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 make a three-dimensional object (58) from a curable material in or placed in a stressed state, in which method the material in the stressed state is introduced into a material reservoir (74). In order to discretely dispense the material from the closable outlet opening, a pressure (p) is applied to a stress state in order to produce the three-dimensional object (58) under at least one process condition, the at least one process parameter being updated in the event of a change in the at least one process condition. A reliable, controlled and reproducible method is provided by providing material-specific data of the material and by adjusting at least one process parameter and / or at least one other process parameter using the material-specific data in order to obtain at least one predefined characteristic of the discrete volume (10) in an unstressed state, no other additional external influence acts on the material in the unstressed state.

Description

[0001] Citation of Related Applications

[0002] This application is related to and claims the benefit of priority from German patent application 10 2022132 825.2 filed on December 9, 2022, the disclosure content of which is hereby expressly incorporated as the subject matter of the present application. Technical Field

[0003] The present invention relates to a method for distributing discrete volumes having certain properties along a trajectory in order to produce a three-dimensional object according to the preamble of claim 1 and an associated machine control for performing the method having the features of claim 15 and a computer program product having the features of claim 16.

[0004] The discrete volume depends on the properties of mass (m) and density (ρ). Depending on the dispensing speed of the continuous volume along the trajectory (s), the dispensed amount per unit time is obtained, which affects the shear rate and thus the flowability of the material.

[0005] As used herein, the term "stress-free state" is understood to mean a state in which no other external influences act on the material. For example, the material is in a stress-free state at room temperature and / or room pressure. The properties (e.g., density) of the material in the stress-free state (e.g., at room temperature and / or room pressure) are typically different from the properties of the material in a stressed state (e.g., at a certain pressure, a certain temperature, and / or in the liquid phase of the material).

[0006] The term "curable material" as used in this application is to be understood in a broad sense and includes (in particular, but not exclusively) plastics, silicones or other thermoplastic and / or elastomeric materials (e.g. ceramics, metals and / or powdered substances) as well as paper, cellulose, starch, cork, etc. and mixtures of such plasticizable materials. In principle, these materials can also be previously plasticized materials or plastic substances that cure after dispensing, either automatically or with the aid of an auxiliary agent. The term also includes recyclables or compounds. Background Art

[0007] Various methods are currently known for producing three-dimensional objects. For example, these objects can be precisely produced using machines for processing and / or machining materials (particularly molding machines or 3D printing machines, such as 3D printers). To this end, the material is brought into a liquid state due to temperature effects and dispensed from a closable nozzle under the influence of pressure as material strands or as individual continuous discrete volumes, thereby producing the object layer by layer. For example, DE 10 2013 003 167 A1 discloses such a combination of dispensing discrete volumes and material strands.

[0008] However, many interactions of existing process parameters are present as a characteristic of the volume to be dispensed or the volume flow.

[0009] Regarding the dispensing quantity per unit time, for example, the shear of the material changes as it flows through the dispensing nozzle. This influences the flow characteristics and, therefore, the dispensing quantity per unit time, while the parameters remain constant. For example, viscosity is a parameter used to describe the flow properties of a plastic material under the influence of a given temperature and applied pressure.

[0010] Different nozzle diameters or opening gaps (e.g. when using a closure device such as a needle valve) can also result in different shear rates and therefore different flow characteristics. Manufacturing tolerances may also have an impact, meaning that reproducibility between nozzles or forming machines cannot be guaranteed.

[0011] Materials may also have batch variations that cause different flow characteristics. Flowability can also be affected by the moisture content of the material or residual moisture in the material being processed. Fillers or additives in the material being processed can also affect flowability.

[0012] To illustrate this, Figure 6 Schematically, various influences on the shear viscosity and / or shear rate, for example due to molecular weight, pressure, filler, temperature or filler, are shown in FIG. For example, the shear viscosity decreases with increasing temperature.

[0013] Different temperature settings from machine to machine also result in different dispensed quantities. In addition, the shear rate and therefore the flow characteristics are temperature-dependent, which means that different pressure loads must also be applied to the material to be dispensed.

[0014] If the process specifies that the dispensed amount per time unit is to be the same, other parameters such as pressure and / or temperature must be readjusted.

[0015] DE 10 201 2 004 988 A1, which serves as the basis for the preamble of claim 1, discloses a method for maintaining a predefined droplet size or droplet volume in the event of viscosity fluctuations. Due to viscosity fluctuations, the applied pressure is readjusted to maintain a constant volume. Viscosity is a parameter that describes the flowability of a plastic material under the influence of a given temperature and applied pressure. This control can be used to compensate for shear-induced flowability.

[0016] However, different materials (especially plasticizable materials) have different fluid densities or volumes, depending on pressure and / or temperature. Consequently, the dispensed amount is affected by pressure readjustment, which can cause weight fluctuations in the produced object. Consequently, the corresponding control is imprecise or prone to errors, and the process is therefore not precisely reproducible.

[0017] Furthermore, the amount of material dispensed in the stress-free state is decisive for the resulting object weight or the resulting object density, which cannot be precisely predefined, for example, using the updating and control systems available in the prior art.

[0018] US2020 / 0338824 A1 discloses an extruder or a method for operating an extruder, wherein the extruder is assigned operating characteristics and a controller controls the axial displacement of a screw based on these operating characteristics. For example, the material flow of the extruder can be controlled for different materials with different viscosities. The rotational speed, temperature, and / or pressure of the screw can also be controlled based on these operating characteristics.

