Method for dispensing discrete volumes

Abstract

The invention relates to a method for dispensing discrete volumes (10) having certain properties along a trajectory in order to produce a three-dimensional object (58) from solidifiable material that is either in a stressed state or is brought into a stressed state, in which method the stressed state of the material is introduced into a material reservoir (74). A pressure (p) is applied to the stressed state in order to discretely dispense the material from a closable outlet opening in order to produce the three-dimensional object (58) under at least one process condition, at least one process parameter being updated in the event of a change in at least one process condition. A reliable, controlled, and reproducible method is provided by providing material-specific data of the material and by using the material-specific data to regulate the at least one process parameter and / or at least one further process parameter in order to obtain at least one predefined property of the discrete volumes (10) in an unstressed state in which no other additional external influences act on the material.

Description

[0001] Method for applying discrete volumes

[0002] Description

[0003] Reference to related applications

[0004] The present application relates to and claims the priority of German patent application 10 2022 132 825.2, filed on December 9, 2022, the disclosure content of which is hereby expressly incorporated in its entirety into the subject matter of the present application.

[0005] Field of the invention

[0006] The present invention relates to a method for applying discrete volumes with specific properties along a trajectory for producing a three-dimensional object according to the preamble of claim 1, as well as an associated machine control for carrying out the method with the features of claim 15 and a computer program product with the features of claim 16.

[0007] The discrete volume depends on the properties of mass (m) and density (p). Depending on the discharge rate of consecutive volumes along a trajectory (s), a discharge quantity per unit of time results, which influences the shear rate and thus the flowability of the material.

[0008] The term "unloaded state," as used in this application, is to be understood as meaning that in an unloaded state, no additional external influences act on the material. For example, the material is in an unloaded state at room temperature and / or room pressure. The properties of the material, such as density, are generally different in the unloaded state, e.g., at room temperature and / or room pressure, from those in a loaded state, e.g., at a specific pressure, a specific temperature, and / or in a fluid phase of the material.

[0009] The term "solidifiable material," as used in this application, is to be understood broadly and includes, in particular but not exclusively, plastics, silicone, or other thermoplastic and / or elastomeric materials, e.g., ceramic, metallic, and / or powdered materials, as well as paper, cellulose, starch, cork, etc., as well as mixtures of such plasticifiable materials. In principle, these can also be previously plasticized materials or plastic masses that harden after application, either spontaneously or with the aid of additives. The term also includes recyclates or compounds.

[0010] State of the art

[0011] Various methods are known today for the production of three-dimensional objects. For example, the objects can be precisely manufactured using a machine for handling and / or processing a material, in particular a forming machine or a 3D printing machine, e.g., a 3D printer. For this purpose, the material is converted into a fluid state by the influence of temperature and, under the influence of pressure, is discharged from a closable nozzle either as a strand of material or as individual, discrete volumes arranged in a row, whereby the object is produced layer by layer. Such a combination of discharging discrete volumes and a strand of material is disclosed, for example, in DE 10 2013 003 167 A1.

[0012] However, there are many interactions of the existing process parameters as properties of the volume to be discharged or the volume flow.

[0013] Depending on the discharge rate per unit of time, the shear of the material changes as it flows through the discharge nozzle, influencing the flow properties, which in turn, assuming constant parameters, influence the discharge rate per unit of time. For example, viscosity is a parameter used to describe the flowability of a plastic under the influence of a given temperature and pressure.

[0014] Different nozzle diameters or opening gaps, e.g., when using a closure device such as a needle valve, can also cause different shear rates and thus different flow properties. Manufacturing tolerances can also have an influence, making reproducibility between nozzles or forming machines impossible to guarantee. Batch variations in the material can also occur, resulting in different flow properties. In addition, moisture in the material or residual moisture in the material being processed can affect flow properties. Fillers or additives in the material being processed can also influence flow properties.

[0015] For illustration, Fig. 6 schematically shows various influences on the shear viscosity and / or shear rate, e.g., due to molecular mass, pressure, a filler, temperature, or a filler. For example, the shear viscosity decreases with increasing temperature.

[0016] Different temperature settings from machine to machine also result in different discharge quantities. In addition, the shear rates and thus the flow properties depend on the prevailing temperature, which also requires different pressure loads to be applied to the material being discharged.

[0017] If the process specifies that the discharge quantity per unit of time remains the same, other parameters must be adjusted, such as the pressure and / or the temperature.

[0018] DE 102012 004 988 A1, which is the basis of the preamble of claim 1, discloses a method for maintaining a predetermined droplet size or droplet volume in the presence of viscosity fluctuations. To ensure a constant volume despite viscosity fluctuations, the pressure is adjusted. Viscosity is a parameter used to describe the flowability of a plastic under the influence of a given temperature and pressure. This control can compensate for shear-induced flowability.

[0019] However, depending on pressure and / or temperature, different materials, especially plasticizable materials, have different densities or volumes of the fluid material. Thus, adjusting the pressure influences the discharge rate, which can result in cumulative weight fluctuations in the manufactured objects. Therefore, corresponding control is inaccurate or prone to errors, and thus a precisely reproducible process is not possible.

[0020] Furthermore, the amount of material discharged in the unloaded state is crucial for the resulting object weight or density. With the current tracking and control systems, this object density, for example, cannot be precisely predicted.

