Method for determining the compression behavior of a moldable material, method for operating a molding machine, and molding machine

Abstract

Method for determining at least one characteristic value for describing the compression behavior of a material (M) prepared in a forming machine (1), wherein at least a part of the prepared material (M liquid ) is introduced via a distribution system (7) and a gate (8) into a mold cavity (9) of a tool (14), in which the prepared material (M liquid ) solidifies, comprising carrying out at least one compression test in which a change in a material (M liquid ) and a measurement of the resulting pressure change is carried out or a pressure drop is applied to the material (M liquid) applied pressure is changed and a measurement of a resulting change in the volume accommodating the material is carried out, wherein at least one parameter for describing the compression behavior is calculated from the result of the at least one compression test using a mathematical model, characterized in that the at least one compression test is carried out with the gate (8) at least substantially solidified or, if the forming machine (1) has a hot runner that can be closed at the gate (8), with the hot runner closed, so that a dead volume (V Tot ) in the calculation of at least one parameter to describe the compression behavior is taken into account, whereby the dead volume (V tot) consists of a sprue system (6), consisting of a distributor system (7) and the gate (8), and a material collecting space (4), and wherein the gate (8) and a part of the distributor system (7) are formed in the tool (14).

Description

[0001] The present invention relates to a method having the features of the preamble of claim 1 and a forming machine having the features of the preamble of claim 13.

[0002] The material prepared in a material collection chamber is introduced via a sprue system formed by a distribution system and a gate into a mold cavity, for example, located in a tool, where it solidifies. The "gate" refers to the part of a sprue system that connects the molded part formed by the material solidified in the mold cavity (in the case of an injection molding machine, this is also referred to as a "sprue") to the distribution system.

[0003] There are various parameters for describing the compression behavior of a compressible material, e.g., the bulk modulus K, which is discussed as an example below. However, the invention can also be implemented using other parameters (such as compressibility).

[0004] The bulk modulus K of a material describes the all-round pressure change required to cause a specific volume change of the material. It is defined as: K=−VdpdV V ... volume dp ... (infinitesimal) pressure change dV ... (infinitesimal) volume change dVN ... relative volume change

[0005] In the following, plastic melt is discussed as an example of the processed material, and an injection molding machine is discussed as an example of a molding machine. The invention is not limited to any of these examples.

[0006] Pressure and volume of a plastic melt are two of the most important physical variables in the processing of plastics using injection molding. This means that the bulk modulus is also extremely important for injection molding. The force applied to the injection piston and the resulting pressure have the primary task of making the melt flow and thus fill a mold cavity. Under the pressure required for this, the melt volume decreases in accordance with the bulk modulus. The change in screw position over time and the resulting calculated volume therefore contains components that correspond to the volume flow into the cavity as well as components that originate from the compression of the melt. In order to recognize and differentiate between these components, knowledge of the bulk modulus and the actual melt volume is required.

[0007] A generic method is disclosed in EP 0 478 788 A1 (Komatsu). The Komatsu document describes the performance of a compression test with reference to the Fig. 7. The compression test is performed with the machine nozzle closed at position 30, thus taking into account the volume of the screw antechamber and the material designated by reference numeral 6. Reference is also made to DE 10 2007 030 637 A1.

[0008] The object of the invention is to provide a method which allows, more precisely than the prior art, to determine at least one parameter for describing the compression behavior of a material prepared in a forming machine, to operate a forming machine depending on a correspondingly determined parameter and to provide a forming machine in which the determined data are stored.

[0009] This object is achieved by a method having the features of claim 1, a method for operating a forming machine having the features of claim 12, and a forming machine having the features of claim 13. Advantageous embodiments of the invention are defined in the dependent claims.

[0010] The invention makes it possible to consider the entire dead volume of a forming machine when determining at least one parameter describing the compression behavior, since the material collection chamber remains unclosed during the compression test. In the Komatsu specification, due to the closed cylinder, only the dead volume in the cylinder, which is already known from the machine design, is taken into account. The sprue system formed in the mold is not considered.