[0019] US2021 / 0154916 A1 discloses a method in which the pressure in a flow path is recorded during a printing process, and based on the pressure, a volume change of 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 relative to the determined volume change of the material. For example, melt pressure is detected and the 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. Summary of the Invention

[0020] Starting from this prior art, the present invention addresses the problem of providing a reliable, controlled and reproducible method for dispensing reproducible discrete volumes with specific properties along a trajectory, wherein changes in the properties due to differently acting process parameters are compensated.

[0021] This problem is solved by a method for dispensing discrete volumes having the features of claim 1 , a machine control system having the features of claim 15 , and a computer program product having the features of claim 16 .

[0022] Advantageous developments are the subject matter of the dependent claims. The features listed individually in the claims can be combined with one another in a technically meaningful manner and can be supplemented by explanatory facts from the description and by details from the drawings, in which further variants of the invention are shown.

[0023] The method for distributing discrete volumes having certain properties along a trajectory in a process (e.g., a fabrication process) for producing a three-dimensional object (e.g., a component) from at least one curable material (e.g., a plastic material) in a stressed state (e.g., in a liquid phase) or capable of being placed in a stressed state (e.g., capable of flowing into a liquid phase) using a machine for processing and / or processing such materials (e.g., a molding machine or a 3D printing machine) comprises the following steps: introducing the material in a stressed state (e.g., in a liquid phase) into a material reservoir, and applying a pressure to the stressed (e.g., liquid phase) material in the material reservoir. For example, depending on the material, a typical temperature of the plastic material in the material reservoir is approximately 50° C. to 450° C., and a typical pressure of approximately 50 bar to 800 bar (5 MPa to 800 MPa). However, other temperatures and / or pressures can also be provided in principle.

[0024] Furthermore, discrete dispensing of material occurs from an outlet opening (preferably a closable outlet) (e.g. a nozzle or a nozzle closable by means of a closing device) under at least one process condition for producing the three-dimensional object (e.g. at a certain pressure and / or at a certain temperature), wherein, in the event of at least one change in at least one process condition (e.g. a change in flow properties, a change in fluidity, a change in temperature or another influence), at least one process parameter is updated during the production of the three-dimensional object, preferably while at least one other process parameter is maintained, so as to obtain predefined properties (e.g. volume, density, mass and / or temperature) of the discrete volumes under stress (e.g. in the liquid phase).

[0025] For example, the pressure in the material reservoir can be readjusted due to changes in flowability in order to maintain a predefined dispense volume per unit time under stress.

[0026] In order to obtain a reliable, controlled and reproducible method for dispensing reproducible discrete volumes with certain properties along a trajectory, wherein changes in the properties due to differently acting 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 the at least one other process parameter are controlled so as to obtain at least one predefined property of the discrete volume in a stress-free state, wherein no other additional external influences act on the material (e.g. the size, volume, density, mass and / or temperature of the at least one dispensed discrete volume).

[0027] Preferably, the predefined properties of the discrete volume in the unstressed state include mass and / or density. This has the advantage of increasing the reproducibility and stability of the component.

[0028] For example, if the pressure is updated due to a change in fluidity, the same volume of material will be compressed, resulting in a greater mass. If an object were manufactured at that volume, this would result in a greater weight. For example, to advantageously achieve a predefined object weight, the dispensed volume can be changed accordingly.

[0029] For example, due to different pressures, the compression of the material may be different, which means that the distribution amount in the stress-free state (e.g., solid state) is different, and therefore reproducible processing (e.g., different from machine to machine) cannot occur. In order to make the discrete distribution amount (stress-free, e.g., solid state) reproducible regardless of the machine or system used, the compression of the material at a specific processing pressure and a given temperature is also considered. Material-specific data (e.g., pVT data) is available. The processing pressure may be varied within the process to reduce flow characteristic fluctuations (see document DE 10 201 2004 988A1). In this way, for example, the distribution amount of each individual droplet can be precisely controlled by varying the pressure or opening stroke or time (discrete distribution). The volume within the compressible phase in the melt form is controlled to achieve a predefined "fixed" distribution amount (mass). The distribution amount can refer to volume, but it can also refer to specific mass because the material data (e.g., material density as a function of pressure and temperature) is known. Therefore, the accurate component weight can be calculated and output at the end of the construction process, for example, using process data. Thus, the control is not "only" based on the volume flow, since the specific density of the material in the respective state is taken into account. Alternatively, the control is also based on discrete dispense masses.

[0030] For example, a typical discrete sediment volume is approximately 0.001 mm 3 to 0.05mm 3 Especially 0.02mm 3 However, the method can also be used for other (especially larger) distribution amounts.

[0031] For example, due to the above-mentioned change in fluidity, the pressure in the material reservoir can be updated to obtain a predefined, reproducible, discrete amount of material. However, this pressure update causes the material to be compressed more, which means that the discontinuous volume with the predefined volume has an increased density in the stressed state. However, due to the update, the volume with increased density is allocated. However, if this volume is allocated, the increased specific density leads to a difference in the object weight of the object produced in the stress-free state. With the help of material-specific data, at least one process parameter and / or at least one other process parameter can be changed so that the discontinuous volume in the stressed state is allocated, for example, to a smaller volume, but still has a predefined mass in the stress-free state. By controlling the at least one process parameter and / or the at least one other process parameter and the material-specific data of the material in the stressed state, it is therefore advantageously possible to obtain a predefined material mass and / or material quantity in the stress-free state.