[0021] US 2020 / 0338824 A1 discloses an extruder and a method for operating an extruder, wherein the extruder is given operating characteristics, and the controller regulates the axial displacement of the screw as a function of the operating characteristics. For example, the material flow of the extruder can be controlled for different materials with different viscosities. Likewise, the screw rotation speed, temperature, and / or pressure can be controlled as a function of the operating characteristics.

[0022] US 2021 / 0154916 A1 discloses a method wherein a pressure in a flow path is recorded during a printing process, and based on the pressure, a volume change of the material in the flow path due to compression of the material during the printing process is determined, and the flow rate of the material in the flow path is compensated for the determined volume change of the material. For example, a melt pressure is recorded, and a volume change of the material due to compression of the material during the printing process is determined, and the flow rate of the material is varied to compensate for the determined volume change.

[0023] Summary of the invention

[0024] Based on this prior art, the object of the present invention is to provide a reliable, controlled and reproducible method for dispensing reproducible discrete volumes with specific properties along a trajectory, wherein changes in properties due to different process parameters are compensated.

[0025] This object is achieved by a method for dispensing discrete volumes having the features of claim 1 and by a machine control having the features of claim 15 as well as by a computer program product having the features of claim 16.

[0026] Advantageous further developments are the subject of the dependent patent claims. The features listed individually in the patent claims can be combined with one another in a technologically expedient manner and can be supplemented by explanatory facts from the description and details from the figures, whereby further embodiments of the invention are shown.

[0027] The method for applying discrete volumes with specific properties along a trajectory for producing a three-dimensional object, e.g. a component, from at least one solidifiable material, e.g. a plastic, which is either in a loaded state, e.g. in a fluid phase, or can be brought into a loaded state, e.g. flowable into a fluid phase, with a machine for handling and / or processing the material, in particular a shaping machine or a 3D printing machine in a process, for example a manufacturing process, comprises the following steps: The loaded state, e.g. the fluid phase, of the material is introduced into a material reservoir and a pressure is generated on the loaded state, e.g. the fluid phase, of the material in the material reservoir.For example, typical temperatures for plastics in the material storage tank range from approximately 50 to 450°C, depending on the material, and typical pressures from approximately 50 to 800 bar (5 to 800 MPa). However, other temperatures and / or pressures can also be provided.

[0028] Furthermore, the material is discretely discharged under at least one process condition, e.g. at a specific pressure and / or a specific temperature from an outlet opening, preferably a closable outlet opening, e.g. a nozzle or a nozzle that can be closed by means of a closing means, to produce the three-dimensional object, wherein, upon at least one change in the at least one process condition, e.g. a change in the flow property, a change in the flowability, a change in temperature or another influence, at least one process parameter is adjusted during the production of the three-dimensional object, preferably while maintaining at least one further process parameter, in order to obtain a predetermined property of the discrete volumes, for example a volume, a density, a mass and / or a temperature, in the loaded state, e.g. in the fluid phase.

[0029] For example, due to a change in flowability, the pressure in the material reservoir can be adjusted in order to maintain a predetermined discharge volume per unit time in the loaded state.

[0030] In order to obtain a reliable, controlled and reproducible method for dispensing reproducible discrete volumes with specific properties along a trajectory, wherein changes in properties due to different influencing process parameters are compensated, material-specific data of the material are provided and with the aid of the material-specific data the at least one process parameter and / or at least one further process parameter is controlled to obtain at least one predetermined property of the discrete volumes in an unloaded state in which no further additional external influences act on the material, e.g. a size, a volume, a density, a mass and / or a temperature, of at least one discharged discrete volume.

[0031] Preferably, the predetermined property of the discrete volumes in the unloaded state includes the mass and / or density. This can advantageously result in increased reproducibility and stability of the components.

[0032] If, for example, the pressure is adjusted due to a change in flowability, the compression of the material results in a larger mass for the same volume. If the object is manufactured with this volume, the object weight will be greater. To advantageously achieve a predetermined object weight, the discharged volume can be adjusted accordingly.

[0033] Due to different pressures, for example, the material can be compressed differently, which means that the discharge quantity in the unloaded, e.g. solid state varies, and thus a reproducible process (e.g. from machine to machine) cannot take place. In order to make the discrete discharge quantity (unloaded, e.g. solid state) reproducible regardless of the machine or system used, the compression of the material, e.g. at the respective existing process pressure and the given temperature, is taken into account. Material-specific data, e.g. pVT data, are available. The process pressure can be varied within a process to reduce fluctuations in flow properties (see document DE 10 2012 004 988 A1). In this way, the discharge quantity of each individual droplet (discrete discharge) can be precisely controlled - either e.g. by varying the pressure or the opening stroke or time.Control is based on a volume within the molten, compressible phase in order to achieve a predetermined "fixed" discharge quantity (mass). The discharge quantity can refer to a volume, but also to a specific mass, since the material data (e.g. material density as a function of pressure and temperature) is known. Therefore, at the end of the construction process, for example, the exact component weight can be calculated and output based on the process data. Control is therefore not "only" based on the volume flow, since the specific density of the material in its respective state is taken into account. Rather, control is also based on a discrete discharge mass.

[0034] For example, typical discrete deposition volumes of approximately 0.001 - 0.05 mm 3 , especially of 0.02mm 3 possible. However, the process is also applicable for other, especially larger, discharge quantities.