[0011] The invention is explained below using an example of an injection molding machine having a plasticizing screw arranged in a plasticizing cylinder and acting as a piston. However, the method is generally applicable to a molding machine with a material collection chamber for processing and collecting the processed material, and in particular to an injection molding machine in which a piston is arranged in a material collection chamber.

[0012] In the current state of the art, the pressure of the plastic melt is usually measured directly or indirectly using suitable sensors. The volume is usually calculated from the measured position of the screw or injection piston and the known cross-sectional area. However, this calculated volume is usually not identical to the actual melt volume. The additional melt volume, which is

[0013] The amount of material present in the screw antechamber (including flange, nozzle, etc.) or in the sprue system is not specifically considered or even indicated on state-of-the-art injection molding machines. Due to tolerances and possibly unknown dimensions, e.g., of the hot runner system, it is often not known exactly a priori.

[0014] The volume V is therefore made up of different parts: V=Vscrew position+Vnozzle+Vflange+Vhot runner+...

[0015] For the present invention, only the distinction between the portions calculated from the screw position and the remaining portions is relevant. The remaining portions (not accessible via the screw movement) are therefore referred to as dead volume (V Tot ) are summarized. V=Vscrew position+VTotal

[0016] The values for the bulk modulus, which depends on the type of raw material and parameters such as pressure and temperature, are also usually not known with sufficient accuracy.

[0017] In general, the bulk modulus itself is pressure dependent, ie K = K(p). The pressure dependence of the bulk modulus of plastics can in many cases be described by a linear relationship of the form K(p)=K0+K1p with constant parameters K0 and K1. Of course, other models can also be used. By inserting the linear

[0018] Model into the definition of the bulk modulus and transforming one obtains the following differential equation dVV=−dpK0+K1p

[0019] Integrating results in lnV=−1K1ln(K0+K1pK0)+c or V=ece-1K1ln(K0+K1pK0)

[0020] By inserting the boundary condition V(p = 0) = V0 one obtains V(p)=V0e−1K1ln(K0+K1pK0)

[0021] These equations are exemplary and change accordingly under different model assumptions for the pressure dependence of the bulk modulus.

[0022] For a pressure-independent compression modulus (lim K1 → 0), this simplifies to V(p)=V0e−pK0

[0023] Using the example of (Eq. 8), the goal is to determine the parameters V0, K0, K1. In order to obtain data from which these values can be calculated, either a change in the screw position and a measurement of the resulting pressure change or a change in the applied pressure and a measurement of the change in the screw position is required. Such a process, in which either the volume (the screw position) or the pressure is varied and the two quantities are measured, is referred to below as a compression test.

[0024] From the measured value pairs of screw position and pressure V S - p, i.e., from a single compression test, all three parameters can in principle be determined. In practice, this problem proves to be difficult to solve numerically. There are numerous parameter combinations that describe the data very well but are far removed from the actual parameter values. Therefore, even slight measurement noise makes it difficult to determine the parameters precisely in practice.

[0025] In order to obtain values for the bulk modulus and dead volume, it is therefore preferable to carry out at least two compression tests under different boundary conditions. Example:

[0026] Two compression tests are carried out at two different melt volumes and thus different screw positions S1 & S2. The results are, for example, pressure values p iand the corresponding volume values V calculated from the respective screw position S1,i and V S2,i . The derivatives dp / dV S1 or dp / dV S2 can be calculated numerically from the value pairs (V S1,i |p i ) or (V S2,i |p i ). Assuming that the bulk modulus of the material is the same in both cases, the following applies: −(VTot(pi)+VS1,i)dpdV|V=VS1,i =−(VTot(pi)+VS2,i)dpdV|V=VS2,i

[0027] Thus, V Tot when printing p i be calculated as VTot(pi)=−VS2,idpdV|V=VS2,i−VS1,idpdV|V=VS1,idpdV|V=VS1,i−dpdV|V=VS2,i

[0028] As assumed here, the dead volume itself can generally be pressure-dependent. Changes in the dead volume result from deformation of the mechanical components under pressure (elongation of the mass cylinder, compression of the piston / screw, drive train, etc.). This pressure dependence can be determined by evaluating Equation 11 at different pressure levels.