[0032] For example, if a change in fluidity occurs as described above, the pressure in the material reservoir can be updated to maintain a predefined, reproducible, discrete amount of material. In the case of various materials (such as plastic materials 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 stressed liquid state. Due to the change in at least one process parameter to obtain, for example, a predefined discontinuous volume flow, the volume is readjusted to a "target value" (constant discontinuous volume flow, as known, for example, from DE 10 201 2 004 988 A1). For example, an increase in pressure causes a decrease in volume while simultaneously increasing the material density in the stressed state. Due to the control for maintaining a constant volume flow, the discontinuous volume is updated or increased to the "target value." However, the material density remains unchanged in the stressed state, so that the dispensed mass of a discontinuous volume having a predefined "target value" of the discontinuous volume in the unstressed state (e.g., at room pressure, atmospheric pressure, room temperature, and / or installation room temperature) is greater than before, despite the same volume in the fluid stressed state. In principle, this can also happen in reverse: a reduction in pressure causes an increase in volume, while the material density decreases under stress. Due to the control used to maintain a constant volume flow, the discontinuous volume is readjusted or reduced to a "target value." The material density remains unchanged under stress, which means that the dispensing quality of the discontinuous volume in the unstressed state (e.g., at room pressure, atmospheric pressure, room temperature, and / or installation room temperature) is lower than before, despite the same volume under fluid stress.

[0033] The same applies to changes in temperature. For example, an increase in temperature causes an increase in volume while the material density decreases under stress. Due to the change in at least one process parameter to maintain a constant discontinuous volume flow, for example, the discontinuous volume is updated or reduced to a "target value". The material density remains unchanged under stress. This has the following effect: the distribution quality in the stress-free state (for example, at room pressure, atmospheric pressure, room temperature and / or installation room temperature) is lower than before, although the volume is the same under fluid stress. In principle, this can also happen in reverse: a drop in temperature causes a decrease in volume while the material density increases under stress. Due to the control for maintaining a constant volume flow, the volume is controlled back to the "target value". The material density remains unchanged under stress, so that the distribution quality in the stress-free state (room pressure, atmospheric pressure, room temperature and / or installation room temperature) is greater than before, although the volume is the same under fluid stress.

[0034] Preferably, the following optimization control is used: when the process parameters are changed, the volume in the stressed state is adjusted so that the same mass is dispensed in the unstressed state as before the change. This has the advantage of achieving better reproducibility from machine to machine, since, for example, the smallest differences may be caused by manufacturing tolerances of the nozzle, which means, for example, that different masses are dispensed at the same pressure setting.

[0035] Thus, batch fluctuations and / or differences in residual moisture content of the material to be processed can also be compensated in this way. Changes in the flow characteristics, which depend on the dispensed quantity per unit time due to the resulting shear stress on the material as it flows through the dispensing nozzle, can also be compensated, as can different temperature settings that vary from machine to machine.

[0036] Preferably, control for maintaining a predefined characteristic of the at least one dispensed discrete volume in an unstressed state is performed based on the updating of at least one process parameter, so as to achieve a predefined characteristic of the discrete volume in a stressed state, for example, in a material reservoir. For example, the control and the updating can be performed in a superimposed manner. The control can, for example, occur after the updating of at least one process parameter, or can be superimposed or combined therewith. For example, if a certain pressure change occurs with respect to the material, resulting in compression of the material or a discrete volume now having a greater mass, a corresponding volume change can occur. This advantageously results in a precise and controlled dispensing of the material.

[0037] Preferably, at least one temperature and / or pressure dependency of the material's specific volume, density, compressibility, and / or temperature, in particular the pressure and / or temperature dependency of the material's specific volume, can be provided as material-specific data. Advantageously, this results in simple relationships between different states of the material (e.g., a stressed state and a stress-free state). For example, a volume difference ΔV can be derived from a stressed state and a stress-free state. In principle, other material-specific data can also be provided, as long as these data represent at least one relationship between the stress-free state and the stressed state.

[0038] For example, material-specific data can preferably be provided as pvT data, for example using a pvT diagram. The material-specific data can be available, for example, as a file in a machine control system or network. The pvT data describes the temperature T and pressure p dependence of the specific volume v. For example, the specific volume can be plotted against temperature for different pressures in a pvT diagram. Specific volume is the inverse of density, or vice versa. Many materials (such as plastics or thermoplastics) decrease in volume when they cool and expand when they are heated. In addition, plastics and thermoplastics are compressible, meaning that pressure causes their volume to decrease. If different pressures or temperatures are present during the process, different material amounts are allocated, resulting in different object weights and object densities. The pvT data can be provided, for example, electronically, by the respective material manufacturer or other testing laboratory. Knowledge of the multidimensional dependence of the material-specific values ​​allows, for example, targeted influence on the stress-free state of the material and, therefore, the stress-free state of a three-dimensional object.

[0039] Advantageously, for efficient and simple control, pressure, temperature, volume, nozzle diameter, opening time, dispensing time and / or size of the outlet opening are preferably controlled as the at least one process parameter and / or the at least one other process parameter.