[0035] For example, due to the change in flowability described above, the pressure in the material reservoir can be adjusted to maintain a predetermined, reproducible, discrete amount of material. However, this pressure adjustment results in the material being compressed more strongly, resulting in the discontinuous volume with the predetermined volume exhibiting an increased density in the loaded state. However, due to the adjustment, a volume with the increased density is discharged. If this volume is discharged, the increased specific density results in differences in the weight of the manufactured object in the unloaded state.With the aid of the material-specific data, the at least one process parameter and / or at least one further process parameter can be changed such that the discontinuous volume is discharged in the loaded state, for example, with a correspondingly smaller volume, which however has the predetermined mass in the unloaded state. By controlling the at least one process parameter and / or the at least one further process parameter as well as the material-specific data of the material in the loaded state, it is thus advantageously possible to obtain a predetermined material mass and / or material quantity in the unloaded state. If, for example, a change in flowability as described above occurs, the pressure in the material reservoir can be adjusted to maintain a predetermined, reproducible, discrete material quantity. For various materials, such asFor plastics and / or plasticizable materials, a change in the pressure load causes a change in volume and a simultaneous change in the material density in the loaded fluid state. Due to the change in at least one process parameter to maintain, for example, a predetermined discontinuous volume flow, the volume is adjusted back to the "target value" (constant discontinuous volume flow, as known, for example, from DE 10 2012 004 988 A1). An increase in pressure, for example, causes a reduction in volume with a simultaneous increase in the material density in the loaded state. Due to the control to maintain a constant volume flow, the discontinuous volume is adjusted back to the "target value" or increased.However, the material density remains unchanged in the loaded state, so that the discharged mass of the discontinuous volume with the predetermined "TARGET value" of the discontinuous volume in the unloaded state (e.g. at room pressure, atmospheric pressure, room temperature and / or a build chamber temperature) is greater than before despite the same volume in the fluid-loaded state. In principle, this can also occur the other way around: A reduction in pressure causes a volume increase with a simultaneous reduction in the material density in the loaded state. Due to the control to maintain a constant volume flow, the discontinuous volume is adjusted or reduced again to the "TARGET value". The material density in the loaded state remains unchanged, which means that the discharged mass of the discontinuous volume in the unloaded state (e.g.at room pressure, atmospheric pressure, room temperature and / or a construction space temperature) despite the same volume in the fluid-loaded state is lower than before.

[0036] The same applies to a change in temperature. A rise in temperature, for example, causes an increase in volume with a simultaneous reduction in the material density in the loaded state. Due to the change in at least one process parameter to maintain, for example, a constant discontinuous volume flow, the discontinuous volume is adjusted or reduced to the "target value". The material density in the loaded state remains unchanged. This means that the discharged mass in the unloaded state (e.g. at room pressure, atmospheric pressure, room temperature and / or build chamber temperature) is smaller than before, despite the same volume in the fluid-loaded state. In principle, this can also happen the other way around: A drop in temperature causes a reduction in volume with a simultaneous increase in the material density in the loaded state. Due to the control to maintain a constant volume flow, the volume is regulated back to the "target value".The material density in the loaded state remains unchanged, so that the discharged mass in the unloaded state (room pressure, atmospheric pressure, room temperature and / or installation space temperature) is larger than before despite the same volume in the fluid loaded state.

[0037] Preferably, an optimized control system is used which, when a process parameter changes, adjusts the volume in the loaded state so that the same mass is discharged in the unloaded state as before the change. This advantageously achieves better reproducibility from machine to machine, since, for example, the smallest differences can occur due to manufacturing tolerances in the nozzle, which can result in different masses being discharged even with the same pressure settings. Batch fluctuations and / or differences in residual moisture in the material being processed can also be compensated for. Likewise, changes in flow properties, which are dependent on the discharge quantity per time due to the resulting shear stress on the material as it flows through the discharge nozzle, can be compensated for, as can different temperature settings from machine to machine.

[0038] The control to maintain the predetermined property of the discrete volumes in the unloaded state of the at least one discharged discrete volume is preferably carried out due to the tracking of at least one process parameter to maintain a predetermined property of the discrete volumes in the loaded state, e.g. in the material reservoir. For example, this can result in an overlap of the control and the tracking. The control can, for example, take place after the tracking of at least one process parameter, superimposed thereon, or in combination. If, for example, a certain pressure change occurs with regard to the material, which leads to a compression of the material or to the discrete volume now having a greater mass, a corresponding volume change can then occur. This advantageously results in precise and controlled discharge of the material.

[0039] Preferably, at least one temperature and / or pressure dependence of the specific volume, the density, the compressibility and / or the temperature of the material, in particular a dependence of the specific volume of the material on pressure and / or temperature, can be provided as material-specific data. This advantageously results in a simple relationship between different states of the material, e.g. the loaded state and the unloaded state. For example, a volume difference Av can result from the loaded and unloaded state. In principle, further material-specific data can also be provided, as long as they show at least one relationship between an unloaded and loaded state.

[0040] For example, the material-specific data can preferably be provided as pvT data, e.g. using a pvT diagram. The material-specific data can be available, for example, as a file in a machine control system or a network. The pvT data describe the dependence of the specific volume v on the temperature T and the pressure p. For example, in a pvT diagram the specific volume can be plotted against the temperature for different pressures. The specific volume is the inverse of the density or vice versa. Many materials, such as plastics or thermoplastic materials, reduce their volume when they are cooled and expand when they are heated. Furthermore, plastics and thermoplastic materials are compressible, which means that pressure reduces their volume. If different pressures orDepending on the temperature during the process, different amounts of material are discharged, resulting in different object weights and densities. The pvT data can be provided, for example, by the respective material manufacturers or other testing laboratories, e.g., in electronic form, and advantageously, through knowledge of a multidimensional relationship between material-specific values, allow for targeted influence, for example, on the unloaded state of the material and thus the three-dimensional object.