[0029] Da V Tot (p i ) is now known, the bulk modulus K(p i ) at a certain pressure p i according to the definition of the compression modulus K(pi)=−(VS1,i+Vtot(pi))dpdV|V=VS1,i can be calculated. From the values K(p i ) at least two different pressure values p i The parameters K0 and K1, which describe the pressure dependence K(p) in a model or the parameters of another model, can then be calculated.

[0030] Similarly, it is possible to calculate from the values V tot (p i ) to create a model for the pressure dependence of the dead volume. As a first approximation, for example, a linear approach V tot (p) = V tot,0 + κ mech p can be selected.

[0031] The determined values for compression modulus or dead volume can be displayed on the machine screen or recorded or documented in the control system.

[0032] By varying other influencing factors (e.g. the temperature of the processed material or the rate of change of pressure or volume during the compression test) and repeatedly determining the bulk modulus and / or dead volume, the relationship to these influencing factors can clearly be determined and, if necessary, described by appropriate models.

[0033] From the combination of the pressure and temperature dependence of the bulk modulus, the V(p,T) behavior can be determined as a characteristic of the material. If the weight of a defined volume is also determined (e.g., by injection), the behavior of the specific volume v(p,T) can be determined and displayed.

[0034] The two compression tests for determining the dead volume can be movement sequences that are part of a "normal injection molding cycle," additional movement sequences that are integrated into the normal injection molding cycle, or movement sequences performed entirely outside of the normal production process specifically for this purpose. The first two variants have the advantage that the determination can take place directly during the ongoing production process under the prevailing conditions, while the third variant allows for more flexibility in the design of the movement sequence. Examples of suitable movements in the normal injection molding cycle are the pressure reduction at the end of the holding pressure phase and / or the pressure relief phase after dosing.

[0035] Since the dead volume in a specific arrangement (machine + tool) can be assumed to be constant, changes in the compression modulus can subsequently be determined from individual compression tests. Such compression tests for repeated determination of the compression modulus can, in turn, be movements that are part of a "normal injection molding cycle," additional movement sequences that are part of are integrated into the normal injection molding cycle or movement sequences carried out specifically for this purpose, completely outside of the normal production process. Examples of suitable movements in the normal injection molding cycle are the pressure reduction at the end of the holding pressure phase or the compression release after the end of dosing. Ideally (but not necessarily) there should be no more melt flow into the cavity at the time of the compression test. If appropriate closing mechanisms are present on the machine or hot runner nozzle, this can be ensured by these. If closing is not possible, the entire unsolidified area of the melt connected to the melt in the screw antechamber is included in the determination of the dead volume and / or bulk modulus.

[0036] It is preferably provided that the at least one compression test is designed in the form of a pressure drop.

[0037] The main aspect of the present invention is to take the total dead volume into account when calculating the at least one parameter for describing the compression behavior. An important secondary aspect of the present invention, however, also lies in the specific purpose for which this parameter is then used to describe the compression behavior. Therefore, protection is also sought for a method for operating a forming machine based on at least one parameter (stored or calculated in a method according to the invention) for describing the compression behavior. Accordingly, on the basis of this parameter, a realistic injection volume is calculated, a compression relief stroke is calculated, a residence time of the melt in the forming machine is calculated, a pressure regulator is parameterized, a pressure dependence of the compression behavior is determined, a melt temperature is determined and / or a material property of the melt is determined.Such a material property can be the composition of the.

[0038] Phase state, viscoelasticity, solid content, proportion of low molecular weight substances or chemical changes in the polymer structure.

[0039] This aspect is described in more detail below, with the specific possible applications of the parameter to describe compression behavior being explained in detail. The first four possible applications described relate to volume and volume flow.