[0040] Preferably, for an advantageously simple and reproducible process, the pressure is updated to achieve a predefined volume for at least one discrete volume under stress, and / or the volume and / or temperature are controlled to achieve a predefined mass for at least one discrete volume under stress. For example, if the pressure is updated due to, for example, a change in fluidity, the compression of the same volume of material results in a greater mass. If an object is produced at this volume, this will result in a greater object weight. For example, to advantageously achieve a predefined object weight, the dispensed volume can be varied accordingly.

[0041] Preferably, for at least one applied discrete volume, the corrected volume in the stress-free state is calculated using at least one ratio of the specific volume of the material in the stressed state to the specific volume of the material in the stress-free state. Advantageously, this results in a simple link between the stressed state and the stress-free state. For example, the link can be expressed as a factor.

[0042] For example, the volume of a discrete volume will remain constant at a predefined value (V(p i ,T i )=constant). Pressure and / or temperature (p i ,T i ) is variable and machine-dependent, resulting in the corresponding density ρ(p i ,T i ). For the stress-free state (p i ->p0;T i- >T room ,T installation space ,T atmosphere ), which yields the conservation of mass:

[0043] ρ(p i ,T i )×V(p i ,T i )=m(p i ,T i )=m(p0,T0)=ρ(p0,T0)×V(p0,T0)

[0044] When (p i ,T i )=constant≡c, so we can get

[0045]

[0046] Furthermore, the at least one process parameter and / or the at least one further process parameter is preferably controlled by means of at least one ratio of the specific volume of the material in the stressed state to the specific volume of the material in the unstressed state and as a function of the prevailing temperature. In this way, a previously defined object density can advantageously be produced.

[0047] Preferably, for each fabricated object, the total dispensed corrected volume of the material in the unstressed state is determined, and / or the mass of the object is calculated using the total dispensed corrected volume of the material in the unstressed state and the material density of the material in the unstressed state. For example, the dispensed corrected volume in the unstressed state may be determined by adding the dispensed discrete volumes, and the mass of the object may advantageously be calculated using the material density of the material in the unstressed state.

[0048] For advantageously simple and clear diagnosis, object data, such as data on the quality of the object after the process and other process-specific data, such as production time and parameters (e.g. pressure, temperature and dispensed quantity for each production process), can preferably be displayed, recorded and / or stored.

[0049] If no material-specific data are available or if these data are unknown, the material-specific data can preferably be provided by performing at least one measurement with the machine. Preferably, this measurement can also be performed 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 buffer) can be measured before or during the process, thereby advantageously obtaining the material-specific data. This procedure can be advantageous if material-specific data for the material are insufficient or unknown. In particular, this can be done with special materials such as material compounds, recyclables, or bio-based materials or material combinations.

[0050] To advantageously and accurately provide material-specific data, at least one position (e.g., screw position, volume, pressure, and / or temperature) is preferably detected for machine measurement. For example, the specific material expansion can be determined by means of the material's expansion at different temperatures and the resulting displacement of the screw, for example, in the reverse direction. For example, the compressibility at different pressure levels for a given temperature (isothermal compressibility or volume expansion) can also be determined by detecting changes in screw position.

[0051] In order to make it possible to quickly and easily provide material-specific data, at least one calibration may preferably be used to adjust the corrected volume of the total dispense for different process conditions and / or machine conditions. An adjustment factor may preferably be used to more accurately determine the dispense volume and / or dispense quality.

[0052] In order to advantageously enable the method to be converted to continuous dispensing (e.g., strands), the flow rate per unit time can preferably be calculated from the total dispensed corrected volume and / or the flow rate per unit time can be varied. For example, this can be used to calculate the shear rate or shear present on the material as it leaves the outlet opening (e.g., from a nozzle), or this can be specifically controlled by varying the flow rate. This is an advantageous way to control molecular orientation to influence mechanical properties.

[0053] In order to achieve advantageous control of the molecular orientation to influence the mechanical properties, temperature variation may preferably be used to further influence the shear taking into account material specific data (eg pvT diagrams and / or predefined dispense amounts).

[0054] Preferably, the material undergoes at least one phase transition between a stressed state and an unstressed state. This allows the special properties of the phase transition of the material to be advantageously used. For example, plastic materials or thermoplastic materials reduce their volume when they cool and expand when they are heated. In diagrams (e.g., pVT diagrams), phase transitions (e.g., from the solid state to the fluid or deformable state of the material) are represented as "kinks" (changes in the gradient of the straight lines), which define, for example, the glass transition temperature or softening temperature in the corresponding isobars. There is a significant density difference between the unstressed state and the stressed state because the molecular chains contract much more tightly during the transition to the solid phase.

[0055] The problem is also solved by a machine control system for a machine for handling and / or processing material, in particular a shaping machine or a 3D printing machine, which is provided, implemented and / or constructed to carry out the method.

[0056] The problem is also solved by a corresponding computer program product with a program code which is stored on a computer-readable medium and is suitable for carrying out the method.