[0041] Advantageously, for effective and simple control, a pressure, a temperature, a volume, a nozzle diameter, an opening time, a discharge time and / or a size of the outlet opening is preferably controlled as the at least one process parameter and / or the at least one further process parameter. For an advantageously simple and reproducible process, the pressure is preferably adjusted to maintain a predetermined volume of at least one discrete volume in the loaded state and / or the volume and / or the temperature is regulated to maintain a predetermined mass of at least one discrete volume in the unloaded state. If, for example, the pressure is adjusted due to a change in flowability, this results in a greater mass for the same volume due to the compression of the material. If the article is manufactured with these volumes, the result is a greater article weight.In order to advantageously obtain a predetermined object weight, the discharged volume can be changed accordingly.

[0042] Preferably, a corrected volume in the unloaded state is calculated for at least one applied discrete volume using at least one ratio of the specific volume of the material in the loaded state to the specific volume of the material in the unloaded state. This advantageously results in a simple link between the loaded and unloaded states. The link can be represented, for example, as a factor.

[0043] For example, a volume of the discrete volumes should be kept constant at a predetermined value (V(pi,Ti) = const.). The pressure and / or temperature (pi,T) are variable and machine-dependent, resulting in a corresponding density p (pi,T) in the loaded state. For the unloaded state (pi -> po; T -> TR aU m, Tßauraum, Tatmosphäre) results from the conservation of mass thus: p (pi,Tj) *V (pi,Ti) = m (pi,Ti) = m (p0,T0) = p (p0,T0)*V (p o ,To) with V(pi,Tj) = const. = c thus follows

[0044] Further preferably, the at least one process parameter and / or the at least one further process parameter is controlled via at least one ratio of the specific volume of the material in the loaded state to the specific volume of the material in the unloaded state and as a function of the prevailing temperature. Thus, a previously defined object density can advantageously be generated.

[0045] Preferably, a total corrected volume of material discharged in the unloaded state is determined for each manufactured object, and / or a mass of the object is calculated using the total corrected volume of material discharged in the unloaded state and the material density of the material in the unloaded state. For example, by summing the discrete volumes discharged, a corrected volume discharged in the unloaded state can be determined, and the mass of the object can advantageously be calculated using the material density of the material in the unloaded state.

[0046] For an advantageously simple and clear diagnosis, data of the object, e.g. the data of the mass of the object after the process, can be displayed, logged and / or saved with other process-specific data, e.g. the production time and parameters, e.g. pressure, temperature and discharge quantity per production progress.

[0047] If no material-specific data is available or if it is unknown, the material-specific data can preferably be provided by at least one measurement with the machine. More preferably, the measurement can be carried out before or during the execution of the process. For example, the displaced volume or the pressure-dependent compressibility in a cylinder, e.g. as a mass cushion, can be measured before or during a process, which advantageously provides the material-specific data. This procedure can be advantageous when material-specific data of the material are insufficient or unknown. This can be done in particular with special materials, such as material compounds, recyclates or bio-based materials or material combinations.

[0048] For advantageously accurate provision of material-specific data, at least one position, for example, a screw position, a volume, a pressure, and / or a temperature, is preferably recorded for the measurement with the machine. For example, the specific material expansion can be determined via the expansion of the material at different temperatures and the resulting displacement, for example, of the screw backwards. For example, the compressibility at different pressure levels for a temperature can also be determined in this way (isothermal compressibility or volume expansion) by recording the change in the screw position.

[0049] To advantageously enable simple and rapid provision of material-specific data, the total discharged corrected volume can preferably be adjusted for different process conditions and / or machine conditions via at least one calibration. An adjustment factor can advantageously be used for a more precise determination of the discharged volume and / or the discharged mass.

[0050] To advantageously enable transfer of the process to a continuous discharge, for example, a strand, a flow rate per unit of time can preferably be calculated from the total discharged corrected volume and / or the flow rate per unit of time can be varied. From this, for example, the existing shear rate or the shear on the material upon exiting the outlet opening, for example, from the nozzle, can be calculated or this can be specifically controlled by varying the flow rate. This can advantageously be used to control the molecular orientation to influence the mechanical properties.

[0051] In order to advantageously achieve control of the molecular orientation to influence the mechanical properties, a temperature change can preferably be used to further influence the shear, taking into account the material-specific data, e.g. the pvT diagrams and / or the specified discharge quantity.

[0052] Preferably, the material undergoes at least one phase transition between the stressed and unstressed states. This allows special properties of the material's phase transition to be advantageously utilized. For example, plastics or thermoplastic materials reduce their volume when cooled and expand when heated. In a diagram, e.g., a pVT diagram, a phase transition, e.g., from the solid to the fluid or deformable state of the material, is expressed as a "kink" (change in the slope of the straight line), which defines, for example, the glass transition temperature or softening temperature in the respective isobar. There is a significant difference in density between the unstressed and stressed states, since the molecular chains contract significantly more tightly during the transition to the solid phase.

[0053] The stated object is also achieved by a machine control for a machine for handling and / or processing the material, in particular a forming machine or a 3D printing machine, which is set up, designed and / or constructed to carry out the method.

[0054] Likewise, the task is solved by a corresponding computer program product with a program code that is stored on a computer-readable medium and is suitable for carrying out the method.