[0040] Calculating a realistic injection volume: From equation 13, the volume decrease due to compression starting from V0 under a certain pressure p can be calculated ΔV(p)=V0−V(p)=V0[1−(K0+K1pK0)−1K1]

[0041] If the constants V0, K0 and K1 are known, the volume fraction ΔV(p) resulting from compression can be approximately calculated.

[0042] The dosing volume V measured on the machine D is calculated from the measured screw position and screw diameter. The change in this measured dosing volume during the injection molding cycle, e.g., during the injection process, is composed of several components: ΔVD=VD,0−VD=ΔV(p)+ΔVFu¨ll+ΔVLeak

[0043] V D,0 denotes the dosing volume at the beginning of injection and V D the current value of the dosing volume during the injection process. The proportion ΔV Füll corresponds to the actual volume change that occurs at the flow front. The proportion ΔV Leckrefers to the reduction in volume due to material losses through leakage (e.g., via the non-return valve) and is neglected for the time being, as it is usually irrelevant during the injection phase (at least when the non-return valve is closed). The actual injected volume in this case would be ΔVFull=ΔVD−ΔV(p)

[0044] It is therefore reduced by the compression component ΔV(p) compared to the volume difference calculated from the change in screw position. Conversely, a hypothetical dosing volume V D ' which contains only the filling components. VD'=VD,0−ΔVFu¨ll=VD+ΔV(p)

[0045] This results in the following equation 17: VD'=VD+V0[1−(K0+K1pK0)−1K1]for K1≠0VD'=VD+V0(1−e−pK0)for K1=0

[0046] The assumption is made that the pressure is constant throughout the entire volume. This assumption is generally only sufficiently fulfilled in the screw antechamber. For more precise results, it may therefore be useful to make assumptions about a pressure distribution p(V) in the melt and integrate the above formula over the melt volume. VD'=VD+∫0V[1−(K0+K1p(V)K0)−1K1]dV

[0047] The negative time derivative of V D ' then corresponds to the actual filling volume flow without compression components. This calculated value can be used, for example, to regulate the screw speed to achieve the desired filling volume flow.

[0048] Calculation of the compression relief stroke: Before and / or after metering the material, it is common practice to relieve the melt pressure by retracting the screw (corresponding to decompression or compression relief). The required decompression stroke depends on the bulk modulus and the melt volume. At a pressure p, the previously mentioned equation ΔV(p)=V0[1−(K0+K1pK0)−1K1] The minimum required decompression stroke can be determined directly. The decompression stroke is therefore calculated in advance based on the knowledge of K(p) from Equation 19 and not (completely) determined from the pressure curve during decompression in the current injection molding cycle. If the value set by the operator is lower than the pre-calculated value, the control system can issue a warning to the operator. The determined value can also be suggested by the control system or set automatically.

[0049] It has also been shown that after compression relief, material flows from the screw flights into the screw antechamber and can lead to a renewed pressure buildup. The actually required decompression stroke is therefore often somewhat greater than that calculated using the above formula. Such a pressure buildup can be detected by the control system and compensated for by automatically increasing the relief stroke. Alternatively, the operator can be alerted to this by a warning or a suggestion. It is also conceivable to multiply the value determined from the formula by a sufficient safety factor. Such a safety factor can also depend on the screw geometry and material type used. Residence time calculation:

[0050] For the raw material (especially for transparent polymers), the residence time of the melt at high temperatures is of great importance. The residence time is determined by the material throughput and the total melt volume (including the melt volume in the screw flights). The melt volume in the screw flights V Schneckengänge can be derived from the screw geometry and stored in the machine. With known compression modulus and dead volume, the actually injected quantity V Einspritz and thus the actual material throughput V Einspritz / t Zyklus be calculated more accurately. In addition, the calculated dead volume V Tot are included in the residence time calculation. The residence time can thus be calculated more accurately than without knowledge of these parameters. tDwell=tCycleVInjection(Vtot+VD)

[0051] The control system can then display the residence time and, based on limit values for different materials, a warning can be displayed if the recommended or permissible residence time is exceeded.