[0057] Further advantages can be found in the dependent claims and in the following description of preferred exemplary embodiments. The features listed individually in the claims can be combined with one another in a technically meaningful manner and can be supplemented by explanatory facts from the description and by details from the drawings, which illustrate further variants of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In the following, the invention is explained in more detail with reference to exemplary embodiments shown in the accompanying drawings, in which:

[0059] Figure 1 、 Figure 2 shows a pvT diagram for describing update and control,

[0060] Figure 3 、 Figure 4 shows the pvT diagram of the material,

[0061] Figure 5 shows a partial cross-sectional view of a machine for handling and / or processing material,

[0062] Figure 6 is a schematic diagram relating to the effects on shear viscosity and / or shear rate. DETAILED DESCRIPTION

[0063] Now, the present invention will be explained in more detail by way of examples with reference to the accompanying drawings. However, these embodiments are only examples and are not intended to limit the present invention concept to a specific arrangement.

[0064] Before describing the present invention in detail, it should be noted that the present invention is not limited to the corresponding components of the apparatus or the corresponding method steps, as these components and methods may vary. The terms used herein are intended only to describe specific embodiments and are not to be used in a limiting sense. Furthermore, when the singular or indefinite article is used in the specification or in the claims, this also refers to a plurality of these elements, unless the overall context clearly indicates otherwise.

[0065] In accordance with Figure 1 and Figure 2 Before discussing the method sequence, the process for treating and / or processing the material to produce the three-dimensional object 58 (e.g., by Figure 5 A machine 40 for producing a part made of a curable material.

[0066] A material that is in a stressed state (e.g., in a liquid phase) or can be placed in a stressed state (e.g., flowable) is used to produce a three-dimensional object 58 by sequentially dispensing discrete volumes 10. This can be accomplished, for example, by sequentially dispensing individual discrete volumes 10 from an outlet opening 62 of a dispensing unit 54 so that the object 58 is formed layer by layer on an object carrier 56 in the installation space 52, and the object carrier can be moved relative to the outlet opening 62 by a drive unit 60. The curable material can be a plasticizing material (such as silicone) or a plasticizable material (such as a thermoplastic material). Any other material can be used as long as it can be machine-cured and preferably plasticized, and in particular can be dispensed by at least one dispensing unit 54.

[0067] The material is plasticized or prepared and / or homogenized in a preparation unit 70 arranged on a machine table 72 under the influence of temperature and pressurized by a pressure generating unit 50. Depending on the current flow characteristics of the material, the pressure is set accordingly, given the opening time of the nozzle and / or the size of the outlet opening 62, in order to distribute the discrete volumes 10 for producing the object 58. The discrete volumes 10 are in particular arranged in a range from 0.01 mm 3 Up to 1mm 3The diameter of the outlet opening 62 is in particular less than or equal to 1 mm, preferably between 0.1 mm and 0.5 mm. The material in the liquid phase in the material reservoir 74 can be distributed to the object 58 via the outlet opening 62 actuated by the drive portion 64. Preferably, a solid joint according to DE 10 2009 030 099 B1 can be used as an orifice plate at the outlet opening 62. The processed materials are generally so-called non-Newtonian fluids. Their flow characteristics are highly dependent on the existing process settings (such as temperature, pressure, residence time at a certain temperature, degree of dryness of the starting solid, etc.) as well as flow rate and the resulting shear stress on the material. Even the smallest change affects the distribution amount, but the layer structure of the object 58 to be formed (in particular calculated from the CAD model) is preferably based on a constant discrete distribution amount.

[0068] Figure 1 The dependence of the specific volume (v) on pressure (p) and temperature (T) in a so-called pvT diagram for a typical amorphous material is shown. In a further preferred exemplary embodiment, these data can be provided as material-specific data. In each case, the specific volume is plotted against the temperature for different pressures. The specific volume is the inverse of the density, or vice versa. Various materials (e.g., plastics or thermoplastics) decrease in volume when they cool and expand when they are heated. In addition, plastics or thermoplastics are compressible, i.e., pressure causes their volume to decrease.

[0069] Figure 1 The phase transition of a material from a solid to a liquid or deformable state is also shown. Figure 1 In the pVT diagram in Figure 1, the phase transition can be identified as a "kink" (= glass transition temperature or softening temperature) in the corresponding isobars (p0, p1, p2, p3). Here, there is a clear difference in density because the molecular chains are much more compact during the transition to the solid phase.

[0070] Figure 1 The dependence of the process parameters in the liquid phase on the amount of material dispensed in the stress-free state and various operating points 20 representing different process settings are shown. In order to dispense a discrete volume 10 in a process for producing a three-dimensional object 58 from at least one curable material (which is in a stressed state, e.g., in a liquid state, or can be put into a stressed state, e.g., can flow into a liquid phase) using a machine 40 for handling and / or processing the following material (in particular a molding machine or a 3D printing machine), the material in a stressed state is introduced into a material reservoir 74 and pressure and temperature effects generate the stressed material in the material reservoir 74. Furthermore, under at least one process condition, discrete dispensing of the material from the pulsable and / or closable outlet opening 62 occurs to build the three-dimensional object 58. This corresponds, for example, to Figure 1Operating point 20#1 (T1, p1) with a specific volume v1. If a discrete volume 10 with a volume V1 is dispensed using the machine under these process conditions (T1, p1), a predefined mass m1 = V1 x 1 / v1 = V1 x ρ1 is thus dispensed.