[0055] Further advantages emerge from the dependent claims and the following description of a preferred embodiment. The features listed individually in the claims can be combined with one another in a technologically expedient manner and can be supplemented by explanatory facts from the description and details from the figures, whereby further embodiments of the invention are shown.

[0056] Short description of the characters

[0057] The invention will be explained in more detail below using an exemplary embodiment illustrated in the accompanying figures. They show:

[0058] Fig. 1 , 2 pvT diagrams to describe the tracking and control,

[0059] Fig. 3, 4 pvT diagrams of a material,

[0060] Fig. 5 is a partially sectioned view of a machine for handling and / or processing the material,

[0061] Fig. 6 is a schematic diagram showing the influence on shear viscosity and / or shear rate.

[0062] Description of Preferred Embodiments The invention will now be explained in more detail by way of example with reference to the accompanying drawings. However, these embodiments are merely examples and are not intended to limit the inventive concept to a specific arrangement.

[0063] Before describing the invention in detail, it should be noted that it is not limited to the specific components of the device and the specific method steps, as these components and methods may vary. The terms used herein are intended solely to describe particular embodiments and are not intended to be limiting. Furthermore, when the singular or indefinite articles are used in the description or claims, this also refers to the plural of these elements, unless the overall context clearly indicates otherwise.

[0064] Before the process sequence according to Figs. 1 and 2 is discussed, the machine 40 for handling and / or processing the material for producing a three-dimensional object 58, e.g. a component made of solidifiable material according to Fig. 5, is first explained.

[0065] The material, which is either in a loaded state, e.g. in a fluid phase, or can be brought into a loaded state, e.g. flowable, is used to produce a three-dimensional object 58 by sequentially discharging discrete volumes 10. This can be done, for example, by sequentially discharging individual discrete volumes 10 from an outlet opening 62 of a discharge unit 54, so that the object 58 is produced layer by layer on a specimen carrier 56 in a build space 52, which is movable relative to the outlet opening 62 by a drive unit 60. The solidifiable material can be a plasticized material, such as silicone, or a plasticizable material, such as thermoplastics.Any other materials may be used, provided that these materials can be solidified and preferably plasticized by the machine and, above all, can be discharged by the at least one discharge unit 54.

[0066] The material is plasticized or processed and / or homogenized under the influence of temperature in the processing unit 70 arranged on a machine table 72 and pressurized by the pressure generation unit 50. Depending on the existing flow properties of the material, the opening time of the nozzle and / or the size of the outlet opening 62, the pressure is adjusted accordingly to discharge the discrete volumes 10 for producing the article 58. The discrete volumes 10 are in particular in the range from 0.01 to 1 mm 3The diameter of the outlet opening 62 is in particular less than or equal to 1 mm, preferably between 0.1 and 0.5 mm. The fluid phase of the material located in the material reservoir 74 can be discharged to the object 58 via an outlet opening 62, actuated by a drive part 64. A solid-state joint according to DE 10 2009 030 099 B1 can preferably be used as a diaphragm at the outlet opening 62. The processed material is generally what are known as non-Newtonian fluids. Their flow properties are highly dependent on the existing process settings such as temperature, pressure, residence time below temperature, degree of dryness of the starting solid, etc., as well as the flow velocity and the resulting shear stress on the material.Even the smallest changes influence the discharge quantity, but the layer structure of an object 58 to be formed, calculated in particular from the CAD models, preferably assumes a constant, discrete discharge quantity.

[0067] Figure 1 shows the specific volume (v) as a function of pressure (p) and temperature (T) in a so-called pvT diagram for a typical amorphous material. This data can be provided as material-specific data in a further preferred embodiment. The specific volume is plotted as a function of temperature for different pressures. The specific volume is the inverse of the density, or vice versa. Various materials, e.g. plastics or thermoplastic materials, reduce their volume when they are cooled and expand when they are heated. In addition, plastics or thermoplastic materials are compressible, i.e. pressure reduces their volume.

[0068] Furthermore, Fig. 1 shows a phase transition from the solid to the fluid or deformable state of the material. In the pVT diagram of Fig. 1, the phase transition can be seen as a "kink" (= glass transition temperature or softening temperature) in the respective isobar (p0, p1, p2, p3). Here, there is a clear difference in density, since the molecular chains contract significantly more closely during the transition to the solid phase. Fig. 1 shows the dependence of the process parameters in the fluid phase on the amount of material discharged in the unloaded state, as well as various operating points 20, which represent different process settings. For the discharge of discrete volumes 10 for the production of a three-dimensional object 58 from at least one solidifiable material, which is either in a loaded state, e.g., in a fluid phase, or brought into a loaded state, e.g.,into a fluid phase, can be flowed, with a machine 40 for handling and / or processing the material, in particular a shaping machine or a 3D printing machine in a process, the loaded state of the material is introduced into a material reservoir 74 and pressure and temperature exposure create a loaded state of the material in the material reservoir 74. Furthermore, a discrete discharge of the material takes place under at least one process condition from a clockable and / or closable outlet opening 62 to build up the three-dimensional object 58. This corresponds, for example, in Figure 1 to the operating point 20 #1 with the specific volume vi(Ti,pi). If the discrete volume 10 with the volume Vi is discharged by the machine under these process conditions (Ti,pi), a predetermined mass mi = Vi*1 / vi = Vi*pi is discharged.

