the Fig. 5 the unaffected current cavity pressure p' WID act (t) lower than the corresponding reference value curve p WID_ref (t). To increase the cavity pressure, ultrasonic energy is applied at n=1 (P105), which leads to a reduction in melt viscosity. A reduction in melt viscosity results in an increase in the cavity pressure p WID , which leads to an adjustment of the current cavity pressure curve to the corresponding reference cavity pressure curve. In case of overshoot, as shown for n=2, the current ultrasonic power P us_actreduced (P106), which leads to an increase in the melt viscosity and thus a reduction in the cavity pressure p WID As in the example according to Fig. 5 is a sufficient adjustment of the current cavity pressure curve p WID_act (t) to the reference tool cavity pressure curve p WID_ref (t) already reached from ca n=3. List of reference symbols 1 plasticizing unit 2 melt channel 3 mold tool 4 Ultrasound unit 5 Plastic melt 6 Sonotrode P us_start Starting value for an ultrasonic power A us_start Starting value for an ultrasound amplitude f us_start Starting value for an ultrasonic frequency RP representation parameters RP ref Reference representation parameters RP ref (t) Reference representation parameter progression RP actcurrent representation parameter P us_act current ultrasound power A us_act current ultrasound amplitude f us_act current value for an ultrasonic frequency VI ref Reference viscosity index p ref Reference pressure s ref Reference screw position t ref Reference time p WID_ref Reference cavity pressure T wand_ref Reference tool wall temperature W inj_ref Reference injection work VI act current viscosity index p act current pressure S act current screw position t act current time p WID_act current cavity pressure T wand_act current mold wall temperature W inj_act current injection work A) Learning phase B) Production phase L100-L106 Procedural steps in the learning phase P100-P110 Process steps in the production phase