[0071] If the process conditions undergo at least one change, for example, if the material undergoes a change in flow characteristics, a change in fluidity, a change in temperature and / or a change due to other effects detected in the stress state, the change is compensated. In order to compensate for the at least one change and obtain the predefined characteristics (e.g., a predefined size) of the discrete volume 10, Figure 1 At least one process parameter (e.g. pressure p1) is updated (p1->p2). For example, this results in a higher pressure: p2>p1 ( Figure 1 2). However, the greater pressure p2 causes a change in the discrete volume 10 (e.g., to a smaller volume V2) and a change in the density (e.g., to a greater density ρ2 of the discrete volume 10). Since the pressure is updated as a process parameter to enable a predefined size with a predefined volume V1, a volume V1 having a mass m2 = V1 × ρ2 > m1 will be allocated. However, this has the disadvantage of, for example, causing the mass of the object to be different, and therefore causing the density of the object to be different from the previously defined density.

[0072] Material-specific data for the material are provided, wherein the volume is controlled with the aid of the material-specific data in such a way that, for example, a predefined mass m1=V2×ρ2 is obtained in the unstressed state of the dispensed discrete volume 10 (e.g., at room temperature and / or room pressure). In principle, if, due to a change in process conditions (p1>p2), a lower pressure is used to obtain this size, the volume can also be controlled accordingly. The volume can then be increased accordingly to obtain the predefined mass m1. This allows the control to be optimized, for example, by adjusting the volume in the stressed state when the pressure changes so that the same mass is dispensed in the unstressed state as before the pressure change.

[0073] Figure 2 Other examples of updating and control for other exemplary embodiments are shown. At operating point 20#1, there is a discrete volume 10 with volume V1 and density ρ1, which is introduced into the material reservoir 74 under various process conditions (e.g., at temperature T1 and pressure p1). If the discrete volume 10 is dispensed using the machine, a predefined mass m1=V1×ρ1 is thus dispensed. In order to compensate for changes, for example, due to changes in fluidity and / or due to another effect detected in the stress state, and in order to obtain a predefined characteristic of the discrete volume 10 (e.g., a predefined size), at Figure 2Update the temperature T1 (T1 -> T2). For example, this results in a higher temperature: T2 > T1( Figure 2 the operating point 20#3) in, which causes a change in the discrete volume 10. Since the temperature is updated to obtain a predefined size with a predefined volume V1, if the volume V1 is allocated, the mass m3 = V1 × 1 / v3 = V1 × ρ3 ≠ m1 or m3 < m1 will thus be allocated. For example, this will also result in a different mass of the object, and as a result, the density of the object is not the previously defined one.

[0074] Provide material-specific data of the material, and with the aid of the material-specific data, control the discrete volume 10 in the following manner: For example, obtain a predefined mass m1 = V2 × ρ3 in the stress-free state of the allocated discrete volume 10. In principle, if a lower temperature is used to obtain this size due to a change in process conditions (T1 > T2), the volume can also be controlled accordingly. Subsequently, the volume can be changed accordingly to obtain the predefined mass m1. This optimizes the control, for example, adjusting the volume in the liquid phase when the pressure changes so that the same mass as before the temperature change is allocated in the stress-free state.

[0075] In another preferred exemplary embodiment, the material exists in a molten form in the nozzle and is pressurized. By opening the nozzle (e.g., a needle valve), the material can flow out of the nozzle. Therefore, the pressure determines the dispensing amount for each opening stroke of the nozzle (e.g., a needle valve nozzle), and is actually constant throughout the process, i.e., independent of the dispensing rate. Due to different needle / nozzle pairings, different pressures must be applied to keep the dispensing amount constant. However, due to different pressures, the compression of the material is also different, which means that the dispensing amount in the stress-free state (e.g., solid state) is different, and thus a reproducible process (e.g., machine-dependent) cannot occur.

[0076] To make the discrete dispensing amount (stress-free, e.g., solid state) reproducible regardless of the machine or system used, the compression of the material at the corresponding processing pressure and given temperature is also considered. Material-specific (e.g., pVT) data is available. To reduce the flow characteristic fluctuations, vary the processing pressure within the process (see document DE 10 2012 004 988A1). Of course, if the dispensing is increased with the same opening stroke of the needle, this must also be increased.

[0077] In this way, the dispense amount of each individual droplet can be precisely controlled by varying the pressure or the opening stroke or time (discrete dispensing). The volume is controlled within the compressible molten phase in order to achieve a predefined "fixed" dispense amount (mass). The dispense amount can refer to the volume, but it can also refer to the specific mass, since the material data (e.g., the material density as a function of pressure and temperature) are known. Therefore, the exact component weight can be calculated and output at the end of the construction process, for example, using the process data. Therefore, the control is not "only" based on the volume flow, since the specific density of the material in the corresponding state is taken into account. Specifically, the control is also based on the discrete dispense mass.

[0078] In a preferred exemplary embodiment, the predefined property of the discrete volume 10 in the unstressed state includes mass and / or density.

[0079] In a further preferred exemplary embodiment, in order to obtain a predefined property of the at least one allocated discrete volume 10 in a stress-free state of the discrete volume 10, a control is performed based on an update of at least one process parameter so as to obtain the predefined property of the discrete volume 10 in a stress state. For example, the control in order to obtain a predefined quality in the stress-free state of the allocated discrete volume 10 is started after the pressure in the stress state is updated.