[0069] If the process conditions experience at least one change, e.g., the material experiences a change in flow properties, a change in flowability, a temperature change, and / or a change due to other influences detected in the loaded state, this change is compensated. In order to compensate for this at least one change and to maintain a predetermined property of the discrete volumes 10, e.g., a predetermined size, at least one process parameter, e.g., the pressure pi, is adjusted in Fig. 1 (p1 -> p2). This results, for example, in a higher pressure: p2> pi (operating point 20 #2 in Figure 1). However, the higher pressure p2 leads to a change in the discrete volume 10, e.g., to a smaller volume V2, and a change in the density, e.g., to a higher density p2 of the discrete volume 10.Since the pressure was adjusted as a process parameter in order to enable a predetermined size with the predetermined volume V1, the volume V1 would be discharged with a mass m2 = Vi*p2> mi. However, this would have the disadvantage of leading to different object masses and, as a result, to unpredictable object densities. Material-specific data of the material is provided, and with the aid of the material-specific data the volume is controlled in such a way that, for example, a predetermined mass nm = V2*p2 is obtained in an unloaded state, e.g. at room temperature and / or room pressure, of a discharged discrete volume 10. In principle, appropriate control of the volume can also take place if, due to changes in the process conditions, a lower pressure is used to maintain the size (pi > P2). The volume can then be increased accordingly to maintain the predetermined mass nm. This results in optimized control, which, for example,B. when the pressure changes, the volume in the loaded state is adjusted so that in the unloaded state the same mass is discharged as before the pressure change.

[0070] Fig. 2 shows a further example of tracking and control for a further exemplary embodiment. At operating point 20 #1 there is a discrete volume 10 with a volume V1 and a density pi, which was introduced into the material reservoir 74 under various process conditions, e.g. at a temperature Ti and a pressure pi. If the discrete volume 10 is discharged by the machine, a predetermined mass nm = VTpi is discharged. In order to compensate for a change, e.g. due to a change in flowability and / or another influence which is detected in the loaded state, and to obtain a predetermined property of the discrete volumes 10, e.g. a predetermined size, the temperature Ti is tracked in Fig. 2 (T1 -> T2). This results, for example, in a higher temperature: T2> Ti (operating point 20 #3 in Figure 2), which leads to a change in the discrete volume 10.Since the temperature was adjusted to maintain a predetermined size with a predetermined volume V1, if the volume V1 were discharged, a mass m3 = V1*1 / v3 = V1*p3* nm or m3< nm would be discharged. This would also lead, for example, to different object masses and, consequently, to unpredictable object densities.

[0071] Material-specific data of the material are provided, whereby with the help of the material-specific data the discrete volume 10 is controlled such that, for example, a predetermined mass nm = Vz*p3 is obtained in the unloaded state of a discharged discrete volume 10. In principle, appropriate control of the volume can also take place if, due to changes in the process conditions, a lower temperature is used to maintain the size (Ti > T2). The volume can then be changed accordingly to maintain the predetermined mass nm. This results in optimized control which, for example, adapts the volume in the fluid phase when the temperature changes so that, in the unloaded state, the same mass is discharged as before the temperature change.

[0072] In a further preferred embodiment, the material is in melt form in the nozzle and is pressurized. By opening the nozzle, e.g. a needle valve, the material can flow out of the nozzle. The pressure therefore determines the discharge quantity per opening stroke of the nozzle, e.g. a needle valve nozzle, and remains almost constant throughout the process, i.e. independent of the discharge speed. Due to different needle / nozzle pairings, different pressures must be applied to keep the discharge quantity the same. Due to the different pressures, however, the material is also compressed differently, which means that the discharge quantity in the unloaded, e.g. solid state, varies, and therefore a reproducible process (e.g. from machine to machine) cannot take place.

[0073] In order to make the discrete discharge quantity (unloaded, e.g., solid state) reproducible regardless of the machine or system used, the compression of the material, for example, at the prevailing process pressure and the given temperature, is taken into account. Material-specific data, e.g., pVT data, are available. The process pressure is varied within a process to reduce fluctuations in flow properties (see document DE 10 2012 004 988 A1). This pressure must, of course, also be increased if the discharge is to be increased with the same needle opening stroke.

[0074] In this way, the discharge rate of each individual droplet (discrete discharge) can be precisely controlled - either by varying the pressure or the opening stroke or time. The control is based on a volume within the molten, compressible phase in order to achieve a predetermined "fixed" discharge rate (mass). The discharge rate can refer to a volume, but also to a specific mass, since the material data (e.g. material density as a function of pressure and temperature) is known. This means that at the end of the build process, for example, the exact component weight can be calculated and output based on the process data. The control is therefore not "only" based on the volume flow, since the specific density of the material in its respective state is taken into account. Rather, it is also based on a discrete discharge mass.In a preferred embodiment, the predetermined property of the discrete volumes 10 in the unloaded state comprises the mass and / or the density.

[0075] In a further preferred embodiment, the control for maintaining the predetermined property of the discrete volumes 10 in the unloaded state of the at least one discharged discrete volume 10 is carried out based on the tracking of the at least one process parameter for maintaining a predetermined property of the discrete volumes 10 in the loaded state. For example, the control for maintaining a predetermined mass in the unloaded state of the discharged discrete volume 10 begins after the tracking of the pressure in the loaded state.