[0052] Use for pressure regulators, pressure limit regulators: The values of the bulk modulus and dead volume can be used to better parameterize pressure controllers or pressure limit controllers. The maximum useful controller gain, for example, can be derived from these values. Likewise, the well-known relationship V(p) can be used for precontrol (e.g., in downstream pressure control). For this, knowledge of the separate values of K and V is not necessarily required; in some cases, knowledge of the K / V ratio may be sufficient.

[0053] The following three described application possibilities refer to the material. Dependencies K(p), K(T):

[0054] The determination of the pressure dependence of the bulk modulus has already been described. As mentioned above, it can be well described by a linear relationship. K(p)=K0+K1p

[0055] Likewise, the values may not be determined in the machine, but may come from literature, pvT data or other sources.

[0056] The dependence of the bulk modulus on temperature can be determined by compression tests at different cylinder temperatures. It is sufficient to determine the dead volume at only one temperature; for other temperature values, a compression test is sufficient to determine the change in the bulk modulus. The temperature dependence of the bulk modulus can be approximated, for example, by a linear approach. K(T)=K0+KTT To set the parameters K0 and K TUnder this assumption, two compression tests at two different temperatures are sufficient. It is of course equally possible to use other models or to determine the bulk modulus at a variety of temperatures and store the paired values in a table. Ideally, a sufficient waiting time should be allowed to ensure that a sufficiently homogeneous temperature distribution is present in the melt during the compression tests. Likewise, the values can be determined outside the machine but, for example, from the literature, PVT data, or other sources. Determination of melt temperature:

[0057] Conversely, if the relationship K(T) is known, the actual temperature of the melt can be deduced from measuring the bulk modulus in a compression test. This is particularly advantageous because the melt temperature is difficult to measure and usually requires expensive, complex, or sensitive sensors. It should be noted that the absolute value of the melt temperature is often less important than relative changes, which can also be directly observed in the determined bulk modulus or the ratio dp / dV without having to know the exact relationship K(T). To keep the melt temperature constant, it would therefore be sufficient to keep the measured bulk modulus or the value dp / dV constant under otherwise unchanged boundary conditions. This could be used, for example, to control the melt temperature. Dependence based on the loading rate - detailed determination of the material properties:

[0058] By conducting compression tests at different loading rates, possibly at different cylinder temperatures (e.g., two rates per temperature), the (viscoelastic) properties of the melt can be characterized. The material parameters determined in this way can serve as input data for simulating injection molding (partial) processes. Furthermore, the data can be used for material identification and subsequently: • To check whether the correct / intended material is being used in production or whether this material meets the quality criteria specified (by the operator). The quality of the material can also be recorded (recorded) via quality management. • to assist the operator in setting the plasticizing process (e.g. dosing speed, minimum / maximum stroke, cylinder temperatures, etc.). Material characterization - composition and phase state:

[0059] The bulk modulus is a material property that depends on the properties of the material in the volume under consideration. This material can consist of several components. The determined values for K0, K1 and / or the curve of K(p) reflect a mixture of the properties of all components of the material in the volume under consideration. In addition to a polymer melt (also conceivable: metal and glass), this material can contain other gaseous, liquid, supercritical and / or solid components. These components can be other substances (e.g. glass, carbon fibers, fillers, low molecular weight substances such as water, nitrogen, etc., natural substances such as talc, wood, etc., ceramic or metal powder), additives (e.g. pigments, masterbatch, etc.), other polymers (e.g. in polymer blends or copolymers) and / or breakdown, transformation and synthesis products of the polymer melt. The components can be dissolved and / or present as separate pure and / or mixed phases.