[0080] Figure 3 An example of the specific volume (v) as a function of pressure (p) and temperature (T) in a pvT diagram for an ABS material called Terluran GP35 is shown. Three operating points 20#1, 20#2, and 20#3 are marked, wherein in each case the processing pressure or temperature is different. Each change results in a change in the specific volume. For example, at operating point 20#1 with process conditions of T1 = 240°C and p1 = 200 bar, the material has v1 = 1.047 cm 3 / g specific volume and ρ1=0.955g / cm 3 For 0.01mm 3 The shifted discrete volume, which gives 0.01 mm 3 ×0.000955g / mm 3 = Mass m1 of 0.00000955 g. If the process conditions change to operating point 20#2 with T1 = 240°C and p2 = 400 bar, this gives v2 = 1.035 cm 3 / g specific volume or ρ2 = 0.967 g / cm 3 For 0.01mm 3 The displaced discrete volume of each droplet is 0.01 mm 3 ×0.000967g / mm 3=Mass m2 of 0.00000967g.

[0081] At operating point 20#3, for example, process conditions T2 = 250°C and p1 = 200 bar exist, resulting in v3 = 1.020 cm 3 / g specific volume or ρ3 = 0.951 g / cm 3 For 0.01mm 3 The shifted discrete volume, which gives 0.01 mm 3 ×0.000951g / mm 3 = 0.00000951g mass m3. Therefore, for example, for a 3 or 21.135cm 3 The volume of the fabricated objects and 1,569,073 distributed discrete volumes 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.

[0082] Similar results were obtained for partially crystalline thermoplastics. In this material group, the temperature-dependent volume changes are more pronounced. Figure 4 A typical pvT diagram of a partially crystalline material is shown. If we now take a polyamide (eg PA6 Ultramid B3K) as an example, different object weights are also obtained for the three different operating points 20#1, 20#2 and 20#3.

[0083] At the operating point 20#1 with process conditions of T1 = 250°C and p1 = 200 bar, the specific volume v1 = 1.0168 cm 3 / g or specific density ρ1=0.984g / cm 3 For 0.01mm 3 The shifted discrete volume, which gives 0.01 mm 3 ×0.000984g / mm 3 = Mass m1 of 0.00000984 g. If the process conditions change to operating point 20#2 of T1 = 250°C and p2 = 400 bar, this gives v2 = 1.0006 cm 3 / g specific volume or ρ2 = 0.994 g / cm 3 For 0.01mm 3 The displaced discrete volume of each droplet is 0.01 mm 3 ×0.000994g / mm 3 =Mass m2 of 0.00000994g.

[0084] At operating point 20#3, for example, the process conditions are T2=260°C and p1=200 bar, resulting in v3=1.022 cm 3 / g specific volume or ρ3 = 0.979 g / cm 3 For 0.01mm 3 The shifted discrete volume, which gives 0.01 mm 3 ×0.000979g / mm 3 = 0.00000979g mass m3. Therefore, for example, for a 3 or 21.135cm 3 The volume of the fabricated objects and 1,569,073 distributed discrete volumes resulted in 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.

[0085] For example, the discrete volume 10 is controlled by adjusting the outlet opening 62 so that the initially dispensed mass is dispensed in a stress-free state, i.e., without a pressure update. However, in principle, the pressure, temperature, nozzle diameter, nozzle opening time, dispensing time, and / or the size of the outlet opening 62 can also be controlled accordingly.

[0086] In a further preferred exemplary embodiment, the pressure is updated so as to obtain a predefined volume of at least one discrete volume 10 in a stressed state (e.g. liquid phase), and the volume and / or temperature is controlled so as to obtain a predefined mass of at least one discrete volume 10 in a stress-free state.

[0087] In a further preferred exemplary embodiment, a corrected volume in the unstressed state may be calculated for at least one assigned discrete volume 10 using at least one ratio of the specific volume of the material in the stressed state to the specific volume of the material in the unstressed state.

[0088] In a further preferred exemplary embodiment, at least one process parameter and / or at least one other process parameter can be controlled by means of at least one ratio of the specific volume of the material in the stressed state to the specific volume of the material in the unstressed state and depending on the prevailing temperature.

[0089] In a further preferred exemplary embodiment, the total distributed corrected volume of material in the unstressed state can be determined for each fabricated object 58, and / or the mass of the object 58 can be calculated using the total distributed corrected volume of material in the unstressed state and the material density of the material in the unstressed state. This can be done, for example, based on Figure 1 or Figure 2This is accomplished by means of the difference in specific volume from the stressed liquid state to the unstressed state (T0, p0).

[0090] For example, material specific data for a material may not be available because the material is an unidentified recyclable or compound.In another preferred exemplary embodiment, the material specific data may be provided by taking at least one measurement using a machine.

[0091] In order to obtain material-specific data using measurements, in a further preferred exemplary embodiment, at least one position (e.g., screw position), volume, pressure, and / or temperature is detected. From this, it is advantageous to deduce the ratio of the specific volume in the screw to the volume in the atmosphere. As already described, this allows for process adjustments in the liquid phase.

[0092] In order to advantageously determine the dispensed volume or dispensed mass more precisely, in a further preferred exemplary embodiment, at least one calibration can be used to adjust the corrected volume of the total dispense for different process conditions. This allows a corresponding adjustment factor to be used for a more precise determination of the dispensed volume or dispensed mass. In principle, this can correspond to a volume difference Δv, for example, Figure 1 or Figure 2 Δv1, Δv2 or Δv3 in .