[0076] Fig. 3 shows, as an example, the specific volume (v) as a function of pressure (p) and temperature (T) in a pvT diagram for an ABS material called Terluran GP35. Three operating points 20 #1, #2, and #3 are marked, each with a different process pressure or temperature. Each change causes a change in the specific volume. For the material, for example, at operating point 20 #1 with process conditions of Ti=240°C and pi=200 bar, a specific volume of vi=1.047cm results. 3 / g or a specific density of pi=0.955g / cm 3 . For a displaced discrete volume of 0.01 mm 3 This results in a mass rrn of 0.01 mm 3 *0.000955g / mm 3 = 0.00000955g. If the process conditions change to the operating point 20 #2 with Ti=240°C and p2=400bar, the specific volume is V2=1.035cm 3 / g or a specific density of p2=0.967g / cm 3. This results in a displaced discrete volume of 0.01 mm 3 a mass m2 per drop of 0.01 mm 3 *0.000967g / mm 3 = 0.00000967g.

[0077] For example, at the operating point 20 #3, the process conditions are T2=250°C and pi=200bar, which results in a specific volume of V3=1,020cm 3 / g or a specific density of p3=0.951g / cm 3 For a displaced discrete volume of 0.01 mm 3 This results in a mass m3 of 0.01 mm 3 *0.000951 g / mm 3 = 0.00000951 g. This results, for example, in a manufactured object with a volume of 21135 mm 3 or 21,135cm 3and 1,569,073 discharged discrete volumes each resulted in the following different object weights: Weight at 240°C / 200 bar: 14.98 g; weight at 240°C / 400 bar: 15.17 g; weight at 250°C / 200 bar: 14.92 g. Similar results are obtained for semi-crystalline thermoplastics. For this group of materials, the temperature-dependent volume change is more pronounced. Fig. 4 shows a pvT diagram for a typical semi-crystalline material. If we now take a polyamide, e.g. PA6 Ultramid B3K, as an example, different object weights result here too for three different operating points 20 #1, #2 and #3.

[0078] At the operating point 20 #1 with the process conditions of Ti=250°C and pi=200bar a specific volume of vi=1 ,0168cm 3 / g or a specific density of pi=0.984g / cm 3 . For a displaced discrete volume of 0.01 mm 3 This results in a mass mi of 0.01 mm 3 *0.000984g / mm 3= 0.00000984g. If the process conditions change to the operating point 20 #2 with Ti=250°C and p2=400bar, the specific volume is V2=1.0006cm 3 / g or a specific density of p2=0.994g / cm 3 . This results in a displaced discrete volume of 0.01mm 3 a mass m2 per drop of 0.01 mm 3 *0.000994g / mm 3 = 0.00000994g.

[0079] For example, at the operating point 20 #3, the process conditions are T2=260°C and pi=200bar, which results in a specific volume of V3=1,022cm 3 / g or a specific density of p3=0.979g / cm 3 For a displaced discrete volume of 0.01 mm 3 This results in a mass m3 of 0.01 mm 3 *0.000979g / mm 3 = 0.00000979g. Thus, for example, for a manufactured object with a volume of 21135mm 3 or 21,135cm 3and 1,569,073 discharged discrete volumes each had the following different object weights: Weight at 250°C / 200 bar: 15.44 g; Weight at 250°C / 400 bar: 15.60 g; Weight at 260°C / 200 bar: 15.36 g.

[0080] The discrete volume 10 is controlled, for example, by adjusting the outlet opening 62, so that in the unloaded state, the mass is discharged that would have been discharged initially, i.e., without pressure adjustment. In principle, however, the pressure, temperature, nozzle diameter, nozzle opening time, discharge time, and / or the size of the outlet opening 62 could also be controlled accordingly.

[0081] In a further preferred embodiment, the pressure is adjusted to maintain a predetermined volume of at least one discrete volume 10 in the loaded state, e.g. in the fluid phase, and the volume and / or the temperature is regulated to maintain a predetermined mass of at least one discrete volume 10 in the unloaded state.

[0082] In a further preferred embodiment, a corrected volume in the unloaded state can be calculated for at least one applied discrete volume 10 via at least one ratio of the specific volume of the material in the loaded state to the specific volume of the material in the unloaded state.

[0083] In a further preferred embodiment, the at least one process parameter and / or the at least one further process parameter can be controlled via at least one ratio of the specific volume of the material in the loaded state to the specific volume of the material in the unloaded state and depending on the prevailing temperature.

[0084] In a further preferred embodiment, a total discharged corrected volume of the material in the unloaded state can be determined for each manufactured article 58 and / or a mass of the article 58 can be calculated using the total discharged corrected volume of the material in the unloaded state and the material density of the material in the unloaded state. For example, this can be done according to Figure 1 or Figure 2 using the difference in the specific volume between the loaded fluid state and the unloaded state (T0, pO).

[0085] It may happen that the material-specific data for the material is not available, for example, because the material is an unidentified recyclate or compound. In another preferred embodiment, the material-specific data can be provided by at least one measurement with the machine.

[0086] In order to obtain the material-specific data through the measurement, in a further preferred embodiment at least one position, e.g. a screw position, a volume, a pressure and / or a temperature is recorded. From this, a ratio of the specific volume in the screw to the volume in the atmosphere can advantageously be derived. In this way, the process can be adapted in the fluid phase as already described. For an advantageously more precise determination of the discharged volume or the discharged mass, in a further preferred embodiment an adjustment of the total discharged corrected volume for different process conditions can be carried out via at least one calibration. In this way, a corresponding adjustment factor can be used for the more precise determination of the discharged volume or the discharged mass. In principle, this can be a volume difference Av, e.g. Avi, AV2 or Ava in Fig. 1 or.2 correspond.