Claims

[1] Injection molding method using a plasticizing unit (1) which is fluidically connected to a mold (3) via a melt channel (2), wherein an ultrasonic unit (4) is provided which is designed and configured to deliver ultrasonic energy to a plastic melt (5), wherein the injection molding method comprises the following steps: A) in a learning phase: A.1) Carrying out at least one learning injection moulding cycle, for example a learning injection moulding cycle to obtain a good part; A.2) Determining at least one value of a representation parameter (RP), at least at one point in time or during a period of time of the molding process; A.3) Recording of at least one learning injection molding cycle, for example the learning injection molding cycle for obtaining the good part, as a reference cycle, wherein for this purpose at least one representation parameter (RP) is used as a reference representation parameter (RP ref) or at least one course of the representation parameter (RP) as a reference representation parameter course (RP ref (t)) is recorded at least during the period of the molding process, in particular during the injection phase, and B) in a production phase: B.1) Carrying out at least one production injection molding cycle, wherein ultrasonic energy is delivered to the plastic melt (5) at least temporarily during a molding process of the production injection molding cycle; B.2) wherein at least during the molding process of the production injection molding cycle, continuously or at least at one or more process points, a current value for the representation parameter (RP act ) at least the ongoing moulding process is determined; B.3) Comparison of the value of the reference representation parameter (RP ref) with the current value for the representation parameter (RP act ) of corresponding process points of the learning injection molding cycle and the production injection molding cycle; B.4) Adaptation of a current ultrasonic energy of the current production injection molding cycle at a level of a value for the current ultrasonic power (P us_act ) during the current production injection molding cycle, if the current value for the representation parameter (RP act ) from the corresponding value for the reference representation parameter (RP ref ) deviates by more than a maximum deviation, [2] Injection molding process according to claim 1, characterized by that during a molding process of the learning injection molding cycle of a plastic melt (5), ultrasonic energy at a level of a starting value for an ultrasonic power (P us_start ) is supplied. [3] Injection molding process according to claim 1 or 2, characterized bythat the supply of ultrasonic energy occurs both in the learning phase and in the production phase during an injection phase and / or during a holding pressure phase. [4] Injection molding process according to one of the preceding claims, characterized by that the emission of ultrasonic energy at the beginning of step B.1) is at the level of the starting value for the ultrasonic power (P us_start ) of the learning injection molding cycle. [5] Method according to one of the preceding claims, characterized by that, for example, if there is a sufficiently high control reserve of the ultrasonic unit (4), a reduction in the heating energy of a cylinder heater of the plasticizing unit (1), a reduction in the hot runner temperature, a reduction in the mold temperature and / or a reduction in the cycle time or an increase in the injection speed takes place. [6] Injection molding process according to one of the preceding claims, characterized bythat the maximum deviation is less than or equal to 10% of the value of the corresponding reference representation parameter (RP ref ), in particular less than or equal to 5% of the value of the corresponding reference representation parameter (RP ref ), particularly preferably less than or equal to 2.5% of the value of the corresponding reference representation parameter (RP ref ), ideally 0% of the value of the corresponding reference representation parameter (RP ref ) is. [7] Injection molding process according to one of the preceding claims, characterized by that the representation parameter (RP) represents a melt characteristic, in particular a viscosity of the melt, or is formed from a melt viscosity and a cavity pressure. [8] Injection molding process according to one of the preceding claims, characterized by that the reference representation parameter (RP ref), which is determined at least once during a molding process and / or during a time period of the molding process, at least one parameter or a combination of parameters from the following group or a derivation from these reference representation parameters (RP ref )is: - a reference viscosity index (VI ref ) the plastic melt (5) of the reference cycle; - a reference pressure (p ref ) an injection pressure or a holding pressure of the reference cycle; - a reference screw position s ref ) a plasticizing screw of the plasticizing unit (1) of the reference cycle; - a reference time (t ref ) of the reference cycle; - a reference mold wall temperature (T wand_ref ), - a reference measurement value from an ultrasonic sensor arranged in the tool; - a reference cavity pressure (p WID_ref ) is; - a reference injection work (W inj_ref ). [9] Method according to one of the preceding claims, characterized by that the current representation parameter (RP act ), which is determined at least once during a molding process and / or during a time period of the molding process, at least one parameter or a combination of parameters from the following group or a derivation from these reference representation parameters (RP act )is: - a current viscosity index (VI act ) the plastic melt (5) of the current production cycle; - a current print (p act ) an injection pressure or a holding pressure of the current production cycle; - a current screw position (s act ) a plasticising screw of the plasticising unit (1) of the current production cycle; - a current time (t act) of the current production cycle; - a current mold wall temperature (T wand_act ); - a current measured value from an ultrasonic sensor located in the tool; - a current cavity pressure (p WID_act ); - a current injection work (W inj_act ). [10] Method according to one of the preceding claims, characterized by that no adjustment of a switchover point and / or no adjustment of a holding pressure or the holding pressure curve is made during the current production cycle. [11] Method according to one of the preceding claims, characterized by that during the molding process of the production cycle, an influence on the viscosity and / or one or more representation parameters (RP ref )of the plastic melt (5). [12] Method according to one of the preceding claims, characterized bythat in case the current value for the representation parameter (RP act ) represents a lower value for the current melt characteristic, e.g. the current viscosity of the melt, than the value of the reference representation parameter (RP ref ), the current ultrasonic power (P us_act ) is reduced. [13] Method according to one of the preceding claims, characterized by that in case the current value for the representation parameter (RP act ) represents a larger value for the current melt characteristic, e.g. the current viscosity of the melt, than the value of the reference representation parameter (RP ref ), the current ultrasonic power (P us_act ) is increased. [14] Method according to one of the preceding claims, characterized by that the starting value for the ultrasonic power (P us_start) a value is selected which is below a corresponding maximum value of the ultrasonic unit (4) used, so that a control reserve is provided. [15] Method according to one of the preceding claims, characterized by that during the learning phase A) a variation of the ultrasonic power (P us ) during a molding process of a learning injection molding cycle, whereby the resulting fluctuations of the reference representation parameter (RP ref ) an influence characteristic of the ultrasonic power (P us ) on the viscosity of the plastic melt (5) is determined. [16] Method according to one of the preceding claims, characterized by that to determine the reference representation parameter (RP) during the molding process, at least n values ​​of the reference representation parameter (RP ref ), whereby the number n is preferably determined process-specifically. [17] Method according to one of the preceding claims, characterized by that for at least one, preferably several molding sub-phases of the molding process of at least one reference cycle, average reference values ​​for the at least one reference representation parameter (RP ref ) can be calculated. [18] Method according to one of the preceding claims, characterized by that during the learning phase A) for setting up the at least one learning injection moulding cycle, for example for obtaining a good part (reference cycle), the ultrasonic energy introduced into the plastic melt (5) during the moulding process, in particular the ultrasonic power (P us ) is kept constant. [19] Method according to one of the preceding claims, characterized by that the starting value of the ultrasonic power (P us) at the beginning of a subsequent production cycle a final value of the ultrasonic power (P us ) of the previous production cycle or an average value of the ultrasonic power (P us ) from one or more of the previous production cycles. [20] Method according to one of the preceding claims, characterized by that in the event of reaching or imminently reaching the maximum ultrasonic energy that can be emitted by the ultrasonic unit (4), additional process parameters which influence one or more representation parameters (RP) of the plastic melt (5) are adjusted in such a way that the ultrasonic unit (4) has a sufficiently high control reserve. [21] Method according to one of the preceding claims, characterized by that the adaptation or variation of the ultrasonic power (P us ) by influencing an ultrasound amplitude (A us) and / or by influencing an ultrasonic frequency (f us ) takes place.

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