[0060] The values K0, K1, and the curve K(p) are compared either with previously measured values (from the same injection molding cycle or from previous injection molding cycles) or with values stored in the machine for the material, material type, or process. From the values K0, K1, and the curve K(p), as well as their changes, conclusions can be drawn about: • the solids content in the melt. Example: Polypropylene (PP) with and without glass fibers. Further details can be found in Fig. 6 can be seen. • the proportions of low-molecular substances in the polymer melt solution or mixture. Example: Detection of supercritical fluid bubbles, e.g., nitrogen bubbles during physical foaming. Further details can be found in Fig. 7 can be seen. • the changes in the material due to chemical decomposition, transformation or build-up reactions of the polymer structure (e.g. also in conjunction with residence time or moisture content). • changes in the material. In other words, this provides an indication of whether the intended material is being used in production and whether this material meets the quality criteria specified (by the operator). The quality of the material can also be recorded using QM technology.

[0061] The Fig. 1 to 3 relate to a first embodiment of the invention. Fig. 4 and Fig. 5 relate to a second embodiment of the invention. Fig. 6 and Fig. 7 illustrate the inference from the calculated compression behavior to characteristics of the melt. Fig. 8 and Fig. 9 show schematic cross-sectional details of a forming machine. Fig. 1 shows the course of dosing volume and injection pressure in two injection molding cycles with different initial dosing volumes. Fig. 2 shows an enlarged section of Fig. 1: This represents the course of dosing volume and injection pressure in the holding pressure reduction phase. Fig. 3 shows the course of injection pressure over dosing volume during the holding pressure reduction phase from Fig. 1 and Fig. 2. Value pairs V S1,i |p i or V S2,i |p i are shown. The holding pressure reduction phase serves as a compression test. The change in the dosing volume is achieved by dosing different melt quantities in two independent injection molding cycles. During the holding pressure reduction phase, the value pairs V S and p recorded. Fig. Figure 4 shows two compression tests in one injection molding cycle. Compression test 1: after the holding pressure phase (solid line), compression test 2: after the dispensing phase (dashed line). The remaining volume and pressure curves are shown in dotted lines. Fig. 5 shows the course of the injection pressure over the dosing volume during the two compression tests from Fig. 4. Value pairs V S1,i |p i or V S2,i |p i are marked.

[0062] The two compression tests at different screw positions are integrated into a single injection molding cycle. Before the end of the holding pressure phase, the pressure is increased to a desired value (in the example, 1000 bar) and then reduced again to approximately 0 bar (compression test 1). A similar pressure profile is run after the dosing process (i.e., with a changed dosing volume) (compression test 2). In the example, the value pairs VS2|p are recorded during the decreasing pressure ramp, and the dead volume and bulk modulus are determined from these. Fig. 6 and Fig. 7 have already been described. Fig. Figure 8 shows a molding machine 1 with a hot runner. The material collection chamber 4 for melted or melted material M liquid is formed between a plasticizing cylinder 2 and a plasticizing screw 3 that is rotatable and axially displaceable within the plasticizing cylinder 2 and functions as a piston 3a. From the nozzle opening 5 in the plasticizing cylinder 2, the material collection chamber 4 passes directly into the sprue system 6. This sprue system 6 is composed of the distribution system 7 and the gate 8. The gate 8 connects the solidified material M rigid in the mold cavity 9 (also called cavity) with the distribution system 7. The mold cavity 9 or the mold cavities 9 is / are formed between the two mold halves 10 and 11 forming the tool 14, which in turn are each attached to mold clamping plates 12 and 13.

[0063] In contrast to Fig. 8 shows Fig. 9 a forming machine 1 with a cold runner. Here, too, a parameter is used to describe the compression behavior based on the total dead volume V Tot up to gate 8. Here too, the material M rigid of the molded parts in the mold cavity 9 solidifies, but not the material M liquid in the distribution system 7 (and in the material collection chamber 4). The measurement of the compression modulus and dead volume V Tot thus also covers the non-solidified areas in the tool 14. The distribution system 7, which is Fig. 9 is formed by a so-called sprue rod, contains in the schematic representation only molten material M liquid In reality, of course, depending on the thickness of the channel and especially on the time of measurement, an at least partially solidified surface layer may have formed.