[0087] In a further preferred embodiment, a flow rate per unit of time can be calculated from the total corrected discharged volume and / or the flow rate per unit of time can be varied. From this, the existing shear rate or the shear on the material upon exiting the outlet opening 62 can be calculated or specifically controlled by varying the flow rate.

[0088] In order to advantageously achieve a control of the molecular orientation to influence the mechanical properties, in a further preferred embodiment, a temperature change could be used to further influence the shear, taking into account the material-specific data, e.g. the pvT data, the pvT diagrams and / or the predetermined discharge quantity.

[0089] The advantages mentioned with regard to the method also arise in a machine control system for a machine 40 for handling and / or processing the material, in particular a forming machine or a 3D printing machine, provided that the machine control system is set up, designed and / or constructed to carry out the method accordingly.

[0090] Likewise, the advantages of the method arise from the use of a computer program product with a program code stored on a computer-readable medium, so that the method can be carried out using the program code.

[0091] It goes without saying that this description is susceptible to various modifications, changes, and adaptations that fall within the scope of equivalents to the appended claims. List of reference symbols

[0092] 10 discrete volume

[0093] 20 operating points

[0094] 40 machine

[0095] 50 pressure generation unit

[0096] 52 installation space

[0097] 54 discharge unit

[0098] 56 slides

[0099] 58 Subject

[0100] 60 drive unit

[0101] 62 Exit opening

[0102] 64 drive part

[0103] 68 snail

[0104] 70 processing unit

[0105] 72 machine table

[0106] 74 material storage

Claims

Patent claims 1. A method for applying discrete volumes (10) with specific properties along a trajectory for producing a three-dimensional object (58) from at least one solidifiable material that is either in a stressed state or can be brought into a stressed state, with a machine (40) for handling and / or processing the material, in particular a forming machine or a 3D printing machine, in a process comprising the steps: - introducing the loaded state of the material into a material storage (74), - generating a pressure on the loaded state of the material in the material storage (74), - discrete discharge of the material under at least one process condition from a closable outlet opening (62) for producing the three-dimensional object (58), - wherein, upon at least one change in the at least one process condition, at least one process parameter is adjusted during the production of the three-dimensional object (58), preferably while maintaining at least one further process parameter, in order to obtain a predetermined property of the discrete volumes (10) in the loaded state, characterized in that material-specific data of the material are provided and that with the aid of the material-specific data the at least one process parameter and / or at least one further process parameter is regulated in order to obtain at least one predetermined property of the discrete volumes (10) in an unloaded state in which no further additional external influences act on the material, of at least one discharged discrete volume (10).Method according to claim 1, characterized in that the predetermined property of the discrete volumes (10) in the unloaded state comprises the mass and / or the density. Method according to claim 1 or 2, characterized in that the control for maintaining the predetermined property of the discrete volumes (10) in the unloaded state of the at least one discharged discrete volume (10) is carried out based on the tracking of the at least one process parameter for maintaining a predetermined property of the discrete volumes (10) in the loaded state. Method according to one of the preceding claims, characterized in that at least one temperature and / or pressure dependency of the specific volume, the density, the compressibility and / or the temperature of the material, in particular a dependency of the specific volume of the material on the pressure and / or the temperature, is provided as material-specific data. Method according to one of the preceding claims, characterized in that a pressure, a temperature, a volume, a nozzle diameter, an opening time, a discharge time and / or a size of the outlet opening (62) is controlled as the at least one process parameter and / or the at least one further process parameter.Method according to one of the preceding claims, characterized in that the pressure is adjusted to maintain a predetermined volume of at least one discrete volume (10) in the loaded state and / or that the volume and / or the temperature is regulated to maintain a predetermined mass of at least one discrete volume (10) in the unloaded state. Method according to one of the preceding claims, characterized in that a corrected volume in the unloaded state is calculated for at least one discharged discrete volume (10) using at least one ratio of the specific volume of the material in the loaded state to the specific volume of the material in the unloaded state.Method according to one of the preceding claims, characterized in that the at least one process parameter and / or the at least one further process parameter is controlled via at least one ratio of the specific volume of the material in the loaded state to the specific volume of the material in the unloaded state and as a function of the prevailing temperature. Method according to one of the preceding claims, characterized in that a total discharged corrected volume of the material in the unloaded state is determined for each manufactured article (58) and / or that with the aid of the total discharged corrected volume of the material in the unloaded state. and the material density of the material in the unloaded state, a mass of the object (58) is calculated. Method according to one of the preceding claims, characterized in that the material-specific data is provided by at least one measurement with the machine (40). Method according to claim 10, characterized in that for the measurement with the machine (40) at least one position, a volume, a pressure and / or a temperature is recorded. Method according to one of claims 9 to 11, characterized in that an adjustment of the total discharged corrected volume for different process conditions is carried out via at least one calibration. Method according to one of claims 9 to 12, characterized in that a flow rate per time is calculated from the total discharged corrected volume and / or the flow rate per time is varied.Method according to one of the preceding claims, characterized in that the material undergoes at least one phase transition between the loaded state and the unloaded state. Machine control for a machine (40) for handling and / or processing a solidifiable material, in particular a forming machine or a 3D printing machine, characterized in that the machine control is configured, designed, and / or constructed to carry out the method according to one of claims 1 to 14. Computer program product with a program code stored on a computer-readable medium for carrying out a method according to one of claims 1 to 14.

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