[0093] In a further preferred exemplary embodiment, the flow rate per unit time can be calculated from the total dispensed corrected volume and / or the flow rate per unit time can be varied. Accordingly, the shear rate or shear present on the material when exiting from the outlet opening 62 can be calculated or specifically controlled by varying the flow rate.

[0094] In order to advantageously achieve control of the molecular orientation to influence the mechanical properties, in a further preferred exemplary embodiment, the shear can be further influenced by temperature changes taking into account material specific data (e.g. pvT data, pvT diagrams and / or predefined dispense amounts).

[0095] The advantages cited with respect to the method also occur in the case of a machine control system for a machine 40 for handling and / or processing material, in particular a forming machine or a 3D printing machine, provided that the machine control system is set up, implemented and / or constructed to carry out the method accordingly.

[0096] Similarly, the advantages according to the method occur when using a computer program product having a program code stored on a computer-readable medium, so that the method can be performed using this program code.

[0097] It goes without saying that a wide range of modifications, changes and adaptations may be made to the present description within the scope of equivalents of the appended claims.

[0098] Reference Signs List

[0099] 10 Discrete Volume

[0100] 20 operating points

[0101] 40 machines

[0102] 50 pressure generating unit

[0103] 52 installation space

[0104] 54 allocation units

[0105] 56 Object Carrier

[0106] 58 objects

[0107] 60 drive units

[0108] 62 Exit opening

[0109] 64 drive unit

[0110] 68 screw

[0111] 70 Preparation Units

[0112] 72 machines

[0113] 74 Material storage.

Claims

1. A method for distributing discrete volumes (10) having certain properties along a trajectory in a process for producing a three-dimensional object (58) from at least one curable material in a state of stress or capable of being placed in a state of stress, comprising a machine (40) for handling and / or processing said material, in particular a shaping machine or a 3D printing machine, said method comprising the following steps: - placing said material in said stressed state in a material reservoir (74), - applying pressure to said material in said stressed state in said material reservoir (74), - discretely dispensing said material from a closable outlet opening (62) in order to produce said three-dimensional object (58) under at least one process condition, - wherein, upon at least one change of said at least one process condition, at least one process parameter is updated during the production of said three-dimensional object (58), preferably while maintaining at least one other process parameter, in order to obtain predefined characteristics of said discrete volume (10) in said stress state, Characterized in that material-specific data of the material are provided and that the at least one process parameter and / or at least one other process parameter are controlled using the material-specific data in order to obtain at least one predefined characteristic of the discrete volume (10) in a stress-free state of at least one assigned discrete volume (10), in which no other additional external influences act on the material.

2. The method according to claim 1, characterized in that The predefined property of the discrete volume (10) in the unstressed state includes mass and / or density.

3. The method according to claim 1 or 2, characterized in that Controlling for obtaining the predefined characteristic of the discrete volume (10) in the stress-free state of at least one allocated discrete volume (10) is performed based on an update of the at least one process parameter for obtaining the predefined characteristic of the discrete volume (10) in the stress state.

4. The method according to claim 1, wherein At least one temperature and / or pressure dependency of the specific volume, density, compressibility and / or temperature of the material, in particular a dependency of the specific volume of the material on pressure and / or temperature, is provided as the material-specific data.

5. The method according to claim 1, wherein Pressure, temperature, volume, nozzle diameter, opening time, dispensing time and / or the size of the outlet opening (62) are controlled as at least one process parameter and / or at least one other process parameter.

6. The method according to claim 1, characterized in that The pressure is updated to obtain a predefined volume of the at least one discrete volume (10) in a stressed state, and / or the volume and / or temperature are controlled to obtain a predefined mass of the at least one discrete volume (10) in a stress-free state.

7. The method according to claim 1, characterized in that For at least one allocated discrete volume (10), a corrected volume in the unstressed state is calculated by means of at least one ratio of the specific volume of the material in the stressed state to the specific volume of the material in the unstressed state.

8. The method according to claim 1, characterized in that: At least one process parameter and / or at least one other process parameter is controlled by means of at least one ratio of the specific volume of the material in the stressed state to the specific volume of the material in the unstressed state and in dependence on the prevailing temperature.

9. The method according to claim 1, characterized in that The total distributed corrected volume of the material in the stress-free state is determined for each manufactured object (58) and / or the mass of the object (58) is calculated with the aid of the total distributed corrected volume of the material in the stress-free state and the material density of the material in the stress-free state.

10. The method according to one of the preceding claims, characterized in that The material specific data are provided by taking at least one measurement with the machine (40).

11. The method according to claim 10, characterized in that At least one position, volume, pressure and / or temperature is detected for measurement by the machine (40).

12. Method according to one of claims 9 to 11, characterized in that At least one calibration is used to adjust the total dispensed corrected volume for different process conditions.

13. Method according to one of claims 9 to 12, characterized in that The flow rate per unit time is calculated from the total dispensed corrected volume, and / or the flow rate per unit time is varied.

14. The method according to one of the preceding claims, characterized in that The material undergoes at least one phase transition between a stressed state and an unstressed state.

15. A machine control system for a machine (40) for handling and / or processing curable materials, in particular a molding machine or a 3D printing machine, characterized in that: The machine control system is set up, implemented and / or configured to carry out the method according to one of claims 1 to 14 .

16. A computer program product comprising a program code stored on a computer-readable medium, the program code being configured to execute the method according to claim 1.

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