Claims

[1] Method for determining at least one parameter for describing the compression behavior of a material (M) prepared in a forming machine (1), wherein at least a part of the prepared material (M liquid ) is introduced via a distribution system (7) and a gate (8) into a mold cavity (9) of a tool (14), in which the prepared material (M liquid ) solidifies, comprising carrying out at least one compression test in which a change in a material (M liquid ) and a measurement of the resulting pressure change is carried out or a pressure drop is applied to the material (M liquid) applied pressure is changed and a measurement of a resulting change in the volume accommodating the material is carried out, wherein at least one parameter for describing the compression behavior is calculated from the result of the at least one compression test using a mathematical model, characterized by that the at least one compression test is carried out with the gate (8) at least substantially solidified or, if the forming machine (1) has a hot runner that can be closed at the gate (8), with the hot runner closed, so that a dead volume (V Tot ) in the calculation of at least one parameter to describe the compression behavior is taken into account, whereby the dead volume (V tot) consists of a sprue system (6), consisting of a distributor system (7) and the gate (8), and a material collecting space (4), and wherein the gate (8) and a part of the distributor system (7) are formed in the tool (14). [2] Method according to claim 1, wherein the forming machine (1) has a plasticizing screw (3) arranged in a plasticizing cylinder (2) and acting as a piston (3a), and the change in the material (M liquid ) absorbing volume by changing a position of the plasticizing screw (3) in the plasticizing cylinder (2). [3] Method according to claim 1 or 2, wherein the forming machine (1) has a plasticizing screw (3) arranged in a plasticizing cylinder (2) and acting as a piston (3a), and the change in the pressure applied to the material (M liquid ) applied pressure is carried out by the plasticising screw (3). [4] Method according to claim 1, wherein the forming machine (1) has a piston (3a) arranged in a material collecting chamber (4) and the change in the material (M liquid ) absorbing volume by changing a position of the piston (3a) in the material collecting chamber (4). [5] Method according to claim 1 or 4, wherein the forming machine (1) has a piston (3a) arranged in a material collecting chamber (4) and the change in the pressure applied to the material (M liquid ) applied pressure by the piston (3a). [6] Method according to one of claims 1 to 5, wherein the mold cavity (9) is formed in a tool (14) and the change in pressure and / or volume takes place via a movable tool element, preferably a core puller or an ejector. [7] Method according to at least one of claims 1 to 6, wherein at least two compression tests are carried out under different boundary conditions. [8] Method according to at least one of claims 1 to 7, wherein the at least one determined characteristic of the compression behavior is displayed. [9] Method according to at least one of claims 1 to 8, wherein the at least one compression test is carried out independently of a production cycle of the forming machine (1). [10] Method according to at least one of claims 1 to 8, wherein the at least one compression test is carried out in a production cycle of the forming machine (1). [11] Method according to claim 10, wherein the at least one compression test is carried out in the form of a pressure reduction at an end of a holding pressure phase and / or during a pressure relief phase before or after a dosing process. [12] Method for operating a shaping machine (1), in particular an injection molding machine or transfer press, wherein, depending on at least one of a parameter calculated in a method according to one of claims 1 to 11, for describing the compression behavior - a realistic injection volume and / or a realistic injection volume flow is calculated and / or - a compression relief stroke is calculated and / or - a residence time of the melt in the forming machine (1) is calculated and / or - a pressure regulator is parameterized and / or - a pressure dependence of the compression behavior is determined and / or - a melt temperature is determined and / or - the speed of a plasticising screw (3) is controlled or regulated so that a predetermined filling volume flow is achieved, and / or - a material property of the melt is determined, such a material property being, for example, the composition, the phase state, viscoelasticity, solid content, proportion of low molecular weight substances or chemical changes in the polymer structure. [13] Shaping machine (1), with an electronic control or regulating device and an electronic memory, optionally formed in the electronic control or regulating device, in which a compression modulus and / or a melt volume determined according to a method according to at least one of claims 1 to 11 are stored.

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